The team found that earthworms do not, as was suspected, stimulate carbon sequestration in the soil, which helps to reduce greenhouse gas emissions. Instead, they actually increase greenhouse gas emissions through a variety of ways.
"There was a hypothesis that earthworms were having a positive effect on the greenhouse balance, but they don't," said co-author Johan Six, a plant sciences professor at UC Davis during the study who is now a professor at ETH Zurich in Switzerland. "I would never say you have to take out the earthworms because of greenhouse gases. It's just that you cannot give them credit for reducing greenhouse gases."
The scientific team was led by Jan Willen van Groenigen of Wageningen University in the Netherlands, and, along with UC Davis, included colleagues from Trinity College Dublin, and the International Center for Tropical Agriculture in Cali, Colombia.
The team gathered all relevant published research to date: 57 different experiments.
The research team then employed a statistical technique called meta-analysis to discern overall patterns in the data.
They found that the presence of earthworms increased nitrous oxide emissions from soil by 42 percent and carbon dioxide emissions from soil by 33 percent. But they found no indications that earthworms affect soil organic carbon stocks -- the carbon stored within the soil.
According to the researchers, earthworms likely increase greenhouse gas emissions several ways: they mix organic plant residues in the soil, which may increase decomposition and carbon dioxide emissions; the earthworm gut acts as a microbial incubator, boosting the activity of nitrous oxide-producing microbes; and the earthworms, by burrowing through the soil, make it easier for greenhouse gases in the soil to escape into the atmosphere.
Small changes in soil greenhouse gas dynamics can have important repercussions for global warming, the researchers said. But lead author Ingrid Lubbers from Wageningen University said it is not yet clear to what extent the effects of earthworms on plant growth may negate earthworm-induced increases in greenhouse gas emissions.
"Our literature search also pointed out a large gap in the published studies," Lubbers said. "We need more experiments that include growing plants, as well as more long-term studies and more field studies before we can decide to what extent global worming leads to global warming."
One study, published online Monday, Aug. 6, in the journal Global Change Biology, finds that changes in precipitation have been underappreciated as a factor in driving bird species out of their normal range. In the other study, published today (Wednesday, Aug. 15) in the journal Proceedings of the Royal Society B, researchers found a sharp decrease in range for the Belding's ground squirrel, but noted some surprising areas where the species found refuge.
The two studies exemplify the type of research being explored through the Berkeley Initiative in Global Change Biology <http://ib.berkeley.edu/labs/globalchange>, or BiGCB, an ambitious effort to better understand and predict how plants and animals will respond to changing environmental conditions by studying how they have responded to earlier periods of climate change.
The first study’s findings challenge the conventional reliance on temperature as the only climate-related force impacting where species live. The authors noted that as many as 25 percent of species have shifted in directions that were not predicted in response to temperature changes, yet few attempts have been made to investigate this.
"Our results redefine the fundamental model of how species should respond to future climate change," said study lead author Morgan Tingley, who began the research as a graduate student in UC Berkeley's Department of Environmental Science, Policy and Management. "We find that precipitation changes can have a major, opposing influence to temperature in a species' range shift. Climate change may actually be tearing communities of organisms apart."
The findings are based upon data gathered from the Grinnell Resurvey Project, which retraces the steps of Joseph Grinnell, founder of the UC Berkeley Museum of Vertebrate Zoology, in his surveys of Sierra Nevada wildlife from the early 1900s. The resurvey project, which began in 2003, was led by Craig Moritz, former UC Berkeley professor of integrative biology, and his colleagues at the Museum of Vertebrate Zoology.
For the bird study, the researchers included 99 species in 77 historic survey sites in Lassen Volcanic, Yosemite and Sequoia national parks, as well as in several national forests. In the century that has passed since the original Grinnell survey, summer and winter temperatures have increased an average of 1-2 degrees Celsius in the Sierra Nevada. Yosemite experienced the most warming — with average temperatures increasing by 3 degrees Celsius — while parts of Lassen actually got cooler and much wetter.
