The year we lost the deserts.
The gravel crunches beneath our boot soles. A prairie falcon circles above the ridge to the south, scanning the ground for packrats and pocket mice.
Four months ago, this road wound past a relatively lush Mojave landscape. There were Joshua trees, the contorted signature yuccas of the Mojave Desert. There were Mojave mound cacti and blackbrush, widely spaced bunchgrasses and iodine bush, and treacherous, heavily armored cholla cacti. A few miles upslope grew ancient pinyon-juniper forests, whose fruit fed the Chemehuevi people for generations before the arrival of Europeans.
Today, all that remains is charred soft, stray singed clumps of cacti, and an occasional blackened Joshua tree. Most of the plant cover is gone, with only charcoal smears where once a shrub or patch of grass grew. The burned land stretches a dozen miles to the south, and about five to our north.
We walk along Black Canyon Road in the heart of the Mojave National Preserve, one of the largest national parks in the 48 contiguous states. On the evening of June 25, 2005, a thunderstorm rolled across the land south of here. Bolts of lightning ignited small fires, one of them near the Preserve's popular Hole In The Wall campground. Within a day and a half, fire had spread to more than 70,000 acres. Most of the preserve's pinyon-juniper forest was lost, perhaps permanently. A number of irreplaceable historical and archaeological sites were damaged or destroyed, as were five private homes. An untold number of wild animals was killed. During one particularly hellish hour and a half on the evening of June 26, the fire front advanced almost five miles--a firestorm so swift that all but the fleetest of animals in its path were doomed.
Here on the margins of the fire, animals have begun to explore the charred landscape. We see a black-tailed jackrabbit, then another, and another. In the month since the fire, some of the yuccas have pushed up new shoots from their underground stems. The hares have eaten some of them. Dragonflies buzz back and forth along the road, several miles from the nearest water. A set of coyote tracks leads along Cedar Canyon Wash. Coyote will dine well for a few weeks on roasted rabbit and packrat. There is some evidence of renewal here.
But this desert landscape may take a very long time to heal. The process could take hundreds of years, if it happens at all. And though the scope of June's Hackberry Fire in the Mojave National Preserve is mind-bendingly huge, this was by no means the largest of this year's desert fires. About a million acres of the Mojave and Sonoran deserts burned in 2005, making it the worst fire year in the deserts' history.
Fire is a crucial component of many North American ecosystems, from the California chaparral to the grasslands of the Great Plains. Over the millennia, plants in these landscapes have evolved adaptations to fire. Some, such as the closed-cone pines of California, even depend on fire for reproduction. Decades of fire suppression in Western forests have caused a significant amount of ecological degradation, and fires are often essential to restoring a semblance of balance to the landscape.
But the desert is different. With less fuel and wide stretches of bare soil characterizing much of the Mojave and Sonoran deserts, fire never became a facet of the landscape. Much of the land burned had not seen fire since the end of the Pleistocene.
Four inches from hell
Between them, North America's Mojave and Sonoran deserts occupy more than 140,000 acres of North America. The Mojave, the smallest of North America's four deserts at 22,000 square miles, is wedged between California's Sierra Nevada and Transverse Ranges to the west, and the Colorado Plateau to the east. Its access to coastal moisture blocked by 10,000-foot mountain ranges, the Mojave is, usually, an exceedingly dry place. At Bagdad, a former water stop on the Santa Fe Railroad, residents went from July 1912 to November 1914--767 consecutive days--without seeing a single drop of rain. No one lives in Bagdad now.
The Sonoran desert gets a bit more precipitation. It abuts the Mojave to the south, running from California and Arizona down into Mexico--120,000 square miles of varied, biodiverse landscape. Closer to the gulfs of Mexico and California than is the Mojave, the Sonoran Desert enjoys two distinct rainy seasons--one in the winter and another during the summer monsoon months. As a result, its vegetation is more abundant than the Mojave's.
Where water is at a premium, plants must fight for every drop. Most years, roots of thirsty established plants keep the soil too dry for seedlings to take hold. Some plants, such as creosote bush, secrete herbicidal chemicals that keep other plants from growing near them. As a result, both deserts comprise immense stretches of what at first glance seems to be bare mineral soil, with widely scattered shrubs at regular intervals.
