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Global WarmingNatureScience

Humans Need the Rivers We are Killing

Rivers across the planet are being drained as a result of human use and climate change in a day and age when we should be ensuring that their safety is one of our top priorities.

Without these rivers remaining healthy, or in many instances returning to being healthy, we are shortening the food chain and making life very difficult for ourselves.

Recent research conducted by a team of scientists led by John Sabo, a biologist at Arizona State University found that, “Floods and droughts shorten the food chain, but they do it in different ways.”

“The length of food chains is a crucial determinate of the functioning of ecosystems,” says Alan Tessier, program director in the National Science Foundation (NSF)’s Division of Environmental Biology, which funded the research.

“Ecologists have long sought to explain why food chain length varies among different ecosystems. This study provides a quantitative answer to that question for stream ecosystems, and provides critical evidence for the importance of flow variation.”

High flows “take out the middle men in the food web, making fish [the top predator] feed lower in the food chain,” said Sabo. “Droughts completely knock out the top predator. The result is a simpler food web, but the effects we see for low flows are more catastrophic for fish–and are long-lasting.”

Studying rivers and streams in the US, the researchers found that large-bodied fish should be more carefully factored into the management of water use, especially as the role of humans and the burgeoning role of climate change begin to impact the waters more.

“Floods simplify the food web by taking out some of the intermediate players so the big fish begin to eat lower on the chain,” Sabo said.

“With droughts, it’s completely different: droughts eliminate the top predator altogether because many fish can’t tolerate the low oxygen and high temperatures that result when a stream starts drying out.”

Humans haven’t been looking after the rivers, using them for agricultural and recreational purposes. Climate change is just another issue that will play a growing role in the years to come. “Climate is giving us a new set of operating terms to work with,” Sabo said. “We will experience overall drying and greater weather variability, both of which will shorten river food chains.

Source: National Science Foundation

Image Source: Steve & Jemma Copley via flickr under a CC license




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