Excerpted with permission from The Next Species: The Future of Evolution in the Aftermath of Man, by Michael Tennesen. All rights reserved. Copyright © 2015, Simon & Schuster.

Of course New York City needs the microbes in the soil and the roots from the trees and plants of the Catskill Mountains to clean up its drinking water. And Central America needs mangroves, marsh grass, and coral reefs to slow down the hurricanes that can ravage its eastern coast. But what about Las Vegas? Certainly it doesn't need nature.

Drive down the strip at 11 p.m. on a Thursday night and the hotels that line Las Vegas Boulevard look like amusement park rides filled with customers. The New York-New York Hotel & Casino is a three-story replica of the New York City skyline and the Statue of Liberty. The Paris Las Vegas has a slightly leaning Eiffel Tower in front of it. The Bellagio looks like Venice, with more than 1,200 dancing fountains that move to music on a lake of more than 8.5 acres of water.

Charles R. Marshall, an ecologist at the University of California, Berkeley, says, “It’s so spectacular, out of control, and extreme. It’s one of my favorite places, though that usually horrifies most people I know.” Marshall, who grew up in Australia before coming to the US, was married in Las Vegas. His father was, too.

Though many visitors see only the man-made side of Las Vegas, it does have a natural landscape and history. In the late 1800s, Las Vegas was just a stage stop on the Santa Fe Trail. It had two freshwater springs. Las Vegas is Spanish for “the Meadows.” In 1900, the population had grown to around thirty, which didn’t even make the census.

But in 1904 the town was picked as the ideal layover spot for crew change and service on the Union Pacific train that ran from Salt Lake City to Los Angeles, and the town started growing. In 1928, President Calvin Coolidge signed a bill authorizing $175 million for the construction of the Boulder Dam (later rechristened the Hoover Dam) outside of Las Vegas, and the town went wild. The State of Nevada had long embraced permissiveness, allowing prostitution, quickie marriages, relatively quickie divorces, and wide-open casino-style gambling.

Reputed gangster Bugsy Siegel built the Flamingo Hotel in the 1940s, which attracted the Hollywood stars that were enamored of the Las Vegas “Sin City” scenario. On January 27, 1951, the Atomic Energy Commission tested the first of a series of atom bombs outside Las Vegas. Soldiers were purposely exposed to the tests to gauge the effects of radiation on human beings. Vegas didn’t seem to mind, though the first test left a trail of broken glass across the city. Eventually these tests were moved underground. Over the years Las Vegas has decorated all of its casinos with neon lights—perhaps to make up for the loss of nuclear illumination.

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On a sunny, desert morning I drove a couple miles off the strip to the University of Nevada, Las Vegas (UNLV), and met with Stan Smith, an ecologist. Cactus and yucca surrounded his office on a campus that advertised itself as an arboretum that included the entire 335-acre campus. Smith had been studying how plants adapted to stress. He’d also looked at how climate change would affect the structure and function of desert landscapes and ecosystems.

Smith was raised in Las Cruces, New Mexico, but spent time in Reno, Nevada, and Phoenix, Arizona, before coming to Las Vegas. He was familiar with the Southwest desert, although he claimed most Las Vegans were more familiar with the gambling. “You see slot machines all over—at the airport, at the end of the line at the grocers. People in Arizona and California utilize their desert for recreation. But when I was last on jury duty, the other members were comparing coupons from different casinos to see which ones gave the best rewards. Though there are true outdoor enthusiasts here, most people just aren’t that interested,” said Smith.

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The outdoors may not impress the majority of its Las Vegas citizens and its fortune-seeking visitors, but nature is the real treasure here. Though the desert shrubs cover only about 20 percent of the desert floor, they are the crucial habitat of lizards, snakes, mice, and birds. Birds and bats are important seed dispersers, eating desert fruits during the wet season and spreading their seeds through droppings. These flowers are essential to the health of migrating birds and raptors. The mountains around Las Vegas contain bobcats, coyotes, mountain lions, desert tortoises, and bighorn sheep. Near Lake Meade on the Colorado River just outside Las Vegas, I stood one hundred yards away from a watering hole at midday and saw twenty bighorn sheep, several with large curling horns, as they came to take a drink.

