- Author: Gabrielle Boisramé
Reposted from the California Water Blog
Now that summer is over and rain has returned to California, it appears that the dramatic 2017 fire season is finally behind us. The effects of fire season can linger, however, with the possibilities of erosion and polluted runoff from burned areas. Napa County has even issued suggestions for how to protect waterways in burned landscapes.
Not all news is bad when it comes to the interactions between fire and water, however. These two seemingly opposite elements can actually work in tandem under the right circumstances, to the benefit of people as well as the environment.
While the North Bay fires were filling the headlines in October, another fire 200 miles away was quietly entering its third month of burning in the Sierra Nevada wilderness. This other fire, known as the Empire Fire, was ignited by lightning. By allowing this fire to slowly burn, the park service allowed natural processes to remove fuels that could otherwise build up and lead to more dangerous fires in the future.
The Empire fire burned through an area in Yosemite where fires have been allowed to burn for over 40 years, the longest period managed with such a strategy anywhere in California. Research in Yosemite and other areas shows that allowing these wilderness fires to burn can increase the amount of water stored in the soil or flowing downstream. In the winter, forest clearings opened up by fires often store deeper snow that melts later than in densely forested areas, meaning more water is released slowly in the spring and summer rather than all rushing out as floods in the winter.
Fires can also open up meadow areas that have been overgrown by forest. Although wet meadows cover only a small percentage of California's landscape, they provide important benefits to the water supply. Meadows reduce the size of floods by storing water during high runoff periods. They also help to store water for the dry summer months by holding that water like sponges and slowly releasing it.
The biggest news about fire and water, unfortunately, is usually about how burned landscapes contribute to erosion, which then pollutes streams and clogs reservoirs. When fires burn homes, pollution risks can be especially high due to the presence of hazardous chemicals. Fires can also lead to larger floods since there is less vegetation to slow water's path from rainfall to stream runoff.
These negative effects, however, usually happen because a large portion of a watershed has been completely stripped of vegetation, and plants have not been able to re-grow in time to stabilize the soil. These kinds of fires are usually caused by a combination of dense fuels and extreme weather. When fires burn under less extreme conditions (lower fuel loads, high humidity, low temperatures, and/or low wind speeds), they can clear out dead fuels and remove a small number of trees while leaving most large trees intact. After the fire, the remaining trees (as well as new growth of understory plants) often enjoy wetter soils and less competition. This increases the ability of plants to survive drought conditions.
Wildfire has always been a part of California – especially northern California and the Sierra Nevada – for as long as it has had lush vegetation and dry summers. Native Californian plants have adapted to this process. Some species, like redwoods, even depend on fire for regeneration. Native Californian people historically used fire as a tool to promote the growth of desired plants.
In the early 1900s, however, those in charge came to what seemed to be a very logical decision: to protect our homes and forests from fire, we should put out all fires as quickly as possible. Although this policy was initially very successful, a century later we have flammable forests with heavy fuel loads, as well as densely packed trees that send large amounts of water into the air through their leaves rather than allowing it to flow downstream or remain underground to be used during droughts.
Large public land managers such as the National Park Service and U.S. Forest Service have lately been shifting away from the strategy of suppressing every single fire. Instead, lightning-ignited fires that are burning under acceptable conditions (not too windy, not too close to infrastructure, etc.) are allowed to burn and perform their natural functions of clearing fuels and thinning forests to sustainable tree densities. Prescribed fires and mechanical thinning are also used in situations where greater control is required to reduce risk.
In this way, letting some fires burn today can prevent catastrophic fires from burning through dense fuel in the future. Preventing such catastrophic fires removes their threat to the water supply – as well as the potentially devastating human losses, as we saw from the Atlas, Tubbs, Nuns, and other fires this year. Increased streamflow, snowpack, and drought resistance in burned watersheds all add to this increased water security. The water benefits of more natural forests are receiving increased attention lately, with some companies even working to set up markets for downstream water users to pay for upstream forest care.
We cannot prevent all wildfires in California. However, by understanding their role in our natural systems and incorporating them into our land management, we can benefit from them.
Gabrielle Boisramé has a PhD in environmental engineering from U.C. Berkeley, where she studied the effects of wildfire on water balance in the Sierra Nevada with Prof. Sally Thompson. She continued this work as a post-doctoral scholar with Prof. Scott Stephens, also at U.C. Berkeley.
Boisramé, Gabrielle, S. Thompson, B. Collins, and S. Stephens. “Managed wildfire effects on forest resilience and water in the Sierra Nevada.”
