Introduction Extreme heat is an invisible but increasingly tangible climate risk. It varies by time and place and has wide-reaching but unequal impacts, particularly to women and vulnerable people. As global temperatures rise, extreme heat events (heat waves) are becoming more frequent and severe. Cities, which are affected by urban heat island effects[1], face heightened temperatures. Projections show that several cities in Asia and the Pacific could see temperatures rise by up to 4°C if greenhouse gas emissions remain unchanged. Urbanization and growth in these regions compound the impact of rising temperatures. By 2050, Asia’s urban population is expected to grow by 50%, adding 1.2 billion people, while Pacific urban populations could reach 51% of the population. This growth will replace natural environments—essential for cooling—with heat-trapping surfaces. Heat impacts vary across cities, often adding to equity and environmental justice issues. Green spaces, usually linked to wealth, are unevenly distributed. Cooler, greener neighborhoods are often home to high-income residents, while informal, lower-income areas experience more extreme heat. In Bandung, Indonesia, a study revealed a temperature difference of up to 7°C between the hottest and coolest neighborhoods. Impoverished communities, including women in developing countries, are especially vulnerable. The Asia and the Pacific region must find ways to implement scalable cooling solutions that ensure equitable access to thermal comfort for its growing urban populations. How do nature-based solutions help cool urban areas? Nature-based solutions (NbS) for cooling include various methods to lower urban temperatures, such as street trees, urban parks, green roofs, and wetlands. These solutions provide cooling by offering shade, promoting evapotranspiration, and acting as heat sinks that mitigate the urban heat island effect. For instance, tree canopies and vegetation can reduce peak summer temperatures by 1° to 5°C. The cooling potential of nature-based solutions varies by type and context. Maximum cooling is achieved when green and blue solutions are combined, but approaches must be tailored to local conditions. For example, dense tree canopies may trap heat and increase humidity, so pairing them with wind solutions could help disperse hot air. Some of the Nature-Based Solutions for Cooling Cities NbS for Cooling Description Cooling Potential Green spaces: street trees, urban parks and forests, grasslands, wetlands Green spaces and vegetation cool cities by providing shade and promoting evapotranspiration, which converts heat from the air into water vapor. HIGH Cooling potential varies by vegetation type, but the amount of green space is the key factor in determining a city's heat levels. Green infrastructure: Green roofs and walls Green buildings and infrastructure use materials and vegetation to create permeable surfaces, enabling evapotranspiration and increasing surface reflectivity (albedo). MEDIUM Green roofs can reduce temperatures by up to 1.7°C. Blue spaces: Rivers, streams, canals Bodies of water act as heat sinks, cooling the surrounding air. A study in India found that Lake Sukhna in Chandigarh city had a cooling effect extending up to 1,200 meters from its center. MEDIUM Cooling effects are variable but can extend beyond the vicinity of the water body. Wind:[2] building placement and orientation, cool corridors Windflow can move heat out of cities and bring in cool air from natural sources. Buildings can be oriented to channel winds, or "cool corridors" can be created by directing winds through green and blue spaces. MEDIUM In tropical regions, wind speeds of 1–1.5 m/s can create a cooling effect similar to a 2°C temperature drop. What additional benefits do nature-based solutions offer beyond cooling? Nature-based solutions are particularly relevant in developing countries due to their cost-effectiveness and multiple benefits. In addition to cooling, well-designed nature-based solutions can help control erosion, improve health, and contribute to climate targets. Studies show that green and blue infrastructure, combined with urban design and reflective surfaces, can offer up to 12 times their cost in net benefits. Nature-based solutions can also offer co-benefits for carbon sequestration, biodiversity value, and health benefits. For example, a green roof can support biodiversity by providing habitat and attracting pollinators. However, careful design is needed to ensure equitable outcomes. For instance, urban parks can offer recreational value but may not be as accessible to women due to cultural norms so careful selection and design of nature-based solutions are crucial to maximizing cooling and realizing co-benefits. Which cities are leading in nature-based cooling initiatives? As urbanization accelerates, cities across Asia and the Pacific have embraced