The world is getting greener, according to a new study published in Nature this week.
Chi Chen, lead author of the study, and his colleagues have been mining data collected by an orbiting NASA camera that monitors green vegetation on Earth's surface, day by day. Even more interesting: They are able to show the exact causes of increasing or decreasing leaf cover in particular areas.
In some cold places, increase in leaf cover apparently resulted from global warming. Since the climate is becoming more and more temperate and the growing season is getting longer and longer, the plants are growing bigger and leafier there.
"One large area of Brazil lost vegetation. I personally checked the data, and that's because of lack of rain," Chen said.
The most striking changes, though, were the result of human decisions in China and India. Both countries have been getting a lot greener.
The greening of India, Chen says, comes from a huge expansion of irrigated agriculture. "Instead of having just crops when it's raining, they also have a whole six months of cropping and greenness when it's not raining," he saves. "This version of greening isn't really so great for the environment, though. The irrigation drains groundwater, vegetation is wiped away at harvest time and the extra chemicals farmers use produce greenhouse gases. "
In China, though, about half of the new leaf cover that Chen detected appears to be the result of a massive reforestation effort. It's a government-supported attempt to prevent disastrous dust storms that resulted from earlier deforestation. "They are really doing a good job," Chen says. "They have a large and comprehensive tree planting program. Those trees will stay in place，capturing(捕捉) dust and also CO2，the greenhouse gas. They'll store it in wood, roots and soil, doing their part to slow global warming. "