Among the bird species that moved upslope are the Savannah Sparrow, which shifted upward by 2,503 meters, and other meadow species such as the Red-winged Blackbird and Western Meadowlark. The ones that shifted their range downslope include both low-elevation species like the Ash-throated Flycatcher and Western Scrub-Jay, and high-elevation species like the Cassin’s Finch and Red-breasted Nuthatch.
"Temperature did not explain the majority of these shifts," said Tingley, who is now a postdoctoral researcher at Princeton University's Program in Science, Technology and Environmental Policy. ''Only when we included precipitation as an explanatory variable did our models adequately explain the movement patterns we observed."
The researchers found that while rising temperatures tended to push birds to cooler regions upslope, increased precipitation, which is more common at higher elevations, pulled them downslope.
"We believe many species may feel this divergent pressure from temperature and precipitation, and in the end, only one wins," said Tingley.
Notably, more than half of the bird species in each of the three study regions did not shift their range despite pressures from climate change. "Moving is a sign of adaptation, which is good from a conservation standpoint," said Tingley. "More worrisome are the species that have not shifted. How are they adapting? Are they moving, but we just can’t detect it? Or are they slowly declining as environmental conditions gradually become less ideal where they live?"
The answers are complex, as illustrated by the second UC Berkeley paper about range changes for a species of squirrel found in the mountains of the western United States.
In that paper, researchers again used information obtained from the Grinnell Resurvey Project. Through visual observations and trapping surveys conducted throughout the mountains of California, they discovered that the Belding's ground squirrel had disappeared from 42 percent of the sites where they were recorded in the early 1900s. Extinctions were particularly common at sites with high average winter temperatures and large increases in precipitation over the last century.
"We were surprised to see such a dramatic decline in this species, which is well-known to Sierran hikers and was thought to be fairly common," said study lead author Toni Lyn Morelli, a former National Science Foundation postdoctoral researcher who was based at UC Berkeley. "In fact, the rate of decline is much greater than that seen in the same region for the pika, a small mountain-dwelling cousin of the rabbit that has become the poster child for the effects of climate warming in the contiguous United States."
Morelli added that the squirrels are thriving in areas that have been modified by humans. For example, irrigated Mono Lake County Park serves as an artificial oasis that sustains squirrel populations despite otherwise hot and dry conditions in eastern California.
"As predictions indicate that the range of the Belding’s ground squirrel could disappear out of California by the end of the century, these areas might be particularly important for this and other climate-impacted species," said Morelli, who is now a technical advisor for the U.S. Forest Service's International Programs in the Democratic Republic of Congo.
Although the Belding's ground squirrel is widespread, the rapid decline in its distribution is of concern because it is an important source of food for raptors and carnivores. However, the paper suggests that even when climate change causes large range declines, some species can persist in human-modified areas.
"Taken together, these two studies indicate that many species have been responding to recent climate change, yet the complexities of a species' ecological needs and their responses to habitat modification by humans can result in unanticipated responses," said Steven Beissinger, professor in the Department of Environmental Science, Policy and Management at UC Berkeley and the senior author on both studies. "This makes it very challenging for scientists to project how species will respond to future climate change."
Funding from the National Science Foundation, National Park Service, and California Landscape Conservation Cooperative helped support this research.
RELATED INFORMATION
- Museum scientists to repeat landmark 80-year-old Yosemite wildlife survey <http://berkeley.edu/news/media/releases/2003/08/05_survey.shtml> (UC Berkeley press release)
- Sierra Nevada birds move in response to warmer, wetter climate <http://berkeley.edu/news/media/releases/2009/09/14_birds.shtml> (UC Berkeley press release)
- Grinnell Resurvey Project <http://mvz.berkeley.edu/Grinnell/>
- Berkeley Initiative in Global Change Biology <http://ib.berkeley.edu/labs/globalchange/>
- Author: Robert Sanders, (510) 643-6998, rsanders@berkeley.edu
In a press announcement accompanying the release of the studies, Secretary of Natural Resources John Laird noted that “significant increases in wildfires, floods, severe storms, drought and heat waves are clear evidence that climate change is happening now. California is stepping up to lead the way in preparing for — and adapting to — this change. These reports use cutting-edge science to provide an analytical roadmap, pointing the way for taking concrete steps to protect our natural resources and all Californians.”
