From ‘Objects’ to ‘Sustainable Development’: The Evolution of Architectural Heritage Conservation in Theory and Practice

Abstract

Over the last century, architectural heritage conservation has evolved and transformed immensely. This study focuses on the origin of contemporary conservation theory from the 19th century and the Authorized Heritage Discourse: the doctrinal texts issued by ICOMOS, UNESCO, and ICCROM. Conservation philosophies from 5 theorists and 23 charters and documents are analyzed from a qualitative perspective. It is structured on three interwoven and complementary theses: first, a study of the 19th and 20th centuries is presented as the backbone of conservation theories; second, a detailed analysis of the Venice Charter is given; and third, an investigation into the authorized conservation policies after the establishment of the Venice Charter. The aim is to understand the evolution of architectural heritage conservation in the dynamics of the time and space of the last century, in theory and practice. The results demonstrate that architectural conservation began with a strong privilege of objectivity in practice to create a real, tangible, and static object that was concerned only with individual monuments or sites vulnerable to the trace of time, stylistic restoration, and armed conflicts. However, recent socio-economic and environmental demands and challenges have transformed this understanding to make conservation a subjective, dynamic, value-linked, and contextual-based approach. Such shifts result from realizing the additional potential of heritage buildings that can enhance viability and livability in communities; as existing resources with high material residual values, embodied material, and energy, their continuous renovation and rehabilitation contribute to urban environment resilience and decarbonization; and as a source of past experience rooted in all aspects of societies that can be used to educate and raise awareness about the crisis of climate change. Accordingly, four chapters in architectural heritage conservation have been identified: 1. It originated to preserve the authenticity and integrity of the material past by experts; 2. then, it moved to the protection of associated values, still with a strong tendency toward conservation of the authentic state of heritage buildings by experts and with local consultation; 3. the significant socio-economic role of heritage for the community made its conservation a democratic exercise by local people with the help of experts and governments; 4. realizing the environmental benefit of reusing existing resources, nowadays, conservation intermeshes with the sustainable development of communities through multi-stakeholder engagement in all decision-making processes.

1. Introduction

One of the potent ways of preserving the past can be achieved through the survival of architectural relics, often considered the most prestigious expressions of past ages [1]. The retention and modification of these significant buildings is not a new phenomenon. For instance, on a quite interesting and larger scale, in the 6th century, at Nimes, the Visigoths transformed an amphitheater into a fortress, which became a little city of two thousand inhabitants [2]. However, the transformation of historic monuments, back then, did not carry a preservationist purpose as we understand it today, but the driving force that triggered these interventions was financial and functional [3,4]. It was during the 18th century that the perception and attitude toward heritage practices shifted, where the conservation of architectural heritage “becomes a public concern and its care an expression of the interests and responsibilities of civic societies” [5] (p. 13). The systematic classification of historic buildings was for the first time implemented in the post-revolutionary Enlightenment rationalism era, with the advocacy of science as the primary way of knowing; romanticism was devoted to the uniqueness of artistic works and esteemed the beauty of ruins; and nationalism exalted the value of national monuments as national identity [6]. The formal architectural heritage conservation management started with heed to the antiquities of the ancient Greek and Roman world [7]. In the early 19th century, conservation had shifted to perceive monuments as relics of the past [8] and the involvement of the public sphere in the protection of art and culture [6,9]. Heritage valorization and interest in the conservation of the past emerged and developed with the socio-political tendencies of the time [5]. In this premise, the most influential structured conservation ideologies emerged within the English Art and Craft movement with the establishment of the Society for Protection of Ancient Buildings (SPAB) in the late 19th century in the United Kingdom [10], while in other parts of Europe, in Norway for instance, the conservation movement was initiated earlier by the establishment of The Society for the Preservation of Norwegian Ancient Monuments (Fortidsminneforeningen) in 1844 [11].

Modern times witnessed new twists by defining the concept of heritage for historic works and conservation as a thinking process rather than scientific. Heritage discourse has expanded and evolved immensely in the past few decades [5,12,13,14]; while some scholars believe that this transformation is paradigmatic [15,16,17], others, however, claim it is revolutionary [18,19].

Evolution encompasses all aspects of heritage. The most important, perhaps, is the broadening of the ideas of heritage conceptualization within the international heritage institutes (e.g., UNESCO, ICOMOS, and ICCOROM) that have been established, fostered, and circulated in the form of documents to regulate and govern the process of heritage identification, interpretation, and protection. This institutional theorization of heritage, also mentioned as “Authorized Heritage Discourse” [20], is, however, based on a universal understanding [21], generally said to be rooted in the materialistic Western convictions [22,23] and relying primarily on the authenticity of the tangible aspects and empirical evidence under the remit of the Venice Charter, while ignoring the intangible perception of the causes. Recently, transformations in heritage appropriation convey deviation. At a more nuanced scale is the expansion of the spatial taxonomy of heritage, which now involves a whole historic town, vernacular built environments, or cultural landscapes, not just a single monument or historic site [24,25,26], and has even shifted to include intangible concepts such as beliefs, environments, and social components [9,20,27]. Along with this is the growing movement that modified conservation to be democratic [28], a diverse public commodity with economic value that can bring good to the social lives in the communities [29,30] through tourism and job creation [31,32,33].

Influenced by the notion of sustainable development and intergenerational equity [34], the Brundtland Report, which emphasized “meeting the needs of the present without compromising the ability of future generations to meet their own needs” [35] (p. 2), bifurcated the initial focus of heritage conservation from inward-looking (the preservation of objects) to outward-looking (the heritage as part of a multilayered environment) [36]. This interpretation of heritage has re-oriented heritage management by reflecting on the heritage instrumental values—the contribution of heritage to environmental protection, social capital, and economic growth—that is intertwined with the heritage intrinsic values [37,38,39,40,41,42]. Concerned with sustainable development, conservation practice has become an integrated practice combining the hierarchical conservation approach (top-down) with an interactive corporation (bottom-up) based on the engagement of multiple stakeholders into policies for an optimized, well-protected, and effectively managed heritage [41]. In many ways, such a participatory governance of heritage, which deals with the multi-dimensional characteristics of heritage along with the different stakeholder benefits, conflicts, and contributions, can enrich the decision-making processes and ensure a sustainable transformation [43,44]. From the need for the adaptive rehabilitation of heritage buildings to contemporary uses [45] and the private financial support and benefits to enable the intervention practice [46,47], to the significant role of development polices to establish regional support through planning, political and governmental systems [48,49] by encompassing heritage protection into urban development, the ecological benefits of reuse and the task of mitigation and adaptation will be accounted for [50,51,52].

Hereon, the vulnerability of heritage stretched afar from the impact of natural wear and tear or the deliberate disfigurements (stylistic restorations) to integrate the issues of rapid urbanization, human migration, natural hazards and disasters, rising sea levels, climate change, advancement of technology, socio-economic change and growth, and war [50,53,54,55,56,57,58,59,60]. For instance, the most concerning issue of today, climate change that induces other natural disasters, threatens people and their cultural heritage globally [51] and seems to push heritage conservation practice to extend [50]. Nowadays, inevitably, environmental sustainability has become a competing aim along with the conservation of cultural heritage [52].

Therefore, the consensus is that heritage conservation is served best by interdisciplinary methodologies [52,61]. Novel approaches in the theme of sustainable development have already started gaining popularity in heritage conservation practice, such as the theory of circular economy [62,63,64], urban mining [65], the methods to reduce emissions from buildings [66], environmental impact analysis of the conservation practice [67], and resource efficiency (material, energy, and waste) [68]. Recently, modern assessment tools are believed to effectively serve sustainable management process, planning, and intervention, such as building modeling information and photogrammetry [69,70,71] and the application of the geographic information system (GIS) [72,73], despite some limitations [74,75]. In this multidisciplinary perspective, the aim is to optimize the conservation process—extending the lifecycles of heritage buildings; saving the cultural, environmental, and economic value; and intending to enhance cultural qualities and reduce resource dilapidation and the related energy use and emissions.

