Better Forests, Better Cities

Sarah Jane Wilson Edith Juno John-Rob Pool Sabin Ray Mack Phillips Scott Francisco Sophie McCallum
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Chapter 1


Forests around the world are under severe threat. Despite this, the evidence base that shows how and where forests provide benefits to cities and their residents is growing. As centers of untapped political, economic, financial and social power, cities can play a role in protecting, restoring and sustainably managing the world’s forests, to ensure the long-term sustainability of the benefits they provide.

Mariano Luis Fraga/Shutterstock

City leaders around the world are working hard to meet the needs of ever-growing urban populations. By 2050, an estimated 70 percent of the world’s population will live in cities (UNSD n.d.). City leaders strive to provide their residents with a safe place to live and work and with access to resources and environments that promote good health. They seek to improve and sustain clean, reliable water supplies and provide protection from natural disasters. And cities are increasingly stepping up to take action on climate change mitigation and to meet other sustainability commitments. International agreements to combat climate change and conserve biodiversity, city-level commitments to reduce greenhouse gas (GHG) emissions, and the need for companies based in cities to reduce their carbon footprints all put pressure on cities to find cost-effective solutions to environmental challenges. At the same time, they juggle these demands in dynamic environments, often with tight financial resources.

At their disposal is a nature-based solution that can help cities meet many of these aspirations: forests and trees. Cities around the world are turning to nature-based solutions11 (NBS) to address their challenges and meet their goals. Forests, in particular, are increasingly recognized as a cost-effective way to deliver multiple benefits. This report synthesizes the literature on how forests can deliver four key benefits12 for cities and their residents:

  • Health and well-being by creating habitable, healthy, and favorable living conditions for city residents
  • Water by securing access to clean and reliable water supplies, both within cities and in the key agricultural regions that feed them
  • Climate by contributing to climate change mitigation and its effects on millions of urban residents
  • Biodiversity by protecting essential global biodiversity, which supports many of the systems people rely upon, such as pollinating crops, providing medicines, regulating climate, and underpinning many spiritual values

Benefits of Forests

Forests—both within and beyond city boundaries—provide benefits to cities and their residents. Our framework (Figure 1) divides forests into three levels—inner, nearby, and faraway—to show what the benefits are, how they differ depending on the location of the forest, and how cities can support forests to harness the greatest benefits. This framework was conceived by the founders of the Cities4Forests13 initiative, based on multiple projects and engagements with both forest and city landscapes.

  • Inner forests include trees and forests growing along streets, in city parks, on private property, as remnant patches of native forests or woodland, and in urban coastal areas within cities. These inner forests can improve air quality, offset heat islands (leading to lower energy use and bills), reduce stormwater runoff and urban flooding, and support human health and wildlife.
  • Nearby forests include forests, woodlands, and trees found in watersheds surrounding cities. They enhance urban air quality, regulate temperature, provide stable supplies of clean drinking water, reduce flooding, and offer opportunities for relaxation and recreation.
  • Faraway forests are intact forests located beyond a city’s watershed. These forests, particularly those in the tropics, sequester large amounts of carbon, generate rain for cities and the world’s farm belts, provide a wealth of useful products, and host the majority of the world’s land-based biodiversity.

Figure 1 | Inner, Nearby, and Faraway Forest Benefits

Note: Inner, nearby, and faraway forests provide multiple benefits to cities, many of which are aligned with the UN Sustainable Development Goals.

Source: Cities4Forests n.d.a.

Threats to Forests

Across the globe, forests are under threat. During the decade 2010–19, global forest cover declined by an average of 4.7 million hectares (ha; 11.8 million acres) per year (FAO 2020).14 In 2019 alone, the world lost an area of tropical primary forest the size of a football pitch every six seconds (Weisse and Goldman 2020). In the world’s largest intact forests, deforestation and forest degradation are driven largely by agriculture, fires, and logging (Figure 2). Inside cities, pollutants, high temperatures, compacted soils, pests, and diseases create challenging conditions for trees to grow and survive. Urban tree cover has been decreasing at an average rate of 0.04 percent per year (Nowak and Greenfield 2020). In the United States alone, this loss represents about 36 million trees per year, equating to an estimated financial loss of US$96 million per year in benefits (Nowak and Greenfield 2018a). Urbanization often encroaches on woodlands surrounding cities, and an estimated 9 in 10 cities have lost significant amounts of natural land cover in their source watersheds to agriculture and development (McDonald et al. 2016).