Lundquist, J. D., S. E. Dickerson-Lange, J. A. Lutz, and N. C. Cristea. Lower forest density enhances snow retention in regions with warmer winters: A global framework developed from plot-scale observations and modeling.
Neary, D., K. C. Ryan, and L. F. DeBano. Wildland fire in ecosystems: Effects of fire on soil and water.
van Wagtendonk, J. W. The history and evolution of wildland fire use.
- Author: Robert Sanders
Reposted from UC Berkeley News
An unprecedented 40-year experiment in a 40,000-acre valley of Yosemite National Park strongly supports the idea that managing fire, rather than suppressing it, makes wilderness areas more resilient to fire, with the added benefit of increased water availability and resistance to drought.
After a three-year, on-the-ground assessment of the park's Illilouette Creek basin, UC Berkeley researchers concluded that a strategy dating to 1973 of managing wildfires with minimal suppression and almost no preemptive, so-called prescribed burns has created a landscape more resistant to catastrophic fire, with more diverse vegetation and forest structure and increased water storage, mostly in the form of meadows in areas cleared by fires.
“When fire is not suppressed, you get all these benefits: increased stream flow, increased downstream water availability, increased soil moisture, which improves habitat for the plants within the watershed. And it increases the drought resistance of the remaining trees and also increases the fire resilience because you have created these natural firebreaks,” said Gabrielle Boisramé, a graduate student in UC Berkeley's Department of Civil and Environmental Engineering and first author of the study.
Boisramé and co-author Sally Thompson, a UC Berkeley ecohydrologist and assistant professor of civil and environmental engineering, found that even in the drought years covered by the study, the basin retained more water than similar areas outside the park. That translated into more runoff into the Upper Merced River, which flows through Yosemite Valley, at a time when other rivers in the surrounding areas without a restored fire regime showed the same or decreased flow.
“We know that forests are deep-rooted and that they have a large leaf area, which means they are both thirsty and able to get to water resources,” Thompson said. “So if fire removes 20 percent of that demand from the landscape, that frees up some of the water to do different things, from recharging groundwater resources to supporting different kinds of vegetation, and it could start to move into the surface water supplies as stream flow.”
The study is published in the current issue of the journal Ecosystems.
If the results are confirmed from other studies, including the UC Berkeley team's new project analyzing the Sugarloaf Creek Basin in Sequoia and Kings Canyon national parks, they could alter the way the federal government as well as water districts deal with fire, benefiting not only the forest environment but potentially also agriculture and cities because of more runoff into streams and reservoirs.
“I think it has the potential to change the conversation about wildfire management,” said co-author Scott Stephens, a fire expert and UC Berkeley professor of environmental science, policy and management who has studied the Illilouette basin since 2002.
This “wildfire management” strategy is counter to the federal government's 110-year-old Smokey Bear policy, which is followed throughout the West and emphasizes suppressing fires wherever they occur for fear they will get out of control. With persistent drought and a warming climate, the U.S. Forest Service budget is increasingly going to firefighting. On most federal land, only forest thinning and human-initiated prescribed burns are allowed as a way to manage the trees and underbrush.
Stephens noted, however, that these agencies have recognized the folly of total suppression — thanks in part to his own studies throughout the Sierra Nevada over several decades — and current draft wildland management policies for three of the state's national forests allow active wildfire management in up to 60 percent of the forests.
The value of forest clearings
Wildfire management, as opposed to suppression, comes with major changes in the way the forest looks, Stephens and Thompson said. Unlike the dense stands of pine and fir most people associate with Yosemite and similar mid-elevation Sierra Nevada and Rocky Mountain forests, the Illilouette Creek basin has thinner forests and more clearings with dead trees.
“There is much more dramatic structural change in this forest than most people would probably feel comfortable with,” he said. “You are talking about low-density forests and gaps of 4 or 5 acres, up to maybe 100 acres. These are the result of major fires about every decade or so, large enough to cause tree scarring and affecting as much as one-quarter of the basin.”
These fire-caused clearings, however, act as natural fire breaks and make the area resistant to catastrophic fires such as the 2013 Rim Fire in the western part of the park, which burned 250,000 acres and left patches up to 20,000 acres in which not a single conifer tree survived. These areas could take a century to recover, Stephens said.
“In the Illilouette basin we lost about 20 percent of the forest cover, but there was a 200 percent increase in wetland vegetation: meadows starting to reemerge from forests that have probably encroached on historical locations,” Thompson said. “That sets us up to think that this new regime should be leakier as far as water goes — leaky in the way that suits us as a society.”
Even if these wildfire management techniques don't produce more runoff, Thompson added, “I think it is a fabulous result in terms of forest management if you end up with a healthier forest with some better intact aquatic habitat, even if you don't see a drop of water further downstream. It is still the right thing to do from an ecological point of view.
