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NYT Syndicate
For decades, scientists have been trying to figure out what all the carbon dioxide we've been putting into the atmosphere has been doing to plants. It turns out that the best place to find an answer is where no plants can survive: the icy wastes of Antarctica.
As ice forms in Antarctica, it traps air bubbles. For thousands of years, they have preserved samples of the atmosphere. The levels of one chemical in that mix reveal the global growth of plants at any point in that history.
"It's the whole Earth ” it's every plant," said J Elliott Campbell of the University of California, Merced.
Analysing the ice, Campbell and his colleagues have discovered that in the past century, plants have been growing at a rate far faster than at any other time in the past 54,000 years. Writing in the journal Nature, they report that plants are converting 31 percent more carbon dioxide into organic matter than they were before the Industrial Revolution.
The increase is due to the carbon dioxide that humans are putting into the atmosphere, which fertilises the plants, Campbell said. The carbon in the extra plant growth amounts to a staggering 28 billion tons each year ” three times the carbon stored in all the crops harvested across the planet every year.
In the mid-2000s, atmospheric scientists discovered a powerful new way to measure plant growth: by studying a rare molecule called carbonyl sulfide, which is present only in a few hundred parts per trillion in the atmosphere.
Plants draw in carbonyl sulfide along with carbon dioxide. As soon as it enters their tissues, they destroy it. As a result, the level of carbonyl sulfide in the air drops as plants grow.
As ice forms in Antarctica, it captures bubbles of air, creating a historical record of the atmosphere. Last year, Campbell and his colleagues analysed carbonyl sulfide records from the past 54,000 years.
Since the Industrial Revolution, humans have added extra carbonyl sulfide to the atmosphere, and plants have been pulling it out. In fact, the scientists found, they have been pulling it out at a staggering rate.
"The pace of change in photosynthesis is unprecedented in the 54,000-year record," Campbell said. While photosynthesis increased at the end of the ice age, he said, the current rate is 136 times as fast.