Figure 2 | Tropical Deforestation Rates over Time

Source: WRI n.d.a.

Global deforestation is not evenly distributed; tropical forests are being cleared at much higher rates than those in temperate and boreal regions. Commercial production of globally traded agricultural commodities—such as soy, beef, and palm oil—is the leading driver of tropical deforestation (Curtis et al. 2018). In response to consumer demand from people—including city residents—thousands of miles away, tropical deforestation rates continue to rise. For the past several decades deforestation rates have been much lower in temperate and boreal regions, although in temperate areas many of these forests were cleared in the past (Currie and Bergen 2008). Forest loss in temperate and boreal regions is now mainly due to fire and harvesting for wood and paper products, and forests sometimes regrow after clearing (Figure 2; Curtis et al. 2018).

Cities suffer the costs. The impacts of deforestation and forest degradation always extend far beyond the cleared region. Cities experience poorer air quality, flooding, landslides, and more extreme weather events, to name a few, as a result of deforestation near and far. Deforestation decreases the benefits that cities receive from forests (Figure 1) with negative impacts on the physical, economic, and mental well-being of urban residents. In a world struggling to combat COVID-19, deforestation and forest degradation have been linked to increased incidence of vector-borne diseases such as malaria (Karjalainen et al. 2010) and the emergence of infectious zoonotic diseases such as coronaviruses (Afelt et al. 2018).

Opportunities for Cities

Cities play a major role in forest loss and degradation. Consumption in urban areas is directly responsible for about 75 percent of global carbon dioxide (CO2) emissions and two-thirds of global energy use (Seto et al. 2014). And although cities cover only a small proportion of the earth’s surface, their footprints are large: as major “net importers,” cities depend heavily upon resource extraction and production beyond their boundaries (Weinzettel et al. 2013). A midsize city in North America, for example, is responsible for thousands of hectares of tropical deforestation per year via the goods it consumes.15

Cities—as places where people increasingly live and work—can make major contributions to addressing these issues. The public policies and procurement practices of cities—as well as the values, votes, and consumption patterns of residents—have enormous potential to support the conservation, restoration, and sustainable management of forests. Many cities already support forests, for example, through efforts to expand urban tree cover and parks. Some cities provide incentives to protect watersheds for their water supplies, and there is growing investment in forests as “green infrastructure.” Some cities are implementing procurement guidelines to reduce tropical deforestation driven by city consumption. But the potential to do more is immense. The Intergovernmental Panel on Climate Change’s (IPCC) Special Report on Climate Change (Jia et al. 2019) estimates that 11 percent of global carbon emissions come from land-use change—especially tropical deforestation. If tropical deforestation were a country, it would rank third only behind China and the United States in GHG emissions (Gibbs et al. 2018). Conserving, sustainably managing, and restoring forests and other ecosystems could reduce global GHG emissions by up to 30 percent and provide 23 percent of the cost-effective mitigation measures needed to prevent global temperatures from rising 2°C (Griscom et al. 2017; Wolosin and Harris 2018). Much more can be done to promote forests as a climate change solution (Seymour and Busch 2016).

About This Report and How to Use It

This report addresses two key questions: How and under what conditions do forests support cities? And what can cities do to support forests? To answer the first question, we rigorously research and explore four ways forests benefit cities16 and describe each in its own section (Table 1).

Table 1 | The Four Sections of This Report

Health and Well-Being




Thriving, vibrant cities provide their residents with ample opportunities for social interaction, with food and water security, with enhanced economic opportunities, and with comfortable, safe living conditions.

Forests in and around cities can promote recreation, mental restoration, and spirituality. They also help to mitigate hazardous urban environmental conditions related to extreme temperatures and exposure to air pollutants. Finally, they can supplement food supplies and provide livelihoods for many–including vulnerable and marginalized populations.

Faraway forests also play a critical role in providing the templates for new pharmaceuticals. And by protecting tropical forests and other biodiversity hotspots from degradation, we may be able to avoid novel infectious diseases.