“Bottom line, this strategy might be a triple win-win-win for water, forest structure and fire risk,” she said.
The ‘jewel' of Yosemite National Park
The findings are the culmination of a 14-year study led by Stephens and his UC Berkeley colleagues to learn how monitoring natural, lightning-caused fires with a bias toward letting them burn affects the landscape, the vegetation and the groundwater. Only four areas in the western U.S., including two in California — the Illilouette Creek basin and the Sugarloaf Creek basin — have allowed lightning fires to burn in large areas for decades.
Most studies of different ways to manage wildland fires have been limited to a few hundred acres, and it's hard to extrapolate from such limited experiments to an entire forest. Luckily, Yosemite National Park started its experiment in 1973 — spurred by a 1963 report authored by the late UC Berkeley forester Starker Leopold — to let nature take its course in the Illilouette Creek watershed, stepping in only when fires in the basin threatened to get out of control or sent too much smoke into Yosemite Valley two miles to the northwest.
“This is the first study that looks at fire regime restoration on a watershed scale with empirical data,” he said. “Others do smaller areas or modeling, but this is 40,000 acres — a big place — over many years.”
One reason the basin was chosen was that it was surrounded by granite walls, which naturally prevented fires from spreading outside the basin. It had not been burned by the indigenous tribes of the region, which often set fires to increase acorn production, and had no history of prescribed burns. In fact, it saw only natural, lightning-caused fires except for an interval of nearly a century — 1875 to 1972 — when the park suppressed all fires.
While Stephens and his many students documented the changes in fire over the past 400 years, Boisramé and Thompson analyzed aerial photos to document vegetation change. Then, with the help of installed sensors and more than 3,000 soil moisture measurements throughout the basin, the team was able to estimate the amount of water in the landscape today versus in the past. They found similar or marginally drier conditions where forests had been replaced with shrubs, but these were balanced by much wetter conditions in small areas where meadows expanded.
They observed more snow reaching the ground because of the clearings, and more snow remaining during the spring, delaying runoff. And in recent drought years, when surrounding basins saw more trees die, there was almost no tree mortality in the Illilouette basin.
“In order to really understand whether this approach should be part of our management toolkit, I would recommend that we give it a crack in a few other places,” Thompson said. “This appears to be a promising management strategy without significant harm and with several very strongly quantifiable benefits and several very suggestive outcomes.”
Boisramé, who spent the past four summers sampling and camping in the Illilouette Creek basin, emphasized that this is not a strategy that would work everywhere. But in wilderness areas where wildfire management is being considered because of its safety benefits — to reduce underbrush and eliminate fuel for out-of-control and catastrophic fires that risk lives and property — the ecological and hydrological benefits are a big bonus. Areas with similar elevation and climatic conditions to the Illilouette basin, and thus perhaps suitable for managed wildfire, comprise about 18 percent of the Sierra Nevada, though the strategy may work at lower elevations as well.
“The whole ecosystem will be better off if we let the natural fire process back in,” she said.
The research was supported by a grant from the federal Joint Fire Science Program.
- Author: Glen Martin
Reprinted from California Magazine
The recent rains have blunted the psychological impact of California's four-year drought, washing down the streets, perking up the landscaping, and heightening anticipation for a stormy El Nino-driven winter. We know, however, that one wet year is highly unlikely to end water shortages. What we may not fully grasp is that the damage done to the state's forests is so far reaching that it may be permanent.
How bad is it? Really, really bad. Horrendous, in fact. Sally Thompson, an assistant professor in UC Berkeley's department of civil and environmental engineering, cites the status of the state's iconic giant sequoias as an example. Thompson notes that Cal biology professor Todd Dawson has been monitoring the biggest trees on earth, “and has found that they're extremely stressed. They're dropping leaves—some of them may die. These are trees that have lived 3,000 years, enduring a wide range of environmental conditions, including other droughts. And now they're being killed by this drought. That's suggestive of what we're facing. We're heading into uncharted territory.”
And it's not just giant sequoias. Virtually all of California's trees are drought-stressed, and many are going down for the count. Thompson observes the U.S. Forest Service conducted flights over 8.3 million acres of woodland in the southern Sierra, the Central Coast and Southern California in April and concluded that about 10 percent of the conifers and oaks—about 12.5 million trees—had died in recent months. They had either expired directly from drought or succumbed to bark beetles, which attack weakened trees.