The soil is not exactly bare between the shrubs. In many places, where no cattle, hikers, or off-road vehicles have churned the landscape, a fragile crust of cryptobiotic organisms covers the land. These half-inch, dusky crusts are made up primarily of cyanobacteria and can include lichens, fungi, mosses, algae, and bacteria. The crusts grow exceedingly slowly, on the order of an inch a century in drier parts of the desert. Where they are disturbed, desert winds can scour the soil beneath.
As parts of the Basin and Range region of the Western US, the Mojave and Sonoran deserts are full of small mountain ranges, with different vegetation at different altitudes. Joshua trees grow in the Mojave from 2,000 to about 6,000 feet. In higher parts of the Sonoran Desert--for example, the "Arizona Upland," near Tucson--saguaros, leguminous trees such as palo verde and mesquite, and other striking plants appear. Conifer woodlands grow in the highest reaches of both deserts; single-leaf pines and junipers predominant, with an understory of resinous shrubs such as blackbrush.
Down on the valley floors, there is little combustible plant matter. Fires burn only a few square feet before exhausting themselves. I camped once in an unnamed California valley in the Sonoran Desert. A grove of ironwoods grew in a wash on the valley floor. Within that grove, hundreds of years worth of dead wood had accumulated. Ironwood is a relative of mesquite; it has a much heavier wood that burns far hotter. It is easy to light, and I burned a few hand-length sticks of it in a small fire. I had to sit six feet away to keep from singeing the hair on my arms. If there had been a wildfire in that valley in the previous four or five hundred years, that valley would have looked very different. It simply had not burned since Columbus landed in the Americas, or perhaps longer.
But the desert is fireproof no longer. Ten thousand years of history changed with the advent of a handful of invasive plant species. Some were introduced accidentally, others deliberately by ranchers or landscapers. Dozens of them now spread across the landscape, each posing its distinct problems. Tamarisk invades washes and watercourses, its deep roots depriving other desert plants of scarce groundwater. It burns like a blowtorch. Invasive grasses, buffelgrass, red brome, and cheat among them, have radically altered millions of square miles of the Western US. The most frightening invader is Sahara mustard; land managers' voices rise in barely suppressed terror when discussing it. In a mere few decades, these plants have brought entire desert ecosystems to the brink of extinction.
Buffelgrass (Pennisetum ciliare) is an African species introduced to Arizona in the 1930s. In the late 1950s ranchers in Sonora, Mexico began to plant it as a forage crop. The grass has spread, if you will pardon the expression, like wildfire throughout the hot Sonoran Desert.
Buffelgrass's deleterious effect on the landscape isn't limited to its extreme flammability. "Imagine that there's a lot of barren space between the shrubs and cacti in the Sonoran Desert," says Julio L. Betancourt, a USGS scientist who for the past 25 years has been based at the University of Arizona's Desert Laboratory in Tucson. "Every El Nino, you get a lot of winter rain, and the land is covered with a 'green-up' of winter annuals that make up the spring desert wildflower display." (Half of the plant species in the Sonoran desert are annuals, with 60 to 80 percent of those winter annuals.) "Otherwise, the soil between the shrubs is bare. Generally, there's a lot of available soil nitrogen [a crucial plant nutrient] in the Sonoran Desert, but no plants take advantage of it until you add water.
"Then, in comes buffelgrass," Betancourt continues. "It's a summer-flowering grass that spreads through this barren space that otherwise is only full during El Nino events. Buffelgrass is a nitrogen hog, and thus suppresses the green-up of spring wildflowers. A lot of rodent species--the kangaroo rats and the other heteromyids--are granivores. They're sustained by the seed crop of those winter annuals. A lot of the biodiversity we see in insects--the native bees especially is sustained by those same wildfiower displays. So you get a kind of cascading effect when buffelgrass is introduced."
But the worst of buffelgrass's impacts is the role it plays in fire. Though native plants provide little fuel for wildfires to consume, buffelgrass is another matter. Fireflghters in Tucson have reported stands of the grass generating walls of flame 25 to 30 feet tall, enough to incinerate the sturdiest desert vegetation, not to mention homes. Rick Flores, an official with the Tucson Rural/Metro Fire Department, summed it up in an interview with the Tucson Citizen: "Just the nature of these burns makes them dangerous. The flame length and how quickly [fires] spread is creating very dangerous situations for our firefighters."
