Urban Political Ecology in Action: Community-Based Planning for Sustainability and Heritage in a High-Density Urban Landscape

Abstract

This paper shows a case study on a novel community-based sustainability planning framework that balances environmental, social, cultural dimensions for a high-density urban setting. The case study presents a community-driven “Four-Zero” sustainability model—zero energy, zero water, zero food, and zero waste—as a foundation for environmental sustainability practices implemented in a high-density estate in Hong Kong, alongside community-led ecological and heritage initiatives that reinforce place-based resilience. Through integrated activities, such as community farming, aquaponics, organic waste composting, biodiversity monitoring, and heritage mapping, the residents co-produced knowledge and activated novel bottom–up planning schemes and fostered social cohesion while advancing environmental objectives. Notably, the discovery of rare species and historic Dairy Farm remnants catalyzed a community-led planning proposal for an eco-heritage park that stimulated policy dialogues on conservation. These collective efforts illustrate how circular resource systems and cultural and ecological conservation can be balanced with urban development needs in compact, high-density communities. This case offers policy insights for rethinking urban sustainability planning in dense city contexts, contributing to global discourses on urban political ecology by examining socio–nature entanglements in contested urban spaces, to environmental justice by foregrounding community agency in shaping ecological futures, and to commoning practices through shared stewardship of urban resources.

1. Introduction

Urban areas have emerged as dominant centers of population, economic activity, and resource consumption, yet they remain fundamentally dependent on external ecosystems for essential resources such as energy, water, and food, while generating waste volumes that exceed local processing capacities. This structural imbalance not only exacerbates ecological degradation but also exposes cities to systemic vulnerabilities and national security risks associated with resource supply disruptions.

Contemporary sustainability frameworks, particularly those embedded within green building certifications, have prioritized technological solutions aimed at achieving zero-energy and zero-water performance at the building scale. However, these approaches frequently overlook other critical dimensions of urban sustainability, including local food production, circular waste management, biodiversity conservation, and cultural heritage preservation. As a result, even cities that achieve technological targets in energy and water efficiency may remain ecologically unsustainable if they depend heavily on imported food, external waste treatment, and fail to protect their natural and cultural assets.

There is a growing need for urban planning paradigms that transcend individual buildings and address sustainability at the community and district scales. Such approaches must leverage economies of scale and spatial planning to enable integrated systems for food production, waste recycling, and ecological and cultural conservation. Urban planning, when strategically aligned with community-based initiatives, can serve as a transformative intervention to reconnect urban populations with nature, foster local resilience, and promote inclusive development. Emerging evidence suggests that embedding human–nature interactions within urban design not only enhances environmental outcomes but also strengthens social cohesion and community well-being.

This study investigates the critical role of urban planning and spatial management in facilitating community-led sustainability initiatives. Focusing on a large private housing estate in Hong Kong accommodating approximately 10,000 residents, this research examines the potential for integrating urban agriculture, circular waste systems, and eco-heritage conservation into a cohesive sustainability framework. Specifically, the case study demonstrates how spatial planning can support our proposed Four-Zero model—zero energy, zero food, zero water, and zero waste—while simultaneously safeguarding rare species and heritage landscapes.

By analyzing the case, this paper contributes to the discourses on urban political ecology, environmental justice, and commoning practices. The proposed urban sustainability planning framework that balances environmental, social, and cultural dimensions is shown in Figure 1. It offers practical insights into how urban space can be repurposed to enable circular economies, strengthen ecological resilience, and preserve heritage values, ultimately advancing more sustainable and self-sufficient urban communities.

2. Literature Review

Community-based sustainability initiatives (CBSIs) are increasingly recognized as critical mechanisms for addressing local environmental and social challenges. As defined by Carmen, Fazey, and Friend [1], CBSIs are “place-based, voluntary, collective endeavors led by actors (initiative actors) from within communities who, as a group, seek to tackle local challenges to benefit the wider community” [2,3,4]. These initiatives often pursue holistic sustainability strategies that span food, waste, water, energy, and biodiversity systems, promoting not only environmental goals but also social and economic well-being.