Though it goes unnoticed by most, among the most important natural elements here are the crusts that cover much of the desert in the Southwest. Biological soil crusts form in open desert areas from a highly specialized community of cyanobacteria, mosses, and lichens that cover up to 70 percent of open spaces.

Biological and mineral crusts help keep soil stable, reports Jayne Belnap, a U.S. Geological Survey research biologist in Moab, Utah. A well-developed biological crust is nearly immune to wind erosion. “It’s tough as nails against all wind forces,” she says. Tests in wind tunnels reveal they can withstand winds up to one hundred miles per hour.

But once these crusts are broken, they may become dust sources and fuel powerful dust storms that can travel quite a distance. Biologists have tracked dust storms over Africa spreading all the way to the Amazon in South America. Dust storms over China have been tracked all the way to the US, across the continent, and out over the Atlantic.

If models of Southwestern responses to climate change are correct, Southwest U.S. deserts should get warmer and drier. With less moisture, crusts may not form, and sandstorms could become much more common. Crusts are as important to Nevada residents as gambling, though they may not appreciate them.

As important as the crusts are, Las Vegas owes its life to the water that is brought to the city by the Colorado River. The river begins its journey from the snowpack in the central Rocky Mountains and travels south 1,450 miles (2,330 kilometers), draining an expansive yet arid area that encompasses parts of seven US and two Mexican states.

The Colorado is the principal river of the Southwestern United States and northwestern Mexico. Prior to European settlement, the river entered Mexico, where it formed a large delta before emptying into the Gulf of California off Mexican shores. But for much of the past half century, intensive water consumption upriver has stolen the moisture of the last hundred miles of the river, and it no longer makes it to the Gulf except in years of heavy runoff. For the last couple decades the population growth along this river has been the greatest in the country.

Between 85 and 90 percent of the Colorado River’s discharge originates in snowmelt, mostly from the Rocky Mountains of Colorado and Wyoming. Nevada and other Western states like California and Arizona are already struggling with the problem of diminishing snowpack in their own states, and rely on the Colorado River for much-needed water. Climate change will decrease the volume of precipitation in the Southwest while decreasing the snowpack in the Rockies. Water will be released earlier, which means winter and spring may have sufficient moisture but summer and fall will be very dry. The critical part of this equation for Las Vegas and the Colorado River is increasing use by other desert cities, including Phoenix and Los Angeles.

Emma Rosi-Marshall, an aquatic ecologist at the Cary Institute of Ecosystem Studies, works with native fish in the Colorado River. The two major dams, the Hoover Dam near Las Vegas and the Glen Canyon Dam below Lake Powell in Utah, have had major effects on wildlife and fish in the Colorado River, altering their natural ecosystems, drowning their habitat, and changing the temperatures of the waters in which they evolved. Worms, snails, and many native aquatic insects have disappeared, important food sources for native fish. The result has been the decline of half the native fishes in the Grand Canyon ecosystem.

State water agencies now release water at different times of the year to try to imitate natural runoff. But the benefits of this strategy remain under investigation. It may be that the Glen Canyon and Hoover Dams have altered the river’s ecosystem beyond the point where regulating the flow of water through the dams is going to achieve anything like the natural flow of water that existed before them.

The fact is the river is rapidly losing its water, an issue with repercussions for practically every animal and every plant that relies on it, including man. The volume of water in Lake Meade is down to about 40 percent. Las Vegas currently has two major pipes drawing water out of the lake, but the city needs more. Below Lake Meade, the river is drying up. One of the biggest water users is agriculture in Southern California, and UNLV ecologist Smith wonders just how important and productive those farms are. But if you get rid of local agriculture, then you have to go farther away for your food, inevitably putting more CO2 in the atmosphere from food transport, and that could result in further decreased snowpack in the Rocky Mountains and diminished rains in the Southwest desert, causing water levels to fall even lower. As at the craps tables at the nearby casinos, in the end you just can’t win.

The Las Vegas Valley, which includes the city, has a population of close to two million, about two-thirds of the people in the entire state. Engineers are proposing to tap underground waters of upstate ranchlands with 145 huge wells spread out over 20 percent of northern Nevada and connected by one thousand miles of pipe. Such a situation occurred about one hundred years ago when Los Angeles went looking for water in the Owens Valley about three hundred miles upstate on the eastern side of the Sierra Nevada mountains. Los Angeles bought up water rights from Owens Valley residents and sent all the water south.