Forests interact with climate and the hydrological cycle at local, regional, and global scales.a

Inner forests can support cities as they strive to provide clean, readily available water to their residents and can also reduce burdens on urban infrastructure and prevent flooding.

Nearby forests improve urban water quality by shielding rivers from high temperatures, pollutants, and erosion that can negatively affect the natural balance of the ecosystem.

Faraway forests—especially tropical forests—influence precipitation patterns in cities and agricultural regions hundreds of miles away as they cycle water into the atmosphere.

Climate change poses a special threat to cities. Cities experience higher temperatures than rural areas, and many cities lie on coasts. As concentrated centers of people, culture, and economic activity, urban areas are extremely vulnerable to natural disasters.

Forests can help to mitigate climate change and promote adaptation.b Photosynthesis—nature’s own carbon capture and sequestration solution—makes forests a highly cost-effective climate change mitigation option.

Investing in forests inside cities can lower city emissions via urban cooling. Conserving and restoring forests outside cities via deforestation-free consumption and sustainable forest management can protect some of the most important carbon sinks on the planet: large, contiguous forests—especially tropical forests.

Biodiversity, the variation of life on Earth, supports ecosystem function,c fosters connection to place, stimulates tourism,d and harbors potential blueprints for nutritional and medicinal products key to human health.e It also provides endless opportunities for discovery and wonder.

Inner and nearby forests can serve as habitat, climate refugia, and corridors for key flora and fauna, including pollinators, edible plants, and iconic birds and mammals.

Forests at all levels can play a key role in preserving biodiversity for future generations and promoting ecosystem functioning, but conserving and sustaining intact tropical forest is vital. Tropical forests contain most of the planet’s biodiversity on land. Yet to date, only 18% of the world’s forests and 27% of tropical forests are currently protected.f

Note: References for the summaries in this table are given in the relevant sections of the report.

Sources: a. van Noordwijk et al. 2014; b. Tye et al. 2022; c. Cardinale et al. 2012; d. Hausmann et al. 2016; e. Karjalainen et al. 2010; f. FAO and UNEP 2020b.

City representatives can use each section separately or all together, depending on their focus and objectives. For example, a city employee concerned with improving air quality could read Section 2 to learn more about how trees and forests can help. An official interested in making trees and green space a focus of the city agenda might read all four sections.

Sections 2–5 have a similar overall structure, with a “Background” section about the topic and its relevance for cities as well as a section that describes what forests do and—when data allows—quantifies their benefits. This latter section is formatted differently between sections to suit the specific subject. The “Caveats and Considerations” section highlights the nuances that are important for realizing the benefits, including when forests will not produce benefits, and what types of forests are most appropriate. This section helps urban decision-makers avoid unintended consequences and get the most from their investment in trees and forests. Collectively, this information can be used by city governments, city managers, other agencies, and groups such as nongovernmental organizations (NGOs) and community-based organizations that work with cities to rethink how they should engage with and use forests to achieve specific end goals.

The question “What can cities do to support forests in return?” is addressed in Section 6, which outlines what city leaders, managers, and other city stakeholders can do. The section includes recommendations on resident engagement and awareness, communications campaigns, public policies and procurement, finance, and more.


This report synthesizes the latest research on how inner, nearby, and faraway forests benefit cities and urban residents. It summarizes research findings gathered through several literature reviews, including several “reviews of reviews” (surveys of published review papers; e.g., van den Bosch and Sang [2017]), supplemented by reviews of primary literature and expert-recommended texts. Reviews covered four main topics: health and well-being, water, climate, and biodiversity. There is a geographical bias of the “reviews of reviews” methodology, which was limited to published documents written in English. We partially correct for this by including findings from relevant empirical papers and by including case studies from under-represented areas identified through reference lists and expert recommendations. Sections of the report, such as Section 6, are also partly based on conversations with city representatives, interviews with topical experts, and experiences from years of projects that World Resources Institute (WRI), Pilot Projects, and Cities4Forests have worked on.

There is no universally accepted definition of forest (Chazdon, Brancalion, et al. 2016), and different fields of study use the term in different ways. We include research on both trees and forests as well as on natural and planted forests, and we make distinctions where appropriate. We also include work on urban nature, green infrastructure, and green spaces more broadly when forest-specific studies are lacking. A more detailed methodology can be found in Appendix A.