2.1. Community-Based Sustainability Initiatives

International case studies—from Detroit’s urban agriculture cooperatives to Freiburg’s community-owned renewable energy schemes and Kamikatsu’s zero-waste village—illustrate the transformative power of local engagement in advancing sustainability goals [5,6].

However, they tend to occur in low-density, low-rise urban or peri-urban settings, where land availability and social cohesion create favorable conditions for commoning practices and shared governance [7]. For instance, transition towns in the United Kingdom thrive in suburban contexts, leveraging available space for food production and community facilities. Similarly, eco-villages in Denmark and the Netherlands successfully integrate circular resource use due to their low-density designs.

In contrast, CBSIs in high-density, high-rise urban environments remain rare and underexplored. High-rise housing estates pose significant challenges for collective sustainability action due to spatial constraints, fragmented social relations, vertical stratification, and complex property management regimes. These challenges demand new conceptual frameworks that account for the embedded power relations and spatial politics of the built environment. Urban political ecology [8] offers a critical lens to understand how urban space, infrastructure, and ecological services are unevenly produced and accessed. It helps articulate how structural constraints shape the viability of CBIs in densely populated contexts like Hong Kong.

The case study of the Chi Fu Valley—adjacent to a seven-hectare estate housing 10,000 residents in Hong Kong—contributes to this emerging body of work. It represents one of the first large-scale attempts to describe how CBSIs can be adapted to dense urban forms with initiatives of localized urban agriculture, circular waste systems, and place-based heritage conservation. These initiatives reflect not only sustainability innovation but also environmental justice concerns, as residents advocated for equitable access to green infrastructure, ecological resources, and heritage landscapes. These “commoning” actions illustrate how community members collectively attempted to manage shared resources and co-produce urban space outside formal planning systems [9].

2.2. Urban Biodiversity and Eco-Heritage Conservation

Urban biodiversity conservation and eco-heritage preservation are increasingly interlinked in global sustainability efforts. Cities like Singapore have integrated extensive greening strategies to enhance urban biodiversity, while places such as Seoul’s Namsan Park combine ecological restoration with the protection of cultural heritage [10]. In Europe, the Eco-museum model in Italy and Sweden showcase how post-industrial landscapes can be repurposed to sustain both biodiversity and cultural identity [11].

Yet, most examples are facilitated by generous land allocations or supportive institutional frameworks, which are rare in hyper-dense urban contexts. Hong Kong, for example, presents an extreme case of spatial scarcity, speculative land markets, and development-driven planning logic. Despite these constraints, the Chi Fu Valley case study demonstrates how the identification of rare species and historical features can serve as anchors for community advocacy and participatory planning.

Through community-led ecological surveys and heritage mapping, residents transformed the valley into a contested site of ecological and cultural commons, informed by principles of environmental justice. These actions reflect a counter-narrative to top–down urban planning, asserting the right of residents to co-determine land use priorities and resist environmental degradation [12].

3. Materials and Methods

3.1. Research Design

This study adopts a mixed-methods case-study approach to examine the processes, outcomes, and policy implications of community-driven sustainability and heritage conservation initiatives in a high-rise, high-density residential estate in Hong Kong. Both qualitative and quantitative research methods were employed to systematically assess the environmental, social, economic, and heritage dimensions of the Four-Zero Scheme—targeting zero energy, zero water, zero food, and zero waste—and the eco-heritage park proposal initiated by the local community.

The author is a resident and a member of the Residents’ Association of the housing estate and was directly involved in developing and implementing these initiatives. Responsibilities included co-authoring project proposals with the estate management office, leading community engagement programs, organizing site tours for residents and external visitors, and coordinating the compilation and submission of the eco-heritage park proposal to the Town Planning Board, etc. This dual role provided privileged access to both formal and informal information sources and enabled an in-depth understanding of the community’s sustainability practices and advocacy efforts.

Data were triangulated from multiple sources, including public reports, academic studies, citizen science databases, and government documents such as Town Planning Board meeting minutes and Heritage or Environmental Impact Assessments.

