A burned-out landscape that once contained lovely stands of Joshua trees (Yucca brevifolia ssp jaegeriana) in southwestern Utah.

In 2004 and 2005, there was a very wet winter in the southwestern states. Arizona, California, Nevada, Utah, and New Mexico all saw precipitation levels well above normal, and many places received record-setting amounts of rainfall and snowfall. This was beneficial for the hydrology and ecology of the region, including a spectacular mass bloom of wildflowers that had not been seen in around 50 years. But it also came with a price in the form of never-before seen desert wildfires in the summer of 2005, once the fuels that had been generated dried out and were ignited by dry lightning storms in late May and most of June that year.

Evidence of the record-wet winter of 2004-2005: Historic flooding in the northeastern Mojave Desert occurred in the region around St George, Utah and southwest into Lincoln County, Nevada and the adjacent portions of Mohave County, Arizona.

Top row, left to right: 1. Damage to a bridge on Highway 91 spanning the Santa Clara River south of Gunlock, Utah; 2. A massive boulder wedged up against a large cottonwood tree in the Bull Valley Wash, moved by impressive flooding; 3. The normally dry Beaver Dam Wash near Motoqua, Utah was still flowing in July 2005, months after the rain ended, indicating how wet the year actually was. Bottom row, left to right: 4, 5, 6. Road damage caused by massive flooding to the Carp-Elgin Highway, which runs through rural Lincoln County, Nevada northwest of the city of Mesquite.

Deserts are by definition dry places. It would therefore seem sensible that wildfires would be an ecological factor, simply due to the predominance of hot aridity for so much of the year. But this is not the case whatsoever. Think about it: Deserts are actually too dry to burn. What I mean is that there simply is not enough fuel in a desert to support wildfires. Sure, it is true that if an individual Joshua tree for example is struck by lightning that it might burst into flames and incinerate, but the lack of nearby vegetation limits the spread of wildfire to just the afflicted individual tree or perhaps a few neighbors. Generally wildfires cannot spread over thousands of acres in most desert biomes.

Nevadagascar article final proof CSJ Nov 2005

Here is a PDF copy of an article I wrote which was published in the Cactus and Succulent Journal of the Cactus and Succulent Society of America (CSSA) in November 2005. It covers details of the weeds/wildfires linkage that has recently appeared in the desert regions of the United States. Part 1 discusses the Mojave Desert and the Joshua tree forests therein.

Until recently, that is. In the past 100-150 years a series of non-native and highly invasive weeds have been introduced into desert ecosystems. These weeds have lately been providing the flammable fine fuels that fill in the normally open spaces between desert perennials (meaning xeric trees, shrubs, and succulents mainly) and have in the past 20 years or so made large wildland blazes possible in an ecosystem ill-equipped to survive this type of pressure.

Cheatgrass (Bromus tectorum) was the main culprit for enabling desert wildfires in the Mojave Desert. While the fire threat posed by cheatgrass has been well-known for decades in other western ecosystems such as pinon-juniper forest and sagebrush steppe located farther north and at higher elevations, the emergence of fires into lower elevation Mojave Desert was not particularly anticipated before 2005.

The worst offenders on this score include cheatgrass (Bromus tectorum), red brome grass (Bromus rubrum), Mediterranean grasses (Schismus arabicus and S. barbatus), buffelgrass (Pennisetum ciliare), Sahara mustard (Brassica tournefortii), and rocket mustards (Sisymbrium irio and related species.) Most of these plants were accidental introductions from Eurasia or the Mediterranean region, and were brought in as unintentional contaminants in agricultural products such as hay, wool, livestock feed, and pasture seed mixes. Buffelgrass however was a purposeful introduction from seasonally dry regions of tropical Africa that was sown widely in the Mexican portions of the Sonoran Desert as a rangeland grass to feed livestock. It has been spreading aggressively into Arizona’s Sonoran Desert, and shows the potential to invade much of the Mojave and Chihuahuan Desert regions as well.

A scene in an unburnt section of Joshua tree woodland in Lincoln County, NV showing the heavy invasion of cheatgrass that fills in the normally open spaces between desert shrubs and Joshuas. Without the interstitial fuel provided by this invasive pest, this desert would be unable to catch fire or spread any appreciable distance.

All of these grasses and mustards have vastly increased the fire threat in North American deserts. They have introduced a new dynamic into our dryland ecosystems that the native plants are generally ill-equipped to survive: flames. It should be noted that not every year is going to be a bad fire year, as the abundance of invasive weeds is directly linked to above-average rainfall. Normal and below-average years of rainfall will generally not produce enough density of weeds to support serious wildfire risks; but once every decade or two, a wetter-than-average year arrives and increases the weed abundance to a level where fires are a severe threat. This is what happened in the winter of 2004-2005, and is happening again this year in 2018-2019.