The Owens Valley slowly surrendered its moisture and the farmers and ranchers moved elsewhere. Water diversions for Los Angeles residents left Owens Lake bone-dry by 1920. Then the dust started blowing. By the 1990s, the Owens Lake playa was the largest producer in North America of PM10 atmospheric dust—particulate matter small enough to enter human lungs. The courts forced Los Angeles to put some water back into the lake, though ecologists continue the fight for more changes in water and land use there. According to Greg Okin, a professor of geography at the University of California, Los Angeles, “Climate models predict that the Southwest should get warmer and drier, and that by 2050 soil moisture could be lower than the US Dust Bowl Era.”

The Dust Bowl occurred in the Great Plains of Midwestern America in the 1930s. An unusually wet period had encouraged people to settle there, and the existing rains convinced many to begin plowing the grasslands deeply. This destroyed the grasses, which normally trapped soil and moisture during times of drought and high winds. Thus when drought came in the 1930s, there was little grass to hold the topsoil. In 1930 an extended and severe drought caused crops to fail, leaving the plowed fields exposed to wind erosion, which carried the fine soils east.

The “black blizzards,” as the dust storms were called, began blowing, with disastrous consequences. In May 1934 two dust storms removed massive amounts of topsoil from Great Plains farms and carried it all the way to Chicago, dumping 12 million pounds of dust on that city, before turning toward Boston, New York City, and Washington, DC. It has been called the worst drought in US recorded history.

Las Vegas is a human phenomenon, an incredibly large futuristic infrastructure that was built almost entirely in the last hundred years. In 1900 there were about thirty settlers in the valley. Today it has two million. If it took only a hundred years to get to where it is now, how many more years—one hundred? two hundred? three hundred?—will it take to get to the point where there is not enough water for the city to survive, the desert crusts vanish, the dust starts blowing, and the tourists go home?

To get a glimpse of that dusty, thirsty future, all one needs to do is head down the Colorado River to where it ends about fifty miles south of the US border. The water that lies in its bed there is but a shallow, narrow swamp of salt and pesticide-laced runoff from crop irrigation. This is a far cry from the past.

Aldo Leopold, an American ecologist, forester, environmentalist, and author of A Sand County Almanac (1949), once described this Colorado River Delta as a “milk and honey wilderness where egrets gathered like a snowstorm, jaguars roamed, and wild melons grew.” Today, the Cucapá Indians eke out a living in an estuary that is filled with weeds, trash, and occasional swamps of unhealthy water.

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Or perhaps the real future of Las Vegas might lie on the banks of the Salton Sea in Southern California, about 120 miles north. This area was born when the Colorado River temporarily diverted into the Salton Sea in 1905. For a time, runoff from farms kept the lake level constant if not polluted. Though the largest lake in California, the Salton Sea is also the lowest, and its water is saltier than the Pacific Ocean.

The Salton Sea enjoyed some success in the 1950s as resort communities grew up on the eastern shore and looked promising for a while. But with no outflow, the lake kept getting more polluted. In the 1970s, most of the buildings constructed along the shoreline were abandoned.

The birds that migrate to the south side of the lake in winter still draw bird watchers, but that is primarily because all the marshlands in the Imperial Valley, where the Salton Sea lies, are taken up by agriculture. There’s no place else for the birds to go.

There are still some scattered houses on the west side, but the east side of the sea around the former yacht club is mostly old abandoned trailers and assorted ruins.

Las Vegas could get there, too. If the water in the soil gets below Dust Bowl levels, the crusts would break down and the sands might pick up and fly with the wind. If the water runs out and the city goes dry, it wouldn’t take long for the golf courses, the fountains, and the swimming pools to lose their appeal. And if the desert gets hotter and dryer, the great migration and construction boom of the last fifty years could take its final bow.

Some future artist might revel in the rusted infrastructure of the famous Sin City, go looking for relics of slot machines in the nearby dump, or collect neon artifacts for some museum. Or he or she might go rummaging through old books or magazines to read tale of how Sin City finally succumbed to drought, dust storms, and sky-high electric bills, and the day the last neon light flickered out.

In the end Nature holds all the cards.