3.2. Study Area

The case study focuses on a large, private high-density residential estate (Chi Fu Fa Yuen) located in the Southern District of Hong Kong. Covering approximately 7 hectares, the estate comprises 20 high-rise towers of 28 stories and 7 low-rise villa blocks of 5 stories, totaling 4328 residential units (Figure 2). Units range in a saleable area from 431 to 957 square feet. The estate also features communal facilities, including a swimming pool, children’s playgrounds, and a shopping center.

As of the 2021 census, the estate’s population was around 10,000 residents, i.e., a population density of about 1400 people per hectare (or 142,900 people per square kilometer), which is regarded as a high-density district by international standards (For example, the estate’s population density was almost 4 times more than that in Manhattan, US, as Manhattan’s population density was about 28,872 people per square kilometer in 2020.). The estate predominantly consists of middle-income households, with a median monthly household income of HKD 35,140 (USD 5020)—approximately 30% higher than the Hong Kong average. Notably, 59.5% of households owned their units outright, and 18.1% owned with mortgages, compared to 32.1% and 16.5%, respectively, for the wider Hong Kong population [13]. This socio-economic profile provided a stable community base conducive to long-term sustainability initiatives.

Historically, the estate occupies part of the former Dairy Farm established in 1886. Following phased residential development since 1972, a portion of the original site was surrendered to the government through land exchange agreements. This undeveloped area, known locally as Chi Fu Valley (Figure 3), has since reverted to a mixed secondary forest interspersed with natural streams, remnants of dairy farm structures, and historically significant masonry walls. After almost four decades, in 2015, the government’s plans to develop this site triggered community mobilization advocating for conservation and eco-heritage recognition.

3.3. Data Collection

A comprehensive data collection strategy was employed to capture the multidimensional nature of the initiatives.

1.

Field Observations and Documentation

The author and members of the Residents’ Association conducted longitudinal field observations to document the ecological state of the site, the implementation of the Four-Zero initiatives, and community engagement activities. Observations focused on species diversity, habitat quality, infrastructure modifications, and the outcomes of educational events. Photographic records, field notes, and ecological monitoring reports were compiled.

2.

Documentary Analysis

Extensive document analysis was conducted, covering the following:

• Environmental impact assessments [14];
• Ecological surveys commissioned by the Housing Department [15];
• Heritage appraisals from the Antiquities Advisory Board (AAB) [16,17,18];
• Community publications and Hong Kong Awards for Environmental Excellence (HKAEE) submissions [19];
• Academic literature on urban biodiversity and sustainability [20,21,22];
• News reports and media coverage [23,24,25,26,27];
• Minutes and reports from Town Planning Board meetings (TPB) [28,29];

3.

Citizen science and ecological data

Biodiversity data were gathered from citizen science platforms, particularly iNaturalist [30], complemented by the author’s and the residents’ observations [31]. Species of conservation interest, including rare and protected flora and fauna, were identified and cross-referenced with expert assessments to validate ecological significance.

4.

Performance Metrics and Quantitative Data

Quantitative data were collected from the Residents’ Association, the estate management office, and a larger-scale community farm at Fanling, Hong Kong. Metrics included the following:

• Waste reduction volumes;
• Organic food production outputs from aquaponics systems;
• Energy savings from solar energy installations;
• Water conservation data from rainwater harvesting and recycling programs.

3.4. Ecological and Heritage Assessments

The research involved conducting ecological field surveys, compiling expert studies and gathering residents’ information to document species of conservation importance. Simultaneously, heritage research focused on mapping and assessing historical Dairy Farm structures, including cow pens, paddocks, and stone walls, some of which received official heritage grading [17].

With the impacts of the community findings on the rare species, the site was then surveyed in detail by government-funded consultancy firms [14,15] to perform professional ecological and heritage assessments. The results of their field surveys reinforce the findings of ecological and heritage values of the site.

3.5. Community Engagement and Public Advocacy

The researcher, in collaboration with the Residents’ Association and the property management office, designed and implemented comprehensive community engagement programs to promote environmental awareness and social cohesion. Activities included the following:

• Children’s barter markets promoting circular economy principles;
• Composting workshops demonstrating organic waste recycling;
• Aquaponics farm tours showcasing local food production systems;
• Eco-heritage guided tours highlighting biodiversity and cultural history.