A section of Arizona’s Mojave Desert that was burned in the Perkins Fire of June 2005 northwest of Kingman, AZ. The foreground fuels are mainly Sahara mustard (Brassica tournefortii) and rocket mustard (Sisymbrium irio) combined with Mediterranean grass (Schismus sp.) The background hills are charred by fire, for the first time in recorded history.

This view was also captured near the Perkins Fire zone in NW Arizona, but contains mostly Mediterranean grass as the fuel. I used to think that a few inches of short, annual grass would be incapable of carrying a significant fire risk across thousands of acres of desert. I was very, very mistaken. Under hot, dry, and windy conditions, even this relatively patchy cover of grass is enough to support fires that can spread far and wide, as seen by the denuded hills in the background.

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Below I am adding a number of photos of the aftermath of wildfires that burned nearly a million acres in the Mojave Desert and nearby mountain regions of Utah, Nevada, and Arizona in late May and June 2005. This portion of the discussion covers the impact of these unprecedented fires upon Joshua trees and other succulent plant species of the Mojave Desert. I address the saguaros and other plants of the Sonoran Desert in Arizona in part two.

The Perkins Fire burned a sparsely vegetated Mojave Desert plant community that has literally never seen fire before now.

Above, a charred many headed barrel cactus (aka cottontop barrel cactus, Echinocactus polycephalus) sits in the foreground while a pair of Mojave yuccas (Yucca schidigera) stand in the background. The short shrubs are mostly white bursage (Ambrosia dumosa) and creosote (Larrea tridentata), a common low desert association whereby both are co-dominant.

The cactus almost surely died from this burning. After losing all of its protective spine cover and the blistering of its photosynthetic green skin, it will be unable to recover. All it took was ONE SINGLE FIRE to permanently remove the entire population of E. polycephalus from this portion of their desert home. These slow-growing plants took centuries to grow this large, and now there are no more. There are too few of them left, and they grow much too slowly to ever recover from this relatively low-intensity fire, a fire that would not have fazed a more flame-resistant plant community at all.

A half-burned red barrel cactus (Ferocactus acanthodes) and a fully burned cottontop barrel (Echinocactus polycephalus). It is unclear whether the red barrel can survive this partial burning. Its prospects are better than that of the cottontop, which will surely die from the trauma of such charring, but it will be forever disfigured at minimum.

I am deeply concerned about the long term future of Echinocactus polycephalus as a species. These barrels are amazingly sluggish to grow to any appreciable size, taking many decades to reach flowering stages, and with large clusters like those burned in the Perkins Fire probably being 200-300 years old or more. They have low seedling recruitment and depend upon their extreme longevity to tide them over during entire decades, or even centuries, during which no reproduction occurs. And here we have one single fire caused by these stupid damn weedy annual grasses that have completely altered the picture for this species. It makes me angry!

Echinocactus polycephalus has a fairly large nominal range spanning portions of three states and much of the Mojave and western Sonoran Deserts. But they are sparsely distributed and cannot be considered to be common or secure anywhere, now that these weeds and the wildfires they introduced are a factor for them to contend with. Add to this the threat of climate change, which will probably increase the difficulty of new seedlings to establish even absent wildfires, and human pressures such as illegal poaching for the plant trade. With all these factors you get a distinct sense that the current adult generation of E. polycephalus may well be the last over most of its natural range. And this makes me sad in addition to angry.  🙁

A burnt red barrel cactus suffers in front of two Mojave yuccas in the Meadow Valley Wash watershed of southeastern Nevada. This was where the fire line went out or was put out by firefighters, since unburnt sections of hillside and undamaged plants stand in the background.

A group of Mojave yuccas died in the Meadow Valley Wash of Lincoln County, Nevada.

I am a little more optimistic about the survival chances of red barrels as a species, partly because the plants are more widespread, more common, and faster-growing than many-headed barrels are. This does not mean they don’t need protection of course, but I don’t see them as being nearly as endangered by tragically slow growth rates and lack of seedling recruitment into the populations as the polycephalus are. Meanwhile, the prospects for Mojave yucca survival as a species is probably also relatively benign. They are also among the slower growing of various yucca species, but they are fairly abundant and widespread. They are also capable of resprouting from the bases at least once after fire passage, and are therefore not as prone to total elimination from a single unnatural fire as the cottontops are.

Joshua trees in the Delamar Valley of central Lincoln County, Nevada. A heavy invasion of cheatgrass makes this a conflagration waiting to happen. All it takes is one single ignition point, whether lightning or a discarded cigarette or a match, and thousands of Joshua trees will die forever.

