This image, from April 2004, shows mortality of some adult Joshua trees resulting from years of hot-dry climate. During the prior year, this area received only 17 percent of its average precipitation and was 4 degrees F warmer than average -- conditions that are projected to become even more frequent in models of future climate. Seedlings and saplings in this southerly stand of Joshua trees are rare to non-existent.

As the climate gets warmer, many forests are feeling the heat. Impacts range from increased forest fire hazards and tree mortality to detrimental beetle outbreaks and alterations to leaf abundance and bloom.

When forest cover or composition changes, there are impacts to the availability of wood products, clean water, recreational opportunities, and habitats for many plants and animals.

In recognition of World Forestry Day, let’s take a glimpse at U.S. Geological Survey science to understand the fate of forests from climate change.

To sustain the health and production of America’s forests, managers need sound science to guide their decisions. The USGS is involved in several initiatives across the nation and in other countries to provide science to understand climate change impacts to forests.

A prescribed fire lights up the night at Sequoia National Park, California. USGS scientists are investigating how fire in an era of climate change are affecting forests across the United States. Credit: USGS, Nate Stephenson

USGS scientists are working to detect what forest changes are happening and the associated impacts, while also developing forecasts and scenarios for what may happen in the future. Scientists are even looking at the potential for our nation’s vegetation, soils and sediments to soak up and store carbon from the atmosphere. This science is the basis on which strategies are developed to manage and protect these environments.

What Changes are Happening Now and in the Future?

Scientists are identifying how climate change is impacting forests by answering questions such as: What’s happening, why, what does it mean, and what does the future hold?

Forest Fires

There is a growing realization that climate warming may be linked to increasing forest fire size, severity, and frequency.  Hotter temperatures result in reduced winter snowpack, earlier snowmelt, longer summer drought, and therefore drier conditions that are more susceptible to fire ignition.

Forest Die-off

USGS scientists have found that warmer temperatures and associated stress from drought are contributing to increased tree mortality in all major forest types around the world. The USGS is developing models to forecast expected changes in tree distributions given projected changes in climate. In the Southwest, for example, Joshua trees will likely be eliminated from 90 percent of their current range in 60 to 90 years. Other USGS research has also identified a rapidly rising death rate for trees in old-growth forests across the West.

Beetle Outbreaks

Hotter temperatures may contribute to outbreaks of insects or diseases, both native and non-native, which are harmful to forests. USGS scientists have linked some recent outbreaks of tree-killing bark beetles in the West to warming temperatures. In Colorado, the USGS is working to evaluate whether and how forest management practices (such as thinning or prescribed burning) increase or decrease forests’ resilience to a currently destructive native insect, the mountain pine beetle.

A hemispherical photo from Pocosin weather station site, Shenandoah National Park.

Leaf Growth and Abundance

As climate changes, it affects the timing of when leaves emerge, the amount of foliage that grows as well as the timeframe when leaves begin to fall. The study of the timing of such events as related to climate is termed “phenology.” USGS scientists are studying how forest phenology may be impacted by climate change, focusing research on Shenandoah National Park in Virginia. Understanding forest phenology patterns is important because it affects water resources, habitat condition, the timing of allergy seasons, vacation planning and tourism, and carbon storage.

Storing Carbon in Forests

Trees naturally soak up CO₂ from the air through photosynthesis. Forests absorb about ¼ of annual anthropogenic (human created) carbon emissions that would otherwise contribute to atmospheric warming.

USGS scientists are assessing the potential of ecosystems to store carbon in vegetation, soils and sediments, which is a process known as biological carbon sequestration. The assessment will help inform land management decisions such as wetland restoration, forest harvesting, or farming techniques. A USGS assessment on the amount of carbon stored in ecosystems across the nation is expected to be completed around 2013.

