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US Cities Lose Tree Cover Just When They Need It Most (scientificamerican.com)

An anonymous reader shares a report: Scientific evidence that trees and green spaces are crucial to the well-being of people in urban areas has multiplied in recent decades. Conveniently, these findings have emerged just as Americans, already among the most urbanized people in the world, are increasingly choosing to live in cities. The problem -- partly as a result of that choice -- is that urban tree cover is now steadily declining across the U.S.

A study in the May issue of Urban Forestry & Urban Greening reports metropolitan areas are experiencing a net loss of about 36 million trees nationwide every year. That amounts to about 175,000 acres of tree cover, most of it in central city and suburban areas but also on the exurban fringes. This reduction, says lead author David Nowak of the U.S. Forest Service (USFS), translates into an annual loss of about $96 million in benefits -- based, he says, on "only a few of the benefits that we know about." The economic calculation involves several such benefits that are relatively easy to express in dollar terms -- the capacity of trees to remove air pollution, sequester carbon, conserve energy by shading buildings and reduce power plant emissions.

3 of 135 comments (clear)

  1. Liberal cities... by Anonymous Coward · · Score: 0, Insightful

    Doing themselves in.

    Liberals, you are hypocrites again. Cutting your own down.

  2. Not a Choice by Tablizer · · Score: 4, Insightful

    Americans, already among the most urbanized people in the world, are increasingly choosing to live in cities. [Emphasis added]

    I don't believe it's a choice in the direct sense, but rather an economic reality. To be competitive globally and against automation requires high collaboration among experts and specialists. You mostly find this in populated areas.

    Farming automation has reduced the need for rural workers, and mining automation is also ramping up.

    If your job allows you to do remote work, then it more likely can be outsourced to Timbuktu for 1/3 your wages.

  3. Re:Compensating by drinkypoo · · Score: 4, Insightful

    With the emerging (but still very small) movement to add a lot of plants to the roofs / sides of buildings, I would like to see a study making a quantitative evaluation as to how much said plants can compensate for the loss of trees.

    I don't know, but I can take a semi-educated guess. Old forests with mature trees typically (that is, for almost all species) sequester more carbon than young ones which are still growing. It seems counterintuitive, but the key is that old forests have substantially more biomass — the trees have to respirate in order to maintain it, and it's their respiration which is the basis of most of the benefits of trees. Therefore, the benefits will essentially scale with the biomass, which is to say that trees are more beneficial.

    Some of the benefits of trees are irrespective of their biomass, for example their effect on albedo. This can as easily be produced by leafy salad greens as a redwood tree. But carbon sequestration, air filtration, and regulation of humidity (just off the top) are all linked to biomass.

    --
    "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"