More cheatgrass in the Virgin River Gorge area along the Utah/Arizona border southwest of St George. I am not 100% sure if this scene still exists today in 2019, since there were fires along the southern slopes of the Beaver Dam Mountains in the background in the summers of 2006 and 2007 that may well have burned over this area. Given how much was lost in the years between 1999 and 2008 around here, I wouldn’t be surprised. My estimate is that nearly 75% of the Joshua tree forests of this tri-state Mojave Desert region were immolated by 2010.

The skirt of dead leaves that Joshua trees and most yuccas have makes them very flammable. And unlike fan palm trees (Washingtonia filifera and W. robusta) the yuccas rarely shrug the fires off and simply grow a crown of new leaves from the blackened trunks. Fire kills them.

Here is why Joshua trees are so exceedingly vulnerable to fires. Most of them, even old specimens, have at least a portion of the dead leaf skirt that extends to ground level. Joshuas retain these dead leaves because they offer a good measure of insulation value to the plants’ trunk and branches, both against sunscald in summer and on freezing winter nights. The shag of dead leaves blocks the intense UV light of the desert sun and helps reduce evaporation and overheating. In most regards this is perfectly adaptive to the demands of the Mojave Desert environment, so long as fire is absent. Which, historically for reasons I have already explained above, it was.

Stricken Joshua trees dot the landscape beneath Bull Valley Mountain, which rises above the slopes in western Washington County, Utah. The area burned in mid-June 2005. I took the photos a few weeks later in early July.

These days however, thanks to invasive non-native weeds, the picture is different. Now that the weeds can carry fires between shrubs and widely-spaced Joshua trees, fire is suddenly a thing in the Joshua tree forest. It does not take much, just flames a few inches high, creeping along the ground, reaching the dead leaf skirt that the large majority of Joshua trees have that at some point are near soil level. Once the flames catch the dead leaves afire, that is pretty much the end for that tree. Flames rapidly explode upwards into the main crown, burning fiercely and killing the entire plant. They were never designed to survive this.

The Joshua trees of this segment of the Mojave desert are beautiful, with numerous branches in a dense, bushy crown that is very attractive. It is also very flammable.

If Joshua trees did not possess this dead leaf skirt, they would likely be much more fire tolerant. The bark on larger trees with well-developed trunks 100 to 200 years old is thick and fairly fire resistant, and often by that age the dead leaf shag has worn off anyway. Well if this is the case, then how come there is nearly 100% mortality on the trees? Why did they virtually all ignite, rather than having the creeping fires pass relatively harmlessly underneath like fires do in open stands of ponderosa pine or live oaks, both trees that are well known to be adapted to surviving low-intensity fires?

The compact, shrubby shape of this subspecies of Joshua tree (Yucca brevifolia ssp jaegeriana) in the eastern Mojave Desert is responsible for why they are so fire prone.

The answer to that question is that eastern Mojave Desert Joshuas have at least two other characteristics that nullify the corky, fire-repellent bark trait. One is the compact, bushy shape of the plants, which have low branches that often swing low towards the ground, and which sometimes reach it. In the photos above, note that on each of these two different trees there is one low-slung branch to the right that comes within a few inches of actually reaching the ground. The invading Mediterranean grasses that are now present everywhere can easily lift flames to that single branch. And once fire has escalated into the leaf crown, it ignites the branches above it, so the rest of the tree burns from there. Note how neither main trunk of either tree above has any dead leaves. In theory, the thick plates of bark might successfully resist the passage of a crawling fire with relatively small flames only a foot or so high, were it not for those singular low branches that are the Achilles Heels of both trees.

Another example of a very low-branching Joshua tree with several branches within a short distance of the ground, and the nasty cheatgrass invasion beneath it. If this area ever catches fire, these trees are all doomed. In fact, as noted in a prior photo, this scene may actually have been burned in summer 2006 or 2007 fires that affected this valley, a year or two after I took these photos. I’d have to go back and check to see if any of these groves of Joshua trees still exist at all. I am not terribly optimistic that they do…. 🙁

A second vulnerability of Joshuas of this region is the grove-forming, colonial nature of the trees.

The other trait that Joshua trees of this region have that makes them fire-prone is their tendency to clump and produce offsets from underground stolons. Joshua trees of the western Mojave Desert (mainly in California and far western Nevada) tend to be more individualized and show little tendency to cluster, but the subspecies Y. brevifolia jaegeriana of the eastern half of the desert does. Young Joshua trees have not developed thick trunks yet, nor have the dead leaf skirts had a chance to abrade off over the years to leave the trunks naked and covered with the corky bark. Therefore, just as with the low-slung branches, if even one of the younger Joshua tree pups catches fire via the dead leaf shag, it tends to sentence the entire grove to death by fire. One can easily imagine how the clumping tree shown above would quickly be a tower of flames thanks to the presence of a number of juvenile offsets crowded around the base of the older mother plants.