"It used to be that 95 percent of what Tucson firefighters did was to provide emergency services to senior citizens," adds Betancourt. "We simply haven't had that kind of wildland fire here. In Hermosillo, Sonora, where the buffelgrass is just all over, they have wildland fires annually. That's what we can look forward to in Tucson."
And after a buffelgrass-infested landscape burns, the native plants suffer, while the invasive grass comes roaring back in the next wet season. "Imagine a Tucson and surroundings burning almost annually," says Betancourt, "all of the charismatic flora and fauna being permanently erased. After a fire, it's buffelgrass forever."
Unfazed by cold winters
In a remarkable bit of Federal cross-purpose ineptness the Department of Agriculture, at the urging of its ranching constituency, has bred a more cold-tolerant strain of buffelgrass, called "Frio," even as federal agencies such as the National Park Service spend thousands of dollars attempting to eradicate it. But until the USDA succeeds in spreading its monstrous progeny to colder deserts, buffelgrass is confined to the Sonoran Desert, where winter temperatures don't drop too far below freezing.
In the colder Mojave Desert, as yet uninvaded by buffelgrass, red brome (Bromus rubens) fills the invasive fuel load grass role. A cool-season annual with a wispy structure, brome grows much more slowly than buffelgrass and provides significantly less fuel for wildfires. But where it doesn't compete with buffelgrass, red brome does an adequate job of fueling wildfires in areas that have not known them in thousands of years.
"Before a fire in the Mojave," says Todd Esque, a research ecologist with the USGS's Las Vegas office, who for decades has studied the effects of wildfire on desert ecosystems, "you might see a diverse set of small native shrubs. There will be cacti, creosote bush or Joshua trees, and so forth, with red brome filling in what were once bare spots between them. Visit the spring after a fire, and you may see just a sea of red brome filling the area up to the margins of the burn."
Some of red brome's growth habits make it an effective competitor to native plants and a notable fire threat in its own right. An annual, brome germinates, grows and sets abundant seed all in the course of one season, robbing critical soil moisture and nutrients from native plants. A typical red brome plant looks to be mostly seedhead, a top-heavy burgundy spray of angular bracts on absurdly thin stems. For some reason, red brome doesn't seem to suffer much grazing pressure from desert animals, with the exception of the occasional desert tortoise. Not only can most brome plants set seed without being grazed, but each year's drying brome crop may add to the desert fuel load for several subsequent years.
The desert climate is characterized by long periods of drought broken sporadically by very wet winters. Red brome can spread even under dry conditions, but it is during the El Nino winters that it marches across the landscape, posing the greatest danger of fire in subsequent springs and summers. After a season of heavy rain, brome seeds will burst into life, suppressing native wildflowers and increasing the species' dominance over the landscape.
In the Mojave's higher altitudes, those wet years also spur a few native shrubs, such as blackbrush (Coleogyne ramossisssima), which are flammable enough in their own right. Even in the absence of invasive plants, a Mojave summer might see a few lightning-ignited fires scattered across the landscape. But with red brome to carry flames from one place to the next, the Mojave's fires now encompass more territory.
Once the desert burns, native plants are very slow to recover. Environmental mitigation workers have found that it's very difficult to revegetate a disturbed section of the Mojave. On highway berms or reclaimed mines, native plants installed carefully by hand enjoy a survival rate rather close to zero. Only with consistent irrigation and protection from herbivores can one expect to have a few transplants survive. In the wild, where the plants must survive from tender seedlings rather than five-gallon-container transplants, very few new plants live to maturity, and they're generally the ones that sprout the next wet winter, five or ten or twenty years hence.
"Even assuming little interference from invasive plants," adds Esque, "the original vegetation may never come back. You have to distinguish between natural recovery and what you could call 'visual erasure' of the damage. Just because it looks recovered doesn't mean the land isn't still damaged. Look at the work Robert H. Webb did in Death Valley. He surveyed old ghost towns ... On some of those sites it took 70 to 100 years for vegetative cover to reestablish, and even after all that time the species composition was different from the original landscape."