The USGS is also actively involved in SilvaCarbon, helping countries build the capacity to monitor and manage their forests and carbon. In a collaborative effort, U.S. Federal agencies have been conducting national assessments in Gabon, Indonesia, Colombia, Ecuador and Peru. They are also providing training workshops such as techniques for forest mapping and how to link ground, aerial and satellite observations. SilvaCarbon also contributes to the Group on Earth Observations (GEO) Forest Carbon Tracking initiative.

Forest Science Requires Long-Term Monitoring and Research

Scenic shots of Rocky Mountain National Park, Mountain Pine Beetle damage to pine forest.

Part of the challenge for understanding how forests are affected by climate change is the need for long-term data. Satellites are a cost-effective way to gather wide-spread information on forests, and the USGS Landsat program has been doing so across the globe since 1972. Landsat records provide the world’s longest continuous collection of space-based data.

The world’s longest ongoing annual record of forest data is in Sequoia and Yosemite national parks in California. For 30 years, the USGS has been tracking the birth, growth, health and deaths of some 30,000 individual trees in these parks. Research is coordinated through the USGS Western Mountain Initiative climate change project.

Start with Science

Long-term monitoring and sound science on climate change impacts to our forests is needed to make the most informed decisions to protect these environments.

Contact: Jessica Robertson

USGS scientists Doug Halm, Paul Schuster, and Kathy Kelsey collecting melt water samples from Gulkana Glacier. Results of recent analyses identified old carbonin the Yukon River, but also indicated that the chemical source was not derived from ancient plant material stored in the glacier, but from fossil fuel sources derived from atmospheric deposition. This add new complications to the interpretation of carbon sources and sinks in high latitudes and of the apparent sources of old organic carbon exported by arctic rivers.

A new study concludes that fossil fuel emissions are likely contributors to a substantial amount of organic carbon found on glaciers in Alaska.

Fossil fuel emissions, which contain organic carbon, can speed up the rate of glacier melt when deposited on glacier surfaces. In addition, the organic molecules associated with these deposits can be transported in rivers and streams, affecting downstream aquatic ecosystems. Knowledge of the source and age of organic carbon in glaciers allows for a better understanding of these and other impacts.

Prior research suggested that the main sources of organic carbon in Alaska’s glaciers were from forests and peatlands overrun by glaciers as far back as ten thousand years ago. While old soil and plant material are still possible sources of glacial organic carbon, new research indicates that human-created, or anthropogenic, sources are also important.

“We knew the organic carbon present in Alaska’s glaciers was old, but identifying the sources of this material has been difficult due to the lack of chemical data,” said USGS scientist George Aiken.

While extensive burning of fossil fuels is, geologically speaking, a relatively modern practice, the fuels themselves and the resulting carbon emissions are ancient. This is because the fuels are formed from plants and microorganisms that lived millions of years ago.

“Now we know that a substantial amount of ancient organic matter associated with these and other glaciers is of anthropogenic origin,” continued Aiken.

Why Study Carbon Levels?

When organic matter and other materials from the atmosphere are deposited on the surface of a glacier, less sunlight can be reflected and, therefore, more radiation and heat are absorbed. Having these materials on snow and ice surfaces causes them to melt faster.

Another concern is impacts to ecosystems and species habitats. As an example, organic matter exported to coastal areas is a potential nutrient or food source for aquatic bacteria, phytoplankton, and small grazing zooplankton. Climate warming or other factors may change the amount and quality of organic carbon available to these organisms. These aquatic organisms are also the base of the food web for all aquatic communities.

“When trying to understand climate change and decipher the carbon cycle puzzle, we need to make sure that we are using all of the right pieces,” said USGS scientist Rob Striegl. “As part of that puzzle, we are studying the source and amount of carbon flowing into the Arctic Ocean. An understanding of the complete picture allows for the most informed decisions to protect our environment.”

Melt water stream discharging from Gulkana Glacier, Alaska. USGS research of the Yukon River has had a long term goal of determining the source and fate of organic carbon transported by the river to the Bering Sea and ultimately the Arctic Ocean.

“The Arctic is of special interest because what happens there, such as extensive glacier melt, has impacts on the rest of the world,” continued Striegl. “Glacier environments, especially those in the high latitudes of the Arctic, are also among the most sensitive to climate warming.”

