The Nature Conservancy’s Planting Healthy Air Study Shows Trees Can Help Improve Air Quality and Overall Health

November 2, 2016

Investing $4 for Every Resident in Tree Planting Can Help Save Tens of Millions of Lives

Rob McDonald, Lead Scientist, Global Cities, The Nature Conservancy

(Arlington, VA, Wednesday, November 2, 2016) – Heat waves are responsible for 12,000 deaths each year, killing more people globally than hurricanes or winter storms. Additionally, 3.2 million deaths can be attributed each year to fine particulate matter, a component of smog, and by 2050 this type of pollution could kill 6.2 million people annually.

Cities around the world suffer from air pollution and extreme heat, affecting the lives of billions of people. The Planting Healthy Air study from The Nature Conservancy shows that trees can help. It identifies the potential return on investment from tree planting in 245 global cities, and finds that, overall, trees can have a meaningful local impact on air quality and temperature.

Investing $100 million per year in tree planting and maintenance globally could provide as many as 77 million people with cooler cities and offer 68 million people measurable reductions in fine particulate matter pollution. Further, if cities globally, invested $4 for every resident in tree planting, tens of millions of lives could be saved.

The Planting Healthy Air study also finds that, with additional investment, urban trees could save tens of thousands of lives annually, while reducing other health impacts for tens of millions of people around the world.

HEAT: Elderly people face particular risk. As the global climate shifts, and average summers temperatures rise, the impacts of urban heat are on the rise. If projections are correct, and cities do not prepare for warmer temperatures, the impact could increase to nearly a quarter million deaths each year by 2050.

PM2.5: The most common sources of fine particulate matter include auto exhaust and factory and power plant emissions. Fine particulate matter is also contributing factor to heart attacks, strokes, asthma and other diseases, affecting tens of millions of people worldwide. The World Health Organization guidelines recommend less than 10 micrograms per cubic meter, but there is no “safe” level of fine particulate matter pollution.

How do trees cool cities? Trees provide shade and they release water vapor into the air as they photosynthesize. Together, these effects can cool the area surrounding a tree by as much as 2 degrees C, with the most significant benefits within 30 meters of a tree.

How do trees clean the air? Leaves remove particulate matter from the air in a tree’s immediate vicinity – within 300 meters – and can reduce local fine particulate matter concentrations by as much as a third.

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