[雅思培训]朗阁雅思达人全球时事瞭望之气候

【时事聚焦】         近一个世纪，*上森林覆盖面积大幅度锐减，除了人为因素的大量砍伐，也有相当数量的树木由于自然气候死亡。自然气候的改变带来的炎热和干旱导致了*上越来越多的树木奄奄一息。下面我们就来看一则建立在几十篇科学文献基础上，有关此话题的报道。

Tree Deaths Linked To Climate Change

Hot and dry conditions triggered by climate change are killing the world's trees, according to a new report which examines dozens of scientific articles on the subject.

Stanford University graduate student William Anderegg has seen this forest die-off firsthand.

His doctoral thesis documents the impact of drought on trembling aspen, the most common tree in North America.

“These are complete hillsides of trembling aspens that are dying off," Anderegg says. "And when the main tree in a forest goes, you tend to see a lot of the other species, especially the grasses and the wild flowers, tend to disappear as well. But you lose a lot of those species from those forests.”

Changing ecology

With colleagues from Stanford and North Arizona State University, Anderegg co-authored the new report which presents a picture of accelerating worldwide tree deaths that appear to be linked to changes in the global climate.

Anderegg says these changes, triggered by rising levels of heat-trapping gases in the atmosphere, are stressing the world’s forests.

“One of the ways that we expect climate change to increasingly play out in forests is through these widespread tree mortality events where you stress the trees enough that you essentially push a whole region of them off the edge and in fact what happens afterwards, after a forest dies from drought is every bit as important and in some sense matters more to humans who rely on forests.”

Trees provide a range of ecological services. They hold soil in place, help purify water and shelter species. They are valued for timber and tourism. When trees die, the ecology and hydrology of a forest change, which in turn promotes insect infestation and fire.

This can result in long-term shifts in the area’s dominant species and may even trigger a transition to a different ecosystem, such as grass land.

Devastating consequence

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