An example of how the basal bark of the main mother trunk did not catch fire, while the dead leaf shag of a side pup did, which doomed the entire tree via close proximity. Without the pup, would the mother tree have made it intact? Hard to say for sure, but certainly the odds would have been better.

The Duzak Fire Complex, which was ignited by a series of lightning strikes and which merged into one mega-fire as the individual hotspots merged, collectively burned a couple hundred thousand acres of southwestern Utah and southeastern Nevada in May and June 2006. The fire complex killed millions of Joshua trees and other desert plants. The distance between where I took this photo in Nevada, and the summits of the Beaver Dam Mountains in Utah on the horizon, is about 12 to 15 miles. None of it escaped burning – the parts that weren’t torched in 2005 instead were in 2006 and 2007.

The result of this unholy combination of Joshua trees that have little fire resistance because evolution didn’t provide them with the chance to do so before now, and the invading exotic weeds that inserted fire dynamics into the region for the first time ever, is ecological devastation. You should have seen how beautiful the biology and scenery of this desert woodland region was before it was ALL burned. Thanks to those infernally invasive, weedy annual grasses that penetrated the Joshua tree forest. Thanks to us, humanity, who introduced them. Yes, their introduction was an accident, but that doesn’t matter much now, does it?

The dead leaves of these Joshua trees burned hot and fiercely, charring the trunks and leaving zero hope for survival. The now-brown leaves that remain on the dead trees were the green parts at the time of the fire and couldn’t burn due to their moisture content. But they died anyway.

The remnants of a Joshua tree grove standing sadly upon a ridge. These were all clones, as is common for the jaegeriana subspecies, and the family died together.

A miraculous lone survivor.

Not every Joshua tree died. The one above obviously did not, whereas all of its neighbors were killed. Note that the trunk lacks the dead leaf skirt and thus was not easily ignited, and the one low-hanging branch to the left was singed by heat but somehow, by some miracle, managed to not catch fire either. If it had, however, you can see how the flames would quickly have set the whole rest of the tree ablaze, since more than about a meter above the ground the dead leaves are everywhere.

It must be pointed out however that just because an occasional solitary Joshua tree didn’t burn doesn’t mean that it has a reproductive future as part of a thriving community anymore. These isolated survivors will in the future have no nearby neighbors to cross-pollinate with, which means no future seeds. Besides, there are nearly no nurse shrubs present anymore either to help protect vulnerable young seedlings through their first decade or two of life until they are capable of withstanding the desert on their own. These Holocaust Survivors are essentially doomed to live out their lonely remaining lifespans without ever reproducing again, depriving the ecosystem of the chance for them to recover their former population. Without a source of seeds to replenish the lost masses, Joshua trees have essentially vanished from vast swaths of the landscape.

I think this is tragic, don’t you?

A formerly lovely stand of red barrels (Ferocactus acanthodes) now sits marred and scarred after all their spines were burned off.

I have been very focused on the Joshua trees in this post, because of course they are the flagship species of the Mojave Desert. They are the largest and most prominent plants in the landscape and their charisma is undeniable. The very popular Joshua Tree National Park in the state of California has been dedicated to preserving them. They are integral to the ecosystem of much of the Mojave Desert, and they capture our hearts and imaginations. But they were far from the only casualties of these never-before-seen desert wildfires. In this next segment I will pay some attention to the other plants that also suffered equally devastating losses.

This little rock outcrop was a good home for a few dozen red barrels, plus hedgehog, pincushion, and cholla cacti as well. It’s not anymore. The fires burned over all of the hills in the background as well and beyond for many miles. Untold millions of plants died as a result of this disastrous first-time fire, never to return.

A rare crested barrel cactus (Ferocactus acanthodes) was killed by the Duzak Fire Complex in the Bull Valley Wash drainage of eastern Lincoln County, Nevada, just a few miles from the Utah state line.

Large numbers of red barrel cacti were also killed by the fires that wrecked the region’s deserts in the early and mid 2000s. These populations of Ferocactus are some of the most northerly that exist, and some of the most cold-tolerant. Most of the barrels that existed in the state of Utah were on the western and southern flanks of the Beaver Dam Mountains and upper drainages of the Virgin River Gorge, which were heavily burned between 2002-2007, sometimes repeatedly. I don’t know if a full census of the loss of barrel cacti in Utah exists, because there was probably little formal population study done before or after the fires, but I don’t think it is unreasonable to estimate that in a few short years about 60% to 75% of the habitat was burned, again thanks to unnatural grass invasion. The destruction of many of the cold-tolerant northerly forms of this species represents a loss to the species as a whole in terms of genetic diversity alone.

