TEMPE, Ariz., Oct. 14 (UPI) — Human and natural impacts on the world’s rivers are affecting their central role in supporting global fish species, U.S. researchers say.
Scientists at Arizona State University say rivers and streams around the world are being affected by human use, or drying up due to climate change, altering the natural variability of river flows, ScienceDaily.com reported.
Some rivers have dried completely and no longer run, while others are experiencing extreme variability of flows due to storm floods.
The two forces are conspiring to shorten food chains, especially by eliminating top predators like large-bodied fish, one researcher says.
“Floods and droughts shorten the food chain but they accomplish this in different ways,” John Sabo, an ASU associate professor in the School of Life Sciences, says. “High flows take out the middle men in the food web making fish (the top predator) feed lower in the food chain; droughts completely knock out the top predator.
“The end result in either case is a simpler food web, but the effects we see for low flows are more catastrophic for fish, and much more long lasting,” Sabo says.
Sabo and his fellow researches urge the fate of large bodied fishes be more carefully factored into water management decisions, especially as growing human populations and climate change continue to affect water availability.
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