Rivers and streams cover much more of the planet than geologists previously estimated, according to a new study published in Science. In total, this new estimate shows that, excluding land with glaciers, Earth is covered by just under 300,000 square miles (773,000 square kilometers) of rivers and streams. That’s more square footage than the state of Texas, and it’s as much as 44 percent higher than previous counts.
The finding has implications for the study of climate change, because rivers exchange greenhouse gasses with the atmosphere, especially when humans pollute their waters.
“It was assumed until about 2006 that rivers and lakes were just a pipe transporting carbon to the ocean,” John Downing, a limnologist and biogeochemist at the University of Minnesota Duluth, told Gizmodo. “But the rivers are leaking gasses into the atmosphere.”
As pollutants like fertilizers and sewage seep into water supplies, gasses including methane, carbon dioxide, and nitrous oxide bubble out and drift up into the atmosphere. More river coverage could mean we’re sending even more of those greenhouse gasses into the air than current calculations account for.
“Here’s another reason not to spoil water,” said Downing, who was not involved in the new study. “If you pollute it, you spoil fishing and swimming, but you also spoil the atmosphere.”
To map out the planet’s rivers and streams, University of North Carolina hydrologists George Allen and Tamlin Pavelsky analyzed thousands of images from a NASA Landsat satellite. Using software developed by Pavelsky, the duo ended up with 58 million river measurements they then used to calculate the total coverage of rivers and streams on Earth.
And they didn’t just blindly trust their software. To make sure the program was reliable, the researchers employed what Allen called “a small army of undergraduates” to vigilantly monitor whether the program was measuring rivers, not roads, and if it was avoiding other mistakes along the way. “They were so enthusiastic,” Pavelsky said. “They did such a great job.”……..More Here