Sunday, June 11, 2006 | 7:31 a.m.
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While Las Vegas residents might find it hard to believe that the Southwest could get any hotter and drier, a new United Nations report is warning just that.
Global climate change is just one factor creating the "Mad Max" scenario for the American Southwest and 11 other desert regions around the world, the U.N. Environment Programme says in its "Global Deserts Outlook." Arid regions, including the Colorado River basin that provides nearly all of Las Vegas' drinking water, could see precipitation declines of 5 percent to 15 percent.
The report, prepared by a team of researchers from around the globe, warns that average daily temperatures could rise as much as 9 to 13 degrees Fahrenheit during the next century. The greatest effect will be felt on areas on the margins of existing deserts and "sky islands," such as Southern Nevada's Spring Mountains, which are important locations for biodiversity and ground water recharge.
Some repercussions are already here. The report discusses increased competition for water resources in arid areas, a phenomenon already seen in the Western United States as the seven states along the Colorado River debate how to share the resource - and put limits on its use.
Global climate change, commonly referred to as global warming, is debated by some, but the overwhelming majority of climatologists believe that the warming is happening now and is being driven by man-made emissions from burning fossil fuels.
Deserts are feeling the heat. According to the U.N. report, the world's deserts have seen an increase of 1 to 3.5 degrees Fahrenheit between 1976 and 2000. The global increase during that time has been about 0.8 degrees.
"Profound changes with important implications for water supplies and people, and desert plants and animals, are likely in some regions unless greenhouse gas emissions are dramatically reduced," the U.N. said in a statement accompanying its report last week.
Kelly Redmond, regional climatologist with the Desert Research Institute's Western Regional Climate Center in Reno, says the report's predictions of temperature increases appear to be on the high side of models, but the account of existing temperature changes is on track. Southern Nevada's temperatures, even subtracting the heat effect from the urban area, have gone up "a couple of degrees," he says.
Experimental models show a shift in the jet stream, the river of air flowing around the world, that could mean drier conditions in the southern tier of the United States, he says.
Some other models, including those discussed at a climate-change conference last year in Las Vegas, have shown different results. One scenario is that the Colorado River basin could get about the same amount of precipitation on average, but warmer temperatures would mean more of the wet stuff would come as rain and less as snow.
That's bad news for managers of water agencies that depend on the river because snow better recharges ground water aquifers.
The Rocky Mountain Climate Organization, a Colorado-based group that includes government agencies, businesses, ranchers and environmental groups, said in September that rising temperatures and shrinking snow packs are having a disproportionate effect on the West. By 2100 temperatures could go up 3 to 10 degrees, the group said, citing various climate models.
Bob Wilkinson, a researcher from the University of California, Santa Barbara, agreed with the change of 3 to 10 degrees, and warned that extreme floods or droughts would become more common in the arid West.
While Southern Nevada scientists agree that the climate is changing and that such a change will affect our region, Redmond and other scientists say exactly how that will happen is debatable.
Stan Smith, a UNLV biology professor, points to several studies that show the long-term trend in the Southwest is actually for a wetter, though warmer, climate.
"The uncertainty gets greater when you look regionally, for example to the American Southwest," he says. "We appear to be in a drought cycle in the Southwest. It could be a 30-year drought cycle, and we're just entering it. That's independent of global warming."
Echoing the U.N. report, Smith blames much of the world's desert growth on unsustainable grazing, which is also happening in the American Southwest.
The Southern Nevada Water Authority is working to diversify the sources of water supplying Las Vegas and its suburbs by drilling wells in Nevada's vast rural areas and piping the water to Clark County. J.C. Davis, Water Authority spokesman, says uncertainty over the Colorado River's reliability makes the case for the ground water development program.
New centers of the state's population growth - such as the Coyote Springs development under construction 60 miles north of Las Vegas - also are dependent on ground water.
The U.N. cautions that such programs can make problems worse: "Underground water supplies, some centered around oases and in 'sky islands' - formed over thousands and in some cases over a million years - are increasingly being drained of water for agriculture and settlements including retirement resorts.
"The biggest casualties may be cities in the deserts of southwestern Asia and in the southwest United States."
Davis says his agency recognizes it must "ensure both the environment and the reliability of the water resources are protected We are going to great lengths to identify sensitive environmental resources that will need to be protected as we develop this new water supply for Southern Nevada's municipal customers."
The Water Authority will take only what the rural areas can naturally replenish, he says.
Exequiel Ezcurra, director of the Biodiversity Research Center at the San Diego Natural History Museum and chief editor of the U.N. report, says it summarizes leading research from at least 600 scientific papers and includes the work of about 100 collaborators worldwide.
The experience in Southern Nevada is included in a chapter discussing the relationship of people to the deserts. David Mouat, a researcher and one of several contributors from Nevada's Desert Research Institute, provided the report's overview of Las Vegas' desert history and future.
"Las Vegas has been the fastest-growing large metropolitan area in the United States " Mouat writes. "The implications are tremendous."
While many have benefited from that growth, it also has costs, he says in the report: "Many unique plant and animal species have vanished. Recreational activities for both residents and tourists mean increased pressure on a fragile desert ecosystem."
Mouat wrote the report's discussion of Las Vegas while he was chairman of a U.N. group working on recommendations to stop desertification: the spread of defoliated, barren lands.
"The long-term use of water in places like Las Vegas is probably not sustainable," Mouat says. "Regardless of whether or not we are seeing a period of unprecedented drought, the bigger concern is whether or not we stress seeing a regional environment in such a way as to bring about irreversible changes in unique ecosystems such as springs and seeps."
Although the Water Authority is taking close to its maximum legal amount from Lake Mead, Davis says growth isn't the problem: "Because virtually all of the water used indoors is returned to the Colorado River system, our community's water consumption is largely a function of irrigation, not population. The best evidence of this effect is that Southern Nevada consumed about 20 billion gallons less water last year than in 2002, despite the addition of more than 200,000 residents during that span."
Jim Deacon, UNLV professor emeritus of Environmental Studies, says growth is leading to higher water costs, just one effect on the quality of life in Las Vegas. He expects growth to continue and to affect residents and wildlife.
"Fundamentally, we've decided that economic growth is more important than long-term sustainability," he says. "That will put huge burdens on future generations. These doom-and-gloom stories you hear are real. Mortgaging the future is not just happening financially but also environmentally."
But the report does more than warn of problems. It also discusses potential for desert regions. Tourism is likely to grow in significance as people become more aware of the ecological importance of arid regions, Ezcurra says.
And in a time of skyrocketing energy costs, the desert has an abundance of one resource: sunshine. Harnessing that resource could provide millions with a renewable energy source, he says.
"As photo-solar cells become less expensive, and they have been coming down in price over the last two decades, it is foreseeable that renewable energies will become more important," Ezcurra says. "Solar energy is likely to become very important. And the areas of the world with the highest potential for that are the deserts."
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