Within these contexts, to build a comprehensive understanding of the latest trends—the developmental trajectories and the cutting-edge shifts—in heritage conservation, this article traces the transformation of heritage conservation philosophies from the formal establishment in the early 19th century to the current multi-perspective understandings and practices. It argues changes in architectural heritage identification, definition, appropriation, protection, and operation from doctrinal texts established by the international organizations, in a chronological order, by focusing on understanding how contemporary advancement and challenges have altered the inward-looking cultural heritage preservation into outward-looking sustainable conservation, see [36], by perceiving development as progress. Thus, it is most important to understand the thematic changes in the official heritage discourses and policies and how they engaged and incorporated these changes into heritage theories and practices. There is no scholarship that has delved deep into this matter. This study aims to rectify this gap by exploring how and why modern conservation theory has evolved, in theory and practice, in the dynamics of time and space through the last century.

The intention of this research is to add to the body of heritage conservation knowledge and enrich the existing literature. The identified thematic pattern of change in the concepts, nature, aims, challenges, approaches, and who is responsible and why is believed to serve academics and practitioners in the initial stage to make better judgments.

In order to achieve an comprehensive answer to the aforementioned question, this article is structured into five sections, as follows: Section 2 describes the research methodology and the data sources used; Section 3 presents the results, the evolution of architectural heritage conservation through content analysis in chronological order; Section 4 discusses the forthcoming trends and methodologies, the theoretical and practical implications; and Section 5 concludes the findings with limitations and suggestions.

2. Methodology

This study was initiated to explore the primary question: how and why has modern cultural heritage conservation evolved, in theory and practice, in the dynamics of time and space of the last century? To answer this question, an inclusive analytical review of the doctrinal texts from the international organizations—the International Council on Monuments and Sites (ICOMOS), the United Nations Educational, Scientific and Cultural Organization (UNESCO), and the International Centre for the Study of the Preservation and Restoration of Cultural Property (ICCROM)—in relation to architectural conservation is carried out. In addition, other prominent theories that have shaped the base philosophy of architectural heritage conservation are identified and studied. This data domain is chosen because these doctrinal texts, as the official heritage discourse, globally govern all aspects of cultural heritage identification, appropriation, protection, and utilization.

The qualitative content analysis is used to systematically study and identify the changes in heritage conservation theories and practices. The qualitative data were collected and coded through focusing on the pattern of changes in heritage conceptualization, spatial dimensions, values, scope of conservation, methods and approaches, stakeholders’ involvement, vulnerability, and the product of the conservation process.

Content analysis is a research method used to systematically and objectively extract specific information and then summarize, categorize, and infer the results [76]. It provides new insights, describes meanings, summarizes existing knowledge, and at the end gives a useful guide to action [77]. For implementing qualitative content analysis, Taher Tolou Del and colleagues [78] used three steps. First, the purpose: developing the themes to outline the underlying meaning of the content; second, the process: identifying the relevant data, building a coding frame, categorizing and analyzing, and using the findings to address the research question; and third, the product: credible and context-bound results.

This approach assisted the author to extract the relevant information from (1) the prominent theories of the seminal theorists (e.g., John Ruskin, Emmanuel Viollet-le-Duc) that have formed the backbone of formal heritage conservation, (2) the charters and doctrinal texts established or adopted by the ICOMOS, and (3) the scientific scholarship in these debates.

Due to the wide scope of this review, the Result section is structured into three parts. It refers to the Venice Charter as a pivotal point in the process of the transformation of the intellectual, perceptual, and practical understanding of the modern conservation of architectural heritage. Therefore, in the first part, it discusses the main ideologies that have influenced the theoretical underpinnings of the Venice Charter; the second part elaborates on what the Venice Charter teaches us; the third part discusses the recent evolutions in conservation understanding from the establishment of the Venice Charter until now, within institutional and recent scholarship. Figure 1 demonstrates the steps used in this research method.

3. Results

3.1. The Formation of Conservation Theory and Its Contribution to the Venice Charter

Many scholars from Europe have pioneered theories and practices to protect and prolong the life of historic buildings. In the end, it was their point of view and grounded circumstances that shaped the establishment of the Venice Charter in 1964. Among all, the utmost theories and philosophies are discussed and elaborated.

Emmanuel Viollet-le-Duc (1814–1879), “the greatest architectural theorist of modern time” [79] (p. 3), managed many restoration works of mostly medieval buildings [80]. Viollet-Le-Duc’s conservation principles were based on an organism metaphor: a progressive approach that the form, material, and technology should not be tied to the traditions, but purposefully serve the designs. The design and construction realization were based on a specific need to be fulfilled [81]. For him, history was a matter of rationalization rather than an instinctive meaning of forms [82], and the historic integrity of the building and aesthetic intuition was “a product of imagination regulated by the reasoning faculty” [83] (p. 100). Thus, stylistic unity in historical monuments, where he added new parts to the monument “in the original style” [84], was not a problem, but a necessity for the building to be restored to its pristine state [80]. As an architect, he felt entirely qualified to fill in the blanks of damaged buildings. He explained, “to restore an edifice means neither to maintain it, nor to repair it, nor to rebuild it; it means to re-establish it in a completed state, which may in fact never have actually existed at any given time” (Viollet-le-Duc, 1866 translated by [6]) (p. 5). Somewhere else in The Foundations of Architecture Selections from the Dictionnaire raisonné, he says, “the best way to preserve a building is to find a use for it, and then to satisfy so well the needs dictated by that use that there will never be any further need to make any further changes to the building” [85] (p. 272).

However, Jokilehto believes his intention for the unity of style was the harmonious adaptation with the architecture of the historic building, and, in addition, that extensive restoration was not his favored practice but a conditional approach [80]. Viollet-Le-Duc’s emphasis was placed on the maintenance of the historic building in the first place. Jokilehto cited his words, “however well done, the restoration of a building is always a regrettable necessity which intelligent maintenance must always prevent” [80] (p. 150). Therefore, Viollet-Le-Duc’s contribution to conservation theory is the restoration of historic buildings and the need to keep them in use, but not necessarily to maintain the trace of history on the monuments’ fabric nor the function that the historic building was built for in the first place.

Anti-restoration was understood to focus on the preservation of the original design of monuments within their own history and context, while restoration relied on a change to some parts of heritage buildings where necessary. John Ruskin (1819–1900), the forthright advocator of the anti-restoration movement, was far from the radicalism of Viollet-Le-Duc; on the contrary, he criticized his approach to consolidating historic buildings. Anti-restoration adhered to the understanding of historic buildings’ protection in respecting the original design and materials and the marks of passing time, the patina on the look of the historic buildings. Thus, he argued that preservation, rather than restoration, was a preferred practice because the latter is tantamount to their destruction. For him, restoration was “the most total destruction which a building can suffer” [86] (p. 353). He considered historic buildings as a “corpse” [87], impossible to restore but possible to maintain. According to him, “it is impossible, as impossible as to raise the dead, to restore anything that has ever been great or beautiful in architecture… Do not let us talk then of restoration. The thing is a lie from beginning to end …Take proper care of your monuments, and you will not need to restore them” [86] (p. 353–357). By defining restoration as a “lie” because of the deliberate change to the appearance of the building that would lead to the falsification of history, instead he proposed continuous repair and maintenance.

Similarly, William Morris (1834–1896), a disciple of Ruskin, highly influenced by his thoughts and theories [88], opposed the ongoing tendency to restore buildings by adding elements, instead of just doing repair works [7,14,80], through conjectural replacements [89]. He advocated a more careful approach, which should be reduced to the minimum level of intervention, and the significant features of the building must be retained [90]. Morris, in his manifesto in 1877, accentuated the importance of the authenticity of historic buildings and valued the existence of a patina on the look of the monument [90]. There, he further contended, “we are guardians of the ancient buildings we inherit, for future generations. We should not feel free to do with them as we please now” [89] (p. 6). A responsible method was first regular maintenance, and then repair and preservation, which should never do more work than is necessary to preserve the building [89], nor should one change the original function of the building [90]. However, he soon realized the impracticality of Ruskin’s vow of chastity regarding the building. Later on, he made a concession: if new work was to be done in an old building, it should be in a contemporary style, and all insertions had to be reversible; that is, they could be removed without leaving a trace [91]. Since then, the concept of authenticity remained present as “the backbone for urban heritage conservation into the 20th century” [7] (p. 41) and the most important model for conservation practices.

