CU News
News from the University of Colorado in Boulder.
CU led mountain forest study shows vulnerability to climate change
Sep 9th
Forests where people live and play to be hit hardest
Led by CU-Boulder researcher Ernesto Trujillo and Assistant Professor Noah Molotch, the study team used the data — including satellite images and ground measurements — to identify the threshold where mid-level forests sustained primarily by moisture change to higher-elevation forests sustained primarily by sunlight and temperature. Being able to identify this “tipping point” is important because it is in the mid-level forests — at altitudes from roughly 6,500 to 8,000 feet — where many people live and play in the West and which are associated with increasing wildfires, beetle outbreaks and increased tree mortality, said Molotch.
“Our results provide the first direct observations of the snowpack-forest connections across broad spatial scales,” said Molotch, also a research scientist at CU-Boulder’s Institute of Arctic and Alpine Research. “Finding the tipping point between water-limited forests and energy-limited forests defines for us the region of the greatest sensitivity to climate change — the mid-elevation forests — which is where we should focus future research.”
While the research by Molotch and his team took place in the Sierra Nevada mountain range in California, it is applicable to other mountain ranges across the West, he said. The implications are important, since climate studies indicate the snowpack in mid-elevation forests in the Western United States and other similar forests around the world has been decreasing in the past 50 years because of regional warming.
Forests are drying and becoming more vulnerable
“We found that mid-elevation forests show a dramatic sensitivity to snow that fell the previous winter in terms of accumulation and subsequent melt,” said Molotch, also a scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “If snowpack declines, forests become more stressed, which can lead to ecological changes that include alterations in the distribution and abundance of plant and animal species as well as vulnerability to perturbations like fire and beetle kill.”
A paper on the subject was published online Sept. 9 in Nature Geosciences. Co-authors on the study include Ernesto Trujillo of INSTAAR and the Ecole Polytechnique Fédérale de Lausanne in Switzerland, Michael Golden and Anne Kelly of the University of California, Irvine, and Roger Bales of the University of California, Merced. The National Science Foundation and NASA funded the study.
Molotch said the study team attributed about 50 percent of the greenness in mid-elevation forests by satellites to maximum snow accumulation from the previous winter, with the other 50 percent caused by conditions like soil depth, soil nutrients, temperature and sunlight. “The strength of the relationship between forest greenness and snowpack from the previous year was quite surprising to us,” Molotch said.
The research team initially set out to identify the various components of drought that lead to vegetation stress, particularly in mountain snowpack, said Molotch. “We went after snowpack in the western U.S. because it provides about 60 to 80 percent of the water input in high elevation mountains.”
The team used 26 years of continuous data from the Advanced Very High Resolution Radiometer, a space-borne sensor flying on a National Oceanic and Atmospheric Administration satellite, to measure the forest greenness. The researchers compared it to long-term data from 107 snow stations maintained by the California Cooperative Snow Survey, a consortium of state and federal agencies.
In addition, the researchers used information gathered from several “flux towers” in the southern Sierra Nevada mountain range, which measure the exchanges of carbon dioxide, water vapor and energy between terrestrial ecosystems and the atmosphere. Instruments on the towers, which are roughly 100 feet high, allowed them to measure the sensitivity of both mid-level and high-level mountainous regions in both wet and dry years — data that matched up well with the satellite and ground data, he said.
“The implications of this study are profound when you think about the potential for ecological change in mountainous environments in the West in the not too distant future,” said Molotch, an assistant professor in the geography department. “If we take our study and project forward in time when climate models are calling for warming and drying conditions, the implication is that forests will be increasingly water-stressed in the future and thus more vulnerable to fires and insect outbreaks.
“When you put this into the context of recent losses in Colorado and elsewhere in the West to forest fire devastation, then it becomes something we really have to pay attention to,” he said. “This tipping-point elevation is very likely to migrate up the mountainsides as the climate warms.”