These initiatives engaged residents across age groups, strengthened environmental literacy, and fostered a collective sense of place and stewardship [26]. Subsequently, the eco-heritage park proposal was prepared and submitted to the Town Planning Board, with the lead researcher coordinating scientific and advocacy efforts and the support of elected Legislative Council members. The proposal emphasized the ecological, heritage, and educational value of preserving the site as a community resource [27].

3.6. Analytical Framework

An interdisciplinary analytical framework was applied to synthesize data and assess the project’s outcomes as follows:

• Biodiversity assessment methodologies were used to guide the identification of species and the prioritization of conservation efforts.
• Tree assessment standards from the Environment, Transport and Works Bureau of the HKSAR Government (ETWB) [32] were adopted for classifying old and valuable trees and stone wall trees.
• Heritage grading criteria from the Antiquities Advisory Board (AAB) informed the evaluation of historical structures [16,17].
• Circular economy principles shaped the analysis of material and energy flows within the Four-Zero Scheme.
• Cost-benefit analysis was conducted to examine the economic viability of the initiatives in relation to their environmental and social benefits.

The analysis integrated community-driven insights with expert assessments, highlighting the potential for high-density, high-rise residential estates to achieve sustainability and heritage conservation through localized action. A sustainable four-zero high-density urban community conceptual model was developed, and an eco-heritage park was proposed, offering replicable pathways for similar global contexts. This case study summarizes the achievements since 2015.

4. Results of the Four-Zero Scheme

4.1. Four-Zero Pilot Scheme Implementation

The concept of zero-energy buildings gained prominence and technical maturity in the construction and engineering sectors starting in the 2000s. Importantly, “zero-energy” does not imply absolute zero energy consumption; rather, it refers to buildings capable of generating as much or more energy than they consume (or less waste than they can reuse) over a defined period. Extending this principle of resource self-sufficiency beyond energy to other critical resources—namely food, water, and waste—provides a conceptual foundation for the circular economy framework [33].

The Four-Zero Scheme builds on the zero-energy concept, expanding it to include zero food, zero water, and zero waste, thereby applying circular economy principles to the scale of a large, high-rise, high-density residential community [34]. This integrated approach represents an innovative attempt to operationalize the circular economy within a complex urban residential context. The scheme received the Gold Award in Property Management (Residential) under the Hong Kong Awards for Environmental Excellence (HKAEE) in 2015 [19], recognizing community-driven sustainability initiatives. A survey on residents’ satisfaction with the green measures, including the subject estate, found that most residents (61.7%) were positive about the measures [20].

4.1.1. Zero-Energy Initiatives

The energy-saving strategy focused on retrofitting shared facilities to improve energy efficiency. Key interventions included (a) replacing traditional lighting in all common areas with LED fixtures fitted with automatic light sensors, and (b) upgrading elevator systems with energy-efficient motors. Leveraging economies of scale, these measures achieved a 40% reduction in electricity consumption for communal areas [35]—a significant outcome facilitated by the Energy Conservation Subsidy Scheme from Hong Kong’s Electrical and Mechanical Services Department (EMSD) in 2015 [36].

The subsidy not only offset initial investment costs but also mandated an independent energy audit, ensuring transparent evaluation and professional supervision of the installed measures. This structured implementation and reporting process enhanced community trust and secured residents’ support for the investment.

4.1.2. Zero-Food Initiatives

Urban farming was introduced as a pilot project within the estate’s landscaped areas. Three experimental initiatives were implemented, namely: (a) checkered fields, where individual tiny plots were made available for residents to rent and grow their own vegetables (Figure 4a), (b) an okra garden, which is a communal vegetable garden co-managed by residents and the property management office (Figure 4b), and (c) aquaponics system installed within an existing decorative fishpond, combining fish farming with vegetable cultivation, managed by the property management team (Figure 4c) [25].

Although the scale of these farming initiatives remained limited due to land constraints, they demonstrated proof-of-concept for local food production in dense urban settings. Lessons learned from these experiments informed the development of a novel urban planning model proposed later in this paper, designed to scale urban agriculture for achieving zero-food and zero-waste targets in high-density communities.

