Shocking changes were uncovered when scientists mapped Earth’s rivers over 35 years

New research shows that over the past 35 years, 44 percent of the largest downstream rivers have seen massive changes in the amount of water flowing through them annually. The cause of these rapid river changes? Fossil-fuel-driven climate change and human activity.

The research was published in the journal Science in early December. However, the cause of the changes wasn’t the main focus of the study. Instead, researchers wanted to focus on the changes themselves. They say that rivers like Africa’s Congo River, China’s Yangtze River, and even South America’s Plata River have seen major declines across the past three and a half decades.

Previous research into river changes has mostly focused on the largest rivers, which means they only produce results that are limited to very specific locations and points in time, Colin Gleason, one of the co-authors of the study, told CNN. However, this new study looked deeper by looking at river changes all around the world at the same time.

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While almost 50 percent of the largest downstream rivers saw differences, Gleason and his colleagues say that 17 percent of smaller upstream rivers saw other drastic changes—an increase in flow rate. Overall, though, the report found that some of the rivers of the world are changing by 5 or 10 percent a year, which is “rapid, rapid change,” Gleason said.

This increased flow rate seen in some rivers is also due to climate change, as snow and ice continue to melt. Faster flows can also have positive impacts, though, allowing for more nutrients to be moved and for fish to migrate quicker. However, not all river changes are good, as those faster flow rates also worsen sediment transportation and can throw wrenches into hydropower plans.

From here, Gleason says that their next step is to determine exactly why these river flows are altering as quickly as they are and devise a way to respond. If we don’t come up with a good response, we could continue to see even more drastic changes over the next several years as climate change worsens.