The global movement to protect and restore biodiversity in urban areas has reached an unprecedented milestone. Two major international platforms CitiesWithNature and the City Nature Challenge have each surpassed 400 participating cities, signaling a fundamental shift in how municipalities worldwide approach environmental stewardship. This remarkable growth demonstrates that cities are no longer content to remain passive observers in the fight against biodiversity loss. Instead, they are emerging as laboratories of innovation, testing ground-breaking approaches to integrating nature into the very fabric of urban life.
The significance of this development cannot be overstated. With more than half of the world’s population now living in cities, urban areas have become critical battlegrounds in the struggle to preserve the planet’s biological diversity. The decisions made by city governments about land use, infrastructure development, and green space management have profound implications for ecosystems far beyond their administrative boundaries. The fact that hundreds of cities have voluntarily committed to tracking, reporting, and improving their biodiversity performance represents a seismic shift in urban governance.
Understanding the Urban Biodiversity Crisis
Before examining the platforms themselves, it is essential to understand why urban biodiversity matters and what is at stake. Urbanization has long been recognized as one of the most significant drivers of ecosystem transformation worldwide. The permanent replacement of natural habitats with concrete, asphalt, and buildings fundamentally alters the composition and abundance of species assemblages. Cities typically support fewer native species and higher numbers of invasive organisms, with the magnitude of these changes increasing with the scale of urbanization.
Yet the story is not entirely bleak. Research increasingly demonstrates that well-managed cities can host significant biodiversity, including endemic and threatened species. Urban areas, when thoughtfully designed and managed, can serve as refuges for pollinators, birds, and other wildlife. The ecosystem services provided by urban nature—including flood risk reduction through improved soil drainage, pest population control, pollination of local flora, and air and water purification deliver tangible benefits to millions of city dwellers.
The challenge, therefore, is not to prevent urbanization but to fundamentally reimagine how cities are designed and governed. This is where the two platforms that have reached the 400-city milestone enter the picture.
CitiesWithNature: Policy, Commitment, and Reporting
CitiesWithNature represents a comprehensive approach to urban biodiversity governance. Launched in 2018 through a partnership between ICLEI-Local Governments for Sustainability, The Nature Conservancy, and the International Union for Conservation of Nature, this platform has become the world’s premier mechanism for cities to demonstrate their commitment to nature-positive development.
The platform’s growth has been remarkable. As of the latest available data, nearly 400 cities and regions from 80 countries have joined CitiesWithNature, collectively committing to report and track local government actions and progress in biodiversity conservation and ecological restoration. This figure represents more than mere membership it signifies a genuine commitment to accountability and transparency in environmental governance.
How CitiesWithNature Operates
The platform’s architecture reflects a sophisticated understanding of how local governments can contribute to global biodiversity goals. Its structure follows a logical progression that mirrors the policy development cycle:
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Action Areas: Cities begin by identifying the broad categories of intervention most relevant to their local context. These fall into three primary domains: protecting and restoring nature, using nature sustainably, and developing tools and solutions.
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Commitments: Within each action area, cities make specific commitments that align with their local priorities and capacities. For instance, a commitment under the “Protect and Restore Nature” action area might involve restoring degraded coastal ecosystems or managing invasive alien species.
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Actions: Once commitments are established, cities document the concrete steps they are taking to fulfill them. These actions are recorded in detail, creating a repository of best practices that other municipalities can learn from and adapt.
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Targets: The final element involves setting SMART targets specific, measurable, achievable, realistic, and timely with baseline measurements and reporting periods. This ensures that commitments translate into measurable outcomes rather than remaining aspirational statements.
This structured approach enables cities to track their progress systematically while contributing data that feeds directly into national reporting under the Convention on Biological Diversity. The platform was formally recognized under CBD Decision 15/12 as the official mechanism for local and subnational biodiversity reporting, giving it a unique status in international environmental governance.
The Kunming-Montreal Connection
The timing of CitiesWithNature’s growth aligns with a critical moment in global biodiversity policy. The Kunming-Montreal Global Biodiversity Framework, adopted in December 2022 by more than 190 national governments, established 23 targets to halt biodiversity loss by 2030. Crucially, the framework explicitly recognized the essential role that local and subnational governments must play in achieving these targets.
CitiesWithNature serves as the bridge between these global aspirations and local implementation. The platform helps cities understand how their actions contribute to their countries’ National Biodiversity Strategies and Action Plans, which are the principal instruments used by national governments for implementing the CBD. Local governments develop Local Biodiversity Strategy and Action Plans, which feed into the national plans, creating a coherent chain of accountability from the neighborhood to the international level.