New Twist to Understanding Carbon in Glaciers

“Our new paper describes, for the first time, the detailed chemical composition of dissolved organic matter associated with glaciers and glacial meltwater in coastal Alaska and in Wyoming,” said Aiken.

“This study adds a twist to previous understandings, showing there is another source of organic carbon out there that needs to be considered,” said Striegl.

This study, published in the journal Nature Geosciences, was a collaborative effort of many institutions led primarily by the University of Alaska Southeast, Skidaway Institute of Oceanography, Woods Hole Research Center, and the USGS.

The Role of USGS Science

Earlier studies by the USGS, in collaboration with university researchers, found the presence of ancient organic carbon in the Yukon River and traced it back to meltwater from glaciers. For further analyses, USGS scientists continued those collaborations to sample meltwater from Mendenhall Glacier and Herbert Glacier in southeastern Alaska. The samples were then analyzed at USGS and university laboratories to develop the conclusions outlined in this new study.

“This truly is a collaborative effort, taking the expertise of many scientists to put the story together on the source of the carbon,” said Striegl. “The original work of the USGS in the Yukon basin helped form the questions and lab results contributed to answering the questions; but it took specialized instrumentation and scientific expertise from several other organizations to determine the final answer.”

Additional samples used for age dating and for other chemical characterization of the organic carbon of glaciers from other locations came from Gulkana Glacier in Alaska and from Fremont Glacier in Wyoming.

USGS scientists Doug Halm, Paul Schuster, Peter Murdoch, and Kathy Kelsey collecting melt water samples from Gulkana Glacier.

The Big Picture of Aquatic Carbon

The USGS has a long term goal of determining the source and fate of organic and inorganic carbon transported to coastal areas and oceans across the entire Nation. USGS research on the Yukon and other Arctic rivers is particularly focused on climate warming effects on mobilizing ancient carbon from permafrost to coastal regions and the Arctic Ocean. The USGS participates in the Arctic Great Rivers Observatory project, which is an international effort to study the six largest rivers, including the Yukon, which flow into the Arctic Ocean.

Learn more about USGS Yukon River Basin studies.

Contact: Jessica Robertson

In 1986, Lake Nyos, in the volcanic region of Cameroon, released a cloud of CO2 into the atmosphere, killing 1,700 people and 3,500 livestock in nearby towns and villages. Since then, engineers have been artificially removing the gas from the lake through piping. The gas burst in 1986 from the 200-meter deep Lake Nyos was so violent that water washed over the 80-meter high promontory in the foreground.

In 1986 Lake Nyos, in the volcanic region of Cameroon, suddenly released a cloud of carbon dioxide into the atmosphere, killing 1,700 people and 3,500 livestock in nearby towns and villages.

The cause was a phenomenon later named “exploding lakes,” a hazard scientists hadn’t even known existed before the 1986 tragedy. But since then, to prevent Lake Nyos from exploding again, an international team of scientists and engineers has developed and implemented a program to artificially remove gas from the lake through piping.

USGS scientists initially advised on the project and have long monitored gas levels in the lake to determine whether this removal has been successful. This winter, USGS again joins a team traveling back to Cameroon to upgrade and re-install the monitoring devices. They’ll also update devices monitoring gas levels in nearby Lake Monoun, another exploding lake, where CO₂ has now been completely removed as part of the same project.

Although most of us may not realize it, volcanoes release more than 100 million tons of CO₂ into the atmosphere each year. (For most of the Earth’s history, volcano emissions were the primary source of CO₂ to the atmosphere; now emissions are estimated to be about 30 billion tons per year, with 100 million tons from volcanoes.) Usually the gas released during an eruption is harmless because it is rapidly diluted to low concentrations. However, sometimes the gas can get trapped underground, where it cools and becomes pressurized. If an earthquake or other disturbance later breaks the seal on this trapped gas, a dangerous, large cloud of cold, dense CO₂gas can be released in a very short period.

