Big Picture

Cities suffer the most from extreme high temperatures. Their cement floors absorb enormous amounts of heat, which is then released back into the air throughout the day. This is called the urban heat island effect, and it can raise temperatures up to 50ºF above what it would be in a rural environment. These extreme urban temperatures cause a wide array of devastating social, environmental and economic consequences, including reducing the amount of available outdoor spaces for recreation, adverse health effects (particularly for vulnerable populations), increased spending on air conditioning and other cooling systems and overall discomfort. As temperatures continue to increase, this problem is becoming increasingly relevant across the United States. The main and cheapest solution to this is preventing cities from reaching these high temperatures through urban forestry.

Operative Definitions

1. Urban heat island effect: According to the EPA, the heat island effect occurs when cities experience higher temperatures than their surrounding rural areas. This is due to the fact that structures such as buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests or water bodies. 
2. Urban areas: An entire area surrounding a city. It includes suburbs and other surrounding settlements.
   Rural Areas: Any geographic area located outside urban areas, usually containing a natural or agricultural landscape.
3. Urban forestry: Includes planting and caring for trees, parks, waterways, and other green spaces within an urban environment.

Important Facts and Statistics

1. Heat island effects can raise temperatures up to 50ºF (10ºC). 
2. A large oak tree can transpire up to 40,000 gallons of water per year, releasing it into the air and reducing the heat island effect. 

Six-Point Plan

(1) Develop a cohesive U.S.-wide infrastructure plan. It is important to be coherent and implement a joint strategy for all cities across the U.S. to implement. Developing a best-practices guide and approach to urban forestry will lead to more successful results. A combination of methods can be used to cool cities, so it is important to take advantage of all of them.

(2) Expand green spaces and green coverage in urban areas. Green spaces, from large parks to trees on the sidewalk, offer great protection against heat retention. Parks retain less heat allogether, but street trees provide shade, capture CO2 emissions, help capture rainwater, and release cool water into the air, all of which helps reduce the temperatures in cities. Green spaces can be developed on building roofs and walls and streets, without having to change the layout of the city or displacing anyone.

(3) Add reflective surfaces to existing and future infrastructure. Making all city infrastructure reflective will help prevent heat absorption. For example, making concrete on sidewalks and roads a lighter color will make it more reflective. This only requires adding dry pigment to the asphalt mix when pouring it. 

(4) Incorporate water into the landscape. Promoting efficient water use, retention, and conservation will lead to better cooling. As water evaporates, it makes the air cooler. Rainwater can be better harvested by expanding green area coverage.

(5) Promote native plant species in public and private green spaces. Everyone likes to have a beautiful garden. Yet the most beautiful plants and lawns can be water inefficient and drain the local water resources. Native plant species are better adapted to fit the local climate. As such, they will perform better in achieving all of these desired results if given the change. They will usually also need less water than other species and therefore release more into the atmosphere.

(6) Ensure an equitable implementation of cooling measures. It should come as no surprise that measures that improve the quality of life are usually first implemented in rich neighborhoods. However, traditionally marginalized communities tend to be at higher risk of suffering from a drastic rise in temperatures. Working collaboratively with local organizations, non-profits, governments, and organized groups would ensure an equitable implementation of urban forestry.

Why This Initiative is Important

As climate change continues to take its toll, extreme temperatures will become increasingly frequent, particularly in urban environments. To protect ourselves and our economies, we need to get ahead of the problem and cool down cities. Urban forestry is a cheap, efficient and long-term oriented way of achieving this all while beautifying our cities. 

Acknowledgements

The following student(s) worked on this nonpartisan proposal: Annie Llombart, University of California, Santa Cruz graduate.

Sources:

EPA. “Heat Island Effect.” EPA, Environmental Protection Agency, 2022, www.epa.gov/heatislands.

Jolma Architects. “How Landscape Architecture Mitigates the Urban Heat Island Effect.” Land8, 14 Oct. 2018, www.land8.com/how-landscape-architecture-mitigates-the-urban-heat-island-effect/.

NASA. (2022, April 14). Overview: Weather, Global Warming and climate change. NASA. Retrieved April 30, 2022, from https://climate.nasa.gov/resources/global-warming-vs-climate-change/.

U.S. Department of Agriculture. (2022). Urban forests. US Forest Service, Urban Forests. Retrieved April 21, 2022, from https://www.fs.usda.gov/managing-land/urban-forests.