In the Burning Desert

Dead and dying yuccas in the wake of the 2005 Hackberry fires, Mojave National Preserve | Chris Clarke photo

Palm Springs caught a break this past weekend; winds that had been buffeting the area for several days died down Sunday night, allowing the local fire department to put out a seven-acre brushfire in Chino Canyon before it spread. The fire, along the road to the Palm Springs Aerial Tramway, could easily have spread to wildlands to the north or west of the city. A moderately wet winter has meant exuberant growth of both native and exotic plants, adding to the fuel load of the surrounding wildlands: an unlucky gust of wind could have sent embers up onto the steep desert slopes of Mount San Jacinto. But the winds were light, and firefighters were able to douse the blaze within about an hour. Bullet dodged.

According to a report released by the National Interagency Fire Center (NIFC) last week, Southern California likely isn't facing a catastrophic wildfire season in the first half of 2011 -- certainly reassuring news for those of us eyeing the millions of acres in Texas that have burned so far this year. But what's true for the coast and mountains may not be true for the state's deserts.

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Fire risk for early 2011 | NIFC

The NIFC's 2011 National Seasonal Assessment Workshop for the Western States, Alaska and Hawaii, compiled by a regional network of fire, weather, and climate specialists, identified a swath of the Southwest from Arizona to Kansas as facing above-average risk of wildfire until July -- bad news for fire-weary Texans -- but their forecast for California is more ambivalent:

Fire season for the majority of California is expected to begin in typical time frames. However, elevations at or above 5500-6000 feet had an April 1st snowpack ranging from 125 to 170 percent of normal. The majority of California has seen precipitation ranging from 100 to 150 percent of normal. The Area is expected to see normal temperatures and near normal precipitation through July, trending toward slightly above normal temperatures and slightly below normal precipitation in August. Due to the abundant rain and snow, there is presently no large-scale drought in California. For the higher terrain, significant activity could be delayed until the start of August. Given expected fuels conditions, it is not likely that a lightning event will produce multiple large fires prior to July 1 at low and mid elevations, or prior to August 1 at high elevations [...] For Southern California, heavier fuels currently possess a large amount of moisture from the heavy precipitation of the past winter, and snow pack surveys indicate 165 percent of snow water equivalent in the Sierras. It appears unlikely that these fuels will dry enough to become highly receptive during the outlook period.

In other words, the wet winter we just got done enjoying has moistened the forests and chaparral, and most of the state isn't expected to burn down until late summer at the earliest.

In California's deserts, though, that wet winter may have increased the threat of fire rather than damping it.

Since the 1980s or so we've learned that fire is a natural part of many Western landscapes, and that suppressing it can cause more injury to the ecosystem than letting it burn. But that's not true of the desert. For most of the last 12,000 years or so, wildfire has been a stranger to most of the deserts of the southwest. Wildfire requires a continuous supply of burnable fuel to spread, but the deserts didn't offer that supply until quite recently, at least not in the lower elevations. Extreme aridity meant plants had to compete for every drop of water; the traditional desert landscape below about 5,000 feet was generally characterized by widely dispersed shrubs and small trees separated by expanses of stony soil. There have always been occasional fires in the desert's higher-altitude conifer forests. Below that altitude, however, an individual lightning-struck mesquite or yucca might burn to the ground, but the fire wouldn't spread.

That changed with the advent of a few species of invasive exotic plants that thrived in the arid desert landscapes.

Red Brome in Nevada. This area burned in a lightning-caused wildfire several months after this picture was taken | Photo by Stan Shebs, used under a Creative Commons License.

There's red brome, for instance; a grass native to the Mediterranean basin, was among the earliest of the problem species to arrive: it was established in California by 1848, and had spread throughout the Mojave Desert by 1950. Red brome's close relative cheatgrass was here not long after, and now forms nearly solid stands throughout the Great Basin Desert.

Buffelgrass, which has marched through the Arizona Upland section of the Sonoran Desert like a conquering army, is expected to do much the same before long in California's low desert. It is closely related to, and closely resembles, the ornamental fountain grass that has escaped cultivation and now dots southern California's mountainsides.

Sahara mustard might be the scariest of the invaders. Thought to have been introduced into the deserts as an undetected hitchhiker in date palm seedlings planted around Coachella, Sahara mustard can grow profusely even in years too dry for red brome and buffelgrass.

A wet desert winter promotes the growth of these exotic plants, and they take advantage of every drop of moisture, filling what had been more or less unvegetated expanses of stony soil between native shrubs and cacti. Where trees struck by summer lightning or careless-tossed cigarettes once burned to the ground, then smouldered and went out once the fuel was gone, the flames now leap into a near-uninterrupted carpet of dry fuel and race on to the next tree or shrub.

Since wildfire is a relative newcomer to the desert, native plants haven't had any reason to evolve adaptations to wildfire. When a swath of desert burns, those native plants often have a hard time re-establishing themselves. The exotic grasses and mustard have no such problems: they spring back readily after destructive fires, freed from competition with the natives. A few big fires and the landscape changes utterly.

After the wet winter of 2004-2005, a series of summer monsoon storms swept across the deserts. One lightning strike after another touched off fires in California, Nevada and Arizona. More than a million acres of formerly fire-proof desert burned in the months of June and July. Much of that land now bears a thick carpet of invasive plant matter.