The Austrian art historian and general conservator Alois Riegl (1858–1905) is considered the father of modern conservation theory [48] because of his postulation of the “age value theory” and the “theory of historical evolution” [92]. He was aware of the socially constructed character of cultural heritage and the demand for its selection based on specific present-day needs [93]. In his famous essay, “Modern Cult of Monuments”, he discussed and distinguished between three different commemorative values in monuments: age value, unintentional value (historical value), and intentional value, as opposed to present-day values, including use value (newness value) and art value (relative art value) [94], meaning that a monument possesses many layers of values, and these values often oppose each other. For instance, he believed the age value is distinct and thus contradicts the historical value.

In conservation, age value tends to be against the protection of buildings, but historical value is the result of faithful conservation [95,96]. He writes, “the contradiction between newness-value and age-value is at the center of the controversy which rages over the treatment of monuments” [94] (p. 44). He believed everything is influenced by the passage of time and that these traces are irreversible and should be considered part of heritage architecture. Thus, his description of “authenticity” demonstrates that it is not the original form of the building to be identified as authentic, but the whole character of the building as it has been transformed over time and handed down to the present [92]. Therefore, according to him, “pure conservation” is impossible [87] (p. 226); any type of intervention in a heritage building will cause some disturbance of the visual elements even though the intrusion is little. So, during conservation, the new work needs to be differentiated from that of the original but should be harmonious with the overall architecture of the building. He proposed three approaches for the protection of wall paintings: “radical”, which is the minimal possible intervention that aims to retain the feeling of the oldness in the works of art; “art-historical”, a compromised approach protecting the work of art as a testimony of the past; and “conservative”, which insists on the completion and reconstruction of the original image as it once used to be [80] (p. 218).

However, according to Jukka Jokilehto [80], Riegl was opposed to the 19th century creative restorations. His theory of use value promotes the reuse of historic buildings as an intrinsic part of conservation. “Where a monument has ceased to have use-value, the consideration of age-value has begun to prevail in its preservation. The situation is more complicated where the use-value comes into play; most would prefer to regard a building in use as something sturdy rather than as something aged and decayed” [94] (p. 44).

Another key influencer in the rise of the Venice Charter indeed was the Athens Charter of 1931 [97]. In October 1930, an international conference was held in Rome to study scientific methods for examining and preserving works of art [80]. Consequently, in Athens in 1931, the First International Congress of Architects and Technicians of Historic Monuments, also famously known as the Athens Charter of 1931, recommended principles for the preservation and restoration of ancient buildings [7], a forerunner to the Venice Charter [98], it laid out the base for it, involving the main principles and scope [99].

The chartered principles indicate the ethics of the protection of historic monuments and their surrounding areas. There, the process of restoration, preservation, and protection of historic buildings and sites emphasized the retention of the original material and form, which is mentioned to be governed by scientific consultation and professional techniques [97]. This process should be executed using authentic documents with respect for the historic and artistic work of the past without disturbing the style of previous periods, discarding the trace for admiration of the unity of style left in place. The use of modern materials and technology for the consolidation of monuments is permitted if it is mandatory. However, the new material should be adapted to the aspect and character of the restored monument (But the adaption of new material to the original architectural style of historic monuments is revised in the Venice Charter (1964) as new material should be harmonious with the original style but recognizable to avoid falsifications), but it should be recognizable in the case of ruins, whenever anastylosis (the practice of re-erecting original fragments that had fallen from the monument) was possible [100].

Cesare Brandi (1906–1988) is, in fact, another paramount figure in this discussion. His 1963 Teoria del restauro (Theory of Restoration) was published just one year earlier than the initiation of the Venice Charter and had been a reference for, and a clear influence on, the development of conservation principles in the charter [101,102,103] as well as in the UNESCO mission [104]. His conceptualization was based on a rationale that creation is a plural work of soft visualization—the artistic—and the hard work of assembling elements—the technical process [105]. From this, he highlighted the need for conservation practices to understand the object within its broader context [106]. Herein, one can assess the various aspects of the place from understanding the evolution of and use of the place, identifying the original material and structure and interpreting the original designer’s intention and the related changes to the physical characteristics of the place and the external disfigurement [107,108].

However, it is not a simple task but a critical way of rationalization and valorization. For him, an artistic object is the result of a “creative process” of its own, and its perception requires a critical process in human consciousness to reclaim its significance [80], an idea that is comparable to “philosophical criticism” [109].

Brandi’s definition of restoration is, “the methodological moment in which the work of art is recognized, in its physical being, and its dual aesthetic and historical nature, in view of its transmission to the future” [110] (p. 50). He elucidates that he believes in a dual time for every work of art, the time of creation and the time of its perception as a work of distinction by universal consciousness [111]. For Brandi, restoration aims to “re-establish the potential oneness of the work of art, as long as this is possible without committing artistic or historical forgery, and without erasing every trace of the passage through time of the work of art” [110] (p. 50). Thus, any work of art has a twofold polarity consisting of the aesthetic and the historical aspects; however, both integrate into the formation of “oneness” or “unity” of the object [80,112]. The aspect of historicity is independent of the aesthetic values and the way it transforms with time [80]. The aesthetic qualities remain intangible [112] and are often neglected in scientific conservation [6]. Brandi asserted that artistic values are of foremost importance, and as historical values, they are essential to be taken into account when contemplating restoration work [6,112]. Therefore, his principles of conservation and restoration are derived from a reverence for the original state and the composite materials as something irreplaceable, with the heed to retaining historical and artistic authenticity [105].

In addition, Brandi particularly defines architectural restoration as “any kind of intervention that permits a product of human activity to recover its function” [104] (p. 24). The act of intervention should be minimal, as he used the term “minimum of needed intervention”, and aiming to respect both the historic and aesthetic integrity of the work of art [113,114].

Another of his accomplishments is the concept of “reversibility”. This concept indicates the necessity of executing a more careful approach toward decisions and the destructive effects of interventions in the authentic state of the object [106,114]. For systemizing the conservation approach, he formulated three principles [80], as follows:

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Any new work should be easily recognizable at a close distance but, at the same time, it should not offend the unity that is being restored.

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The part of the material that directly results in the formation of the aesthetic images is irreplaceable.

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Any restoration should be made so that it will not be an obstacle for necessary future interventions; indeed, these should be facilitated.

In addition to these principles, [115] contended other key principles, as follows:

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The unacceptability of creative conservation—conservation should not be an imitation of the original design.

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The imperative of preservation of the patina—conservation should not erase the layer of passing time.

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The uniqueness of an individual conservation case—conservation should be executed based on the specific needs and conditions of the object.

These concepts and principles soon reappeared in the Venice Charter [98], shaping the bases of the modern theory of conservation. Hence, the philosophical recognition of the particularity of artistic works, including architecture, as unique creations by individuals became the basis for the description of the modern understanding of conservation and restoration. Thenceforth, the legitimacy of restoration as a practice that simply re-establishes or returns to an earlier form was disregarded; rather, identifying the place in its actual state, the original intention of the designer, the purpose for which it was built, the historical transformation it has gone through, and the patina and physical condition of the historical building define the criteria for monument conservation. A summary of the theories and concepts that influenced the principles of the Venice Charter 1964 is presented in Figure 2.

3.2. The Venice Charter

The Venice Charter, a product of its time and place [116], reflected the situations shaping the emergent need for heritage protection due to the immense loss of cultural properties resulting from the armed conflicts during the first and second World Wars [25,48,117]. After its enactment, it became the foundation stone of the ICOMOS [98] and embodies the theoretical frameworks [118] for safeguarding architectural heritage. Its aftermaths were, first, the rationalization of the notion of unity of human value and conservation as international cooperation and responsibility; second, the reconciliation of the at the time polarized views of the reconstruction and preservation movements as it considered that the postwar reconstruction was completed, and it was the time to protect monuments by means of conservation, restoration, and anastylosis; thus, reconstruction was hindered [119].

The Venice Charter 1964, described as the “canonical text of modern” [120] heritage practices, exalted to become the “international best practice” [121] (p. 3) and has remained unrevised [122] until today; despite all the socio-economic and environmental changes, it stands as the basic code governing the practice of historic preservation [119].