With the advent of red brome, the land is consigned to what ecologists call the "grass-fire cycle." Fires might happen as often as every five or ten years. Even "visual erasure" may be forever delayed.
The weed with roots in hell
Along with brome and buffelgrass, a handful of other grasses have altered the fire ecology of the desert. Cheatgrass (Bromus tectorum), a relative of brome, has spread throughout millions of acres of the cold Great Basin Desert. Buffelgrass' cousin fountain grass (Pennisetum setaceum), still sold by nurseries, thrives in colder Sonoran Desert mountain canyons. A few other species, especially tamarisk, have been identified as fire risks.
But no other plant sends a chill down the spines of both land managers and firefighters the way Sahara mustard does. The mustard (Brassica tournefourtii) is a supremely tough annual weed that can survive in a huge range of conditions. Growing on roadsides or trackless wilderness, sand dunes, valleys, or solid rock faces, Sahara mustard is a fast-spreading plant that poses a fire risk orders of magnitude greater than its colleagues'.
In a few short weeks, Sahara mustard can grow to three feet tall, and as wide. The plants are thought to be self-fertile, needing no other plant's pollen to set viable seed. A single seed germinating in an empty valley can mean thousands of offspring the next year. After the plant sets seed, it dies back, often becoming uprooted and blowing around the landscape as a tumbleweed. Seeds from one plant can thus scatter over several miles of landscape. Rodents find the seeds tasty; they collect and cache them, and the caches often germinate in the next wet year. A field of Sahara mustard is a monoculture, with a thick carpet of leaf rosettes smothering any native wildflowers, and three-foot flower stems covering any low-growing native shrubs.
The mustard was introduced to California's Salton Sea area sometime in the early 1930s. It arrived in Arizona in 1957, and by the 1990s was well-established throughout the California and Arizona portions of the Sonoran Desert. With wet years in 1997-8 and since, the plant has exploded into previously uninvaded desert, reaching the south end of Death Valley this year.
Valleys south of Joshua Tree National Park that once hosted stunning displays of evening primrose and sand verbena now hold a single-species stand of mustard. At Lake Mead near Las Vegas, Elizabeth Ann Powell, a Park Service botanist, wrote a blunt summation on a Web page dated April 2005:
"There is no need to nit-pick details on Sahara mustard--we have a disaster on our hands ... These infestations have now gotten so huge, we can't deal with them all. Plants get huge along the shoreline where there is ample water and these huge ball-like plants break off and the plants blow up onto the dunes. A great deal of the shoreline is now infested and plants have moved up out of the drawdown zone into open desert. We can't stop it."
When Sahara mustard dies in late spring, it becomes tinder. As it grows in a thick, uniform carpet across all but the stoniest ground, a lightning strike or a tossed cigarette, or hot tailpipe, or campfire--can cause a fire that spreads for miles. Any low-growing plants not yet smothered by the weeds die in short order from the flames. Taller plants such as saguaros or Joshua trees fare little better. Burned Joshua trees might linger for a few weeks after a fire, perhaps sending up new, healthy shoots from one damaged tree in ten. Saguaros may live a bit longer. In studies of desert wildfires, Esque and his colleagues note that "middle-aged" saguaros those between eight and 35 feet tall--survived fire moderately well. (Of course, survival is probably reduced by repeated fires.) Even those saguaros that succumb to fire may linger for five or six years, adequate time to set thousands of seeds. But if fire returns, those seeds--or the sprouts that germinate from them--will die. Once an area burns, unless measures are taken in perpetuity to control the invasives, that area is irrevocably altered.
With each wet winter, as invasive plant species expand their range and then burn, more and more of the desert is erased.
Is there any hope at all?
What can be done to control the plants? The question makes experts sigh.
"I honestly don't know how we're going to fix this problem," says Esque. "I don't know if we can. Everything we've thought might work has failed. Now we're in the position of looking at things we don't think will work. But we can't just give up." Betancourt agrees. "What I tell people is, 'You better know full well what the consequences of doing nothing are.'"
