**1. Introduction**

The considerable increase in the consumption of fossil fuels and the overexploitation of resources are some of the various points that prove how the causes of climate change are anthropogenic. The most polluting human activities include agriculture, energy transformation, industry, such as manufacturing, transportation, and commercial activities. Cities and urbanizations are among the leading causes for this, considering that they consume 40% of the final energy and are related to 70% of global greenhouse gas emissions [1].

Currently, the urban footprint in Panama City is 23 times larger than it was in 1905, where 65.08% of all Panamanians live in urban areas [2]. The urban footprint in the metropolitan area is growing faster compared to the population residing outside these areas.

During the First World Climate Conference, scientists from different parts of the world agreed that climate change trends were alarming. Since then, similar alarms have been raised through the Rio Summit, the Kyoto Protocol, and the Paris Agreement in 2015. Among the globally agreed goals, there are the Sustainable Development Goals; of which this paper will address: Water and Sanitation (SDG 6), Affordable and Clean Energy

Zarzavilla, M.; Tejedor-Flores, N.;Mora, D.; Chen Austin, M. Sustainability Assessment of the Anthropogenic System in PanamaCity: Application of Biomimetic Strategies towards Regenerative Cities.*Biomimetics***2021**,*6*,64.

**Citation:** Quintero, A.;

AcademicEditor: NeginImani

https://doi.org/10.3390/

biomimetics6040064

Received: 13 September 2021 Accepted: 29 October 2021 Published: 16 November 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

(SDG 7), Sustainable Cities and Communities (SDG 11), Climate Action (SDG 13), and Life of Terrestrial Ecosystems (SDG 15).

In addition, it is stated that, with the efforts made so far, the global warming of 2 ◦C will be exceeded during the 21st century, above the objectives of the Paris Agreement, which established limiting the average temperature increase to 1.5 ◦C. Although, according to the latest United Nations report, over the next 20 years, the global temperature is expected to reach or exceed the 1.5 ◦C mark unless rapid and deep actions against climate change are made. It is possible to maintain these figures if nations are told to keep their emissions reduction commitments, which should be in the range of 25 GtCO2e and 41 GtCO2e by 2030 [3]. If these values are exceeded, by the year 2040, there could be a rise in sea level, affecting coastal cities, such as Panama. For instance, a sector that needs real action in its operating and embedded emissions is the energy sector. According to Panama's National Energy Secretariat, about 70% of the national consumption is concentrated in the capital city, and the National Energy Plan 2015–2050 also states that by 2050, per capita consumption will increase by 90% [4].

In the search for new sustainability strategies in cities that attack these problems, designers have adopted biological research knowledge. In recent years, biomimicry has become relevant in engineering and architecture, giving way to intelligent, self-sufficient, and distinctive buildings in form, structure, and operation. Author Janine M. Benyus gave biomimicry's first definition in 1997. She defined it as the art of imitating or drawing inspiration from the forms and processes of nature to solve human problems [5].

In architecture, many buildings have already adopted this approach by addressing formal biomimetic design methods in their envelopes and integrating functional solutions, such as the Eastgate Building in Harare (Zimbabwe), the Taichung Metropolitan Opera House, and the Council House 2 (CH2) in Melbourne, Australia.

There are three main levels in biomimicry: organism, behavior, and ecosystem. The organism level refers to a specific organism, such as a plant or animal, where part of it, or the whole organism can be mimicked. The second level refers to the imitation of behavior, where an aspect of behavior is translated into a broader human design context. Finally, the third level is the imitation of entire ecosystems and their principles for working successfully, along with their actual functions. Within each of the levels, there are five possible dimensions; following theses aspects, the design can be biomimetic in how the organism looks (form), what it is made of (material), how it is made or produced (construction), how it works (process), or what it is capable of doing (function) [6].

On the other hand, many of the biomimetic case studies examined by Pedersen Zari in [7], suggested that ecosystem biomimicry may be the most effective way to respond to climate change and biodiversity loss. Yet, right now, ecosystem biomimicry remains the least explored aspect of this branch. A well-known example of ecosystem biomimicry can be seen in the industrial region of Kalundborg (Denmark), where a model of industrial ecology was used. This industrial park is an enduring collaboration between public and private organizations where participants exchange waste materials, residual energy, heat, and water for mutual benefit [8].