Laird and others appeared yesterday at a press conference in Sacramento, where Robert B. Weisenmiller, chair of the California Energy Commission, called the reports “historic” and praised the scientists who contributed.
“We scientists know that climate change is and will be significantly affecting the state’s energy supply and demand system,” he said. “The research in these assessments furthers our understanding of the impacts …. The challenges are enormous, but certainly this state has the capability to rise to those challenges, and with these types of studies we are going to be prepared. We will use these in the energy commission planning … to maintain a reliable grid, but also use this as a way of planning our research.”
Laird and Weisenmiller were joined at the press conference by Chief Ken Pimlott, director of the California Department of Forestry and Fire Protection (Cal Fire), who painted a grim picture of the state’s fire future. Of the 20 worst fires in California history, 11 have occurred since 2002, he said. The fire season in some areas has increased by an average of two months, and a few areas in Southern California now have a year-round fire season.
“Studies like those being released today are key in helping us move forward to prepare California” to deal with these large and damaging fires, said Pimlott.
State’s fire season longer, fires more intense
UC Berkeley fire expert Max Moritz, who contributed a paper about increased vulnerability to wildland fires in the state, has been warning of increasing fire danger for years.
“Our results reveal that California should prepare — regardless of the future we may face climatically — for quite different fire activity levels in the future,” said Moritz, UC Cooperative Extension specialist in the Department of Environmental Science, Policy and Management at UC Berkeley. “Though our models continue to improve, we still don’t know which future climate scenario will actually emerge. The challenge is to learn to ‘coexist’ with this natural hazard and move toward fire-resilient ecosystems and fire-resistant urban development.”
Speaking for the more than 120 scientists in 26 teams who contributed to the studies, Susanne Moser, a Social Science Research Fellow at Stanford University’s Woods Institute for the Environment, said that the report “spells out our new understanding of what climate change might mean to California. We are trying to inform the public, we are trying to inform the decision makers, with valuable information that they can use in … planning.”
The reports represent the third assessment commissioned by the California Climate Change Center since 2006, following up on discussions and topics presented at the Governor’s Conference on Extreme Climate Risks and California’s Future held last December in San Francisco. The new studies will provide a foundation for the 2012 Climate Adaptation Strategy, which is expected to be completed in December 2012.
David Ackerly, who co-authored three of the papers released yesterday, provided a new vegetation map that will allow planners to see how the Bay Area will likely change in the future.
“The big result that comes out of the models — and we have to remember that they are models — is a very wide expansion of chaparral and the loss of the cooler oak woodlands. And as climate change becomes more extreme, the Bay Area looks more and more like Santa Barbara or areas farther south, and the vegetation begins to look like Southern California, which is mostly scrublands,” said Ackerly, a professor of integrative biology. “That could take a hundred years or more, but the short-term result is that the dead trees become a fire danger and alien weeds invade.”
The short-term impacts are the most uncertain, he said, though UC Berkeley scientists hope to fill in these gaps through a broad research effort, the Berkeley Initiative in Global Change Biology.
“We hope to answer the question, ‘How fast can these changes really occur?’” he said.
Ackerly said that through his reports, which synthesized previous and ongoing research, he particularly wanted to link the expected decline of biodiversity throughout the state with a more visible impact on the ecosystem services people take for granted. The predicted march of desert northward into the San Joaquin Valley will make some areas unsuitable for agriculture, for example, while warmer winters may mean that plums and peaches will not get the winter chill they need to produce fruit.
“This is not merely nature for nature’s sake; nature and the services we expect from nature are all connected,” he said.
Gov. Jerry Brown is listening to these reports, according to Ken Alex, Brown’s senior policy advisor and director of the Office of Planning and Research, who also spoke at the press conference.
“Here in California, we do make policy decisions based on the science,” he said. “Gov. Brown actually reads the science, and he takes it very seriously, and I know that at a very deeply personal level, he wants to do something about climate change and wants to see California take the leadership role.”