This integration represents a paradigm shift in how biodiversity governance operates. Instead of treating cities as problems to be managed, the framework recognizes them as essential partners in conservation. The data generated through CitiesWithNature allows cities to showcase their contributions to the global review of collective progress, ensuring that urban nature is counted and valued in international assessments.
Recognition Through Awards and Designations
Beyond its functional reporting mechanisms, CitiesWithNature operates a recognition program that celebrates outstanding municipal achievements. The “Biodiversity Charming Cities” designation, awarded during the biennial UN Biodiversity Conference, honors cities that have demonstrated exceptional commitment and innovation in urban biodiversity conservation.
Chinese cities have featured prominently in these recognitions. Following CBD COP15, which was hosted in Kunming and Montreal, 26 Chinese cities joined the platform, with six Chengdu, Huzhou, Jiaxing, Kunming, Nanyang, and Shenzhen being honored as “Biodiversity Charming Cities” for their leadership in integrating nature into urban development. This recognition reflects China’s “Ecological Civilization” strategy, which positions harmony between humans and nature as a central development objective.
The award program serves multiple purposes. It provides tangible incentives for cities to improve their performance, creates opportunities for peer learning, and generates public awareness about urban biodiversity. Cities that receive the designation are invited to attend the Global Biodiversity Summit of Local and Subnational Governments, where they share their achievements and best practices with an international audience.
City Nature Challenge: Citizen Science in Action
While CitiesWithNature focuses on policy and governance, the City Nature Challenge takes a fundamentally different approach to urban biodiversity. This initiative harnesses the power of citizen science to document and celebrate the wild life that thrives in cities.
Launched in 2016 by the Natural History Museum of Los Angeles County and the California Academy of Sciences, the City Nature Challenge began as a friendly competition between two cities to see which could record more wildlife observations. The concept was simple yet powerful: encourage residents to use the iNaturalist app to photograph plants, animals, and fungi in their neighborhoods, then upload the observations to a global database.
Exponential Growth and Participation
The initiative’s growth trajectory has been extraordinary. From its modest beginnings, the challenge has evolved into an international movement involving more than 400 cities across 40 countries. Each year at the end of April, participants worldwide come together for four days of intensive bioblitz-style observation. By 2021, the event had already spread to over 400 cities, and participation has continued to grow.
The scale of data collection is staggering. Recent iterations of the challenge have recorded over 3 million wildlife observations from more than 100,000 participants during a single long weekend. These observations include tens of thousands of species, with several thousand classified as rare, endangered, or threatened. The 2026 edition, scheduled for April 24-27, will involve more than 400 cities, continuing the tradition of global collaboration in urban biodiversity documentation.
The Science of Citizen Observation
The City Nature Challenge operates on the principle that everyone can contribute to scientific knowledge. Using the free iNaturalist app, participants take photographs of wild organisms they encounter whether in a backyard, a city park, a community garden, or even a sidewalk crack. These observations are then uploaded to the platform, where a global community of experts and enthusiasts helps identify the species.
The data generated through this process has proven remarkably valuable for scientific research. A significant proportion of observations reach “Research Grade,” meaning they meet quality standards for inclusion in scientific datasets. In 2026, nearly half of all observations achieved this classification, demonstrating the reliability of citizen-generated data.
Research published in journals such as BioScience has documented how the City Nature Challenge contributes to biodiversity knowledge and informs local government practices. The data collected helps scientists understand species distributions, track invasive species, monitor threatened populations, and identify biodiversity hotspots within urban areas. This information can then be used to guide conservation planning, green space management, and urban development decisions.
Fostering Connection and Community
Beyond its scientific contributions, the City Nature Challenge serves a broader social purpose. By encouraging residents to observe and document nature in their immediate surroundings, the event fosters a deeper connection between people and the natural world. The act of looking closely at a city park or garden transforms it from a blur of green into a rich, diverse ecosystem full of detail and discovery.
This transformation in perception has profound implications for conservation. Research consistently shows that people who feel connected to nature are more likely to support environmental protection measures. The challenge thus serves as both a data collection exercise and a public engagement tool, building constituencies for urban biodiversity conservation.
The event also creates opportunities for community building. In many cities, local organizations coordinate group activities such as guided nature walks, bioblitzes, and identification workshops. These activities bring together people of diverse backgrounds around a shared interest in nature, strengthening social cohesion while advancing scientific knowledge.