Currently, there are two main approaches used in biomimicry, from the perspective of the design problem:


In a survey for the strategies that have been taken in different groups of biomimicry practitioners, five of the most recognized groups were discussed: Biomimicry 3.8, Ask Nature, the Biomimicry Institute, Biomimicry Switzerland, and Biomimicry San Diego, concluding that the majority of the groups specialized in the problem-based approach for biomimetic designs [10].

Besides, there are many projects in the current European Union research framework program for nature-based solutions (NBS), known as HORIZON 2020. Many of them strive to explore how NBS works in different urban contexts with respect to the political, social, cultural, institutional, environmental, and economic context [11].

Moreover, the concept of regeneration is emerging extensively in recent investigations by biomimicry practitioners. Pawlyn and Pedersen Zari explained that regenerative systems examine several relevant contemporary examples, which deal with biomimetic technologies and architectures that help the urban built environment adapt to climate change and be favorable factors for the ecological health of the ecosystems. The regenerative design restores the ability of ecosystems to function optimally through the design and development of the built environment [6,12].

One of the concepts most closely linked to regenerative design, which seeks to approach its real application, is ecosystem services. These services are the benefits that humans obtain, directly or indirectly, from ecosystems that support human physical, psychological and economic well-being [6]. The services that humans obtain from the ecosystem are usually divided into provisioning services, such as food and medicine; regulatory services, such as pollination and climate regulation; supporting services, such as soil formation and solar energy fixation, and cultural services, such as artistic inspiration and entertainment. Based on these, strategies have been developed to apply these services in the urban environment [13,14] so that humans themselves contribute to their wellbeing and to the ecosystems with which they coexist. These services apply to the urban developments and can be described as follows:


Examples of ecosystem services analysis (ESA) applied to design include the Lavasa Hill project in Maharashtra, India, and the Lloyd Crossing project proposed for Portland, Oregon. Lavasa was redesigned using the Ecological Performance Standards framework designed by the Biomimicry 3.8 organization and identified six ecosystem services essential to the ecological functioning of the site that was relevant to the development of the urban project in the area. These are water uptake, solar gain; carbon sequestration; water filtration; evapotranspiration, and nitrogen and phosphorus cycling [13].

Considering all the above, the general objective of this study is to conceptualize a reference framework for the proposal of a design methodology based on biomimicry with a vision towards restoration-regeneration at the city scale. This would be done by consulting nature's models to solve several aspects that must be covered in cities with wrongdoings. The solutions will mainly focus on clean energies, energy efficiency, air purification, urbanism, and sustainable mobility with nature's strategies and guides. Through this approach, possible opportunities in applying renewal and regeneration in cities are evaluated, using a qualitative and quantitative study through sustainable indicators.

#### **2. Materials and Methods**

The design of this research was based on the use of a biomimicry problem-based approach to conceptualize and propose a reference framework towards a regeneration model at the city scale. This starts by assessing the current potential for sustainability to identify the main problems within the different systems that make up cities. Figure 1 describes the proposed structure to implement this methodology and the stages that make up this work.

**Figure 1.** The schematization of the structure proposed for this paper. Own elaboration.

#### *2.1. Baseline: Urban Metabolism of the City*

The metropolitan area of Panama is governed by a tropical climate, specifically under two main climatic regions: the Central Region (or R4) and the Eastern Pacific Region (or R5). Both have similar precipitation levels, with rainfall decreasing considerably from December to April (dry season) [14]. As a result, Panama's average outdoor air temperature remains in the range of 23 and 27 ◦C for the coastal areas and the countryside.

For the temperature of the city itself, the analysis carried out in [15] showed that the area adjacent to Calidonia and Santa Ana had the highest temperatures, ranging from 28 ◦C to 30.5 ◦C; while the area with the lowest temperatures was the segmen<sup>t</sup> between Clayton and Metropolitan Park with 25.83 ◦C. This happens since the latter is mostly low-density housing with very dense vegetation. On the other hand, there is a high concentration of economic activity and population in Panama City and the Panama Canal core. Therefore, these territories can be described as "Metropolitan Areas of the Pacific and Atlantic" where approximately 80% of the country's Gross Domestic Product (GDP) is generated [2].

