题目： Are Urban Trees Worth It?
作者： Scott Steen
来源： Guardian News，September 30,2014
Some people don’t love trees as much as they used to. After the severe storms we have had this year, including Hurricane Sandy, city trees can seem like a dangerous liability. Are urban trees worth the risk they pose to houses, cars and people when a violent storm comes through?
Urban environments are tough on trees. Street trees are often boxed in without enough room for healthy roots or they don’t have a sufficient water supply to sustain them. Branches on street trees can be broken by buses or trucks that travel or park too close, or they can be damaged by overly aggressive pruning. The damage often goes unreported, and the trees weaken. High winds can bring those branches — or the trunk itself — down on cars, houses or power lines.
But there is another side to it, too. Trees are green infrastructure. Unlike gray infrastructure — concrete and metal sewers, pipes, bridges, sidewalks — trees are an investment that increases in value throughout their lifetime, which can last a lot longer than concrete.
In Baltimore, Md., it’s estimated that a single tree provides $57,000 in economic and environmental benefits over its lifetime. In a single year, Baltimore’s canopy provides
$3.3 million in energy savings.