Posts Tagged: climate change
How wood is used after it is cleared from a forest and where that forest is located largely affects the amount of greenhouse gas emissions released into the atmosphere, according to a new study by UC Davis.
The study, published this week in the advance online edition of the journal Nature Climate Change, provides a deeper understanding of the complex global impacts of deforestation on carbon storage and greenhouse gas emissions.
When trees are felled to create solid wood products, such as lumber for housing, that wood retains much of its carbon for decades, the researchers found. In contrast, when wood is used for bioenergy or turned into pulp for paper, nearly all of its carbon is released into the atmosphere. Carbon is a major contributor to greenhouse gases.
“We found that 30 years after a forest clearing, between 0 percent and 62 percent of carbon from that forest might remain in storage,” said lead author J. Mason Earles, a doctoral student with the UC Davis Institute of Transportation Studies. “Previous models generally assumed that it was all released immediately.”
The researchers analyzed how 169 countries use harvested forests. They learned that the temperate forests found in the United States, Canada and parts of Europe are cleared primarily for use in solid wood products, while the tropical forests of the Southern Hemisphere are more often cleared for use in energy and paper production.
“Carbon stored in forests outside Europe, the USA and Canada, for example, in tropical climates such as Brazil and Indonesia, will be almost entirely lost shortly after clearance,” the study states.
The study’s findings have potential implications for biofuel incentives based on greenhouse gas emissions. For instance, if the United States decides to incentivize corn-based ethanol, less profitable crops, such as soybeans, may shift to other countries. And those countries might clear more forests to make way for the new crops. Where those countries are located and how the wood from those forests is used would affect how much carbon would be released into the atmosphere.
Earles said the study provides new information that could help inform climate models of the Intergovernmental Panel on Climate Change, the leading international body for the assessment of climate change.
“This is just one of the pieces that fit into this land-use issue,” said Earles. Land use is a driving factor of climate change. “We hope it will give climate models some concrete data on emissions factors they can use.”
In addition to Earles, the study, “Timing of carbon emissions from global forest clearance,” was co-authored by Sonia Yeh, a research scientist with the UC Davis Institute of Transportation Studies, and Kenneth E. Skog of the U.S. Department of Agriculture Forest Service.
The study was funded by the California Air Resources Board and the David and Lucile Packard Foundation.
UC Davis geophysicist Gary Acton is one of 34 international scientists that set sail from the Azores Islands on Nov. 17 aboard the drilling vessel JOIDES Resolution. They finished their Mediterranean voyage on Jan. 17, docking in Lisbon, Portugal.
“The climate change recovered at one of the drill sites will be dedicated to providing the most complete marine record of climate change over the past 2 million years of Earth’s history,” said Acton.
The vessel is run by the Integrated Ocean Drilling Program and has the unique ability to core into the deepest reaches of the ocean. The IODP Expedition 339 targeted thick sediment drifts that accumulated from warm, salty water—called Mediterranean Outflow Water—flowing from the Mediterranean through the Strait of Gibraltar. The researchers drilled, sampled and analyzed the sediment to understand the influence that the MOW water mass has on climate, sea level change and the environment.
“A fascinating aspect of these sediments is their ability to record subtle changes in environmental conditions through measurable changes,” said Acton.
Made heavy by its high salt content, the MOW’s warm waters plunge over 3,000 feet—a drop greater than that of Angel Falls, the world’s highest waterfall—into the Atlantic Ocean. It scours the rocky seafloor, coursing along the margins of Spain and Portugal. Passing Scotland and heading toward Norway, the MOW becomes part of the global conveyor belt that overturns the oceans and circulates water and heat around the globe. Along its journey, sand, silt, clay and microorganisms are deposited along the continental margin as thousands of layers of mud, eventually building into sediment drifts. Each layer contains information about Earth’s history.
“My goal is to reconstruct centennial-scale changes in climate and in Earth’s magnetic field for a time period spanning the past 400,000 years,” said Acton. “Only thick, rapidly deposited sedimentary units like those we are coring provide that ability. They are virtual prehistoric observatories.”
During the expedition, the scientists sailed more than 1,200 nautical miles, drilled 19 holes in 7 different locations, and collected 681 sediment cores—equal to about three miles of mud and sand. Now that the researchers have returned to their homes, they will continue to collaborate as they sift through the data.
