城市树木每年为美国节省多达120亿美元
The cooling effect of trees permeates a few blocks downwind of Central Park in New York City.
树木的冷却效应渗透在纽约中央公园下风向的几个楼群当中。
It’s well known that urban trees provide a huge range of environmental, economic and health benefits. However, a new study has highlighted the extent of these benefits by showing how the urban tree cover saves the U.S. up to $12 billion annually. This includes reduced deaths, injuries and electricity usage for air-conditioning.
我们通常都是从定性的角度了解到城市树木能提供大量的环境、经济和健康效益。然而，有一项新研究给出了定量的结论，通过展示城市树木覆盖每年为美国节省多达120亿美元的研究成果强调了城市树木覆盖的效益范围，这其中包括减少死亡人数、受伤人数和空调耗电量。
In the hot U.S. summer, high air temperatures and heat waves pose significant risks for people with existing health conditions. Those with cardiovascular, renal and pulmonary conditions are particularly susceptible. To combat the extreme heat, air-conditioner usage spikes, putting increasing loads on the electrical grid during the day.
在美国炎热的夏天，高温和热浪对于存在身体健康问题的人来说是极大的风险，特别是那些有心血管、肾脏和肺部疾病等容易得病的人群。为了战胜极端的酷热，每天城市中空调的使用量达到了峰值，电网用电负荷日益增加。
A great way to reduce heat-related injury and death, while also smoothing out electricity usage, is to increase urban tree cover. Trees provide much-needed shade in urban areas. They also cool down the air around them through evapotranspiration – a process trees use to move water through their branches.
减少与高温相关的伤亡、缓解用电负荷最好方法是增加城市树木覆盖。树木可以为城市提供急需的阴凉地，还可以通过蒸散作用降低空气中的温度，树木的蒸散作用是一个通过枝干转移水分的过程。
In the recent study, researchers from the Nature Conservancy, NASA and Stanford University surveyed urban tree cover in 97 U.S. cities. They applied their findings across the country’s entire urban population. The study is one of the most comprehensive on the impact of heat in urban cities, especially since it quantifies the connection to human health and electrical demand across a large and diverse data set.
最近来自美国自然保护协会、NASA和斯坦福大学的研究者做了一项研究，他们调查了美国97座城市的城市树木覆盖情况，并将他们的发现应用于美国所有城市人口。这是一项关于酷热对城市的影响非常全面的研究，特别是它通过大量丰富的数据集对人类健康与用电需求的关系进行了量化。
In previous decades, before air-conditioning became popular in U.S. households, urban tree cover prevented more heat-related mortality. However, as air-conditioning has become more common, electricity costs have increased. The study aimed to determine the costs saved by urban tree cover from reduced electricity consumption, as well as mortality and morbidity from heat-related health problems.
在过去的数十年，空调还没有在美国家庭普及之前，城市树木覆盖防止了绝大多数与酷热相关的死亡，然而，随着使用空调成为普遍的现象，电力成本随之增加。这项研究的目的是确定通过城市树木覆盖从减少电力消耗中节约出来的成本，以及由与酷热相关的健康问题引起的死亡率和发病率。
The study found that, in the 97 cities, each person saved between $21 to $49 each year from the presence of tree cover. When these findings were applied across the entire U.S. urban population, the total amount saved in “heat-reduction services” is estimated to be between $5.3 to $12.1 billion each year.
这项研究发现，这97座城市中的人，每人每年可以从城市树木覆盖中节省21至49美元。如果把这些发现应用到美国全国城市人口中，则每年在“减少酷热服务项目”中总共可节省53至121亿美元。
Shade from urban trees alone can reduce the temperature of buildings and pavement by 10 to 20 degrees Celsius on a summer day. Air temperature changes are more modest at 0.5 to 2.0 degrees Celsius, but even this minor reduction significantly reduces impacts on health and the electrical grid.
在夏季，每一颗城市树木的产生的阴凉地可以为建筑和人行道降温10℃至20℃。空气的温度则较为温和地在0.5℃至2℃下降幅度之间变化，虽然空气温度只是小幅度的下降，但是对于人们的健康风险和电网的用电负荷的影响来说确实是相当大的下降。
While urban trees benefit everyone, it’s worth noting that urban tree cover is thicker in cities with a higher socioeconomic status. Populations in poorer areas where there are fewer urban trees are suffering more from heat waves. When implemented with other changes, increasing urban tree cover in these areas could save more lives and prevent expensive hospital visits for people who can’t afford them.
尽管城市树木的效益惠及每一个人，但是值得关注的是，在经济地位越高的城市，城市树木的覆盖率越密。而在经济基础薄弱的地区，城市树木覆盖越少， 这些地区的人们经受着更多的酷热，这些地方要将城市热效益同其他想要实施改变的状况一同考虑，增加城市树木覆盖可以拯救更多的生命，为付不起昂贵的医药费的人们节省钱财。
来 源：Urban Tree Cover Saves The U.S. Up To $12 Billion Annually
原作者：Linh Anh Cat
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