Comparative Analysis: Two Approaches to Urban Biodiversity
The two platforms represent complementary approaches to the challenge of urban biodiversity conservation. Understanding their differences and synergies provides insight into how cities can most effectively address biodiversity loss.
CitiesWithNature operates primarily at the governance and policy level. Its focus is on institutional commitments, structured reporting, and alignment with international frameworks. The platform targets city officials, planners, and decision-makers who have the authority to implement systematic changes in urban planning and management.
City Nature Challenge operates at the community and individual level. Its focus is on citizen engagement, data collection, and awareness building. The platform targets residents, community groups, and local naturalist organizations who can contribute observations and advocate for nature-positive policies.
Together, these approaches create a comprehensive ecosystem for urban biodiversity action. CitiesWithNature provides the policy framework and accountability mechanisms that ensure municipal governments take concrete action. The City Nature Challenge generates the public interest, scientific data, and community engagement that sustains and informs these efforts.
The synergy between the two platforms is evident in how cities leverage both approaches. A municipality might join CitiesWithNature to formalize its commitment to biodiversity conservation, develop a Local Biodiversity Strategy and Action Plan, and report on its progress. Simultaneously, it might promote participation in the City Nature Challenge to engage residents, collect baseline data on local biodiversity, and build public support for conservation initiatives.
How Cities Are Taking Action
The 400-city milestone is significant not merely as a numerical achievement but because of the concrete actions that cities are taking. Across both platforms, municipalities are implementing innovative approaches to integrating nature into urban environments.
Protecting and Restoring Nature
Cities are employing a range of strategies to protect and restore natural systems within their boundaries. These include:
A) Decreasing conversion of natural areas: Municipalities are revising zoning regulations and development policies to protect remaining natural habitats from conversion to built uses. This includes establishing urban growth boundaries, protecting riparian corridors, and designating significant natural areas as permanent conservation lands.
B) Restoring degraded ecosystems: Many cities are actively restoring terrestrial, freshwater, and coastal ecosystems that have been degraded by past development. Examples include daylighting buried streams, restoring native vegetation to former industrial sites, and rehabilitating coastal wetlands.
C) Increasing protected areas: Cities are establishing new protected areas, including urban parks, nature reserves, and green corridors. These areas provide habitat for wildlife while offering recreational opportunities for residents.
Using Nature Sustainably
Sustainable use of nature involves managing urban ecosystems to provide benefits for both people and biodiversity over the long term. Key approaches include:
A) Implementing nature-based solutions: Cities are increasingly turning to nature-based approaches for challenges such as stormwater management, temperature regulation, and air quality improvement. Green infrastructure including rain gardens, green roofs, and constructed wetlands provides these services while creating habitat for wildlife.
B) Promoting sustainable food systems: Urban agriculture initiatives, including community gardens and rooftop farms, contribute to food security while supporting pollinators and other beneficial organisms. Some cities are integrating edible landscapes into public spaces, creating productive green infrastructure.
C) Managing invasive species: Invasive alien species represent one of the most significant threats to urban biodiversity. Cities are developing management programs that combine early detection, rapid response, and long-term monitoring to control invasive populations and protect native species.
Developing Tools and Solutions
Effective urban biodiversity conservation requires robust tools, data, and governance frameworks. Cities are responding with:
A) Biodiversity indices and monitoring systems: Tools such as the City Biodiversity Index and the IUCN Urban Nature Indexes help cities measure their biodiversity performance and track progress over time. These systems provide standardized metrics that enable comparison and learning across municipalities.
B) Policy integration: Cities are working to integrate biodiversity considerations into all aspects of municipal governance, from procurement policies to infrastructure planning. This “mainstreaming” approach ensures that biodiversity is not treated as a standalone issue but as a fundamental consideration in all decisions.
C) Partnership development: Successful biodiversity conservation requires collaboration across sectors and scales. Cities are building partnerships with businesses, academic institutions, community organizations, and other levels of government to leverage resources and expertise.
The Role of Technology and Innovation
Technology plays an increasingly important role in urban biodiversity conservation. The two platforms that have reached the 400-city milestone both leverage digital tools to achieve their objectives.
The iNaturalist platform, which powers the City Nature Challenge, represents a powerful example of how technology can democratize scientific data collection. The app’s artificial intelligence capabilities help users identify species, while its social features connect observers with a global community of experts. The resulting database, which now contains millions of observations, provides an invaluable resource for researchers, planners, and conservation practitioners.
