Are trees the most important green infrastructure in cities?

Trees might not get all the attention when it comes to sustainable cities, but their benefits shouldn't be overlooked.

An urban forest might seem like an oxymoron. But according to a report from the United States Department of Agriculture Forest Service, it's an important green infrastructure system for sustainable cities.

You'll have to revise your understanding of a forest because, technically, an urban forest refers to the public and privately owned trees within an urban area. They're the trees that line streets, provide shade in backyards, and they're also the trees that make up parks and wooded areas.

There are an estimated 3.8 billion urban trees that are valued at about $2.4 trillion.

Not convinced about the value of urban forests? Here are some of the benefits of trees to cities according to the report.

  • Air quality: Urban trees in the conterminous United States remove about 784,000 tons of air pollution each year.
  • Storing carbon: In the U.S. urban trees store about 770 million tons of carbon.
  • Energy use: 100 million mature trees around buildings in the U.S. leads to an annual energy savings of $2 billion.
  • Real estate: Landscaping with trees increases property values.
  • Water flow and quality: Trees can lower the expenses because cities don't have to invest as much in expensive storm water treatment plants. They also help filter water impurities.

And besides the economic and energy saving benefits, urban trees can help to enhance the sense of place in neighborhoods and communities at a relatively low cost compared to other costly beautification projects.

But it's not a cost-free solution. Like anything, urban forest need to be thoughtfully managed and well planned. According to the report:

The costs to maintain and manage urban forests are substantial. A statewide survey of 18 California cities revealed an annual expenditure of close to $80 million. Most of these funds were spent on addressing problems related to the growth of street tree roots, which are severely impeded by sidewalks, curbs, gutters, and street pavement. However, most urban forests do not require such intensive management, and the overall benefits of urban forests likely outweigh their planning and management costs. With proper planning and management, costs can be reduced and benefits enhanced.

And certainly, it's not a one-size-fits-all solution. Cities must work with the challenges of their environment. The dry Southwest will need to use drought-resistant trees, while other regions will have the plan for the threat of fires during dry seasons.

Nonetheless, while it's an aspect of sustainable cities that's easy to overlook, when you take a moment to appreciate urban trees, their benefits are hard to ignore.

[Via The City Fix]

Photo: asterix611/Flickr

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