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The Salton Sea is Crucial Wildlife Habitat. Here's Why.

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The Colorado Delta and Salton Sea | Photo: NASA Earth Observatory
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The Salton Sea as we know it is doomed unless the State of California takes action, and that's bad news for wildlife. The sea's 340 or so square miles of open water, and its hundreds of miles of shoreline, are perhaps the most important bird habitat of comparable size in North America, with only Big Bend National Park in Texas as a potential rival.

More than 375 bird species have been recorded in the Salton Sea and surrounding Imperial Valley area. Most of them are visitors during spring and fall migrations, but the sea hosts a year-round population of birds as well, including shorebirds, raptors, and birds native to the surrounding desert. The sea and its surroundings host about a third of the total North American population of white pelicans, about half the burrowing owls in California, and protected species ranging from the Endangered Yuma clapper rail to bald and golden eagles to peregrine falcons.

But why is the sea such important bird habitat? Part of the answer lies about 350 miles northeast of the Salton Sea, in that large gash in the Arizona desert we call the Grand Canyon.

The precise time when the Colorado River started carving out the Grand Canyon is a matter of dispute, but the majority of Canyon geologists conjecture that that work started somewhere between six million and five million years ago. The scientists agree that the rising of the Colorado Plateau and pulses of higher river water during ice ages both contributed to the creation of the canyon: uplift meant that the Colorado was steeper as it flowed to its outlet, giving it greater erosive power, and wet periods merely added to that power.

That's about all the scientists agree on. There's dispute over just how the Ancestral Colorado, which had once fed landlocked lakes well to the southeast of the present-day canyon, started flowing down toward the newly opened Gulf of California. Some geologists say that one of those lakes eventually overflowed into the Hualapai drainage to the west, while others suggest the Hualapai actually captured the Ancestral Colorado by eroding its headwaters east and into the Colorado's watershed. Still others think the canyon carving got started significantly earlier, with one 2008 study suggesting that the Canyon was actually eroded in two sections that eventually joined in the middle where the Colorado makes a right turn from south to west. That study suggested the cutting started 17 million years ago, which claim is still controversial.

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Regardless of how and when the Canyon got started, however, one fact is incontrovertible: the Colorado River brought a huge amount of sediment downhill to its new outflow between the Baja Peninsula and the mainland.

What does all this geology have to do with birds? Simply this: that sediment is what the Salton Sea's crucial wildlife habitat is made from.

When the swift-flowing river met the sea and its water slowed, it could carry less sediment. Most of the canyon carving waste fell out of suspension and dropped to the seabed, building the Colorado Delta. When most people talk about the Colorado Delta, they're referring to a network of tidal sloughs between the border river town of San Luis Rio Colorado and the gulf, about sixty miles of now almost completely dewatered river channels. In truth, though, the Delta extends another 150 miles north to Indio. Without the immense amount of sediment the Colorado dumped at its outflow, the Gulf of California would reach all the way to Interstate 10, and the Salton Trough would be habitat for saltwater fish instead of burrowing owls. Instead, the land in the Salton Trough is mainly Colorado River sediment, the majority of it once having been rock and soil where the open air of the Grand Canyon is now.

That's even more impressive when you consider that the land from Indio to the gulf is what geologists call a rift valley: a crack in the earth that gets deeper as tectonic forces pull its edges away from each other. The Colorado River had to work hard to fill the Salton Trough with Grand Canyon shavings, as the floor of the trough was dropping almost as fast as the Colorado River could fill it. In some places in the Imperial Valley the sediments are 18,000 feet thick or more. That's three times the maximum depth of the Grand Canyon.

And that basement is still dropping out. The floor of the Imperial Valley, currently covered by the Salton Sea, lies at around 260 feet below sea level. Only a 30-foot berm of deposited river sediment near Mexicali keeps the Gulf of California from flowing in to cover the Polo Grounds in Coachella.

A huge amount of that sediment, as I've said, came from carving the Grand Canyon. But the Colorado Delta and Salton Trough also hold sediment from the entire Colorado River basin, which covers almost a quarter million square miles from Wyoming to New Mexico to Southern California. Thousands of different kinds of soils and bedrocks contributed to that sediment, making it incredibly rich in soil nutrients. That means that not only are the delta and Salton Basin very well watered compared to the hundreds of miles of desert all around them, but they're also fertile -- and that means lush and diverse plant growth, which means even better habitat for local wildlife.

