二氧化碳排放量增多竟有益處

　　5月12日BBC聽力：二氧化碳排放量增多竟有好處

　　There is a general scientific consensus that growingcarbon dioxide emissions are contributing to globalwarming and climate change. A new study suggeststhat carbon dioxide levels caused by human activityhave also had a positive effect. They’ ve led to amassive increase in plant growth. Our environmentanalyst Roger Harrabin explains.

　　Today’s study in the journal Nature Climate Change has been compiled by a team from eightcountries. Using satellite data, they calculate that between a quarter and a half of the earth’svegetated land has become greener over the thirty-three years since the records began. That’sequivalent to more than four billion giant sequoia trees, the biggest trees on the planet. Thescientists say the rising global temperature has helped fuel the plant boom along with morenitrogen in the environment and shifts in land management. But they estimate that seventypercent of the change has been caused by plants absorbing more of our emissions of carbondioxide because CO2 is a plant fertilizer. This is good news because as plants soak up thecarbon, they are slowing somewhat the pace of climate change by keeping the carbon out of theatmosphere. Some people skeptical about the dangers of the global warming say this provesthere is less need to worry. But the paper’s lead author from Boston University says thebenefit from greening is outweighed by other climate effects, melting sea ice, risingtemperatures, ocean acidification and more.

　　If we tally the beneficial and the harmful effects of having too much carbon dioxide in the air,the net effect is largely negative.

　　And there is another warning, the authors say if the governments don’t cut emissions as theyagreed, there will come a point where the climate warms so much that the capacity of plants tosoak up some of our CO2 is overwhelmed by the carbon that will be released from soils dryingup in the heat. No one knows when that moment will happen.

　　The BBC’s environment analyst Roger Harrabin.

　　Now do you have a fondness for red and black? You may want to rethink that. A study in theUS has found the bedbugs have a strong preference for some colours. The BBC health editorMichelle Roberts came in to explain the scientists’ findings.

　　They got lots of these adult bedbugs and they put them in a dish. And with little triangles oftent-like card of different colours, they found that the bedbugs seem to gravitate towards redor black whereas the ones that they really didn’t like were the yellow and the green.

　　Any indication why they prefer certain colours?

　　It’s difficult to know.

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