The residents were found to be “positive with the increased area for water planting (aquaponics), which the plants are used as gifts for appreciating the participation of residents” [20]. The installation cost of the aquaponics system is also negligible in this case, as the fishpond was designed and built when the estate was developed in the 1980s.

4.1.3. Zero-Water Initiatives

Two main strategies were adopted to reduce reliance on potable water, they are: (a) rainwater harvesting: two disused fiberglass tanks, previously abandoned after rooftop repairs, were repurposed to collect rainwater. The harvested water was utilized for irrigation of landscaped areas, thereby reducing potable water consumption and lowering water bills, and (b) aquaponics integration: the aquaponics system not only contributed to food production but also reduced the frequency of fishpond maintenance by controlling microorganism growth, resulting in water savings. These low-cost, practical interventions demonstrated the potential for circular water use in residential settings.

4.1.4. Zero-Waste Initiatives

The estate significantly expanded its recycling program, increasing the number of recyclable material categories to 29, one of the most comprehensive in Hong Kong. In addition to standard recyclables (paper, plastics, metals), the program included the collection of toner cartridges, used batteries, electronic transformers, old clothes, food waste, etc. Collected items were sorted for recycling or composting. The 3 hectares of landscaped areas also serve as a source of natural organic materials, including leaf litter and pruned branches, which are systematically collected for circular processing via composting or upcycling.

To further promote waste reduction and resource circulation, a sharing and exchange scheme was launched, enabling residents to (a) borrow tools and equipment from the property management office, (b) exchange household goods such as furniture, appliances, baby items, and toys through a managed platform with storage and facilitation provided by the management office. Popular items for exchange included electrical appliances, baby products, and toys. Additionally, upcycling workshops were organized to promote creative reuse, including (a) furniture making using reclaimed wood, and (b) DIY production of eco-friendly cleansing agents.

While food waste collection achieved moderate success, scaling up composting efforts faced limitations due to the insufficient size of the urban farm. The experience highlighted the need for adequate land allocation to circularize the organic waste loop fully. A proposed urban planning model, presented below, addresses the spatial requirements for high-density communities to achieve functional zero-waste and zero-food targets.

4.2. A Novel Urban Planning Model for a Zero Food and Zero Waste Scheme

This section proposes a novel urban planning model for a zero-food and zero-waste community designed around a medium-density urban block typical of Hong Kong’s urban landscape. The model envisions a self-contained community of 10,000 residents within a 40-hectare area (400,000 m²), achieving a population density of 25,000 persons per square kilometer—comparable to Hong Kong’s current urban average. The scale is intentionally designed to optimize sustainability performance: large enough to realize economies of scale in resource cycling yet compact enough to minimize internal transportation costs of food and waste in a high-density community.

The land-use framework allocates 8 hectares for residential development, housing 4000 high-rise units (by assuming a floor area ratio, FAR = 5.0, and average gross floor area of each housing unit, GFA = 100 square meter), as shown in Column 1 of

Table 1. Parameters for the zero-food and zero-waste urban planning model.

Population and Housing Footprint		Land Use Distribution		Food Production		Kitchen Waste Consumption
Total housing area	8 ha	Residential	8 (20%)	Ave. production of vegetables per ha per year	50 tons	Ave. amount of kitchen waste generated per person per year	182.5 kg
FAR (plot ratio)	5	Agriculture	8 (20%)	Ave. consumption of vegetables per person per year	100 kg	Ave. amount of kitchen waste compostable per ha per year	240 tons
Total GFA of housing	40 ha	Commercial	6 (15%)	Total consumption of vegetables per year (100 × 10,000)	1000 tons	Total amount of kitchen waste generated per year (182.5 × 10,000)	1825 tons
Total housing units	4000	Others (incl. GIC, open space, roads)	18 (45%)	Total production of vegetables per year (50 × 8)	400 tons	Farmland area required to compost all kitchen waste (1825/240)	7.6 ha
Total population	10,000	Total land area	40 ha (100%)	Self-sufficiency rate	40%

Notes: FAR: floor area ratio (assumed FAR = 5). GFA: gross floor area (assumed average GFA of each housing unit = 100 sq. m.), GIC: government, institution, community uses. Sources: information based on [37] which estimated: average production rate of vegetable per ha per year from AFCD [38]; average consumption rate of vegetables per person per year from AFCD [38]; average amount of kitchen waste per person per year in Hong Kong from ENB [39]; average amount of kitchen waste compostable per ha per year from the authors’ on-site record of a farm in Fanling, Hong Kong.