The situation has only grown more grim. Two weeks ago, Gov. Jerry Brown declared a state of emergency, warning that the U.S. Forest Service estimates “more than 22 million trees are dead and that tens of millions more are likely to die by the end of this year.” He asked for federal assistance and called for an accelerated program to cut and clear dead trees, expand the practice of prescribed burns and temporarily allow more burning of wood waste.
Greg Asner, a biologist with the Carnegie Institute for Science, used spectrometers and lasers to evaluate forest canopies on flights out of Sacramento and Bakersfield. The procedures yielded 3-D topographic displays that show the forest in varying shades of blue (healthy) yellow (somewhat stressed) and red (deeply stressed to dying or dead). Bottom line: There's a lot of red in them thar hills. Asner concluded about 20 percent of California's forests are doomed—up to 120 million trees.
The images reveal the trees are dying in a mosaic pattern, says Thompson.
“You'll see patches of dying trees in the middle of healthier forest,” she says. “That's probably due to such things as south-facing slopes or shallow soils. You'd expect such areas to experience (drought-related) stress first. But there's a tremendous volume of dead wood building up all across the forests, and that's pointing to a future that is potentially very
Such a vast accumulation of fuels could lead to wildfires that are perhaps unprecedented in their ferocity. They could be so intense and of such a vast scale that they could lead to broad “ecotonal shift” —the evolution of entire forests from one vegetative regime to another. Ponderosa pine forests, for example, could convert to chaparral fields. Oak woodlands could change to grassy savannas. (As California previously noted, such ecotonal changes already may be occurring on Mt. Laguna in Southern California.)
That all sounds pretty apocalyptic no matter how you burn it, but Thompson observes we don't have to just sit back and take it. It turns out there's quite a bit that could be done to fireproof our forests—and perhaps increase water availability in the process. All it will take is a fair amount of money and political will.
“It's clear that there is more standing biomass—trees—in our forests than existed before active fire suppression began a century or so ago,” says Thompson. “Studies show that the canopies are heavier, and the forests are more vulnerable to fire as a result.”
A little background: Prior to Euro-American settlement, California's coniferous forests were characterized by extremely large, widely-spaced trees. Annals of the day—both textual and pictorial— made it clear that you could ride a horse through the forests unimpeded. There was little or no fuel (branches and dead trees) on the ground. The character of the forests was due to the occurrence of fire, both natural and human-induced; California's natives burned the forests periodically to make hunting easier and encourage the growth of food plants, including acorn-bearing oaks, seed-producing grasses, and bulbs.
The good news: The forests of our forebears probably can be reclaimed. All we have to do is burn and cut down a lot of trees.
In the old days, fire noodled around in a low-energy fashion on the forest floors, killing insect pests, nibbling back the underbrush, and converting deadwood to ashes that ultimately nourished the great pines and firs. Today, wildfires rip through entire landscapes of closely-packed trees, immolating everything down to mineral earth.
“Ultimately, the fires can be so intense that they take out all tree seed sources,” says Thompson, “so the system shifts to chaparral.”
Today's dense forests also have less biodiversity and suck up much more water than the forests of yesteryear. Thompson says studies of today's Sierra Nevada forests indicate they transpire 35 percent more water—that is, extract it from the ground through the roots and transfer it to the air as vapor via foliage—than 19th Century forests.
The good news: The biologically rich, fire resilient and amply watered forests of our forebears probably can be reclaimed. All we have to do is burn and cut down a lot of trees.
“There are three ways to go about it,” says Thompson. “Mechanical thinning, prescribed fire, and managed fire.”
Mechanical thinning would be the removal of trees by chainsaws or heavy equipment. Prescribed fire would be controlled burning—setting blazes when fuels are relatively damp and conditions are cool and humid, allowing for fires that reduce the forest canopy without destroying every standing tree and living creature. Managed fire is basically letting nature run its course. Wildfires would be allowed to burn in unpopulated areas, ideally when weather conditions aren't excessively hot and dry. The U.S. Forest Service is increasingly convinced of the wisdom of this approach. It recently inaugurated new management plans for three of California's national forests, approving managed fire for 50 percent of their acreages.
Thompson and UC Berkeley professor of environmental science, policy and management Scott Stephens are working on a project in Illilouette Creek basin in Yosemite National Park that seems to confirm the healing properties of fire.
“The National Park Service backed off fire suppression and began using managed fire in the basin in 1973,” says Thompson. “Scott and I are seeing strong evidence for increased plant diversity in the basin. There's much more meadowland and scrubland, and the resulting patchiness across the landscape reduces the risk for catastrophic wildfire. We're also seeing greater diversity in water conditions. There are more areas with persistently wetter soils than were recorded under the old completely forested state. We're now trying to determine whether these changes are increasing run-off from Illilouette Creek into the Merced River. “