For the new study, Boston University researchers examined remote sensing data collected by NASA satellites from 2000 to 2017. Interestingly, the total amount of green areas on the earth's land surface increased by about 5% during this period. This is about 5.5 million square kilometres. Researchers were surprised that China and India were in the lead. According to the study, China alone accounted for 25% of global vegetation growth.
Given that plants are a huge natural carbon sink, an increase in surface "green" is generally considered a good thing. This is correct in theory, but in practice, different plants play different roles in the carbon cycle, so increasing green vegetation may not necessarily slow down climate change. New forests are conducive to carbon capture, but new farmlands often release any captured carbon back into the atmosphere during the harvest season.
According to the team, 42% of China's new greening comes from forests and 32% from farmland. On the other hand, in India, 82% of the increased green plants come from crops, while 4.4% come from new forests. Of course, more farmland means more food production. Researchers say grain, vegetable and fruit yields in China and India have increased by 40% since 2000, mainly thanks to crop rotation, increased fertilizer use and improved irrigation.
Another major surprise of the study was that human activity was responsible for the dramatic increase in new green coverage. In advance, the researchers thought that rising carbon dioxide concentration would be the biggest factor. These new findings indicate that human land use practices need to be included in future Earth system models.
The study was published in the JournalNature SustainabilityIn the magazine.