. It can accommodate 10,000 residents if the average household size is about 2.5 people. In addition to the 8 hectares allocated for residential use, 6 hectares can be designated for commercial purposes and 18 hectares for Government, Institution and Community (GIC) uses, with 8 hectares reserved for community farming, as shown in Column 2. As shown in Column 3, the average vegetable yield is estimated at 50 tons per hectare per year. With 8 hectares of farmland, the community can produce approximately 400 tons of vegetables annually. Assuming an average annual consumption of 100 kg of vegetables per person per year, this output achieves 40% self-sufficiency for a population of 10,000 in vegetable consumption. While not fully self-sufficient, this level of local production substantially reduces food-related carbon emissions by cutting vegetable transportation needs by an equivalent percentage. More critically, the community farm serves as a circular waste processor, capable of absorbing 100% of the community’s organic kitchen waste—estimated at approximately 1825 tons annually, based on an average generation of 182.5 kg per person per year of kitchen waste (as shown in Column 4). The 8 hectares of farmland can absorb all the kitchen waste generated by the housing estate, based on an average composting capacity of approximately 240 tons per hectare per year. This effectively eliminates landfill-bound organic waste and associated greenhouse gas emissions. This integrated design thus transforms the farm into a dual-purpose hub for both food production and waste processing, embodying the circular economy principles.

Additionally, community farming offers socio-economic co-benefits by generating approximately 400 local employment opportunities (4% of residents) under organic farming operations, particularly benefiting low-skilled, unemployed, or retired residents. By embedding food production, waste recycling, and employment generation within the urban fabric, this model advances the concept of “productive landscapes” and aligns with global sustainable urban development principles that emphasize mixed-use, livable, and resilient high-density cities (Table 1).

5. Discussion

5.1. Community Engagement and Social Impact

The success of the Four-Zero Scheme hinged on active and sustained community participation. A diverse range of community engagement activities were designed to foster environmental awareness, social cohesion, and a strong sense of collective ownership over the sustainability initiatives. These activities targeted residents of all ages, with a particular emphasis on engaging children and families to instill environmental values from an early age.

One of the activities was the children’s barter market, an event that provided a platform for young residents to exchange toys, books, and other items in a cash-free environment. This initiative not only promoted the principles of reuse and waste reduction but also cultivated a spirit of sharing and community responsibility among the younger generation. Parents and children worked together to prepare items for exchange, creating valuable opportunities for intergenerational learning on sustainability practices. Kid farmer’s classes were also organized to let children practice growing vegetables or trees.

In addition, tours of the aquaponics farm and other facilities were organized to educate residents and visitors on these innovative circular economy methods. These tours provided a tangible demonstration of circular economy principles applied within a high-density residential setting, enhancing environmental literacy and inspiring broader support for sustainable food production.

An annual autumn carnival became a highlight of the community calendar. This event featured children’s presentations, sustainability-themed activity booths, and demonstrations of upcycling and green technologies. The carnival not only celebrated the community’s achievements but also served as a vibrant platform for further engagement, attracting both residents and external visitors. It reinforced a positive identity for the community as a leader in urban sustainability and environmental stewardship.

Through these sustained efforts, the project significantly strengthened social cohesion within the estate. Residents reported increased interaction, a stronger sense of belonging, and greater pride in their living environment. The transformation of previously underutilized spaces—such as locked sports facilities, landscaped areas and open courtyards—into active community hubs was a visible testament to the project’s success. These spaces now host urban farming plots, green walls [22], educational tours, and social events, promoting continuous interaction and collaboration among residents.

Importantly, the initiatives also fostered intergenerational learning and knowledge transfer. Children learned environmental values and sustainable practices directly through participation, while senior residents contributed their experience and traditional knowledge, particularly in areas such as urban farming and composting. This mutual learning strengthened the social fabric and empowered the community to take collective action toward a more sustainable future.