The first importance that the wording of this charter identifies is the taxonomy of architectural heritage, “historic monuments” that are “imbued with a message from the past”, valorized as the “living witnesses of [people’s] age-old traditions”, which must be safeguarded “in the full richness of their authenticity” [99] (Preamble). It further explains the concept of “historic monuments” to also include the “urban or rural settings” and the “modest works of the past” (Article 1). In Articles 5 to 7 and 13, it clearly demonstrates that the appropriate conservation approach is the one to keep historic monuments in compatible use; however, it should not change the inside (layout and decoration) or the outside and immediate surroundings such as setting, scale, color, and proportion. In the next section, it emphasizes that heritage intervention seeks to protect the aesthetic and historic values embedded into the heritage through a highly specialized operation based on respect for the original material and authentic documents (Article 9). The final production of conservation must prefer the traditional craftsmanship and the trace of time on the heritage, and if new work is necessary for heritage consolidation, it has to bear contemporary prints to avoid falsification (Articles 9–13).

Thenceforth, this doctrinal document teaches us the ethics and methods of conservation, which seeks “truth” through objective methods [123], and only expert knowledge can identify and furnish their heritage innate values and significance, with the help of authorities.

3.3. Reinterpretations at the Institutional Level: After the Venice Charter 1964

The United Nations Educational, Scientific and Cultural Organization (UNESCO) and its advisory body, the International Council on Monuments and Sites (ICOMOS), are the main international institutes that enact the philosophical and doctrinal frameworks and govern the regulation policies of heritage. While a strong consensus on the conceptual understanding of architectural heritage and the need to protect it exists and is clear between UNESCO and all its partnering organizations, the scope of heritage is interpreted slightly differently.

The first impression of a conceptual evolution in the architectural heritage after the enactment of the Venice Charter in 1964, probably flourished in the establishment of the Norms of Quito [124]. It has expanded the theorization of heritage beyond conventional understanding. The concept of heritage, then, broadened to comprise the environment surrounding the monument, as mentioned: “since the idea of space is inseparable from the concept of monument, the stewardship of the state can and should be extended to the surrounding urban context or natural environment” ([124], II.1). It further described the correlation of architectural heritage with urban planning and economic development [7]. An effective conservation approach is defined to be urban-based practices that integrate architectural heritage into urban development [125]. The vulnerability of architectural heritage is not only a matter of decay or stylistic restorations, but it includes the issues of environmental impact and acceleration of development [126]. Despite the fact that the Norms of Quito 1967 centered on the listed heritage, by the next year, the Recommendation Concerning the Preservation of Cultural Property [127] expanded the spatial scale to encompass not only scheduled architecture but unscheduled as well by identifying them as “cultural property”.

Another noteworthy milestone in the development and institutionalization of the heritage discourse, indeed, is the World Heritage Convention (WHC) (The convention mentioned cultural and natural heritage. This article focuses on cultural heritage only.) [128]. It recognized cultural heritage as “monuments”, “groups of buildings”, and “sites” that are of outstanding universal value from the point of view of history, art, or science (Article 1). The Convention recognizes cultural heritage as a common part of the “world heritage of humankind” that possesses universal interest [128] (Preamble), which promotes international recognition and protection of cultural heritage [129]. According to Jukka Jokilehto, it is based on the “firm conviction that culture is a vital condition of the well-being of all human society” [130]. Thus, heritage as a cultural product is fundamentally linked with the notion of universality [130]. Furthermore, the Convention aimed to establish an effective system of collective protection of the architectural heritage of outstanding universal value, to be organized on a permanent basis and in accordance with modern scientific methods (ibid). There, it further asserted that the changing social and economic conditions are challenging the acceptance and protection of heritage as the natural process of deterioration. Thus, this ideology made it the first international normative text that requires an integration of the conservation principle into comprehensive planning programs. A complementary document is the Operational Guidelines for the Implementation of the World Heritage Convention [131]. It outlines the measures to be met by architectural heritage to be listed as world heritage and is continuously being revised [132]. For instance, its 1992 version added the new spatial category, “cultural landscapes”, presenting a place that is a blend of cultural and natural elements [12].

Right after the proclamation of the WHC by UNESCO in 1972, the definition of heritage and conservation began to expand more to be an inclusive part of its host community, despite the core principles remaining unaltered. The International Recommendation concerning the Safeguarding and Contemporary Role of Historic Areas, the Nairobi Recommendation [133], shifted the idea of singularity of cultural heritage to any “groups of buildings, structures and open spaces…constituting human settlements in an urban or rural environment” (Article 1). Of which, “every historic area and its surroundings should be considered in their totality as a coherent whole” (Article 3). Along with the valid tangible elements, the intangible ones, however modest, thus have significance. The recommendation mentioned that historic areas are part of the “daily environment of human being” vulnerable to urban transformation and whose destruction may often lead to social disturbance and economic loss. Therefore, the challenges of modern urbanization are identified to pose a major threat to the visual integrity of traditional built environments. Article 5 [133] sets a measure to ensure a harmonious integration of historic areas with new development by protecting the views to and from the monuments and historic areas. The trending universal modern architectural style is another problem that this document is concerned with, as it tries to make identical urban environments across the world. As stated, safeguarding cultural diversity in the historic area can “contribute to architectural enrichment” in expressing a diverse world (Article 6). However, at the decision and execution level, national authorities are responsible for legal, technical, economic, and social measures, while the practice of protection and enhancement is an act of specialists and scientific methods. The cooperation of the community is encouraged but remains in a consultation role.

Among the documents on heritage, some have twisted the heritage worldview from its seminal European theorization, a departure from being merely oriented on “object”, “objectivity/truth”, and “scientific approach” to entail “values”, “subjectivity”, or “functionality” and a “people-centered approach.” The foundations that embodied the notion of heritage and conservation laws and methods were initially challenged by non-European audiences, particularly in Asia, Africa, and Australia. The Cultural Charter for Africa [134], The Burra Charter [135], and The Nara Document on Authenticity [136] are among the many with a major influence on heritage discipline.

The Burra Charter, drafted by Australia ICOMOS in 1979 [135] seems to be among the first ones that questioned the authorized principles of heritage and heritage management and conservation. Even though the charter confirms the underlying doctrine of the Venice Charter, profound changes are evident in what heritage is, how to assess the heritage, and who makes the decision. A social dimension rules the document. The concept of “significance” demonstrates the value that people assign to the heritage; “place” includes not only the physical fabric of a monument or site but also embraces the setting, use, and intellectual properties pertaining to it instead of “monuments and sites”, which looks only to the physical characteristics of heritage or “cultural property”, which induces a lucrative and commodity sense. The other important aspect is the concept of “meaning”, which brings in the intangible associations people make with their heritage [137]. It fosters a strategy that links the management of places of cultural significance with the assessment of cultural values [138]. The charter’s mutually inclusive formulation, which overarches the philosophy of the Venice Charter and is a source promoting community inclusion in heritage conservation, made it internationally appreciated and practiced [139]. ICOMOS Australia revised the charter to reflect the current concern of heritage and conservation [25]; it was amended in 1981, 1988, 1999, and 2013.

A non-Western point of view on cultural heritage discipline flourished within the Nara Document [136] on Authenticity in Japan. The document’s intention was to legitimize the intangible cultural tradition of Japanese ritually rebuilding replicas of their temples [80,140]. It marked the transition from a belief in universal international absolutes to a relative and contextual judgment of heritage assets [140]. As declared in the protocol, “all cultures and societies are rooted in the particular forms and means of tangible and intangible expression that constitute their heritage, and these should be respected” [136] (Article 7). It further emphasized the micro-level significance of heritage, “the cultural context to which they belong”, by including the locality aspect in the understanding of the heritage environment and emphasizing cultural diversity over conventional thinking [136]. The document redefined the concept of authenticity to involve specific cultural contexts and draw attention to the need that heritage should be evaluated accordingly. Therefore, it transmitted the focus from the historic physical fabric to a more comprehensive understanding of the essence of cultural heritage assets [141]. Subsequently, the document was recognized by the World Heritage Committee. In the following edition of the 2005 Operational Guidelines for Implementation of WHL, UNESCO extended the definition of authenticity according to the Nara Document [142]. There, the concept of the “test of authenticity” has disappeared and been replaced by the “conditions of authenticity” [143]. This represents a significant rectification of the Eurocentricity of the international conservation standards, the Venice Charter of 1964, and the World Heritage Convention of 1972 [141,144,145,146], toward inclusivity of ideas from East and West.