A close-up view of the burned crested barrel. Cresting, also known as fasciation, is a genetic anomaly present in most species of cacti and many other succulents. The normally radial cell division of the apex of the thick central stem goes haywire and become linear and elongated, leading to a sort of “cockscomb” appearance. It’s a unique and often desirable trait coveted by many succulent collectors. Alas, this barrel is one of the “standing dead”. 

I am certain that within a few weeks or a months of me taking this photo that the crested plant collapsed into a mushy pile of rot. The burning was obviously too intense for it to survive. All the formerly green skin that did the photosynthesis is gone, replaced by dead tan scar tissue. There is virtually no way the plant can survive this, not any more than an untreated human fire victim with third degree burns over their entire body would either. Left wide open to various infections and insect attacks, all of these severely burned barrels died. I went back here a number of years later and saw none alive.

A Mojave claret cup hedgehog (Echinocereus mojavensis) is one more casualty of the Duzak Fire Complex. Somehow the hillside in the background was spared.

Large and ancient clumps of banana yuccas (Yucca baccata) were also lost. Some of these clumps spread 15 to 20 feet wide and must have persisted for centuries to become this size.

Another component of the northeastern Mojave Desert ecosystem is banana yuccas (Yucca baccata) which can be co-dominant with the Joshua trees in places. They also can be found with Mojave yuccas (Yucca schidigera) discussed earlier and occasionally all three yucca species grow sympatrically. When that happens it is a yucca-dominated landscape that is not equaled in most other places, although sometimes several different species can do the same thing in parts of Mexico or Texas.

Fortunately for the desert, banana yuccas are quite capable of rapid resprouting from the chunky subterranean stems and root bases. This makes banana yuccas a more prominent component of interior chaparral and pinon-juniper forest zones, because this capacity makes them significantly more fire tolerant than Joshua trees. After all, both interior chaparral scrublands and P-J woodlands are places where periodic fires (preferably spaced 50-100 years apart to allow for proper regeneration times in between) are expected and where occasional fires can actually improve the health of the ecosystem.

Prickly pear cactus (Opuntia phaeacantha) also suffered major losses in the fires.

This region of Utah and Nevada is known for a diversity of prickly pear cacti, comprised of a hybrid swarm involving up to 4 or 5 different species. They are found in both desert and adjacent interior chaparral, as well as at higher elevations amidst the lower reaches of the pinon-juniper forest that was scorched in the surrounding hills.

Unlike the Joshua trees and barrels and hedgehogs, and somewhat like the banana yuccas, prickly pears might manage to resprout from the bases and centers of larger clumps. Note how there is some green stem tissue present in the middle of the bunch above. This may well be enough surviving material for the plants to put forth new pads and resume growth. They will suffer a setback in size and reproductive capacity for a few years, and the outer pads are a loss since they were probably most exposed to the grass-fed flames, but many of them will likely survive in the long run. That is at least one small bright spot amidst all the other damage. (Y)

The border zones of Federally-managed BLM lands between two states, and a partly burnt sign that tells us something about the story at hand.

It is important to note that while the aforementioned interior chaparral and P-J forest zones are indeed by nature and evolution more adapted towards periodic burning than arid deserts ever were, there are limits to how often they can burn without severe ecological degradation. Indeed, even very fire-dependent ecosystems cannot be burned too often. If they are, they suffer species losses as well, especially seed-reliant plants that take some years or even decades to start reproduction. If fire intervals are spaced too close together, some plants will not be able to reproduce in time if they are seed-obligate reproducers. Adults are killed by burning without first generating an adequate seed bank in the soil to replace themselves. Obviously the loss of these plants from a patch of landscape can have follow-on effects upon populations of insects, animals, and other plants.

I am estimating that the foreground landscape of the photo was burned between 1995 and 1999, although I cannot currently verify this. The background landscape was burned just a few weeks prior to the taking of this photo in July 2005. In places the road was used as a fire break, with one side being burned and the other side intact.

Above is a stretch of BLM land in the Ely District of southeastern Nevada that was burned before 2005. My guess, based upon the partial regrowth of some of the crown-sprouting shrubs such as scrub oak and silk tassel bushes that the first fire zone in the foreground (the not currently blackened section) was maybe burned 7 to 10 years ago, perhaps in the late 1990s. The shrubs would have taken a minimum of 4 to 5 years, and possibly as much as 10 years to regrow to the size they are in 2005, when the Duzak Fire Complex moved over the region again.

While the Duzak Fire burned a great deal more desert, interior chaparral, and P-J forest than this prior fire did, it highlights the extreme ecological danger posed by the weedy brome grasses in the foreground. Note how the grasses are perfectly well dense enough to burn yet again, long before the P-J forest and chaparral shrubs and assorted succulents have had any chance to recover to near their former size and abundance, much less start to reproduce and rebuild lost populations. Nope. The goddamned weeds are present now, and what if they make these hills and valleys burn every 5 or 10 or 15 years, rather than the 50 to 100 year intervals that are closer to ideal for these biomes? What effect will closely spaced repeated burnings do to the natural biological processes of this region?