In 1986, Lake Nyos, in the volcanic region of Cameroon, released a cloud of CO2 into the atmosphere, killing 1,700 people and 3,500 livestock in nearby towns and villages. Since then, engineers have been artificially removing the gas from the lake through piping. A small CO2 cloud from Lake Monoun killed 37 people in 1984.

Cameroon’s exploding lakes are a unique example of this phenomenon, where CO₂ is trapped in the bottom water of deep volcanic craters. The gas stays at the bottom of the lake, held down by the pressure of the overlying water. But eventually, CO₂ gas can start to bubble up to the top of the lake, which reduces the water pressure that usually holds the gas down. When this happens, the gas from the bottom of the lake can vent with exploding force, creating a suffocating cloud that can kill people and animals in low-lying areas.

In 1986 scientists from all over the world, including USGS scientists, traveled to Cameroon to study the disasters. Over the following years, they helped establish a plan to prevent CO₂ from ever again harming the people and livestock in the surrounding villages. Beginning in 2001, a French engineering firm installed pipes that reached the very bottom of the lakes. Pumps initially push some of the lower water upward, releasing water pressure and allowing CO₂ gas bubbles to form. Once bubbles form, the gas naturally flows up and out of the pipe at a controlled rate.

This technique has successfully resulted in the complete degassing of Cameroon’s Lake Monoun, which now poses no risk of gas release. Much of the gas in Lake Nyos has been removed as well, but degassing will continue for several more years before the CO₂ is completely gone.

The USGS continues to monitor water conditions at these two lakes. The probes that measure the dissolved gas pressure are built at USGS, and are permanently installed in the lakes. After a decade of use, the most recent probes now need to be replaced.

In 1986, Lake Nyos, in the volcanic region of Cameroon, released a cloud of CO2 into the atmosphere, killing 1,700 people and 3,500 livestock in nearby towns and villages. Since then, engineers have been artificially removing the gas from the lake through piping. This photo shows a pipe top and raft at Lake Nyos. The self-driven fountain (inset) can reach a height of 150 feet above the lake surface while dissipating carbon dioxide.

These probes allow the USGS and other scientists to understand the natural recharge rate of gas to Lake Monoun, which will reveal the number of years required for gas to build back up to dangerous levels. Also, the probes help scientists track the build-up of methane, another potentially dangerous gas and a byproduct of the degassing. (When the water is piped up, nutrient-rich bottom waters settle on the surface and boost algal growth, resulting in a larger supply of organic material that eventually settles back to the bottom of the lake and produces methane.)

While exploding lakes in Cameroon are unique, volcanic CO₂ poses problems in some areas of the U.S., as well. In fact, in 1994, USGS researchers discovered that large volumes of CO₂ were seeping from beneath Mammoth Mountain, a young volcano in the Long Valley area of California. The seepage was triggered by a persistent swarm of earthquakes, and killed more than 100 acres of trees. The CO₂also forced the U.S. Forest Service to close the area to camping. The USGS continues to monitor this area, where earthquakes and gas seepage remain a concern.

In 1986, Lake Nyos, in the volcanic region of Cameroon, released a cloud of CO2 into the atmosphere, killing 1,700 people and 3,500 livestock in nearby towns and villages. Since then, engineers have been artificially removing the gas from the lake through piping. This photo shows the Lake Nyos pipe in operation. The 200-meter-long pipe is suspended from the raft and allows gas-rich water from the lake bottom to vent to the surface, where the CO2 dissipates into the atmosphere at a controlled rate. The shed on the control raft is about 6 feet high and the fountain is about 120 feet high. There are no pumps involved because the CO2 drives the fountain, just like a shaken bottle of champagne.

Every year in the U.S. and around the world, natural hazards cost lives and billions of dollars in damage. The USGS provides policymakers and the public with a clear understanding of natural hazards and their potential threats to society, and assists with developing smart, cost-effective strategies for achieving preparedness and resilience. The CO₂ removal in Cameroon and monitoring near Mammoth Mountain both save lives and underscore the value of sound science in mitigating natural disasters.