The 26 teams submitting reports were led by researchers from around the state, including 15 from UC Berkeley, 19 from other UC campuses and two from Lawrence Berkeley National Laboratory. For highlights from the reports, link to the CEC’s press release (PDF). To download the full reports, link to CEC’s website.
“The incredible breadth of studies, as well as the depth of their analyses, reveals just how much the University of California has to offer in preparing us all to adapt to a changing climate,” Moritz added. “Hopefully, it also demonstrates how important it is to grow this scientific capacity within our public university system.”
The UC Davis research appears in a report, "Our Changing Climate," released today by the California Natural Resources Agency and the California Energy Commission. The report is the third assessment from the California Climate Change Center since 2006.
UC Davis scientists authored nine of the 35 studies contained in the report. The UC Davis work addresses climate change impacts on native fishes, agriculture, urban planning, water management and other issues:
* Peter Moyle, a wildlife, fish and conservation biology professor in the UC Davis Center for Watershed Sciences, studied the predicted effects of climate change on native fishes. His team found that most native fishes will suffer population declines, and some will likely go extinct. Fishes requiring cold water are particularly vulnerable.
Meanwhile, non-native fishes are expected to increase, although they will also experience habitat loss during severe droughts.
"California's unique native fishes are already in steep decline, and climate change is making the situation worse," Moyle said. "This is likely to increase the complexity of managing California's water supply. Preventing predictable extinctions is possible but will require planning now for increased water temperatures and more variable flows."
* James Thorne, a researcher in the Department of Environmental Science and Policy, helped create a model that simulates how rainfall interacts with the landscape. Thorne's research group looked at hydrologic data from the past and present to help predict what may happen in the future. That model was used for other studies in the report, such as those regarding fire and agriculture, allowing cross comparisons among the researchers' work.
Thorne also looked at six different policy options for urban growth, including smart-growth, infill and "business as usual" approaches.
"If we want the most lands preserved for a variety of different purposes -- agricultural and biodiversity protection, reduced fire threats -- the infill policy was best," Thorne said.
* Studies by Louise Jackson, UC Cooperative Extension specialist and professor in the Department of Land, Air and Water Resources at UC Davis, complemented Thorne's growth policy conclusion. Her group's case study focused on greenhouse gas emission mitigation and adaptation to climate change in Yolo County. They found that "channeling much or all future urban development into existing urban areas" will help preserve agricultural land and open space, reduce Yolo County's greenhouse gas emissions and enhance agricultural sustainability. Their research also found that farmers concerned about climate change were more likely to voluntarily adopt practices that would conserve water and reduce greenhouse gas emissions.
Jackson's group also developed an agricultural vulnerability index for California that identified four areas as especially vulnerable to the effects of climate change: the Sacramento-San Joaquin Delta; Salinas Valley; the corridor between Merced and Fresno; and the Imperial Valley.
* Jay Lund, director of the UC Davis Center for Watershed Sciences, examined climate change adaptations for managing water in the San Francisco Bay Area. His group's research suggests that Bay Area urban water demands can be largely met even under severe forms of climate change, but at a cost. The cost includes buying water from agricultural users, using more expensive alternatives such as water recycling and desalination, and some increased water scarcity. A shared connection of public water systems, or interties, recently completed for emergency response, greatly aids adaptation, the study reports.
* Joshua Viers, associate director of the Center for Watershed Sciences, co-authored a study analyzing "water year" classifications.
These indices determine whether a year is considered wet, dry or in-between, as well as how much water is allocated and who gets it.
"Unfortunately, the method to distinguish different water year types is indexed to historical climatic conditions and is intended to represent an equal chance for any given year," said Viers. "Our science suggests that future climatic conditions are not likely to represent this history, and thus water management agencies may need to reconsider these arbitrary indexing thresholds going forward to achieve a more equitable situation."
Viers also co-authored a study about climate change's impact on hydropower production in the Sierra Nevada. It found that an 11 F increase in air temperature would reduce hydropower in the area by about 10 percent, and that most reductions would occur in the northern Sierra Nevada. The central Sierra Nevada would adapt better to changes in runoff, while hydropower generation in the southern watershed would decrease.