Betancourt has seen some limited success in buffelgrass control on Tumamoc Hill, the mountain near downtown Tucson where the Arizona Desert Laboratory is located. The oil pipeline company Kinder Morgan has provided some funding for buffelgrass removal on Tumamoc Hill as part of a mitigation arrangement, and local native plant fanciers organize "weed whacks" in the nearby Tucson Mountains. But piecemeal efforts, though they may protect patches of land in the short term, are not a solution. "It doesn't help much for us to work on buffelgrass if the people who manage the land right next door don't do anything with their problem," says Betancourt. "It's all for one, one for all or not at all. I don't think you can eradicate buffelgrass. The issues are so complex. There are international issues, inter-agency issues." Indeed, while land managers in the US increasingly turn their attention to buffelgrass control, some of their counterparts in Mexico are still planting the species, in a legacy of the 1960s-era forced agriculturalization of the desert. Mexican environmentalists who might be moved to work on the issue have their hands full.
"There are so many environmental problems pressing Mexico," Hombre Aridjis--of the Mexican environmental group Grupo de los Cien--told Tucson Weekly in 1996. "Certainly zacate buffel is one. But it is only one. We have so many battles to fight."
And buffelgrass, for all that, is relatively easy to eradicate from a small area, requiring only consistent and diligent glove-and-pickaxe labor. Annual plants pose a much greater problem, especially Sahara mustard, whose stout taproot resists pulling from all but the sandiest soils. "A perennial you can just pull up mechanically," says Betancourt. "With annuals spread over a wide area, you're talking herbicides, and in the Sonoran Desert you may have less than a month's window to use them in."
Esque admits to having reached the point of desperation. "We have to do something. I would be willing, on an experimental basis to try grazing in small plots. With goats, perhaps. Kochia prostrata [a non-flammable desert-adapted forage plant currently thought to be non-invasive] could be planted as a firebreak: Put in some small plots, watch it very, very carefully, and if it gets too out of hand, nuke the stuff and wipe it out. Whatever it takes. We were here and saying the same thing in 1993, during that big fire year. If they don't do something this time, we'll be back in this same place in another ten years, except that the situation will be that much worse."
One solution being touted in the immediate wake of the Hackberry Fire was to reverse the Mojave National Preserve/National Park Service (MNP/NPS) policy of removing livestock from the Preserve. In a widely-forwarded e-mail, Preserve neighbor Dennis Casebier--an outspoken desert lover who is no particular admirer of environmental activists--said:
"The point is that if cattle had been present they would have eaten much of the grass and other fuel[,] making it more difficult for the fire to spread. This of course reflects on another disaster MNP/NPS is responsible for, i.e., removal of cattle from the East Mojave. There are, however, cattle yet on the 7IL Ranch, so MNP/NPS is quick to point out that fires burned in areas where cattle are yet grazing. And that is true. Yet you don't have to be a rocket scientist to deduce that if cattle have grazed an area, that area will be less susceptible to fire."
Esque is skeptical. "The problem is that the different management goals have conflicting needs. We know we can reduce fuel to reduce fire, but if we do it puts us in conflict with preservation of wildlife species. Less vegetation results in less food for desert tortoises. If you increase food for livestock, you reduce food for wildlife and change ecological processes. Dilemmas like this make me glad I am a researcher and not a land manager."
Even if cattle do turn out to be a way to reduce fuel loads in the short term, they have markedly increased fire risk in the long term. Aside from the fact that buffelgrass wouldn't be nearly so widespread were it not for cattle ranching, cattle spread seeds of plants such as brome and Sahara mustard on their hides and in their manure. Their hooves churn the cryptobiotic soil crust that can impede seed germination when intact. Developed water sources for livestock provide oases in which newly imported invasives can ride out dry years. It is hard to picture a long-term fire management policy in the desert that does not involve removal of domestic livestock.
Many shrubs native to the Mojave cope with drought (and repel browsing animals) with resinous secretions that also make them highly flammable. At elevations higher than 5,000 feet, such species form relatively dense shrub communities, often mixed with pinon pine and Utah junipers. Even in normal rainfall years, these communities can present a fire threat. Rob Fulton, the manager of California State University's Desert Studies Center in the tiny Mojave hamlet of Zzyzx, thinks it's possible that native plants would have supported the Hackberry Fire even without invasives. "These fires were the result of 'perfect storm' natural conditions," says Fulton. "There was certainly brome in the area, and cheat-grass. But this was after a 50-year rainfall event. There was just a huge amount of fuel up there, and strong winds during the early days of the fire played a role in rapidly expanding the fire complex. Even in the lower elevation portions of the burn, where normal fuel densities are less, this year saw a huge growth of annuals in the spaces between shrubs, some of them nonnative, but many of them native to the Mojave, and capable of spreading fire between shrubs on their own when driven by wind."
