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A November 10, 2015 news release from the U. S. Geological Survey describes a paper posted in the U. S. Proceedings of the National Academy of Sciences “Dynamic response of desert wetlands to abrupt climate change”. From examination of fossils in a region North of Las Vegas, NV, researchers determined periods of extreme warmth in which wetlands dried up with extinction of wild life. These warm periods were warmer than today in which wetlands exist. The paper mentioned the timing paralleled ice core data from Greenland.
Below is the graph of Greenland’s temperature in the last 10,000 years. The changes are probably very indicative of temperatures changes across all of the Northern Hemisphere.
Temperatures from Greenland.
About 1,000 years ago average temperatures were about 1 degree higher than today (which makes our concern about a 0.4 degree rise since 1980 rather minor). About 3200 years ago average temperatures were about 2 degrees above current temperatures; all these changes with a relatively constant atmospheric carbon dioxide level of 280 parts per million.
The Las Vegas data is a powerful support for past warming and cooling periods existing during times of constant atmospheric carbon dioxide of 280 ppm. The comparison with Greenland ice core data should be exploited.
James H. Rust, professor of nuclear engineering and policy advisor The Heartland Institute.
Posted: 09 Nov 2015 11:00 AM PST
Summary: According to new U.S. Geological Survey research published today in the Proceedings of the National Academy of Sciences USA, springs and marshes in the desert outside Las Vegas expanded and contracted dramatically in response to past episodes of abrupt climate change, even disappearing altogether for centuries at a time when conditions became too warm
Heidi Koontz ( Phone: 303-202-4763 );
According to new U.S. Geological Survey research published today in the Proceedings of the National Academy of Sciences USA, springs and marshes in the desert outside Las Vegas expanded and contracted dramatically in response to past episodes of abrupt climate change, even disappearing altogether for centuries at a time when conditions became too warm. This new record, gleaned from dirt and rocks exposed in the desert just outside the city limits, provides an unprecedented look into how climate change can affect fragile desert ecosystems in the American Southwest.
Kathleen Springer, a geologist with the USGS and former Senior Curator at the San Bernardino County Museum, was the principal investigator and lead scientist for this study showing that desert wetlands are extremely sensitive to climate change.
“This is a story of water,” said Springer. “Water was plentiful in the desert at times in the past, but when climate warmed, springs and wetlands dried up, and the plants and animals living in the harsh desert environment were out of luck.”
During the Pleistocene, between approximately 100,000 and 10,000 years ago, wetlands dotted the landscape in the area just north of Las Vegas, attracting a plethora of ice age animals, including mammoths, sloths, sabre-toothed cats, dire wolves, and extinct species of bison, horse, and camel, and later, the first human inhabitants to the area.
Today, existing desert wetlands are home to a number of threatened and endangered species that rely on the ecosystem for water in an otherwise arid landscape. Their fate may lie in the hands of a rapidly changing climate.
“What we’re seeing in the geologic record frames what we are observing today,” said Springer. “The drought that California is currently experiencing is extreme, but droughts are an inherent part of the climate system and have occurred repeatedly in the past.”
The study was initiated by the Bureau of Land Management, which called for an integrative approach to studies that emphasize the geological age and context of fossils, as well as a comprehensive analysis of how local hydrologic systems responded to climate change in the past.
“Scientists collect fossils all the time,” said Scott Foss, a senior paleontologist with the BLM. “What is remarkable about this work is the vision that Kathleen had of making sure her team understood the intricacies of the deposits in incredible detail, which allowed them to determine how climate affected the local landscape. It was an immense undertaking, and one that will serve as a benchmark for generations to come for those interested in understanding the effects of climate change on desert ecosystems.”
Studies examining the effects of climate change on springs and desert wetlands will continue through the USGS’s Climate and Land Use Change Research and Development Program, and will build upon the investigations conducted in the Las Vegas Valley, a large portion of which is now protected as Tule Springs Fossil Beds National Monument.
When the monument was established in December 2014, the BLM turned their stewardship over to the National Park Service, who will determine how to interpret the unique land and its former inhabitants for the public.
“The future of this newly designated national monument and what it can tell us about the effects of climate change is all about the past,” said Springer. “And the past is the key to the present.”
Dynamic response of desert wetlands to abrupt climate change
Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming.