認為全球暖化效應將反映在主要城市中的英國科學家們表示,都市公園與路樹數量的穩定成長,將可抵銷數十年的預期上昇溫度。這些公園與路樹同時也可望有助於降雨的保存,否則降雨將流至小溪、河流,最後回歸到海中。
英國曼徹斯特大學研究估算,在高樓林立的都市中心,只要增加10%的綠地,都市表面溫度就能降低攝氏4度,等同於華氏7.2度。
上述關於溫度降低的數值,相當於受全球暖化影響之下2080年代的平均預測值。此種降溫的情況,導因於水分從樹葉與植物中蒸發到空氣裡的降溫作用,而這個過程我們稱之為蒸散作用。
安諾斯博士(Dr. Roland Ennos)為曼徹斯特大學生命科學院生物力學專家,身兼一研究團隊領導者,其進一步解釋,「綠地可以匯集並儲存水分,效果比人工造景好上許多。當水分從植物與樹木的葉子中蒸發出來時,它可使週遭的空氣降溫,此種方式類似我們人體的排汗作用。」
British scientists looking at the effect global warming will have on major cities say a modest increase in the number of urban parks and street trees could offset decades of predicted temperature rises. The parks and trees also would help retain rainwater that otherwise drains away into streams and rivers, eventually returning to the sea.
The University of Manchester study has calculated that a mere 10 percent increase in the amount of green space in built-up centers would reduce urban surface temperatures by as much as four degrees Celsius, or 7.2 degrees Fahrenheit.
This drop in temperature, which is equivalent to the average predicted rise through global warming by the 2080s, is caused by the cooling effect of water as it evaporates into the air from leaves and vegetation through a process called transpiration.
"Green space collects and retains water much better than the built environment," explained Dr. Roland Ennos, a biomechanics expert in Manchester’s Faculty of Life Sciences and a lead researcher in the team. "As this water evaporates from the leaves of plants and trees it cools the surrounding air in a similar way to the cooling effect of perspiration as it evaporates from our skin," he said.
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