Earth has 117 million lakes: study

Scientists have finally pinned down the number of lakes that exist on Earth - a grand total of 117 million.
Most of the world's lakes are in places where humans don't live, said David Seekell, an environmental scientist at Umea University in Sweden.
"This is something one would have assumed had been done long ago, and was in a textbook somewhere," Seekell said.
Instead of counting lake by lake, earlier estimates were statistical guesses, based on the number of lakes in a parcel of land or on average lake size. One widely cited study from 2006 estimated the lake total at 304 million, 'LiveScience' reported.

The new study, published in the journal Geophysical Research Letters, used high-resolution satellite data and supercomputers to discover that there are 117 million lakes in the world.
However, the bodies of water cover more land (3.7 per cent of Earth's surface) than previous studies had predicted.

This is because quite a few medium- to large-size lakes were missing from older databases, said Cory McDonald, a research scientist with the Wisconsin Department of Natural Resources, who was not involved in the study.
About 90 million of the lakes fall in the smallest size category, measuring 0.5 to 2.5 acres (0.2 to 1 hectare), the study found.

"Most lakes are in the far North, and there's actually quite a few of them," said Seekell, co-author of the new study.
According to the study results, the world's lakes cover about 5 million square kilometres, which is 3.7 per cent of the land uncapped by glaciers.
Most lakes are in the Northern Hemisphere between 45 degrees north latitude and 75 degrees north latitude.
This results from the tectonic scattering of continental landmasses and the past positions of glaciers, the researchers said.
There is less land in the southern high latitudes, and the North's sizable plains were scraped by ice age glaciers, leaving behind millions of pothole lakes.

The majority (85 per cent) of Earth's millions of lakes are at low altitudes, found at elevations less than 1,600 feet above sea level.
The study excluded the Caspian Sea, the world's largest lake, which covers an area of about 371,000 square km. Antarctica and Greenland were also left out of the study.