Bill Evans is the USGS scientist traveling to Cameroon for this work, which is part of the USGS National Research Program. NRP researchers study the flow and chemistry of water in the environment, and the techniques they develop can be applied in many fields, including in this case, the mitigation of natural hazards.

For more information, contact Kara Capelli.

Stream lines form a tangled web in this image derived from a set of data on water flow. Credit: David Butman, Yale University

Rivers and streams in the United States are releasing substantially more carbon dioxide into the atmosphere than previously thought. These findings could change the way scientists model the movement of carbon between land, water, and the atmosphere.

The findings were recently published in a Nature Geoscience article entitled “Significant efflux of carbon dioxide from streams and rivers in the United States” by David Butman and Professor Peter Raymond of the Yale School of Forestry and Environmental Studies, as part of David’s Ph.D. thesis. Funding for the study was from NASA, NSF, and the USGS.

Butman and Raymond found that a significant amount of carbon accumulated by plant growth on land is decomposed, discharged into streams and rivers, and outgassed as carbon dioxide (CO₂) into the atmosphere. It is estimated that streams and rivers release almost 100 million metric tons of carbon each year. This release is equal to a car burning 40 billion gallons of gasoline, enough to drive back and forth to the moon 3.4 million times.

Average concentration at and distribution of USGS gauging stations used to calculated CO2 efflux from US streams and rivers. The names correspond to the subregions discussed in the text. Graph published in Nature Geoscience

Water chemistry data from more than 4,000 rivers and streams throughout the United States were incorporated with detailed geospatial data to model the flux of carbon dioxide from water. The river and stream samples were collected at USGS gaging stations and the geospatial data was produced by both the USGS and EPA.

This research is being incorporated into the USGS LandCarbon effort to characterize the current and future fluxes of carbon influenced by both natural and anthropogenic processes. One part of this effort is looking at the potential for carbon storage in the Nation’s vegetation, soils, and sediments, which is known as biological carbon sequestration. For more information on that project, visit the National Assessment of Ecosystem Carbon Sequestration and Greenhouse Gas Fluxes.

Additional information on the Nature Geoscience article can also be found in the National Science Foundation press release.

Contact: Rob Striegl

One of the NSF Harvard Forest Long Term Ecological Research site's many waterways. Credit: David Butman, Yale University

Research on carbon sequestration provides critical information for considering mitigation options for greenhouse gas emissions to the atmosphere and adaptation opportunities for climate change. These research and assessments activities are conducted under the requirements of the Energy Independence and Security Act of 2007 (P.L. 110-140).

This USGS graphic shows the concept of geologic carbon sequestration.

Geologic Carbon Sequestration:

USGS scientists are conducting a national assessment to assess the capacity to store CO₂ in geologic formations. They will be using a USGS science-based methodology for this assessment. This USGS method will also serve as the first step in developing a global sequestration roadmap by the International Energy Agency and as an international standard for global geologic carbon sequestration assessment potential. In addition, the USGS is conducting research to understand what happens in the subsurface when CO₂ is injected into rocks, to better understand the effects of this practice.

Biological Carbon Sequestration:

The USGS is working to create a series of national maps depicting annual carbon storage for U.S. ecosystems. This project will allow the United States to be the first nation in the world to complete such a cutting-edge biological assessment. This product will help land managers visualize and understand the effects of land use, management practices, and wildfire on carbon storage and greenhouse gas emissions. The USGS previously developed a science-based method for conducting a national assessment of biological carbon sequestration, and that is being used to produce these maps.

This USGS graphic shows the concept of biological carbon sequestration

For more information on the USGS methodology for geologic carbon sequestration, visit http://pubs.usgs.gov/of/2010/1127/. For more information on biological carbon sequestration, visit http://pubs.usgs.gov/sir/2010/5233/.

Contact: Jessica Robertson                                        (703) 648-6624