Folks, this is what invasive species cost us. It’s not just human economic expenditures related to wildfires, such as firefighting in the billions of dollars annually and the loss of human property like houses and farm yields and pesticides that need to be applied. It is also more hidden costs associated with the changes in watershed holding capacity, reductions in ecological productivity, losses of biodiversity, and damage to intangible senses of place including wilderness, recreation, and beauty values. Invasive species take a toll on society from all of these fronts.

This banana yucca (Yucca baccata) has resprouted from underground roots over the past 5 to 10 years since the passage of the first fire. However it is not large enough to have reproduced, and possibly not yet large enough to have stored enough starch and energy in its subsoil rootstock to survive a second burning and resprout a second time in only a few years. It turns out that the Duzak Fire did not quite cross over this newly recovering landscape, but given the density of the cheatgrasses, it could have. And the consequences for the incompletely recovered ecosystem could be rather dire!

With the presence of invasive annual weeds in the ecosystem, the threat from overly frequent wildfires increases dramatically. Annuals tolerate fire very well, because their seeds can readily survive even intense fires by being buried in protective layers of soil. Their accelerated life cycles and ability to produce high biomass in short times spanning only a few months to a year actually fuels fire threats, especially since once they die their remains dry out quickly and are usually of a fine texture that ignites easily and spreads rapidly. Plus, once the terrain is cleared of competition by a fire, the niches are more open for the annual weeds to invade further. Essentially, the weedy annual mustards and grasses set the stage for their increasing ecological dominance by being so fire prone that they clear competition and open the spaces for their further spread. It is truly a vicious cycle.

A tragic scene of blazed out desert plants in the Tule Desert, a broad valley in south-central Lincoln County, Nevada that used to have an amazing stand of Joshua trees. Over half of this valley burned in 2005. A dust devil vacuums up ash and dust in the background left as blackened Joshua trees and red barrels say a final goodbye to their ability to survive here. The invasive pests will be back next year. The succulents will not. This area has undergone a permanent conversion away from diverse Joshua tree woodland to a species-impoverished arid grassland comprised mainly of non-native weedy grasses.

Above are two photos of the Tule Desert that were not burned in 2005. Note the density of the beautiful Joshua trees – it is magnificent! Given the extensive devastation all around the surviving sections, I am not quite sure of how this region didn’t also burn, although presumably firefighters had something to do with it. Sadly, the fire hazard has not gone away. The weeds are still present and there is nothing to stop the remainder of the forest from burning at some point in the future….

A different border sign displays the same basic fate as the other one.

A black-tailed jackrabbit (Lepus californicus) watches me warily in an unmarred section of the Tule Desert. It was lucky to escape the fires a few weeks before. So was it’s entire habitat.

Unfortunately, this jackrabbit was not as lucky and burned to death.

Even sparsely-vegetated limestone hillsides experienced burning. Above are a set of photos from a steep, rocky hillside near Lime Mountain which overlooks the Bull Valley Wash in southeastern Nevada.

What really drove home for me the dangers of invasive weeds bringing wildfires into desert ecosystems was the set of photos above. These jagged limestone hills have almost no soil upon them, just thin pockets of clay and sand and rock fragments that nonetheless hosted a variety of succulents in sizable numbers. I counted 9 different succulent species upon this one hillside alone, which is fairly good diversity, especially considering the northerly locality for most of the species found and elevation of about 4000 feet/1300 meters.

Yet even in this thin, stony soil gathered in pockets and clefts in the rocks, cheatgrass and Mediterranean grass had found a foothold, greatly increasing the fire risk. If you had asked me in April of 2005 whether I thought this rocky steep slope was at risk for a conflagration, I would have dismissed it out of hand as more or less impossible. But the charred barrels and blackened patches of ash proved me very wrong. I believe that the late June dates that the Duzak Fire Complex passed over Lime Mountain were hot and windy, Red Flag Warning fire conditions which demarcate that extreme fire behaviors are possible. I don’t think that Lime Mountain and its foothills would necessarily have burned under non-Red Flag Warning circumstances, but with the aid of wind and high temperatures, clearly most of them did. Sadly, the succulents paid the price for these extreme fires in the same way they did everywhere else.

Another fire break with the flames being contained to one side of the roadway while the opposite side was lost.