On Mount San Jacinto just uphill from the site of the Chino Canyon fire of this weekend, red brome grows in abundance. It gave the once-russet slopes above Palm Springs an odd greenish cast from January through April. It's turning yellow right now. A stray spark from a cigarette, a lightning strike, or an overheated muffler could send fire racing up the incredibly steep slope. It may not happen this year, but it will happen, some hot June or July after a wet winter, with fire season in the rest of California still months away.

About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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The evidence of fire in the CA deserts prior to the past century is not easily obtainable, so it's a stretch to purport that fires have dramatically increased with the introduction of several exotic species. Though lightning-ignition is common during summer thunderstorms, human-caused ignition has increased in the past century. So I'm not sure how exotics have increased fire frequency, but humans sure have. While exotic species may enhance fire intensity, native annual growth (which by June or July is a significant part of the dry standing biomass) also contributes to carrying fire, as it did in 2005 at the Hackberry Complex (Mojave National Preserve) where a 70,000 ac burn occurred with little help of exotic species (which were largely absent). The research on this complex interaction of fire with vegetation (both native and exotic) is incomplete and needs funding not only from fire management sources, but from non-special interest sources. A component of fire in our deserts may well be quite "natural" and may have varied with historic climate regimes. Fire is clearly enhanced by exotics, but it' important not to assume that every fire that burns is the result of Bromus, Schismus and Brassica. This blanket assumption fuels not fires, but the industry of fire management, which utilizes public fear and bad science to stimulate funding for fire management. Examples of fire management in the CA deserts includes spending millions of dollars to eradicate weeds that are ubiquitous and cannot be removed over the millions of ac. they now cover. And yet the agencies continue to pour money into this fruitless task. Worse, agencies are beginning to utilize aerial herbicide drops to remove all annual grasses, including the more than 30 species of native annual grasses known to the CA deserts. These monies could be instead utilized to actually achieve something meaningful: put it into research so that we can more fully understand the complex processes both natural and altered, between fire, climate and vegetation in the CA Deserts.

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Great comment, FD.

My sense that fires have increased since the last days of ground sloths comes from conversations I had a few years back with Todd Esque and Julio Betancourt of USGS (and a few others) in the wake of the 2005 fires, which conversations I had in the process of putting together an article for Earth Island Journal on that fire season.

It seems likely to me that there are places in the deserts that have not burned in millennia β€” Betancourt certainly told me as much, with regard to the creosote and ironwood habitats in southwestern AZ β€” but I'm also well aware of historic fires in the better-watered upper elevations. (Perhaps I didn't make that plain enough.)

You are correct in saying that the Hackberry Complex Fire cannot be attributed to exotics β€” though it certainly looks like they're there now and it might not be as easy to excuse them from the next fire.

What you say about fire management is compelling. It's certainly the case that in 2005, the above scientists and others I talked to were understandably in crisis mode at the time. The science has surely progressed in the half dozen years since, and those sources may not agree with what I've written here.

In any event, I'm with you on concern over indiscriminate annual grass control and on the need for more and better research. Part of the problem with writing about big potentially scary issues is the temptation to find a course of action, ANY action. And you're right that we don't know enough here to ensure that our actions won't make things worse.

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Thanks for the reply Chris. Your interest in this issue is very admirable and it certainly is an ongoing discussion.
Commenting further on a few points:
First, Todd and Julio can only speculate on historic burn patterns without sufficient evidence (lower elevation sites lack tree-ring data). Second, we really need to get away from justifying fires as new events because deserts lack "fire-adapted" species. Most leading plant ecologists now reject the notion of adaptations to fire as a driver to structuring vegetation, or even a reality (see recent paper by Rundel). Just like prairies, NW coniferous forests, Central coastal CA fog forests, and the deserts around the world burn too. Their species are not adapted to fire, but the vegetation burns. In Phil Rundel's recent paper makes a compelling argument to this effect. The coastal chaparral of SoCal may contain fire adaptations, but the species? And for example, name a plant species in the mid-elevation coniferous forests of the Sierra that is fire-adapted? Does the system burn? Yes. Is the vegetation burn adapted? Maybe. The notion that because deserts lack fire-adapted species it is proof that deserts do not naturally burn is weak evidence that exotics alone have spurned a burning regime. That notion is being rejected soundly from both ecologists and plant evolutionary biologists.
Finally on the point of repeat burning in already burned vegetation, with the Hackberry Complex at MNP as an example. When I say the initial fire in 2005 was not carried by fire, it does not mean Bromus, Schismus and Erodium cicutarium was not present within the footprint of the project. But they were joined by dozens or hundreds of native annuals, and dwarfed by them. I would conclude that absent of the exotics, that burn would have happened just as it did. Until this year, the burn area at Hackberry was nearly absent of Bromus and Schimus, even while those species were present nearby outside the burned area. This year Bromus tectorum and B. madritensis rubens covers a good portion of the lower elevations of that burn. One could conclude that this is a response to the fire. But in truth, those two species are having banner years throughout the eastern Mojave in unburned areas as well. So again, have to be careful to focus only on the burn area to understand the dynamics going on there. Would the Hackberry burn footprint be more likely to burn this summer than adjacent unburned areas when both sites have high cover of Bromus AND native annuals?