“Part of the true value of participating on an expedition like this is the incredible amount of science that can be completed, particularly when scientists with a variety of expertise are confined to a 471-foot-long ship and asked to work 12-hour shifts for two months,” said Acton. “That may seem an odd thing to do over the holidays, but we were all thrilled to be a part of this expedition and to have the chance to continue to work together following the cruise.”
There are options for managing water resources to protect the salmon runs, although they would impact hydroelectric power generation, said UC Cooperative Extension associate specialist Lisa Thompson, director of the Center for Aquatic Biology and Aquaculture at UC Davis. A paper describing the study was published online recently in the Journal of Water Resources Planning and Management.
“There are things that we can do so that we have the water we need and also have something left for the fish,” Thompson said.
Working with Marisa Escobar and David Purkey at SEI's Davis office, Thompson and colleagues at UC Davis used a model of the Butte Creek watershed, taking into account the dams and hydropower installations along the river, combined with a model of the salmon population, to test the effect of different water management strategies on the fish. They fed in scenarios for climate change out to 2099 from models developed by David Yates at NCAR in Boulder, Colo.
In almost all scenarios, the fish died out because streams became too warm for adults to survive the summer to spawn in the fall.
The only option that preserved salmon populations, at least for a few decades, was to reduce diversions for hydropower generation at the warmest time of the year.
“If we leave the water in the stream at key times of the year, the stream stays cooler and fish can make it through to the fall,” Thompson said.
Summer, of course, is also peak season for energy demand in California. But Thompson noted that it might be possible to generate more power upstream while holding water for salmon at other locations.
Hydropower is often part of renewable energy portfolios designed to reduce greenhouse gas emissions, Purkey said, but it can complicate efforts to adapt water management regimes to a warming world. Yet it need not be all-or-nothing, he said.
“The goal should be to identify regulatory regimes which meet ecosystem objectives with minimal impact on hydropower production,” he said. “The kind of work we did in Butte Creek is essential to seeking these outcomes.”
There are also other options that are yet to be fully tested, Thompson said, such as storing cold water upstream and dumping it into the river during a heat wave. That would both help fish and create a surge of hydropower.
Salmon are already under stress from multiple causes, including pollution, and introduced predators and competitors, Thompson said. Even if those problems were solved, temperature alone would finish off the salmon — but that problem can be fixed, she said.
“I swim with these fish, they're magnificent,” Thompson said. “We don't want to give up on them.”
Other co-authors of the paper are graduate student Christopher Mosser and Professor Peter Moyle, both in the Department of Wildlife, Fish and Conservation Biology at UC Davis. The study was funded by the U.S. Environmental Protection Agency.
A common assumption has been that native plants and animals would “move,” or migrate, to higher elevations as temperatures rise, to maintain their “preferred” temperatures, but a new report by Jonathan Greenberg at UC Davis, shows that many California plant species moved downhill over the past 70 years.
According to Greenberg, “While the climate warmed significantly in this period, there was also more precipitation. These wetter conditions are allowing plants to exist in warmer locations than they were previously capable of.”
According to the news release summary:
“Many forecasts say climate change will cause a number of plants and animals to migrate to new ranges or become extinct. That research has largely been based on the assumption that temperature is the dominant driver of species distributions. However, Greenberg said the new study reveals that other factors, such as precipitation, may be more important than temperature in defining the habitable range of these species.
“The findings could have global relevance, because many locations . . . have had increased precipitation in the past century, and global climate models generally predict that trend will continue, the authors said.”
Many studies are showing that climate change is impacting plant and animal species, but because of the overlapping influence of so many factors, including temperature, precipitation, and elevation, and even factors such as increases in smog and carbon dioxide, it is too early to predict precisely how climate change will impact native species . . . and agricultural crop production.
Here are some UC Davis news summaries in just the last year on the impact of climate change on plant and animals species:
- Plants moved downhill, not up, in warming world – news summary
- Climate change impact on mountain plants at low elevations – news summary
- Warmer ocean waters favor aliens over natives – news summary
- Warming climate means harsher smog – news summary
- Rising CO2 levels threaten crops – news summary
- Changes in agriculture needed as world warms – news summary
- Climate tipping points may give no warning – news summary
- Butterflies reeling from impact of climate – news summary