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Earth’s dry zones support a surprising number of trees

New study boosts estimate of forested area in parched zones by at least 40 percent

By
7:00am, June 26, 2017
open baobab forest in Senegal

COUNTING TREES  Researchers analyzed Google Earth imagery of dryland forest plots (one example of an open baobab forest in Senegal, shown) to reveal millions of forest hectares not previously reported.

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Earth’s dry regions have more trees than once thought — a hopeful note in the fight against climate change.

An analysis of high-resolution satellite imagery reveals that drylands globally have 40 to 47 percent more tree cover (an extra 467 million hectares) than reported in earlier estimates. An international team of researchers used Google Earth and Collect Earth, a program developed by the Food and Agriculture Organization of the United Nations in Rome, to estimate tree cover on more than 210,000 half-hectare plots in dry areas of Australia, Africa, the American West and elsewhere.

The new estimate, reported in the May 12 Science, increases by about 9 percent Earth’s total area with more than 10 percent tree cover, adding a zone the size of the Amazon Basin. This is good news: Drylands cover almost 42 percent of Earth’s land surface, and climate change could expand the parched zones by 11 to 23 percent by 2100. The new finding suggests that these dry regions might be able to support the planting of additional trees to help ease climate change and offset expected desertification, the researchers write.

Surprisingly green

This map shows forested (green) and nonforested (yellow) dryland regions in 2015. These areas occupy about 40 percent of Earth’s land surface and harbor more forest than anyone knew, a new study suggests.

map of forested and arid areas on Earth
Citations

J.-F. Bastin et al. The extent of forest in dryland biomes. Science. Vol. 356, May 12, 2017, p. 635. doi: 10.1126/scienceaam6527.

Further Reading

C. Samoray. Parched parts of Earth expanding. Science News Online, October 27, 2015.

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