nature-based solutions for cooling and broader sustainability. The following examples showcase how thoughtful urban planning and green infrastructure can combat heat and create vibrant, livable spaces. Case Study 1: Green Buildings | Singapore Singapore exemplifies how green buildings can cool cities. City planning incentivizes greening the built environment through sky gardens, green facades, landscaping, water features, and urban farms. Green infrastructure promotes evapotranspiration, creates shade, and increases the albedo of built surfaces. Today, 40% of Singapore is green, with a target to green 80% of its buildings by 2030 under the City in Nature vision. Green roofs and walls, depending on vegetation type and density, can reduce surface temperatures by ~17°C, contributing to ambient temperature drops of up to 5°C. A key driver of this is the Landscaping for Urban Spaces and High-Rises (LUSH) programme, initiated in 2009. LUSH mandates on-site greenery equivalent to the size of the development and incentivizes rooftop greenery through gross floor area exemptions. The government also covers 50% of the costs for green roofs and facades on existing buildings. Learn more here. Case Study 2: Tree Planting | Kochi, India Kochi, India, is mitigating heat through a tree planting campaign that unites diverse stakeholders. As one of India’s 24 cities expected to face average summertime temperatures over 35°C by 2050, Kochi launched this campaign in 2019 to reduce heat and manage coastal flooding. Research found a strong correlation between vegetation cover and cooling, with temperature differences of 5.5°C between the hottest and coolest neighborhoods. The campaign used geospatial data and community input to identify planting areas, involving the Kochi Municipal Corporation, World Resources Institute India, and Cities4Forests, among others. The Kawaki initiative has planted over 1,200 trees, provided jobs for 100 women, and fostered community engagement. Learn more here. Case Study 3: Parks and Urban Forests | Seoul, Republic of South Korea Seoul's restoration of the Cheonggyecheon stream transformed a former expressway into a mixed-use green space. This 10km area provides cooling, with temperature drops of 3.3°C to 5.9°C compared to a nearby road. The project enhanced cooling by reducing pavement, cutting vehicle traffic, and increasing wind speeds. Beyond cooling, the park reduced air pollution by 35%, increased biodiversity, and became a major recreational hub, drawing 64,000 visitors daily. However, the project also displaced small businesses, causing financial hardships for some. This highlights the need for careful planning to prevent negative social impacts in urban greening projects. Learn more here. What challenges do cities face in adopting nature-based cooling methods? Despite their broad potential, nature-based solutions are often overlooked in city cooling strategies. Key barriers include a lack of supportive policies, financial constraints, and limited institutional capacity. Addressing these challenges requires a multi-pronged approach that maximizes the benefits of nature-based solutions and integrates them into broader heat action plans. This must involve reducing waste heat (e.g., from transport and buildings), addressing cooling needs efficiently, and ensuring equitable access to thermal comfort. Key considerations for incorporating nature-based solutions into urban cooling strategies include: Integrated planning: A systems approach ensures nature-based solutions are complemented by other solutions to maximize their benefits. Equity: Cooling solutions must be distributed fairly, with heat equity embedded in planning to prevent future injustices. Community participation: Involve women and vulnerable groups in designing and implementing cooling programs that deliver real benefits. Local solutions: Nature-based solutions should be tailored to local climates, needs, and traditional approaches (e.g., architecture). Studies suggest that 30% of cities should be dedicated to green or blue spaces. Achieving this requires enabling strategies like raising awareness, building institutional capacity, and securing financing. It also involves assessing current natural assets and identifying vulnerable communities. Partnerships with the private sector can help provide technical expertise and funding. In developing countries, protecting existing green spaces from development is the most effective way to maintain cooling. Creating a cooling-friendly urban form requires time and sustained effort. In the near term, practical, no-regret actions to build resilience to heat stress through nature-based solutions include: Establishing champions and authorities to protect and enhance green and blue spaces Conducting baseline assessments of green and blue spaces and identifying vulnerable communities Investing in green and blue