MISSOULA, Mont., Aug. 20 (UPI) -- Plant productivity around the world, once on the rise with warming temperatures and a longer growing season, is declining because of droughts, researchers say.
Researchers at the University of Montana analyzed NASA satellite data to discover the global turnaround of productivity, a NASA release said Friday.
Plant productivity is a measure the photosynthesis process green plants use to convert solar energy, carbon dioxide and water to sugar, oxygen and eventually plant tissue.
Researchers Maosheng Zhao and Steve Running said they expected to see similar results as global average temperatures continued to climb. Instead, they found the negative impact of regional drought overwhelmed the positive influence of a longer growing season, driving down global plant productivity between 2000 and 2009.
After a 6 percent increase in the 1980s and 1990s, plant productivity declined 1 percent in the last 10 years.
"We see this as a bit of a surprise, and potentially significant on a policy level because previous interpretations suggested global warming might actually help plant growth around the world," Running said. "This is a pretty serious warning that warmer temperatures are not going to endlessly improve plant growth."
Although the 1 percent decline is not large, it could affect food security, biofuels and the global carbon cycle, scientists say.