Other institutions, including UC Berkeley, UC Santa Cruz, Stanford, the Scripps Institution of Oceanography, and Lawrence Berkeley National Laboratory researched climate change impacts on electricity consumption, sea level, wildfires and coastal flooding.
This assessment will provide a foundation for the state's 2012 Climate Adaptation Strategy, with completion expected in December 2012. Comprised of scientific studies from several academic institutions, the assessment is directed by the Governor's Office and intended to help state and local communities protect public health, grow the state's economy, ensure energy reliability and safeguard the environment.
By the end of the century, almost all of North America and most of Europe is projected to see a jump in the frequency of wildfires, primarily because of increasing temperature trends. At the same time, fire activity could actually decrease around equatorial regions, particularly among the tropical rainforests, because of increased rainfall.
The study, to be published Tuesday, June 12, in Ecosphere, an open-access, peer-reviewed journal of the Ecological Society of America, used 16 different climate change models to generate what the researchers said is one of the most comprehensive projections to date of how climate change might affect global fire patterns.
"In the long run, we found what most fear — increasing fire activity across large parts of the planet," said study lead author Max Moritz, fire specialist in UC Cooperative Extension. "But the speed and extent to which some of these changes may happen is surprising."
"These abrupt changes in fire patterns not only affect people's livelihoods," Moritz added, "but they add stress to native plants and animals that are already struggling to adapt to habitat loss."
The projections emphasize how important it is for experts in conservation and urban development to include fire in long-term planning and risk analysis, added Moritz, who is based at UC Berkeley’s College of Natural Resources.
UC Berkeley researchers worked with an atmospheric scientist from Texas Tech University to combine over a decade of satellite-based fire records with historical climate observations and model simulations of future change. The authors documented gradients between fire-prone and fire-free areas of Earth, and quantified the environmental factors responsible for these patterns. They then used these relationships to simulate how future climate change would drive future fire activity through the coming century as projected by a range of global climate models.
"Most of the previous wildfire projection studies focused on specific regions of the world, or relied upon only a handful of climate models," said study co-author Katharine Hayhoe, associate professor and director of the Climate Science Center at Texas Tech University. "Our study is unique in that we build a forecast for fire based upon consistent projections across 16 different climate models combined with satellite data, which gives a global perspective on recent fire patterns and their relationship to climate."
The fire models in this study are based on climate averages that include mean annual precipitation and mean temperature of the warmest month. These variables tend to control long-term biomass productivity and how flammable that fuel can get during the fire season, the researchers said.
Variables that reflect more ephemeral fluctuations in climate, such as annual rainfall shifts due to El Niño cycles, were not included because they vary over shorter periods of time, and future climate projections are only considered representative for averages over time periods of 20-30 years or longer, the authors said.
The study found that the greatest disagreements among models occur for the next few decades, with uncertainty across more than half the planet about whether fire activity will increase or decrease. However, some areas of the world, such as the western United States, show a high level of agreement in climate models both near-term and long-term, resulting in a stronger conclusion that those regions should brace themselves for more fire.
"When many different models paint the same picture, that gives us confidence that the results of our study reflect a robust fire frequency projection for that region," said Hayhoe. "What is clear is that the choices we are making as a society right now and in the next few decades will determine what Earth’s climate will look like over this century and beyond."
Study co-author David Ganz, who was director of forest carbon science at The Nature Conservancy at the time of the study, noted the significance of the findings for populations that rely upon fire-sensitive ecosystems.
"In Southeast Asia alone, there are millions of people that depend on forested ecosystems for their livelihoods," he said. "Knowing how climate and fire interact are important factors that one needs to consider when managing landscapes to maintain these ecosystem goods and services."
The researchers noted that the models they developed focused on fire frequencies, and that linking these to other models of fire intensity and vegetation change are important next steps.
"Our ability to model fire activity is improving," said Moritz, "but a more basic challenge is learning to coexist with fire itself."
The Natural Sciences and Engineering Research Council of Canada, the U.S. Forest Service, the National Science Foundation and The Nature Conservancy helped support this study.
RELATED INFORMATION
- Climate change to spur rapid shifts in fire hotspots, projects new analysis (2009 UC Berkeley press release)