When it comes to the operation of cities, it can be said that a city works similarly to a superorganism that runs through mechanisms and interactions both internally and with the ecosystem. A similar concept is known as urban metabolism (UM), this can be described as the process in which a city obtains its resources from the local environment or by exchanges, then the city consumes these inputs to produce economic outputs in the form of products and services, and then it releases the residues into the environment [16]. There are different types of UM, however, this paper will be focused on the metabolism that occurs in cities through their carbon footprint.

Due to the urban footprint mostly distributed in the Pacific Metropolitan Area, it was necessary to obtain a delimitation of which systems maintained a larger carbon footprint within its limits or boundaries. Therefore, for this baseline case, the Green House Gas (GHG) emissions figures for each sector were collected.

In the results of the GHG emissions inventory according to the year 2013, the latest updated, each inhabitant of the city's urban area emitted around 4.90 tCO2e. When discussing total emissions, it is denoted that the sector that contributes with the highest emissions is the transport sector, accounting for 46%; this means that the transport system should be taken as a priority. This is followed by stationary sources (residential, services, institutional and industry), which account for 37% of total emissions. The next sector is waste management, with 7%, and the industrial processes and product use (IPPU) sector with 6% of the total. Finally, the energy, agriculture, livestock, and fisheries (AFOLU) sector is a net absorber of CO2, with 960,270 tCO2e in 2013 [17].

#### *2.2. Sustainability Assessment and Problem Definition*

There are different ways to evaluate the performance of a city. For instance, among the different urban sustainability indicators, we can mention the Wellbeing Index, which has not been widely used during the last decade due to the appearance of several new sustainability indicators. Besides, the City Development Index (CDI) is considered as a way of measuring urban development and the accessibility to urban facilities. In this regard, between 1993 and 1998, the United Nations Human Settlements Program calculated this index for 232 cities in 113 countries. In conjunction, when evaluating the dimensions measured by the specific index, it is noteworthy that three of them, Ecological Footprint, Environmental Performance Index, and Green City Index, are responsible for covering the environmental and social dimensions. In contrast, the Human Development Index covers the social and economic dimensions [18].

Here, for the case of Panama City, the Green City Index (GCI) is selected, because it has been used since more recent years (2009) and is applicable at the urban scale. Such is the research project conducted by The Economist Intelligence Unit (EIU), sponsored by Siemens, consisting of a series of estimates that began in 2009 and covered more than 120 cities in Europe, Latin America, Asia, North America, and Africa [reference].

Moreover, the GCI has a specific weighting for each indicator; this weighting should be multiplied by the results of the final value for the quantitative data and the qualitative section. Table 1 shows the result obtained from this estimation, where each indicator was compared with a standard value from the guide presented by the Latin American Green City Index [19]. This standard has an optimum minimum and maximum value for a city that is on average sustainable. Data for calculations were obtained from scientific publications, statistics, regulations, and plans or studies generated by the Panamanian government. See Appendix A for the detailed table.


**Table 1.** Summary of the evaluation for the Green City Index indicators (Ranges based on [19]).

Inadequate/poor, high risk, behind schedule. Reasonable, moderate risk, partially behind schedule Good,low risk, on schedule.

According to the weighting for all indicators in the GCI, the city is within the average sustainable performance in the total result, with 55.95%. However, in the case of the individual indicators, there is an alarming risk in terms of air quality, with 16.67%. For the transportation indicator, there is below-average management, with 39%. On the other hand, the sections on land use, with 47.95%, and energy and CO2, with 51.14%, despite being within the average, are at moderate risk and they could be improved to achieve the programmed agenda of goals. Due to this distribution, the priority sectors for action must include air quality and transportation. Additionally, the Energy and CO2 sectors and Land Use and Buildings are rated as average with the same need for intervention. These were considered in the analysis due to their contributions to GHG emissions, inorganic waste, and pollution, which are significantly high.

Some of the indicators used for this index showed a score of 0.00 because of a lack of reliable data sources, as in the sulfur dioxide level indicator. In some cases, values exceeded the internationally established standards (20 μg/m<sup>3</sup> maximum) [19], for example, in the levels of nitrogen dioxide in Panama (36 μg/m3) and suspended particulate matter (49 μg/m3).

