Satellites show Earth is greener

Daily observations from space for nearly 2 decades indicate that our planet is getting greener.

Satellites gathered data from 1982 to 1999, measuring the amount of chlorophyll on Earth. Analyses show that Earth’s net primary production–a measure of how much foliage plants generate and, by inference, the amount of carbon dioxide they absorb–jumped about 6 percent over the period. On a global basis, land plants pulled 12.5 billion metric tons more carbon dioxide from the air in 1999 than they did 18 years earlier, says Ramakrishna R. Nemani of the University of Montana in Missoula.

Although the concentration of carbon dioxide in Earth’s atmosphere rose about 9 percent during that period, not all of the extra greenery stemmed from that gas’ fertilizing effect. For example, large swaths of India received extra rainfall in the 1990s from that decade’s strong monsoons, says Nemani. Also, decreased cloud cover over Amazonian rain forests enabled the trees there to slurp up 5 billion more metric tons of carbon dioxide in 1999 than they did in 1982.

Net primary production in some regions did decline from 1982 to 1999. Cooling in Siberia led to a shorter growing season there, and a drop in precipitation in northern Mexico and the southwestern United States stunted growth of vegetation.

Nemani and his colleagues report their analyses in the June 6 Science.

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