Overall, the community engagement strategy not only enhanced the environmental outcomes of the Four-Zero Scheme but also produced measurable social impacts by creating a more connected, resilient, and environmentally conscious residential community.

5.2. Ecological and Heritage Exploration by the Community

In response to the government’s announcement of a large-scale public housing development plan in Chi Fu Valley [40], the residents of the estate initiated a systematic exploration of the site’s ecological and heritage significance. Motivated by longstanding local anecdotes regarding the remnants of historic Dairy Farm structures and sightings of rare species, the community mobilized experts among their ranks to conduct comprehensive surveys.

Multiple resident-led groups, each with specialized knowledge, contributed to this grassroots assessment. A team of tree experts documented the presence of numerous mature and old-growth trees, identifying over 30 large Ficus species forming unique “Stone Wall Trees”—natural sculptures where roots entwined historic masonry walls, showcasing a rare ecological and cultural phenomenon (Figure 5).

Simultaneously, heritage enthusiasts within the community mapped the remaining agricultural structures of the former Dairy Farm, recording features such as silos, paddocks, and stonewalls that evidenced the site’s colonial-era dairy operations dating back to 1886.

A group of resident ornithologists conducted systematic bird surveys, identifying 72 avian species inhabiting or migrating through the valley. Their findings included 36 resident species, 24 winter migrants, 5 summer migrants, 5 spring migrants, and 2 autumn migratory species—underscoring the site’s importance as a seasonal habitat and migratory corridor.

Further ecological surveys by community members specializing in aquatic and herpetological species revealed a rich diversity of fauna along the valley’s natural streams. Species recorded included various fish, lizards, freshwater shrimps, crabs, and 11 dragonfly species. Notably, the team made significant discoveries of two globally recognized amphibians: the short-legged toad (Megophrys brachykolos), classified as an Endangered species on the IUCN Red List, and the lesser spiny frog (Quasipaa exilispinosa), listed as a Vulnerable species.

These critical findings were widely publicized through local media coverage, sparking public concern and advocacy for the preservation of Chi Fu Valley [23]. In response to growing community pressure, the government commissioned professional ecological and heritage consultants to undertake a comprehensive site survey. The subsequent consultancy report [14] confirmed the valley’s significant conservation value, identifying 25 faunal species and 9 floral species of conservation importance.

In parallel, the heritage assessment revealed that the valley contained extensive remnants of the historical Dairy Farm operations, comprising 63 heritage structures. Among these, eleven structures within the study area were officially assessed as Grade 2 or Grade 3 historic buildings, including stone masonry walls, cow pens, and paddocks. Further research suggested that some of these structures predated earlier estimates by several decades, amplifying their historical significance [17]. The study also situated Chi Fu Valley within a broader heritage landscape, closely connected to other significant sites in the vicinity—Pokfulam Village (listed on the World Heritage Monitoring List), Bethany Seminary (a Declared Monument), and Pokfulam Reservoir (a Declared Monument). This contextual relationship reinforced the valley’s dual ecological and cultural heritage value.

Among the scientifically notable species identified, at least four faunal species and three floral species were recognized for their conservation and heritage importance [14]. Of particular significance was the discovery of the Hong Kong slender gecko (Hemiphyllodactylus hongkongensis), a species newly described in scientific literature and classified as Near Threatened on the IUCN Red List [21]. Its presence underscored the Valley’s ecological importance and catalyzed a reassessment of the proposed development. As a direct result of these community-led findings and professional verifications, the government revised its development plans, incorporating buffer zones (designated as Reduced Development Areas in Figure 3) to protect critical habitats and high-value ecological sites within Chi Fu Valley.

This case exemplifies how community-driven ecological assessments can influence urban development policies, highlighting the essential role of citizen science in heritage preservation and biodiversity conservation within dense urban environments.