infrastructure, especially in public areas Tree planting is perhaps the simplest and most effective action to reduce urban heat—provided the right trees are planted in the right places as part of a coordinated city-wide greening effort. Steps taken today will help future generations benefit from nature-based solutions for cooling. [1] The urban heat island effect occurs when urban areas experience higher temperatures than surrounding rural regions. This is due to materials in cities—roads, pavements, roofs, and walls—retaining heat and, coupled with less vegetation, raising temperatures. The temperature difference can be significant. Cities in Indonesia, Malaysia, and the Philippines can be up to 5.9°C warmer than nearby areas. As cities grow, more people will face heat extremes—by the 2050s, this could be 700% more than today. Energy use, especially air conditioning, worsens the situation by straining the electric grid during extreme weather and creating a feedback loop by adding heat. In many Asian and Pacific cities, humidity compounds the heat. Humidity reduces the efficiency of heat convection, trapping it in water vapor instead of letting it evaporate. It also limits the body’s ability to cool through sweating, increasing discomfort. Addressing humidity is crucial in finding cooling solutions, as some options may increase moisture in the air. As cities warm, it's essential to provide equitable access to cooling without worsening the urban heat island effect. Reducing the need for cooling and cutting emissions is vital to mitigating global warming. [2] A common characteristic across various classifications of nature-based solutions is that they are designed to benefit nature. While wind alone may not directly contribute to biodiversity outcomes, in urban design, wind solutions are often classified as nature-based solutions, as they utilize natural processes to optimize wind flow for cooling. Resources Integrated Research and Action for Development. 2021. Working Paper: Nature-Based Solutions for Heat Stress Management in Cities. United Kingdom Green Building Council. 2021. Principles for delivering urban Nature-based Solutions. United Nations Environment Programme (UNEP). 2021. Beating the Heat: A Sustainable Cooling Handbook for Cities. Urban Climate Change Research Network (UCCRN). 2018. The Future We Don’t want: How Climate Change Could Impact the World’s Greatest Cities. World Bank. 2022. Piloting Nature-based Solutions for Urban Cooling Overview. Ask the Experts Celina Garcia Nature-Climate Policy Specialist, International Consultant Celina is an experienced policy professional with a background in the public and not-for-profit sectors across Australasia and the Pacific. Her work spans biodiversity protection and natural resource management in both land and marine environments. Recently, she has focused on sustainable oceans and climate change policy in Pacific Island countries. Deborah Robertson Climate Change Specialist, Climate Change and Sustainable Development Department, Asian Development Bank Deborah’s work focuses on increasing nature-positive investments through country programming, operational support, and results management. In previous roles, she led the ADB Healthy Oceans program and helped Pacific Small Island Developing States build climate resilience and sustainable blue economies. Before joining ADB, Deborah worked for the New Zealand Government, Beca, and several NGOs. She has extensive experience in policy analysis, natural resource management, coastal adaptation, and marine conservation. She holds master's degrees in environmental planning and marine conservation. Zonibel Woods Senior Social Development Specialist (Gender and Development), Gender Equality Division, Climate Change and Sustainable Development Department, Asian Development Bank Zonibel Woods is an expert in gender mainstreaming, policy development, and capacity building, with leadership roles in organizations like the International Women’s Health Coalition and Ford Foundation. Since the 1992 Earth Summit, she has focused on gender and climate change. After relocating to the Philippines in 2012, she worked as a gender consultant and joined ADB in 2020 as a Senior Social Development Specialist. Zonibel has published on gender, health, climate change, and is passionate about animal welfare. Asian Development Bank (ADB) The Asian Development Bank is committed to achieving a prosperous, inclusive, resilient, and sustainable Asia and the Pacific, while sustaining its efforts to eradicate extreme poverty. Established in 1966, it is owned by 68 members—49 from the region. Its main instruments for helping its developing member countries are policy dialogue, loans, equity investments, guarantees, grants, and technical assistance. Follow Asian Development Bank (ADB) on Leave your question or comment in the section below: View the discussion thread.