1.17 x 10^8 and counting…

Ever wondered just how many lakes there are in the world? It turns out, a whole lot!

Scientists based at Uppsala University in Sweden surveyed more than 8000 high-resolution Landsat 7 [1] images to create the largest database of the world’s water bodies, to date. Their estimate: 117 million lakes (> 0.2 hectares) cover the earth, making up nearly 4% of its glacier-free surface area. Laid end to end, the shoreline of these numerous lakes would circle the globe 250 times!

To ensure a reliable analysis, the lakes included in the new global lakes database, GLOWABO, needed to be 2000 square meters or larger, an area nearly the size of two Olympic swimming pools. Even the larger lakes could be tricky to identify: mountain shadows, nearby vegetation, and cloudy water confounded the analysis so the researchers needed to design an algorithm which could untangle any visual uncertainty.

Global lakes databases, like GLOWABO, can help scientists estimate the amount of carbon stored in lake-bottom sediments, as well as the amount of greenhouse gases (like carbon dioxide and methane) lakes release into the atmosphere each year.

While Minnesota boasts more than 10000 lakes, its lakes make up only a fraction of the world's lakes, according to recent research by Verpoorter et al. 2014.  Source:   http://geology.com/satellite/cities/minneapolis-and-st-paul-satellite-image.shtml
The new global lakes database, GLOWABO, quantifies the total number of the world’s lake, including the more than 13000 lakes of Minnesota (the author’s home state), some of which are shown here in the Twin Cities’ chain of lakes. Source: http://geology.com/satellite/cities/minneapolis-and-st-paul-satellite-image.shtml

[1] Landsat is an Earth Resources Technology Satellite that was launched starting in 1972 to collect data and take remote images of the Earth. Earth-observing satellite missions are jointly managed by NASA and the U.S. Geological Survey.


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