I’d like to close this extensive discussion with some thoughts on public policy regarding the threats posed by invasive species in general, and by cheatgrasses and Mediterranean grasses and certain mustards in particular. First, and perhaps most importantly, I feel that more attention should be paid to biological control methods focused in particular upon the weedy annual grasses that are causing such an escalation in fire extent and frequency. These pestiferous exotic grasses have spread across tens of millions of acres of western rangeland, desert, and forest. They need to be controlled biologically because by this point they are far too widespread and established in the wilderness to be managed any other way. We’ve seen successful example of biological controls used elsewhere (most notably the use of cactus moths to control rampant populations of the prickly pear Opuntia stricta in Australia) and we need to dedicate some research to solving this issue with respect to cheatgrasses and Mediterranean grasses, using biocontrol methods.

A red band of fire retardant slurry was dropped on this stand of Mojave yuccas to stop a June 2005 fire in the Cerbat Mountains just northwest of Kingman, AZ. It appears to have helped somewhat since the zones in the distance were not charred.

These grasses have been an unintentional part of the Western United States’ ecosystem (and also in adjacent parts of Canada and Mexico, so they are a transnational problem) for 100 or more years. They weren’t always this troublesome, but many plant invasions take some time to build up, year after year, gradually gaining ecological turf until a threshold is reached. At some point, once they reach critical mass, they break out and gallop ahead, running roughshod over local ecosystems. Invasive plants and animals might not seem to be a serious problem until suddenly they are.

Cheatgrass fueled wildfires have been recognized for several decades in other Western US ecological zones such as sagebrush steppe and several semiarid forest and woodland types, but this desert phenomenon is a new development as of the mid-2000s. It took the grass populations awhile to spread and achieve a consistent enough density over enough acreage to begin to carry widespread wildfires. In fact it took at least 50 years. But now, seemingly suddenly, an avalanche of new and never-before-seen desert wildfires have burst upon the scene with genuinely tragic results. The threat that was always there but remained somewhat hypothetical has quickly become very real. And very expensive!

Fire retardant is tinted red to help airplane drop pilots see where they have already deposited a load of slurry. The red staining is quite persistent and can last for years after a fire drop. It’s also costly at over $2.00 per gallon, with many drops dumping 1200 to 3000 gallons per round. This dollar figure does not include the fuel, personnel, maintenance, and mechanical costs of the planes or helicopters either, which are thousands of dollar more per hour of use. It costs a lot of money to fight fires using people and advanced equipment. Why not invest in reducing the prevalence of some of the weeds that cause, or worsen, the fires in the first place?

The damage to a number of western biomes caused by cheatgrasses alone has been economically incalculable, although a quick review of the most directly impacted arenas of agriculture, farming, livestock production, firefighting and associated costs, and severe declines in species such as sage grouse will easily place the costs of the cheatgrass invasion at hundreds of millions of dollars annually if not more.

And again, there are so many hard to quantify spheres of influence as well. How much water is evaporated into the air by these grasses via their roots and leaves over millions of acres, as opposed to being available for runoff into watercourses and storage in reservoirs for urban and agricultural uses? What is the loss to wildlife and livestock productivity thanks to the dominance of spiky, unpalatable, and low-nutrition weedy cheatgrass? Would there be more deer and elk and bighorn sheep around with less cheatgrass and a better food supply of nutritious native plants? Would hunting opportunities improve with better rangeland for wildlife, not to mention livestock productivity again? What about insect populations that cannot utilize cheatgrass for larval food sources, and are therefore themselves less abundant as a food supply for reptiles and birds and fish? What is the value of intangibles such as wilderness and open space and recreation and scenery, and a sense of history and place?

Fire retardant stains the leaves of a Mojave yucca. Granted it did work to protect the plants of that area, but the dollar costs of retardant drops on wildfires is not trivial!

What is fairly clear in my mind is that doing something to biologically control cheatgrass and other particularly obnoxious invaders should become a scientific priority for various State and Federal land managers and agencies. Spending a few million or a few tens of millions of dollars on research into fields such as genetic modification, brome-specific pathogens or seed predators, fungi or bacteria that stunt the growth of the plants without affecting other species, and the like could over time yield some amazing benefits. These benefits would be in terms of reduced ecological and economic costs associated with wildfires and agriculture and ranching, etc. It would seem that investing some educational attention into these areas would possibly pay back the research costs many times over in the future, while helping to stabilize and eventually recover the damaged ecosystems that have been so harshly affected by the invasions.

A small wildfire survivor, a desert beehive cactus (Coryphantha vivipara ssp deserti) that escaped incineration in the Duzak Fire.

I would like to also make a plea for wildland managers and firefighters of the future to consider the immense damage to rare and/or declining species such as the Joshua tree and the many-headed barrel cactus when making decisions to allocate resources to firefighting concerns. It is one thing for fire crews to ignore or put as a low priority fighting a fire in rugged, remote wilderness in ecosystems that are relatively abundant. I think it is another to not understand the immense damage that these unchecked wildfires of 2005 did to millions of Joshua trees and other plants in deserts that had never before been subjected to fires.