By a million years ago or so, the landforms between the Gulf of California and the Coachella Valley looked roughly as they do today, and the Colorado ruled over all. Even in the relatively arid 19th Century the river was feared for its catastrophic floods. 18,000 years ago, fueled by Ice Age snowmelt in the Rockies and more frequent rains in the deserts, the Colorado must have been formidable indeed. Laden with sediment as it entered its nearly level delta complex northeast of present-day Yuma, the Colorado sprayed back and forth across the landscape like a slow-motion firehose, blocking its path with its own sediment and changing its course with some regularity.

At times, instead of flowing outward into the gulf, the river would bend northwest and flow into the Salton Basin, forming lakes in the Imperial and Coachella Valleys that made the Salton Sea look like a childrens' wading pool. Eventually those lakes would overflow out into the Gulf, and the river would change course again, leaving the remnants of the northern lake to dry up over a few decades. The most recent iteration of that lake, Lake Cahuilla, occupied the Salton Basin until around 1500 A.D. It's uncertain how many times that lake's predecessors filled up and dried out.

So for hundreds of thousands of years, the downhill end of the Colorado River was a 200-mile long complex of freshwater and saltwater wetlands, hypersaline ponds in the process of drying out, and relatively well watered uplands with fertile soil collected from an area the size of France, all surrounded by less hospitable desert stretching for hundreds of miles. It's no surprise that the Colorado Delta complex became incredibly important for wildlife.

Sometimes the river would change course and flow into Ancient Lake Cahuilla, leaving the delta's outflow into the gulf high and dry. That was bad news for the plants and shellfish in the delta that depended on fresh water inflows, but the delta's birds could just pick up and move the 40 or so miles to Lake Cahuilla. Then, when the river changed course again and flowed back out to the Gulf, shorebirds fledged in Indio could head back out to the delta.

In other words, the Colorado Delta complex's sheer scale and diversity brought with it ecological stability. And that was incredibly important for birds all up and down the West Coast of North America from Alaska to Central America, because the Delta and Lake Cahuilla were a crucial rest and refueling stop on the arduous migration along the Pacific Flyway. With hundreds of miles of desert all around, it's no wonder wildlife flocked to the area. And not just birds, but jaguars, pronghorn, pumas and an incredible range of other animals made the Delta and the Salton Trough their home.

That's changed, of course. For a few years in the 1930s as Lake Mead filled behind Hoover Dam, and then again starting in the 1960s with Lake Powell behind the Glen Canyon Dam, no water at all reached the Colorado Delta. Increasing demands for the river's water since have meant that except for rare occasions like this year's famous "pulse flow," none of the Colorado River reaches the Gulf of California.

And even if it did, the silt and sediment that built the delta for millions of years wouldn't get there anymore: it's being impounded behind the chain of dams on the Colorado and Green Rivers, from Flaming Gorge to the Morelos Dam on the border. What was once close to two million acres of thriving wetland habitat has been degraded and eroded to about five percent of its former extent.

That won't last forever. As I wrote a couple years ago, the dams on the Colorado will inevitably fail, releasing all that stored silt in a catastrophe that may be as much mudslide as flood. But unless that happens in the next few years, it won't do the birds on the Pacific Flyway much good.

So we've got the Salton Sea instead: a pale, thin ghost of the massive desert lake that once substituted for the delta's habitat. It's no surprise that so many birds find themselves at the Salton Sea: they've been crowded into a tiny remnant of the habitat that was.

What's more, the Salton Sea isn't just the last remaining piece of the Colorado Delta wetland complex: it's also one of the last large, essentially intact wetlands in the California section of the Pacific Flyway. The chain of coastal wetlands that once lines the state's ocean front has mainly been destroyed over the last century and a half. Interior habitat from Owens and Tulare lakes -- which together offered more than twice the open water surface area of the Salton Sea -- and the chain of wetlands up the spine of the Central Valley have likewise been essentially destroyed. Though the Salton Sea is an artifact of human engineering failure, it offers a few hundred square miles of refueling station and rest area in a part of the Pacific Flyway where most of the other such places have been replaced with industrial harbors, cotton fields, and suburbs.

In fact, recent studies of birds banded at the Salton Sea show that many of the birds actually depart from migration paths traditionally assumed to be part of the Pacific Flyway, ending up in the Great Salt Lake and even as far east as the Midwest's prairie potholes.

And that's what makes saving the Salton Sea so important. Until we decide to decommission the dams on the Colorado and restore the Delta to its full and former glory, the Salton Sea is the stopover habitat that remains, like a shack with a hot dog stand serving travelers while the ancient four star restaurant next door is closed indefinitely for repairs.

If we don't save at least some of the sea's habitat, that leaves nothing for the descendants of the birds that once filled the Delta to overflowing during the migration season, and that loss will echo in habitats from Anchorage to Panama to Wisconsin.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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