After the 1990s, concepts such as cultural significance, meanings, or social values have shifted the focus of conservation from the object—independent of context and immutable—to the subject—people-oriented and mutable [147]. Along with this, other movements raised voices from Europe, as well, to include other aspects such as human rights, ecological concerns, and matters related to sustainable development. The Charter on the Built Vernacular Heritage [148], the Budapest Declaration on World Heritage [149], the Convention on the Protection and Promotion of the Diversity of Cultural Expressions [150], the Convention for the Safeguarding of the Intangible Cultural Heritage [151], the Vienna Memorandum on World Heritage and Contemporary Architecture [152], and the more recent documents such as the Valletta Principles for the Safeguarding and Management of Historic Cities, Towns and Urban Areas [153], the Recommendation on Urban Historic Landscape [154], the People-Centred Approaches to the Conservation of Cultural Heritage: Living Heritage [17], and The Future of Our Past: Engaging Cultural Heritage in Climate Action [50] are the standards that have shoved this evolution into paradigmatic shifts.

The 21st century began with the scarcely debated dilemma of sustainable development into cultural heritage conservation, the Budapest Declaration on World Heritage [149]. It is the first official document that acknowledged the need for encompassing sustainable development along with heritage conservation. The Declaration highlights the need to ensure an appropriate and equitable balance between conservation, sustainability, and development so that heritage environments can be protected and the quality of life in communities is improved through appropriate activities [149]. Likewise, other official documents according to the Budapest Declaration have adopted a similar scope: the Convention on the Protection and Promotion of the Diversity of Cultural Expressions [150] and the Vienna Memorandum [152]. The former emphasizes the importance of the protection of cultural diversity and the traditional knowledge, which have the capacity to positively enable sustainable development at the local, national, and international levels for the benefit of present and future generations (Article 2). This can enhance the social, economic, and cultural resources, which, if protected and continued, can contribute to shaping territories and identities (Article 1). Furthermore, it appeals to all parties to integrate culture into sustainable development policies (Article 13). Building on the Vienna Memorandum [152], it expresses a harmonious integration of conservation of monuments with modern development based on existing historic patterns, building stock, and context (Article 5). By acknowledging the continuous changes of the utility value of heritage, social structure, political context, and economic development in societies, it calls for “mutual understanding between policy makers, urban planners, city developers, architects, conservationists, property owners, investors and concerned citizens, working together to preserve the urban heritage while considering the modernization and development of society” (Article 15). It continues, stating that conservation management demands careful consideration of a heritage history, architecture, and sustainability, while the intervention process should not compromise the authenticity and integrity of the heritage asset (Articles 18–21). In collaboration, UNESCO and its advisory bodies (ICOMOS, ICCROM, and IUNC) produced a resource manual on managing cultural world heritage [41]. It provides a framework for governments, heritage protection authorities, site managers, and local communities on the implementation of the World Heritage Convention by placing emphasis on accommodating the current challenges such as inequalities, globalization, climate change, and massive urbanization in the conservation management plan to maintain the values of heritage to societies. It expresses that heritage may be privately owned and used for non-heritage purposes, local community livelihood depends on the beneficial uses of heritage places, and that conservation needs should be placed into policy requirements such as engaging conservation into urban planning and economic development. Furthermore, conservation is a collaborative work between all stakeholders to make decisions on the allocation of resources (human, financial, and intellectual) to plan, implement, and monitor the conservation work in sustainable ways.

The Valletta Principles [153] identifies itself as “the significant evolution in definitions and methodologies concerning the safeguarding and management of historic towns and urban areas”. It reveals that the challenges of globalization, human movements, and political and economic changes in societies concern human settlements but historic towns in particular [153] (Preamble). The nature of historic towns and urban areas is a metaphor for “living organisms” and is subject to continual change. These changes need to be carefully controlled and managed, otherwise they can have adverse effects. Such issues can put at risk the continuity and identity, the traditional urban morphology, and the role of public space in a community [153] (Preamble). Therefore, as asserted in the Valletta Principles, it demands an international framework to redefine and further develop the objectives, skills, tools, and roles into a comprehensive and systematic management plan for heritage protection which at the same time responds to the needs of contemporary life [153] (Part. 1). To accomplish such a holistic attitude, the principle identifies architectural heritage simultaneously as a “resource” and as a “part of urban ecosystem” [153] (Preamble). Such a percept is mandatory for the harmonious development of historic towns and their settings. The process of conservation of a historic town or urban area is focused on a balanced approach, which is meant to safeguard the tangible and intangible values along with the enhancement of the quality of life of residents in accordance with the principles of sustainable development [153] (Preamble). Primarily, the practice is based on multidisciplinary evaluation and valorization of the architectural heritage, and continuous dialogue and consultation with all stakeholders is indispensable because the process concerns them first and foremost, whereas the authorities are responsible for the provision of regulations amongst all stakeholders [153] (Part 3).

An equipotential document, the Recommendation on the Historic Urban Landscape [154] was established concurrently with and complements the conceptual and practical prospect of the Valletta Principles [153]. The distinction, however, is the different interpretation of urban heritage as “an historic layering of values that have been produced by successive and existing cultures and an accumulation of traditions and experiences, recognized as such in their diversity” [154] (Preamble). The concept of historic urban landscapes tries to expand the notion of “historic center” or “ensemble” to comprise the historic areas in their regional settings [154] (Introduction 1). It identifies cultural diversity as an asset that potentially can enhance the livability of urban areas and that fosters economic development and social cohesion in its host community. The process of conservation here aims to protect architectural heritage through a balanced approach between natural and urban environments and between the needs of present and future generations, in a sustainable manner. This aim can be achieved, first, by integrating urban heritage conservation into general urban policy planning and second, by the cooperation of all stakeholders, from public and private to national and international entities, from the very beginning level of valorization to decision-making, planning, and execution on the field to ensure a successful conservation project delivery.

Another significant attempt is made by ICCROM: the proposition of the “living heritage” concept for the well-being of both people and the environment. The guidance notes that People-Centred Approaches to the Conservation of Cultural Heritage: Living Heritage [17] is centered on a people-based conservation approach through the contribution of community participation. It considers heritage places as a “living” part of communities [17] (Part. 1) having the potential to play an active role in the community and to bring benefits to people instead of understanding heritage as an isolated place that needs a resource for its conservation. Living heritage is a percept that heritage should be kept in continuous use by its associated community, and thus, is subject to progressive evolution as changes are embraced as part of the living nature of heritage places.

The guidance [17] further describes living heritage conservation in communities as the responsibility of three groups—those who live within or near the heritage (community members), those who are interested (decision- and policymakers), and those who work with heritage (practitioners). This approach emphasizes strengthening the ability of locals to participate meaningfully in the process of making conservation and management decisions for themselves and their heritage. Such mechanisms can be implemented through different tools, such as training, which provides capacity-building initiatives to raise awareness and knowledge for a community member to participate effectively in the conservation process; stakeholders analysis, to identify the range of participants; cultural mapping that can provide an active role for locals to promote their dignity, social inclusion, and other enhancements in their societies; heritage interpretation, which can reveal the true meaning and potential of heritage through dialogue between all stakeholders; and using the capacity and assets of community members and learning from the experience of previous projects.

The traumatic impact of global environmental crises such as natural disasters and the adverse impact of climate change has been a key driver for legislative document formation [152]. The Valletta Principles [153] and the Recommendation on the Historic Urban Landscape [154] warn of the adverse impact of climate change and the increasing frequency of natural disasters in addition to human migration and uncontrolled urbanization. Aimed particularly to assist actors affected by such crises, a Guidance on Post-Disaster and Post-Conflict Recovery and Reconstruction [155] provides a context-tentative framework to assist damaged heritage places to recover, while not distinguishing between natural and human causes. The framework is thematic and considers factors related to the heritage place and the destructive events in the preparation and response phase and a collaboration between top-down (organizations) and bottom-up (locals’ participation). The role of organization is coordinating expertise and skills, engaging affected locals, effectively allocating resources, and providing capacity building for the active engagement of locals to address the damage to heritage and determine effective recovery.

