Greening, but not so great

摘要

Half our planet's vegetated surface has become significantly greener in the past three decades. Plants in many regions - from stocky shrubs of the Arctic to towering trees of the rainforest -are growing more and bigger leaves, according to the latest evidence. Leaf for leaf, it's as if 4.4 billion giant sequoia trees have been added to Earth. This sounds like good news and may buy us a little time, but there is a sting in the tail: the Arctic is greening rapidly, which could be catastrophic. The effects seen are mostly the result of unabated greenhouse-gas pollution. It is no surprise that plants thrive when there's more carbon around, but the impact of extra CO_2 in the air - estimated as causing 70 per cent of greening in the new research - has never been shown on this scale before.