Changes in Net Primary Production (NPP, in green), a measure of the speed of the photosynthesis process is closely tied to the overall amount of CO2 in our atmosphere (red). For each rise in NPP, CO2 levels fell by a similar amount, and when NPP fell, CO2 rose. Credit: Maosheng Zhao and Steven Running
The blossoming hopes that plants will thrive as the world warms up have been pruned this week by measurements of how much CO2 is absorbed by species on land. Net primary productivity – which measures the speed of the photosynthesis process crucial to plants – fell by 1 percent from 2000-2009, researchers found this week. As photosynthesis turns solar energy, CO2 and water to sugar, oxygen and eventually plant tissue, it’s one way that the world keeps the greenhouse effect in check.
“We see this as a bit of a surprise, and potentially significant on a policy level,” explained Stephen Running from the University of Montana, Missoula. The surprise comes because a previous study had shown that between 1982 and 1999 net primary productivity (NPP) increased by 6 percent, which, Running explains, “suggested global warming might actually help plant growth around the world.” While 1 percent is only a small reverse in comparison to the earlier increase, it still means 550 million tonnes of carbon per year less are being taken into plants than at the beginning of the decade.
Simple Climate 