Recently, the serious concerns on the climate emergency resulted from the anthropogenetic greenhouse gas emission compelled ICOMOS to voice the adverse impact of climate change on cultural heritage and the potential of cultural heritage to be an asset in our attempts to adapt and mitigate the impacts [51]. Contradictory with the conventional mindset of heritage understanding, the Climate Change and Heritage Working Group (CCHWG) of ICOMOS in their following report, The Future of Our Past: Engaging Cultural Heritage in Climate Action, adopted an uncommon position toward heritage conservation policies and methodologies [50]. The distinct feature of this report, along with cultural heritage conservation, is the focus on the climate justice action, which is rooted within community-induced measures. Therefore, in the spirit of the Paris Agreement [156] and the Special Report Global Warming of 1.5 °C [157], this report calls for a “fundamental shift” in heritage conservation policies toward a multidisciplinary methodology to cope with the “cross-cutting” crises of climate change by “urgent collective action” to safeguard cultural heritage and environment [50].

It consists of two parts. The first part focuses on the theoretical and principle measures—understanding the impact of climate change on the socio-environment and the adaptive capacity of cultural heritage to respond to the risks and anticipate to mitigate the impact. In the second part, it provides a framework for systematically recording the impact of climate change in cultural heritage. According to this report, cultural heritage is an indispensable aspect of society and can play a profound role in raising awareness about climate hazards, contribute to climate science by deploying Indigenous knowledge, and promote climate action through resilience and sustainability. Thus, heritage definition and protection should be acted upon in its broadest sense. Methods centered on the physical conservation of selected buildings will not realize heritage’s full potentials; therefore, they will need to adapt or in “some cases a fundamental shift in approach may be needed” [50] (p. 44). It further emphasizes the need to accommodate these changes into conservation policies to meet the challenges of climate change. The principal changes should consider more flexible measures toward building evaluation, sheltering, relocation, and reconstruction; the development of more inclusive and resilient tools that allow for future adaptation, such as circular economy, including lifecycle analysis and resource management; and the need to use more environmentally compatible resources (technologies and materials) during conservation. Suitable approaches to enable the heritage sector to contribute to decarbonization of the environment without compromising heritage significance, as mentioned, are “the sensitive reuse and retrofitting of built heritage for energy efficiency” [50] (p. 10) by adopting new models to assess conservation and adaptation measures from the perspective of circular ideas, such as analyzing the lifecycle impact of buildings, and actions by focusing on materials, energy, and waste minimization, while these procedures can benefit from employing digital technology tools. The gravity of the climate change impact made ICOMOS launch a Triennial Scientific Plan in 2021–2024 to further support the groundbreaking ideas and methodologies proposed by this report and to ensure the development of efficient tools [60].

4. Discussion: Forthcoming Trends and Methodologies in Conservation

What can be accentuated from the preceding discussion is that the theories postulated by the great theoreticians of the late 19th and 20th centuries greatly influenced the core concepts of architectural conservation. The most recognized theories and practices initiated two distinct ways of perceiving, interpreting, and protecting historic monuments: the most permissive to the most restrictive; the stylistic restoration, the Viollet-le-Duc approach, versus the maintenance and preservation of Ruskin’s. In spite of the fact that their philosophies can hardly be reconciled, many theorists tried to find a balance between the two extremes. However, Ruskin’s philosophy of conservation, which revolves around the truth to the nature—preservation of historic monuments in respecting the original design, material, and function and the importance of the marks of passing time and the minimum possible level of disturbance—left more trace on the later theorists’ works, including the Venice Charter, compared with his opponent, Viollet le-Duc.

Among the dozen doctrinal documents on the conservation of cultural heritage, the Venice Charter holds a specific position. Since its establishment 60 years ago, it has been treated as a sacred text and was intended to remain unrevised by ICOMOS [119]. Its establishment created a centralized universal policy for the protection of architectural heritage; later, this was further reinforced by the enactment of the World Heritage Convention in 1972 and other doctrinal documents that developed afterward in the spirit of this charter. A summary of these evolutions is presented in Figure 3.

The conventional concept we might deduce from the Venice Charter [99] is objective. The inherent value and the significance of heritage resides in its authentic form and substance, and the appropriate conservation practice is an approach that preserves this authentic state. While this static point of view focuses on individual objects, e.g., monuments, as being divorced from their subjects, the people and the traditions that gave them meaning [8]. Such notions in the heritage policies and practices imply that heritage is “an end in itself” [41] that has to be protected as it was built and passed to the next generation. However, recently, philosophical understanding draws strong percept that cultural heritage is a concept dependent on time and space [136,158], and its conservation is a “cultural practice” rather than being a merely technical or managerial matter, a “form of cultural politics” [12] inducing a subjective conception of heritage [53]. This means that heritage does not exist as a stand-alone entity, “separate from a subject—a human being, social group, nation, country, [and] culture” [159], while each subject defines its heritage in accord with its values and demands [160]. Similarly, Neil Silberman [161] asserted that the meanings and values of heritage are neither inherent nor static but ascribed by particular people according to their preferences for socio-political purposes.

In the normative texts ordained mostly by UNESCO and ICOMOS, the conceptual shifts can be traced as follows: the term “heritage” appeared as “historic monuments” in the Venice Charter [99]; one year later, it was reinterpreted by ICOMOS as “monuments and sites”; and later on, in 1968, UNESCO revealed it as “cultural property” [127] and a few years later reclaimed it as the common “cultural heritage of mankind” [128]. The perception of the criteria that endorse their culturally significant qualities, such as tangible characteristics (form, material, and design) and universal qualifications [128], also broadened to include, as importantly, the aspect of human attachments to the place, inclusivity, and continuity, as well as other aspects such as commodity values, quality of life, and sustainable development [54,151,153].

Correspondingly, the perceptual shifts broadened to also entail the modification of the key guidance principles in architectural conservation. The concept of “authenticity”, as it appeared in the seminal normative texts, was defined to be dependent on the relics’ original form and design, materials and substance, and location and setting [99,128]; later on, it was improved to embrace intangible properties such as use and function, traditions and techniques, spirit and feelings, and other intangible factors [136,143], implying that the soft dimensions in the protection of physical fabrics are equally important [162,163,164]. Likewise, other concepts, such as “object integrity”, “reversibility”, and “minimal intervention”, that once unconditionally governed the conservation work [8], have been tailored as “cultural significance” [137], “re-treatability” [165], and “minimal meaning loss” [6,166].

Simultaneously, the spatial scale of heritage expanded enormously from a single “monument” [99] to include the building premises’ “site”, then to “setting” [136] areas, and recently, to cover a whole historic city [26], including the historic urban landscapes [154,167], and even to encompass vernacular environments [148]. The expansion of territorial dimensions placed heritage as a member of a multilayered environment of mutually interdependent components that shares responsibility for its viability and livability [37,41]. Thus, its conservation is a matter of multi-criteria decision-making that should serve the heritage and the user, in general, its community.

Not only did the spatial scale of heritage evolve and expand during the second half of the 20th century, but also the value of heritage. During the 1960s–1970s, there was a growing movement of democratization of heritage and conservation against professionalism [28] that started to redefine heritage as a social construct [20]. These radical shifts resulted from the politicization of heritage conservation that later altered the formal policies toward multiplicity of the notion of authenticity and significance [37]; examples are the establishment of the Burra Charter [135] and the Nara Document on Authenticity [136].

Such innovative thinking was a turn from intrinsic values—historic, aesthetic, and scientific—toward a new paradigm of valorization, and it began with the Burra charter [135], as it has brought in the theory of social values. Avrami and Mason believe that social values modified heritage conservation as a “politicized social construction” that can drive or hinder the success of the conservation process as it is highly dependent on governmental support and administration through logistics and funding, and also that the political and market will could be a force behind its destruction (p. 22). Gradually, this paradigmatic shift in heritage valuation evolved to include economic and ecological values as well. The combined social, economic, and ecologic values were coined by some authors as instrumental values [41,168,169]. These values place heritage in its broadest context, create multiple objectives for its conservation, and account the heritage sector (buildings and actors) for progressive development [153]. It should provide for sustainable development of societies instead of just being concerned with sustainable heritage [36].

