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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, face heightened temperatures. Projections show that several cities in Asia and the Pacific could see .

Urbanization and growth in these regions compound the impact of rising temperatures. By 2050, , while Pacific 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, 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, .

The cooling potential of NbS varies by type and context. Maximum cooling is achieved when , 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

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 NbS 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, .

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 NbS 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.

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 NbS benefits 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 NbS into urban cooling strategies include:

• Integrated planning: A systems approach ensures NbS 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: NbS should be tailored to local climates, needs, and traditional approaches (e.g., architecture).

Studies suggest that . 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 NbS 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 NbS for cooling.

This article was first published on 

The views expressed in this article are those of the authors and do not necessarily reflect the views of the Asian Development Bank, its management, its Board of Directors, or its members.