Cooling Cities Naturally: Experts Highlight Nature’s Role in Beating Urban Heat

Cities around the world are grappling with record-breaking heat. According to a multi-city Lancet study on urban heat mortality, in the Mediterranean alone, the number of days of strong heat stress more than doubled in the summer of 2024. Amid rising global temperatures, Air-conditioning remains indispensable for public health, yet running ever more compressors on fossil-fuelled grids risks driving a vicious warming cycle. Nature-based solutions (NbS) offer an indispensable complement: trees, green roofs, wetlands and other interventions can shave several degrees off neighbourhood temperatures, cut peak electricity demand and deliver health, biodiversity and economic co-benefits.

To turn that promise into financeable reality, the United Nations Environment Programme (UNEP) Cool Coalition convened the fourth session of its Cool Talks webinar series, Cooling with Nature: Financing Nature-Based Solutions in Cities, on 14 May 2025. The 60-minute event brought together experts in heat resilience, biodiversity policy, architecture, finance and building science to answer a single question: how do we mobilise investment and move from isolated pilots to city-wide deployment of NbS for cooling?

Financing Cooling Justice

Opening the session, Dr Zhuolun Chen, Cool Coalition and NEP Copenhagen Climate Centre (UNEP-CCC) Senior Advisor on Energy Efficiency and Green Finance, framed the scale of the challenge. “Nature-based urban cooling is powerful yet under-utilised,” he said. Investment remains a trickle. UNEP’s State of Finance for Nature 2023 finds that only 17 per cent of global NbS finance comes from private sources, leaving a 700 billion USD annual gap. Chen urged participants to develop blended models, including public funds to de-risk and private capital to scale, because “nature can deliver cooling at a fraction of the lifetime cost of purely mechanical fixes, while generating jobs, cleaner air and climate resilience.”

Keynote speaker Dr Eleni Myrivili, Global Chief Heat Officer at UN-Habitat and the Atlantic Council’s Climate Resilience Center, distilled the stakes: “Cities are ground zero for escalating heat,” she stated, referring to urban heat as a “threat multiplier” that undermines water, food, health and infrastructure systems simultaneously. Citing the latest Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, Myrivili reminded the audience that urban greening ranks among the most effective and cost-effective adaptation strategies. “Cities built for a 20th-century climate have become heat traps,” she concluded. “So we must redesign them around shade, airflow, water and, above all, nature.”

Planning for Vertical Ecosystems

Moderating the panel, Dr Geronimo Gussmann, Advisor on Nature-based Solutions at the UNEP-CCC, underlined that policy signals now favour NbS. More than half of updated Nationally Determined Contributions (NDCs) under the Paris Agreement mention nature-based measures, yet few specify urban cooling. Meanwhile, the Kunming–Montreal Global Biodiversity Framework (GBF) commits Parties to expanding green and blue spaces in cities by 2030 (Target 12). “The alignment is there with Paris for climate and the GBF for biodiversity. The next step is to align money and municipal action,” Gussmann stressed. He also advocated blended finance to pull adaptation, biodiversity, and health budgets into single NbS pipelines, and pointed to UNEP-CCC’s Business Models for Financing Nature-Based Solutions in Urban Climate Action as a useful framework for supporting cities in developing tailored financing approaches.

Architect Richard Hassell, co-Founder of WOHA, shared a practitioner’s vision of weaving nature into city architecture. Hassell, known for pioneering green building projects in tropical cities, showcased how “urban architecture and passive cooling can go hand-in-hand.” He described a paradigm shift from seeing buildings as isolated boxes to acknowledging them as living parts of the urban ecosystem. “High-rise greenery is not just for the building’s occupants, but performs environmental services for everyone,” Hassell explained. “Plants filter air pollution, provide shade, block out noise, absorb heat, and even create habitats for birds and insects.”. Hassell called for updating building codes and incentives, so that features like green roofs, vegetated facades, courtyards, and permeable, reflective materials become standard practice in development. With successful examples now in place from Singapore to Milan to Bogotá, architects and planners have a growing toolkit to design climate-resilient buildings that stay cool naturally.

Bringing a policy perspective, Eva Gurría, Partnerships Lead at the NBSAP Accelerator, focused on mainstreaming urban NbS through national biodiversity strategies and climate plans. Too often, she noted, countries address heat adaptation in one silo and urban greenery in another. “We need to break silos. Think of urban nature as infrastructure,” she urged. Gurría pointed to London’s natural-capital accounting, where every £1 spent on parks yields £27 in health, environmental and social benefits, all proof that robust valuation can unlock budgets. The Accelerator’s matchmaking facility now links similar city-level cooling proposals with national ministries and financiers, requests already span Antigua and Barbuda to Zimbabwe.

Closing the panel session, Dr Zahra Jandaghian, Nature-Based Solutions Lead at the National Research Council of Canada’s Construction Research Center, made the engineering case for NbS. Her team’s modelling shows that combinations of reflective cool roofs, increased urban tree canopy, and ventilated street canyons can cut peak temperatures by up to 4 °C, and reduce building energy demand by double digits in Canadian cities. “If we can measure it, we can finance it,” she said. Embedding these measures into building and planning codes will give developers certainty and insurers confidence. Jandaghian sees potential in resilience bonds and green sukuk that reward verified reductions in heat-related mortality or energy consumption, plus public “ecosystem-service payments” for projects that deliver social value beyond property lines.

Q&A Takeaways

Throughout the Q&A, speakers converged on several funding strategies. Climate Policy Initiative’s Global Landscape of Climate Finance 2024 report suggests that the scale of money now circulating in climate finance allows room to manoeuvre, with total flows having reached 1.3 trillion USD in 2023. Carbon markets can underwrite urban reforestation, as demonstrated by Freetown, Sierra Leone, where street-tree carbon credits fund local stewards. Public-private partnerships, such as Singapore’s green plot-ratio incentives, have proven that developers will pay for vertical greenery when zoning bonuses reduce other costs. Insurance-linked products could reward property owners who install certified cool roofs or shade trees by lowering premiums. Finally, outcome-based grants that disburse against quantified cooling or health benefits can attract private co-investment.

As Zhuolun Chen concluded, “We have the science, the policy frameworks and a growing roster of success stories. What we need now is coordinated capital and political will. Investing in cooling with nature will lower the thermometer and create healthier, more resilient communities.”

Dive Deeper

To view the webinar recording and access presentation slides, visit the event page.

To watch the April Cool Talk on cooling-as-a-service, go here.