5.3. Planning Outcomes and Policy Implications

In 2015, the government proposed a large-scale public housing development within Chi Fu Valley. Recognizing the valley’s ecological and cultural significance, the community mobilized public campaigns and environmental petitions to garner wider support [41], and the residents formulated and submitted a formal planning proposal under Section 12 of the Town Planning Ordinance (Hong Kong) in 2017, advocating for the designation of the site as an Eco-Heritage Park [23,24]. Although the Town Planning Board ultimately rejected the proposal due to a lack of resources, the initiative underscored the viability of an eco-heritage park model. Such an approach—integrating biodiversity conservation, heritage preservation, environmental education, and public recreation—is the first community-led eco-heritage park proposal in Hong Kong which is consistent with international sustainable-urban-planning practices and offers a replicable framework for future projects.

The reduced development areas, as shown in Figure 3, successfully avoided areas of high ecological sensitivity, including the habitats of the Hong Kong slender gecko and endangered amphibian species, while maintaining the planned housing capacity [15]. This outcome demonstrates that urban development and ecological protection are not mutually exclusive and that well-informed planning processes can achieve a balanced integration of conservation priorities within dense urban environments.

6. Conclusions

The Four-Zero Scheme presented in this case study illustrates a pioneering and integrative model for advancing urban sustainability at the community scale. By integrating energy efficiency, local food production, water reuse, and waste reduction into a high-density residential estate, the initiative addresses critical limitations in conventional sustainability frameworks by emphasizing localized resource loops and active community engagement. This holistic framework addresses critical gaps in dominant sustainability paradigms, which often neglect the importance of self-sufficiency, participatory governance, and socio-ecological integration.

Several key insights emerge from this case study as the following:

• Local food production and circular resource flows are essential components in reducing urban ecological footprints and enhancing community resilience in high-density cities.
• Community-led initiatives play a pivotal role in driving sustainability transformations, fostering a strong sense of ownership and social cohesion.
• Integrating four-zero principles generates both economic and social benefits, offering pathways toward more inclusive, participatory and sustainable urban environments in high-density cities.
• Balanced planning approaches can offer win-win solutions that accommodate housing development needs while preserving biodiversity and heritage assets [42].

This case advances the conceptual model of “Sustainable Communities 2.0”, offering valuable lessons for urban planners, policymakers, and environmental advocates striving to build self-sufficient, resilient high-density compact cities.

The Chi Fu Valley ecological and heritage conservation efforts further demonstrate how community-based sustainability initiatives can effectively integrate biodiversity protection and cultural heritage preservation into urban development processes. Notably, the discovery of rare and endangered species, such as the Hong Kong slender gecko, strengthened the scientific and moral arguments for conservation, while the historical assets of the former Dairy Farm enriched the site’s cultural significance [43].

Although full preservation of the valley was not realized, the revised development plan successfully safeguarded critical ecological habitats and heritage features within a high-density urban context. This outcome illustrates the feasibility of balancing urban growth with environmental and cultural conservation—providing a replicable model for compact cities facing similar development pressures.

Future research should focus on long-term ecological monitoring, evaluation of community engagement outcomes, and further development of eco-heritage park frameworks to support policy integration. Such studies will be crucial for refining sustainable urban planning models that align with global biodiversity targets and heritage conservation goals while fostering resilient and vibrant communities.

However, it must be acknowledged that this study is limited in terms of objectivity and methodological robustness in the data collection process. Being both a resident of the estate and an active member of its Residents’ Association, my positionality inevitably influenced the research. This insider perspective offered unique advantages, including privileged access to community narratives, events, and informal knowledge networks, which enriched the depth and authenticity of the data. However, it also presented challenges, including the potential for selective emphasis on favorable outcomes or advocacy-driven interpretations. To mitigate potential bias, a triangulation approach was adopted, incorporating independent ecological and heritage assessment reports, media documentation, and findings from third-party consultants. This integration of both internal and external sources aimed to strengthen the study’s validity and relevance for both academic inquiry and policy discourse.

Furthermore, the generalizability of this case study is subject to important limitations as the housing estate is characterized by relatively high levels of homeownership, educational attainment, and household income—factors that may have contributed to stronger civic participation, resource mobilization, and capacity for sustained engagement. As such, the success of the Four-Zero Scheme may be partially attributable to the specific social capital and stability of this context. Future research should therefore examine how these models can be adapted or scaled to diverse socio-economic settings, particularly in under-resourced or marginalized communities, to evaluate their broader applicability under different structural constraints.