3. Wildlife Habitat
Without trees, you can't establish much wildlife. Wildlife provides opportunities for informal education and nurturing curiosity, and it is essential to our urban ecosystem. Native trees are especially valuable, as a single species can host literally hundreds of species of native insects that in turn feed birds and other animals. In a few weeks I'll be writing about the value of native wildlife and biodiversity, so tune in for an exciting discussion.
4. UV Radiation Protection
A tree's shade can reduce UV exposure and delay sunburn. The benefit will vary depending on the density and spread of the canopy, but dense shade can offer up to a 95% reduction in UV radiation.
5. Greenhouse Gas Reduction
Trees use the carbon dioxide in the air to make the sugars they need to live, and this helps offset the carbon dioxide we produce both biologically and through burning fossil fuels. In one year, an acre of trees can consume enough carbon dioxide to match what is emitted by an average car driving 26,000 miles. Our urban forests aren't large enough to totally compensate for the amount of carbon dioxide we produce, but they certainly reduce it.
6. Air Quality Improvement
Producing oxygen and capturing carbon dioxide are types of air quality improvement, but urban trees don't stop there. They can also reduce air pollution as the trees catch particulate matter in the air that might otherwise turn into unhealthy smog.
7. Water Quality Improvement
Whenever we get a heavy rain in Indianapolis, we are at risk for a combined sewer overflow. What this means is that so much rain is running off of our paved surfaces and into our sewer system that raw sewage overflows and gets into our natural waterways (see the diagramon the left). Trees can reduce the number and severity of combined sewer overflows by collecting rain on leaves, bark, and in the soil. Indianapolis is doing great work in using green infrastructure to manage stormwater, and was even featured in a 2013 report from the Natural Resource Defense Council, but there is still a long way to go.
8. Health Benefits
Beyond reducing UV radiation, trees offer some surprising and substantial health benefits. Trees reduce asthma and respiratory disease by reducing air pollution. Being around trees and other plants can have psychological effects similar to antidepressants and ADD medication, and they have been shown to reduce stress. Hospital patients with a view of greenery recover faster, require less pain medication, and have fewer complications than patients without such a view.
9. Aesthetic and Socio-Economic Benefits
We intuitively understand the aesthetic benefits of trees. They're beautiful, and they make the spaces around them more beautiful. The socio-economic benefits of trees are less obvious, but studies show that trees reduce crime rates, increase business sales, and reduce traffic speeds, and we also know that they increase property values and strengthen communities.