Important, but limited to public heritage buildings, is the realization of the economic potential of heritage. Generally, historic buildings’ protection relied on the national government to designate resources for conservation [47]. However, due to the expansion of the spatial scale of heritage identification [26] where the majority are owned privately, and the owner’s livelihood is dependent on the heritage [41], the protection process became problematic because provision of governmental financing was limited and heritage building stock was large [170]. It became a necessity to find a suitable solution. Therefore, there was a market shift in the 1990s, where instead of seeing architectural heritage conservation as wholly relying on subsidies or as an obstacle to development, international organizations (e.g., UNESCO, ICCROM, the World Bank) reinterpreted heritage to potentially be capable of providing benefits to the viability and livability of their host societies [31]. Conservation thus becomes a public investment sector and engages the market and local people for their interests [170], financing a profit-making investment [47]. Therefore, private investors and heritage owners got involved directly in decision-making and taking responsibility for conservation of their heritage based on economic measures [153,154]. It was a justification between the preservation of intrinsic values against the heritage buildings’ use/reuse values [171,172,173].

The logic behind the ecological value of conservation is linked with the environmental benefit of reusing existing buildings. New building construction is highly material- and energy-intensive, and demolition generates waste [174]. Natural materials used for building construction are finite [175], and there is a supply risk [176]; energy used for the extraction of new material, transportation, construction, and operation leads to greenhouse gas emission; and the end-of-life demolition waste and landfills are the factors causing critical environmental deterioration and global warming [177]. Continuously using existing buildings is the most environmentally friendly measure [178] for the embodied material and energy accumulated in them. As they are already built, reusing them leads to a significant reduction in greenhouse gas emission related to energy consumption, fossil fuel consumption, freshwater consumption, and material use [64]. It can also significantly reduce construction and building waste [179,180], and the development of new land for new construction can be avoided [178]. Thus, conservation of heritage buildings is a substantial contribution to recirculating the embedded resource—the socio-cultural values, materials, and energy—for a resilient and sustainable built environment [50,65,181]. Originating from such logic, the reuse of cultural heritage buildings has been recognized by high politics and policy makers. For example, in Europe, many projects are initiated to support the adaptive reuse of heritage, e.g., the EU Horizon 2020-funded project “Circular Models Leveraging Investments in Cultural Heritage Adaptive Reuse”, “Buildings as Material Banks”, or the 2020 building Renovation Wave Strategy [64,182].

At the time of multiple shared values, the presence of multiple challenges nowadays hinders the effectiveness of cultural heritage protection and implementation. Global issues such as urbanization, human movement, and reduced financial and environmental resources and climate change [41,50,153,154,183], put further pressure on the heritage vulnerability beyond natural decay, stylistic restoration, and the impact of war. For instance, human movement increases the population in immigrated areas and the need for more space, while on the other hand, regions from where people have migrated suffer from heritage obsolescence, abandonment, and stagnation. The Vienna Memorandum [152], Valletta Principles [153], and the Recommendation on the Historic Urban Landscape [154] emphasize the need for sustainable urban development by integrating the historic built environment into modern architecture. The ICOMSO [183] suggests ensuring the appropriate reuse of heritage and maintaining the integrity of spatial distribution by “limiting urban sprawl and plac[ing] conditions on the right to build” with new development respecting traditional settlement patterns [183] (Article 1).

Among these, climate change has been identified to be “the most significant and fastest growing threat to people and their cultural heritage worldwide” [51]. The immense greenhouse gas emissions driven by human activities have led to climate changes and global warming, including melting glaciers and rising sea level, drought and wildfire, and heavy precipitation and flooding [184,185]. The severity and urgency of this issue demanded that heritage organizations and governments began campaigns to raise awareness and adjust their policies and strategies in order to meet these challenges [186]. The impacts of these climate-induced disasters damage infrastructure, ecosystems, and social systems. Particularly, concerning cultural heritage [155], the impacts are characterized as human tragedy; loss of life, home, and community; population displacement; major economic disruption; and loss of traditional culture. ICOMOS CCHWG [50] accentuated the important role that heritage conservation can play to cope with them by embarking on two themes, heritage as a source of resilience for communities and the Endogenous Ways of Knowing (past human experience); it believes that cultural heritage conservation can contribute to the mitigation of and adaptation to the negative impacts.

The presence of multi-dimensional challenges requires integrated and holistic strategies, methods, and tools that can more effectively protect and maintain historic buildings while improving their functionality and sustainability. Novel approaches such as resource management, circular economy and the environmental impact analysis of products and practices, managing the use of energy and materials, and minimizing waste [50,63,68] are now in heritage conservation policies [50,60]. As it encourages the deployment of modern tools for the identification, analysis, and intervention impact assessment, innovative methods are developed.

The existing literature and research increasingly recognizes the role of information technologies in cultural heritage. Digital-based integrated methodologies aimed at providing efficient tools and services are employed to properly document, analyze, and manage heritage buildings [187,188]. Building Information Modeling (BIM) and photogrammetry scanning facilitate better aesthetic analysis, conditional assessment, and examination and simulation of intervention scenarios [70]. It provides accurate information required for material quantification, cost–benefit analysis, and design optimization for testing different intervention scenarios, reducing resource consumption and waste generation [69]. The use of BIM can be extended to simulate building energy use and calculate the different building life-stage environmental impacts by linking to a secondary program, e.g., SimaPro or EnergyPlus. When BIM models are paired with real-time operational data provided by on-site sensors through Internet of Things techniques, a digital twin (DT) of the heritage will be developed [188,189]. In contrast to the static process of conservation, it facilitates a dynamic interaction between the physical state of heritage and the digital model that can perform analyses and predictions related to the behavior of the physical building under changing environments and defeat physical and cognitive barriers [188,190,191]. Beyond supporting a preventive conservation method [189], DT can provide opportunities for virtual visits to heritage places and museums [190,192,193] in contexts with limited accessibility or to digitally reconstruct endangered or lost heritage assets [194]. Likewise, the application of the geographic information system (GIS) enables resource mapping, spatial analysis, risk prediction, and evaluation monitoring [72,73] and has become integral to advancing and optimizing conservation practice; specifically, it is mentioned to be useful in assisting better decision-making during natural disasters [195,196].

The implication of conservation practice on the field that had conventionally centered on preventing decay and maintaining the physical authenticity and integrity of the architectural heritage has been re-examined and amended to perceive the heritage place as part of a multilayered city composed of natural and cultural values, both tangible and intangible [48]. Historic urban areas are dynamic and progressively shaped and will be shaped by economic, cultural, social, and environmental forces [197].

Thus, the conservation approach journey first started with a reverence for material-based conservation with the establishment of the Venice Charter 1964, mostly driven by curatorial percepts [168]; then, to value-based conservation that aims to keep a balanced approach toward the “aesthetic, historic, scientific, spiritual, and social values held by past, present, and future generations” [168]; then, to human-based conservation as it focuses on a dominant role of the community in the whole process of architectural conservation [30]; and now, to sustainable development-based conservation as a balanced approach between heritage, people, and nature, where the practice should be environmentally cautious and enhance the quality of life of inhabitants while protecting the physical characteristics of heritage through the participation of community members (those who are attached to, care for, and experience these places). In such a mechanism, the authorities’ and experts’ role and remains to act as a catalyst providing intellectual, financial, and logistic resources to assist the locals do the work while promoting capacity building through education, training, and dialogue [29].

Figure 3. The process and the different aspects of the evolution of architectural heritage conservation from its seminal understandings to the latest interpretations. * This aspect is acknowledged in addition to the previous ones. Sources: [17,41,50,99,124,127,128,135,136,137,143,148,150,151,152,153,154,198].

Figure 3. The process and the different aspects of the evolution of architectural heritage conservation from its seminal understandings to the latest interpretations. * This aspect is acknowledged in addition to the previous ones. Sources: [17,41,50,99,124,127,128,135,136,137,143,148,150,151,152,153,154,198].

5. Conclusions: The Future of Heritage Conservation

After one and a half centuries, heritage conservation—its theories, appropriation, and methods—is subject to new and difficult challenges that cannot be treated by using conventional arguments. The grounded circumstances in the world are in fast-paced change due to globalization, urbanization, human migration, social and technological advancement, and of course the negative impact of climate change, thus demanding we rearrange our percepts, techniques, tools, and reasoning toward the protection of architectural heritage accordingly.