CitiesWithNature similarly employs digital tools to facilitate reporting, knowledge sharing, and performance tracking. The platform’s online interface allows cities to document their commitments and actions, access resources and case studies, and connect with peer municipalities facing similar challenges. The integration of CitiesWithNature data into the CBD’s Clearing-House Mechanism ensures that local actions are visible at the global level.
Emerging technologies promise to further transform urban biodiversity monitoring and management. Remote sensing, environmental DNA sampling, and automated acoustic monitoring are beginning to provide new ways of understanding urban ecosystems. Cities that embrace these innovations will be better positioned to make informed decisions about biodiversity conservation.
Challenges and Limitations
Despite the impressive growth of these platforms, significant challenges remain. The 400-city milestone, while historic, represents only a fraction of the world’s municipalities. Many cities particularly in developing countries lack the resources, capacity, or political will to participate in international biodiversity initiatives.
Resource Constraints
Effective biodiversity conservation requires investment. Cities need funding for green space acquisition, habitat restoration, monitoring programs, and staff time dedicated to biodiversity management. For municipalities facing competing demands for limited resources, biodiversity can be perceived as a lower priority than immediate concerns such as housing, transportation, or economic development.
The platforms themselves are aware of these constraints. CitiesWithNature is designed to be flexible, allowing cities to make commitments appropriate to their capacity and context. The City Nature Challenge requires minimal financial investment, relying primarily on volunteer participation. However, the deeper structural issue of insufficient funding for urban biodiversity remains unresolved.
Data Gaps and Equity
The data generated through these platforms is not evenly distributed. Cities with more resources and stronger scientific communities tend to generate more observations and more comprehensive reports. This can create a skewed picture of global urban biodiversity, with under-sampled regions often those with the highest biodiversity value remaining poorly documented.
Addressing these gaps requires intentional efforts to support participation in underrepresented regions. This includes providing technical assistance, translation services, and capacity-building support to cities that wish to join but face barriers to entry.
From Commitment to Implementation
Perhaps the most significant challenge is ensuring that commitments translate into meaningful action. Joining a platform and making pledges is relatively easy; implementing the changes needed to protect and restore urban biodiversity is far more difficult. It requires sustained political will, institutional capacity, and public support over many years.
The reporting mechanisms built into CitiesWithNature help to maintain accountability by creating transparency about progress. However, the platform has no enforcement power; it relies on peer pressure, public scrutiny, and the intrinsic motivation of cities to fulfill their commitments.
Looking to the Future
The trajectory of urban biodiversity governance suggests that the 400-city milestone is not an endpoint but a stepping stone. Several trends point toward continued growth and evolution.
The upcoming CBD COP17, scheduled to be held in Armenia in 2026, will provide another opportunity for cities to demonstrate their commitment to biodiversity conservation. The Ninth Global Biodiversity Summit of Local and Subnational Governments, co-hosted by ICLEI and the CBD Secretariat during the conference, will showcase municipal achievements and announce new cities joining the movement.
Beyond the formal platforms, a broader cultural shift is underway. Cities are increasingly recognizing that nature is not a luxury but a necessity—that green spaces, clean water, and healthy ecosystems are fundamental to human well-being. This recognition is driving investment in green infrastructure, changing how cities are designed and built, and creating new expectations for municipal governance.
The 400-city milestone also reflects a growing recognition that global environmental challenges cannot be solved without local action. International agreements and national policies are essential, but they must be translated into concrete changes at the community level. The two platforms that have reached this milestone demonstrate that cities are ready to take on this responsibility.
Conclusion
The achievement of 400-city participation in both CitiesWithNature and the City Nature Challenge represents a watershed moment in the global effort to protect and restore urban biodiversity. These platforms have demonstrated that cities can be powerful agents of environmental change when equipped with the right tools, incentives, and frameworks.
CitiesWithNature has established a robust architecture for municipal commitments, reporting, and accountability, creating a pathway for local actions to contribute to global biodiversity goals. The City Nature Challenge has harnessed the power of citizen science to document urban wildlife, engage residents, and build public support for conservation.
Together, these initiatives are transforming how cities relate to the natural world. They are demonstrating that urbanization and biodiversity conservation need not be opposing forces that with thoughtful planning, sustained commitment, and active citizen engagement, cities can become havens for nature rather than threats to it.
The challenge now is to build on this momentum. The 400 cities that have joined these platforms are pioneers, showing what is possible. The task ahead is to expand participation, deepen implementation, and ensure that the commitments made through these platforms translate into tangible improvements in urban biodiversity. If the growth of the past years is any indication, the future of urban nature looks increasingly promising.
