Eight-year study found that more frequent and severe drought, dropping water tables and springs dried up prompted some of the aquatic ecosystems of the desert in "catastrophic regime change" that many would not be resumed.
The results, recently published in the journal Freshwater Biology, suggest that climate change, over exploitation of groundwater for urban use of water and land management can permanently affect the species can survive. The research was funded by the National Science Foundation.
"People that have persisted for hundreds or thousands of years are now in danger of extinction," said David Lytle, a professor of zoology at Oregon State University. "Springs used to be in permanent dry. They were intermittent perennial streams. And a kind used for raising and lowering of the population are disappearing."
The study, conducted by Michael Bogan and Lytle PhD, explore the full effect of dehydration and its impact on aquatic insect communities in the former perennial desert stream in Arizona, French Joe Canyon, before and after a severe drought in early 2000.
The river has dried completely in a period in 2005 and again in 2008 and 2009, leading to what researchers call a "regime change" in which rapid species have disappeared locally, and others have taken their place. Dynamic ecosystems are now different, and shows no sign of returning to their previous state. Six species were eliminated when the river dried up, and another 40 were more abundant. Large "predator" as the giant waterbug disappeared and were replaced by smaller "mesopredators" such as water beetles.
"Before 2004 the area was like a beautiful oasis with lots of vegetation, birds and rare species," said Lytle. "Spring has lost several important species of insects, the water is much less, and now has very different properties."
Phenomena, the researchers say, is not so much to show the loss of human life - is plenty much as before. It is not the same.
"Our study focused on a single stream in isolation, but the drying process and the local extinction occurs throughout the southwestern desert," said Weiser. "Ultimately, this could lead to the loss of species throughout the region, or the extinction of species that depend on these desert oasis. "
Small streams of this type are of particular interest because it may be easier to observe and study the major rivers and streams, and may represent a microcosm of similar effects occurring in much of the American West, the researchers said. The speed and the speed of some species do not change given sufficient time to adjust.
"It's like comparing old growth forests to second," said Lytle. "There are still trees, but this is not the same ecosystem, it used to be. These streams of the desert can be a window to help us see the forces at work around us, if it is due to climate change, land management and other factors. "
The researchers noted in their report that the last 30 years have seen a significant increase in the severity of the drought in the southwest. The drought that helped dry French Joe Canyon in 2005 resulted in low stream flow in Arizona for 60 years and in many cases, the lowest ever recorded. In French Joe Canyon, the creek bed was completely dry for the base, leaving many aquatic invertebrates, dead in the sediments.
It 'was probably an "unprecedented chaos", the researchers said in their report. Community composition changed radically, and long-lasting insects are dying off and a smaller, shorter than those taking their places.
Similar happened in the past of Everglades plant communities in Florida, floods in Australia, and boreal forests following fire disturbances, other researchers have found. Climate change in the southwest to predict periods of drought longer, more frequent and more intense in the next century, scientists have discovered in his investigation.
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