Other indicators also exceeded the standard, such as length of the collective transportation network (0.03 km/km2, which is much lower than the minimum of 0.30 km/km2), electricity consumption per capita (2226 kWh/inhab/yr, which is higher than the maximum of 815 kWh/inhab/yr) and water consumption per capita (274 L/inhab/day vs. the maximum of 126.90 lt/inhab/day).

The GCI score for the Pacific Metropolitan Area of Panama (1.5 million inhabitants) was favorable, however, it ranks poorly in transport and air quality compared to other cities in the index with similar populations, such as Quito (2.1 million), Curitiba (1.8 million), Montevideo (2 million) and Porto Alegre (1.4 million). Table 2 presents the comparison of GCI results in these cities.

A biomimetic analysis of the problem-based approach is sought, where the problems encountered through the index were classified into elements, and those of priority were chosen. In Figure 2, a scheme of the most significant issues among the city sectors is presented to highlight their role in the GHG emissions contribution.

**Table 2.** Comparison of Panama City and other Latin American cities from the Green City Index final evaluation. Adapted from [19].

**Figure 2.** Categorization of the identified problems as a priority. Own elaboration.

According to these problems, some of the challenges defined to start searching in nature include the following:


• Exploring alternatives to the motorized mobility for reducing its emissions, focusing on the strategies of nature's organisms to "transport" themselves while foraging and communicating with each other.

#### *2.3. Biomimicry Abstraction: Search for Biological Analogies*

Since the most affected sectors were identified (Table 1) as the ones related to the GHG emissions, along with the challenges involved, the search for biological analogies is now performed to accomplish successful biomimicry abstraction. For this, the main problem of reducing such GHG emissions was examined from the point of view of three main elements: energy, mobility, and atmosphere. These will be the themes to be followed during the search for biomimetic solutions. For each topic, a study of the most essential processes that nature performs on its own is presented.

A method of exploration based on the one presented by [20] known as "BioGen" was included in this paper. Developing a biomimetic design solution, required executing multiple stages, such as the following:


The pinnacle search required classifying the different strategies used by living organisms. This was possible by a comprehensive biological literature review. Some of the sources used were Ask Nature, Biomimicry 3.8, and expert knowledge from different sectors.

Figure 3 presents the exploration model intended to be covered. The three elements or approaches (energy, atmosphere, and mobility) were segregated into four levels of exploration. These levels are the function level (the challenges to be explored, what they need to do), mechanism level (how they handle the identified function), factor level (they affect the distinguished processes or are ways of performing that mechanism), and finally, the pinnacle level, representing the example of nature that complies with the previous levels for that function.

For selecting essential pinnacles, first, the main forms of energy production were considered, by selecting those pinnacles that perform processes using the sun and water, which could be replicated in cities, taking plants and *Fenestraria aurantiaca* as examples.

In thermal regulation, pinnacles that could reduce the environment's temperature, either by evaporation or convection, were extracted, e.g., how the elephant's skin works with evaporative cooling and the termite mound's natural ventilation. Finally, analogies were sought in nature that minimizes solar irradiation, with a particular focus on shading; hence, the role of trees and the orientation of the flower *Strelitzia*, were considered.

In filtering, attention was paid to examples from nature with surfaces where particles adhere, as does the *Saintpaulia*. This was taken as a priority rather than other features mentioned in the model, such as the aspect "shape".

Purification was more linked to the sequestration of CO2, VOCs, and other harmful substances, where the biological analogy of microalgae was selected to add to the design's features. In addition, the use of trees as natural air purifiers was considered because of the amount of pollutants they absorb, while also providing shade for the heat regulation function.

Finally, strategies focused on route optimization were chosen in the transportation challenges, such as ant colonies and the *Physarum polycephalum* mold. Table 3 shows the strategies carried out by each selected pinnacle for this model.

**Figure 3.** Exploration model for energy, atmosphere, and mobility approaches. Own elaboration.

To reduce the search and complexity of the different pinnacles, an imaginary pinnacle is evaluated for each category analyzed. The "X" symbols will denote the corresponding characteristic for each pinnacle according to the category analyzed. Then, the imaginary pinnacle will acquire the most dominant characteristic in every category, which is repeated in two or more pinnacles. If there are no coincidences, all features will be inherited by the imaginary pinnacle.