Calling the winter of 2004-5 a "50-year rainfall event" is probably conservative. The previous August, severe thunderstorms raked the Mojave, causing widespread flash floods. One destroyed a main road into Death Valley, and moved two large concrete bathrooms 200 feet off their foundations at the Zabriskie Point overlook. Each of them weighed 21 tons. The subsequent winter storms blowing in off the Pacific Ocean were Noachic in scale. The two weeks from December 27, 2004 through January 10, 2005 were the wettest in downtown Los Angeles since record keeping began in 1877.
On January 17, I drove to the lowest spot in the Western Hemisphere at Badwater, and looked out on an immense lake. There I stood, in the middle of Death Valley, wishing I'd brought my kayak along with me. The rocky slopes had sprouted odd green fuzz, like an orange kept too long in the back of the refrigerator. Six weeks later, tourists flocked to the desert to see the staggering bloom.
By June all that annual foliage, whether native or invasive, had dried. When the heat distilled thunderstorms from the summer air, fires were inevitable. Across the deserts of the west in June and early July, one fire after another raged across the landscape. Large fires merged into huge ones. Just two fires--the Southern Nevada Complex north of Las Vegas and the Cave Creek Complex near Phoenix--together burned about 1,200 square miles of desert, an area three times the size of Los Angeles. In the remote reaches of the Sonoran Desert, the Goldwater Fire burned about 58,000 acres. "The Goldwater Fire was probably unique in the last 10,000 years," says Betancourt. "When you drove by that area this spring it looked like amber waves of grain, a continuous field of Sahara mustard with the creosote tops just sticking out." In the eastern Mojave near Kingman, Arizona, the Perkins Fire blackened 21,000 acres of desert scrub. Dozens of smaller fires of less than 2,000 acres dotted the desert. All in all, perhaps a million acres of the Mojave and Sonoran deserts burned in about six weeks.
The Hackberry Fire in the Mojave National Preserve surpassed 70,000 acres. Whether or not invasives can be blamed for it, they will very likely be responsible for the next one. Under the best of circumstances, the native vegetation would take a generation to recover to the point of "visual erasure." Though some shrubs have already started to recover, starving herbivores will make short work of many of them. Red brome and cheatgrass will spread throughout the burn site. And Fulton has already noted Sahara mustard growing not far away, in the southern reaches of the Preserve.
"I honestly don't know how we're going to fix this problem," says Esque, resignation in his voice. "I don't know if we can."
Betancourt is, if anything, even blunter. "Within five or ten years, I think people will look back to this year as a time when they should have heeded the alarm. I think we're going to remember 2005 as the year we lost the Sonoran Desert."
Beautiful and doomed
Leaving the Hackberry site, the washed-out dirt roads require my full attention. Deprived of vegetative cover, the soil has washed out in places with each new thunderstorm. We retreat to our campsite atop Cima Dome, a lush Joshua tree forest and informal campground within the reserve.
I've been here dozens of times, but I eye the landscape with new suspicion. The resiny native shrubs are just as thick here as they were on the burn site, and a century of grazing has spurred the growth of a good amount of brome. Cima Dome hosts the largest forest of Joshua trees in the world, and their spent leaves provide a perfect fire ladder from the brome to the treetops.
I realize with a shudder that the Cima Dome Joshua tree forest, one of my favorite places in the world, is very likely doomed. If it does not burn this year, it probably will in the next ten.
A couple of hours later the storms roll over us, giant thunderheads from off to the west. One splits in two, and tracks just to the north and south of the campsite. We are surrounded. For an hour lightning flashes, and the temperature drops to an oddly chilling 90[degrees]F. At least one bolt sparks a fire. We watch a wind-driven column of smoke curl from the slopes of the Kingston Range, 30 miles north. The storms break up around sunset. There are still two months left of fire season, and an endless stretch of burning years to follow.
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|Title Annotation:||Mojave Desert|
|Publication:||Earth Island Journal|
|Date:||Jan 1, 2006|
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