With such premises, looking at the usefulness of the Venice Charter to provide holistic principles for the management of architectural heritage in response to the challenges facing societies is very limited. The main features that can be identified within this text are: (a) the rationalization of the unity of human values, monuments are common heritage and their protection is a common responsibility; (b) the protection of architectural monuments from mass destruction, and at the time stylistic restoration; (c) the specific type of architecture it is focused on, monuments and sites (In Article 1, the Venice Charter explains the concept of historic monuments to also include “urban or rural settings”. However, the application of formal and controlled methods of heritage conservation defined in the Venice Charter, such as the requirements in Article 5 that a prerequisite of a useful function is that “it must not change the lay-out or decoration of the building”, seems to be strict on the protection of heritage buildings located in urban or rural areas, where most of them are private properties and the owners’ livelihood is dependent on these heritages. Thus, historic monuments, highly significant buildings, are considered appropriate for the use of this charter.), the emphasis is on protection of their fabric and form inside and outside and the trace of history they bear. Nowadays, a collective agreement is that cultural heritage is diverse and contextual, meaning that the majority of them do not hold universal values, their values are not intrinsic but relative, and the most sustainable way of heritage conservation is the one carried by the local people. Such precepts are very far from the core criterion of the Venice Charter, authenticity, as a primary parameter that determines the historical, aesthetic, and scientific values of heritage. Thus, it is best to leave the Venice Charter “in peace” [116].

Yet, the dynamic and changing situation of the last few decades has accompanied an additional benefit of the built heritage by realizing its full potential as a resource (material and energy) for the present and future for environmental protection. Therefore, these challenges question the validity of the Venice Charter as a holistic approach.

The main streams in perceiving heritage from intellectual discourse are the evolving concepts of heritage conservation, from

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the protection of objective values, intrinsic values embedded within the heritage materials,

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to defining and retaining relative values, or socially constructed qualities,

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recently to perceiving heritage as a source of Indigenous knowledge that can contribute to climate science and to mitigating and adapting to the risks of climate change, and

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the demand to achieve environmental sustainability highlights the importance of the ideas and practices of Circular Economy and Resource Efficiency—minimizing energy and resource consumption and making the most use of what already exists highly increases the potential of existing building stock for reducing the environmental impact of/from buildings.

Considering the vast spatial scale of architectural heritage building stock, which is still growing every day, the reusing and repurposing practice is a win-win situation: the protection and continuation of cultural heritage and the protection of the environment.

It also concluded that such conceptual and urban dimensional developments place architectural heritage management in a broad socio-environmental practice, demonstrating the key role of local people while limiting the power of authorities and experts to make decisions and carry out conservation work of/for others. Whereas the former gain the role of the main actor, the latter roles remain at providing logistics and facilities for the work taking place.

Almost all the authorized conservation policies issued in the last two decades encourage a sustainable development in communities rather than just sustainable heritage, e.g., [36], through integrating heritage conservation into urban development planning for a balanced cultural heritage protection and progressive development; recognizing the economic potential of heritage conservation for communities, and thus, providing opportunities for private sectors and heritage owners to directly participate in the decision-making and protection process, for their support and benefit; and considering the health of natural environments.

There is an urgent need to consolidate the problem of climate change into the cultural heritage debate. Current climate crises affect every aspect of life, and cultural heritage is not sheltered from the adverse impacts. Cultural heritage is an element of a large multilayer environment, and it thrives and degrades with its health; thus, its conservation is not an “end in itself” anymore. As acknowledged by ICOMOS [50], cultural heritage has the potential to play a significant role in enhancing the quality of life and in building resilience and sustainability in socio-environmental aspects because it directly intersects. Therefore, heritage conservators must reach beyond their traditional ways of conservation to engage climate change as a baseline, along with cultural significance, for the competency of heritage management.

Another profound concern is the needs of the present generation that must be addressed. Conceptual approaches such as the “preservation of heritage for future generation”, that reduce the role of the present generation to sole “custodians or caretakers of that heritage”, is not enough to promote sustainability in heritage building stocks. It maintains the physical fabric authenticity and integrity of the heritage architecture, but it excludes the right of the present generation to use and enjoy their loved assets. This approach cannot always trigger the will and benefit of the current people who own and use those heritage buildings. In the end, this may lead to heritage obsolescence, which is a socio-cultural, environmental, and economic loss. Hence, we need to perceive and approach architectural heritage as an asset that belongs to everyone, to the present and the future.

In conclusion, the transformation demonstrates different prospects from a restricted expert act, focused to arrest the decay of a single monument that was divorced from its environment for its age, historical, and aesthetic values. This precept identified heritage to be immutable, which by means of preservation, the future generation could have access to authentic assets under the remit of the Venice Charter. Considering the massive destruction of historic monuments from armed conflicts (World War I and II) and the subsequent boom in the reconstruction and restoration of historic monuments experienced post-war, which contradicted the pre-war preservation doctrine, the Venice Charter was established to return to the initial views of protection and preservation of historic monuments. There is a consensus that it was successful in dealing with the threats facing architectural heritage and its conservation for the time. However, nowadays, the challenges facing heritage and environment are not the same, thus, the validity of the Venice Charter to respond accordingly is in doubt; perhaps, the argument that identifies it as a “historic document” [97,119] is correct.

Gradually, such perceptions have shifted to identify heritage as a metaphor of a living entity, in which change is indispensable, and as a resource in the environment that can be managed. Architectural heritage can potentially bring benefits to the quality of people’s lives and the viability of the community, which is vulnerable to social, technological, and environmental changes more than gravitational forces. Extending their life is not only a continuation of socio-cultural values, but the environmental benefits are also profound. Heritage buildings, as already built, act as reserves of refined building materials, they can save the security of raw materials, reduce the consumption of energy to build new buildings, and reduce the production of waste from demolition. Therefore, regardless of time, the conservation of architectural heritage is always a way of interpreting history through material remains that are shaped by the meanings, values, and circumstances of the community in which the conservation takes place. Here, heritage conservation tries to control the negative impacts while ensuring diversity, continuity, and inclusivity in communities and sustainable and resilient urban development, which produces a plausible heritage for the present and future through a collective integrated practice that involves all stakeholders—authorities, experts, and local people.

5.1. Limitation and Future Research Direction

What I have raised for consideration in this article is a comprehensive overview of thematic changes in architectural heritage conservation, theory, and practice. It is an attempt to learn the history of heritage conservation transformation, the present needs, and to anticipate future directions. The thematic transformation is identified, and various relative factors are highlighted. However, there is a great variety in what, how, and why of the causes, effects, and approaches in each theme. It is substantially informative if each theme is inclusively studied for an in-depth understanding of the challenges and facilitators from different contexts for an efficient and effective heritage protection.

5.2. Definition of Some Terminologies

The following definitions are adopted from ICOMOS [50]:

Circular economy is a regenerative approach, opposing the traditional method of the linear economy—take, use, and dispose. It is built on the precepts of the continuous use of resources by slowing, closing, and narrowing energy and material loops that will result in minimizing the use of natural materials and energy and the production of waste. It can be achieved through long-lasting designs, maintenance, repair, reuse, remanufacturing, refurbishing, and recycling.

Resource management deals with controlling and managing the inputs and outputs of materials, energy, and waste in order to minimize the use of raw materials, consumption of energy, and waste disposition into the environment. It aims to lessen the climatic impacts, improve the security of the raw materials supply, and reduce waste generation.

Lifecycle analysis is the compilation and evaluation of the inputs, outputs, and the potential environmental impacts of a product or service throughout its lifecycle.

Climate adaptation is human interventions to adjust to expected risks of climate change in order to moderate harm and to control the effects of climate on heritage buildings.

Climate mitigation is a human intervention to reduce emissions or enhance the sinks of greenhouse gases.

Indigenous knowledge refers to the understandings, skills, and philosophies developed by societies with long histories of interaction with their natural surroundings. This knowledge is integral to cultural complexes, which also encompass language, systems of classification, resource use practices, social interactions, values, ritual, and spirituality.