The analysis matrix of the pinnacles selected for the energy approach is presented in Figure 4. The relevant characteristics for power generation and heat regulation are highlighted in the yellow and red box, respectively, representing the imaginary pinnacle for each challenge to be analyzed.

**Table 3.** Strategies carried out by the selected pinnacles. Own elaboration.



**Figure 4.** Pinnacle analysis matrix for the energy approach. Own elaboration.

The analysis matrix for the atmosphere approach and the selected pinnacles are presented in Figure 5. Features relevant to filtration and purification are highlighted in the purple and blue box, respectively, representing the imaginary pinnacle of each challenge.


**Figure 5.** Pinnacle analysis matrix for the atmosphere approach. Own elaboration.

Finally, Figure 6 shows the analysis matrix with the pinnacles selected for the mobility approach. The relevant function for this challenge was transport, in grey. In this analysis, the chosen pinnacles had behavioral adaptations, and both required constant feedback, allowing them to find optimal routes in their search for food.

#### *2.4. Characteristics of the Pinnacles*

According to the three design-pathway matrices, they indicated several dominant properties within the different categories relevant to the design concept, these are:

Passive flow predominated in heat regulation and filtration; however, active flow persisted in purification, generation, and transport.

The influence of morphological adaptation was observed in all heat regulation and particle capture processes, while physiological adaptation was more prevalent in energy generation and purification. Finally, for both mobility functions, behavior predominated.


**Figure 6.** Pinnacle analysis matrix for the mobility approach. Own elaboration.

The mesoscale is considered relevant in all the functions presented. However, the environmental context was precise: tropical for each function, and arid, or moderate only in certain processes. Therefore, pinnacles that share the same climate as Panama were considered more relevant.

The morphological characteristics most present in the pinnacles were pigments for energy generation, filtration, and purification, texture, heat regulation, and ramifications in transport. Other characteristics to be considered in the bio-inspired solutions are:


#### *2.5. Solutions Based on Nature*

In accordance with the most dominant characteristics of the biomimetic abstraction, it is proposed that certain strategies influenced by nature ge<sup>t</sup> adopted in Panama City, taking into consideration ideas from the biomimetic model, such as:


The dominant characteristics presented from the selected pinnacles will be part of a proposal for regenerative solutions in Panama City. Table 4 presents a description of these proposals and their successful applications.

*Biomimetics* **2021**, *6*, 64


position and the opportunities brought by the Panama Canal.

HEAVENN.



Panama City.

algorithm (minimum paths algorithm).

## **3. Results Analysis**

Regenerative urbanization seeks to develop a built environment that coexists with ecosystems and enhances their health instead of diminishing it. However, ecosystems' services to society are currently not adequately protected because of cities' poor regulation, solutions, and policies. Therefore, urbanization must contribute more than it consumes to ecosystems, while also remedying past and current actions in terms of environmental damage. This would allow moving towards truly regenerative efforts.

Since it is greatly difficult to replace all buildings and infrastructure for regenerative development, even with retrofitting techniques, an alternative would be to provide ecosystem servicesinhumanity'sownway,toreduce theexistingpressureonlocalecosystems[49].

In the previous section, different sustainable alternatives based on nature were discussed to contribute to Panama City's capacity to be regenerative. As a result, it is possible to respond to the problems arising from poor sustainable managemen<sup>t</sup> and, in general, to the impacts of climate change, through biomimetic solutions and the so-called ecosystem services analysis (ESA). Figure 7 presents the trajectory of a roadmap proposal for regeneration in cities.

**Figure 7.** Roadmap for the development of a methodology towards regenerative cities. Own elaboration.

Ecosystem services analysis can work as a starting point for the creation of a regenerative design that is measurable. This is vital to establish the credibility of regeneration in urban design [49]. As a strategy to measure the sustainability of urban regeneration and ensure the principles of sustainable development, a set of indicators will be employed, which focus on the ecosystem services described above. These indicators are described and evaluated in Table 5.

These indicators could be considered for the objectives and targets established in the last Nationally Determined Contribution (CDN1) of Panama, for a circular economy, energy, resilient human settlements, sustainable infrastructure, forests, and biodiversity.


**Table 5.** Summary of methodological sheets of indicators based on Ecosystem Services Analysis. Own elaboration.
