Plants are a highly effective carbon sink. Globally, forests absorb about 7.6 billion metric tons of carbon dioxide per year, about 1.5 times the annual emissions of the United States.Since the 1980s, climate warming, prompted by rising levels of carbon dioxide and other greenhouse gasses in the atmosphere, has caused an increase in plant productivity in the Northern Hemisphere outside the tropics.But new research published May 30 in Nature Climate Change estimates that summer warming in this region will begin to have the opposite effect within the next half-century, causing photosynthesis—or plant productivity—to decline. The global land carbon sink will likely take a hit as a result, the authors write. The researchers found that generally in the Northern Hemisphere, warmer temperatures will mean less summer plant productivity by 2070 for most regions below 60° N—the approximate latitude of Oslo, Norway, and Anchorage, Alaska. Plant productivity in Arctic areas, however, will continue rising as the temperature increases.“It’s an interesting paper,” says Kai Zhu, an environmental scientist at the University of California, Santa Cruz, who was not involved in the research. The ability of vegetation to capture carbon has grown over the past few decades, but whether this would continue into the future was previously unknown, he explains. The research shows that increased temperatures will eventually lead to decreased photosynthesis, which “will be bad news.” The study focused on the extratropical Northern Hemisphere because it is responsible for 40 percent of the planet’s terrestrial carbon sink, and the hemisphere’s productivity is strongly linked to temperature. In the tropics, water is a larger driver of productivity, so the researchers excluded this region. Scientists used two different ways of estimating the effects of rising summer temperatures on productivity: models that represent photosynthesis based on a variety of environmental factors, and climate models combin …
Climate Change Likely to Slow Plant Growth in Northern Hemisphere – The Scientist