Range Map of Joshua trees within the United States. Note how the map is really more of an archipelago of island-like populations separated by large areas of no trees, rather than a continuous landmass evenly covered in abundant stands of the plants. The range is very discontinuous despite spanning most of the Mojave Desert. Basically, only about 10% to 12% of the Mojave Desert’s surface area has any Joshua trees at all, while nearly 90% of the land has none.

Joshua trees are not all that common, to be honest. While there are massive numbers of them in selected zones, such as the Tule Desert Valley in Nevada, the Beaver Dam Mountains of Utah (formerly), the Joshua Tree Forest Parkway in Arizona, and Joshua Tree national Park in California, the basic fact remains that on balance Joshua trees are globally uncommon and occur mostly in concentrated populations. Now that many or most of these populations are desperately threatened by unprecedented wildfires, I’d like to ask wildfire and land management professionals to consider giving extra protective priority to those places where the trees occur, especially if they occur in high numbers.

Protecting dense Joshua tree groves, especially ones also containing high numbers of other succulent plants (and subsequently also wildlife) is more important from a holistic ecological standpoint than protecting a remote desert valley filled mainly with common creosote and bursage, which are in no way endangered. I don’t want to demean those lower-diversity valleys, but the truth is that when costs are high and money is limited, that the focus should be on the higher priority ecological zones with greater diversity and biotic value first, for the reasons I have been laying out in this long treatise. In other words, all deserts are not of equal biological and ecological value.

It should also be mentioned that in most ways, fighting desert wildfires is actually relatively easy when compared to the difficulty of firefighting in many other biomes. Despite the fact that the weedy grasses and mustards are bringing fires to places never before seen, the other truism is that these fires are generally low intensity simply because there still isn’t all that much fuel to burn when compared to a coniferous forest in Montana or a dense chaparral zone in California.

Fires in many western forests and shrublands are often set in dangerous, steep terrain with frightful fuel loads that can create deadly firestorms and flames leaping a hundred feet or more into the air. Desert fires are often in relatively flat or moderate terrain and are generally low and creeping, similar to that of a controlled burn in a well-managed forest or grassland. The point is not to compare these fires and claim that desert firefighting is always easy and with zero risks, but to say that in so many cases a crew of people working to stamp out a small line of crawling flames a few inches or a foot high could save hundreds of thousands of desert plants. Because these plants will generally not be able to survive even the slightest loss of their protective spines or leaves, as I hope I have more than adequately explained above.

Here is my urgent plea for changing the way decisions are made, when considering how to allocate firefighting resources in desert situations in the future: Dedicating some extra resources to these unnatural desert wildfires early on, rather than “letting it burn because it’s a natural occurrence and is good for the ecosystem”, is a standard that emphatically DOES NOT apply to deserts. It would apply perfectly well to prairies in Kansas, to oak savannas in California, and to pine barrens in Florida, but it does not apply to deserts anywhere in any state.

Fire has no natural role in intact desert ecology, just as it has no role in a tropical rainforest or an alpine tundra ecosystem. These are two other examples of biomes where fires are ruinous to the natural regime and have never existed under normal circumstances. I hope that after reading this, fire and land management agencies will understand why it is both important to prioritize stopping desert wildfires ASAP, and also not unreasonable to actually accomplish given the nature of most desert fires and what is at stake for the plants and animals of these newly threatened ecosystems.

A more detailed map of Arizona populations of Joshua trees, showing densities of the trees in two different colors. The darker green zones are the best, most dense Joshua tree forests, while the light green are places where trees exist, but in lower numbers. In other words, not every population is created equal in terms of conservation value. And while this map deals only with Arizona, a similar pattern would apply to the entire regional map in the four states where Joshua trees exist.

Joshua trees and cottontop/many-headed barrels are two of the most prominent species of desert succulents that are at greatest risk from this new menace of weed-fueled wildfires. These two species in particular suffer from a convergence of factors that limit their flexibility to recover from said fires, including restricted and discontinuous natural distribution, slow growth, limited capacity to reproduce via seeds, and vulnerability to both future and already-in-progress climate changes. There are other plants that also fall into this vulnerable category but the main focus of this article is obviously Joshua trees. For if we protect those from unnatural fires first, we often also protect them all.

Coming next: The same situation applies to the saguaro cactus and other important iconic cacti of the Sonoran Desert, with some key differences. Stay tuned as I lay out explanations for that ecosystem as well.

Thank you for reading and for taking action to spread awareness of this issue.

A burned saguaro cactus (Carnegiea gigantea) in Sonoran Desert in July 2005. More on this in the next article….