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Commander Scott Carpenter to attend rededication of Scott Carpenter Park Sept. 20
Sep 7th
The City of Boulder Parks and Recreation Department will host a park re-dedication of Scott Carpenter Park with Commander Carpenter in attendance at 4 p.m. on Thursday, Sept. 20.
The park, located at 30th Street and Arapahoe Avenue in Boulder, was dedicated to honor Mercury 7 astronaut Scott Carpenter in May 1963. Carpenter was the second American to orbit the earth, and 2012 marks the 50th anniversary of his historic space flight.
“We are honored that Commander Carpenter is able to attend this park rededication,” said Parks and Recreation Director Kirk Kincannon. “As a Boulder native and a truly exceptional American, the City of Boulder is proud of Scott Carpenter and delighted to host this rededication of the park named in his honor.”
For more information about the park rededication event, please contact Sally Dieterich at 303-413-7242.
CU study: Global warming increasing heavy metals in streams
Sep 7th
in Rocky Mountain watershed
tied to warming temperatures
Warmer air temperatures since the 1980s may explain significant increases in zinc and other metal concentrations of ecological concern in a Rocky Mountain watershed, reports a new study led by the U.S. Geological Survey and the University of Colorado Boulder.
Rising concentrations of zinc and other metals in the upper Snake River just west of the Continental Divide near Keystone, Colo., may be the result of falling water tables, melting permafrost and accelerating mineral weathering rates, all driven by warmer air temperatures in the watershed. Researchers observed a fourfold increase in dissolved zinc over the last 30 years during the month of September.
Increases in metals were seen in other months as well, with lesser increases seen during the high-flow snowmelt period. During the study period, local mean annual and mean summer air temperatures increased at a rate of 0.5 to 2.2 degrees Fahrenheit per decade.
Generally, high concentrations of dissolved metals in the Snake River watershed are primarily the result of acid rock drainage, or ARD, formed by natural weathering of pyrite and other metal-rich sulfide minerals in the bedrock. Weathering of pyrite forms sulfuric acid through a series of chemical reactions, and pulls metals like zinc from minerals in the rock and carries these metals into streams.
Increased sulfate and calcium concentrations observed over the study period lend weight to the hypothesis that the increased zinc concentrations are due to acceleration of pyrite weathering. The potential for comparable increases in metals in similar Western watersheds is a concern because of impacts on water resources, fisheries and stream ecosystems. Trout populations in the lower Snake River, for example, appear to be limited by the metal concentrations in the water, said USGS research biologist Andrew Todd, lead researcher on the project.
“Acid rock drainage is a significant water quality problem facing much of the Western United States,” Todd said. “It is now clear that we need to better understand the relationship between climate and ARD as we consider the management of these watersheds moving forward.”
Warmer temperatures and earlier snowmelt runoff have been observed throughout mountainous areas of the western United States where ARD is common, but it is not known if these changes have triggered rising acidity and metal concentrations in other “mineralized” watersheds because of lack of comparable monitoring data, according to the research team.
CU-Boulder Professor Diane McKnight, a collaborator on the project, has generated much of the upper Snake River data through research projects conducted with her students since the mid-1990s. McKnight said students in her environmental engineering and environmental studies class like Caitlin Crouch — a study co-author who received her master’s degree under McKnight — are highly motivated to understand ARD problems.
“Student can see that their research will have direct applications to addressing a critical issue for Colorado,” said McKnight, professor in the civil, environmental and architectural engineering department and a fellow in CU’s Institute of Arctic and Alpine Research.
In cases where ARD is linked directly with past and present mining activities it is called acid mine drainage, or AMD. Another Snake River tributary, Peru Creek, is largely devoid of life due to AMD generated from the abandoned Pennsylvania Mine and smaller mines upstream and has become a target for potential remediation efforts.
The Colorado Division of Reclamation Mining and Safety, in conjunction with other local, state and federal partners, is conducting underground exploration work at the mine to investigate the sources of heavy metals-laden water draining from the mine entrance. The new study by Todd and colleagues has important implications in such mine cleanup efforts because it suggests that establishing attainable cleanup objectives could be difficult if natural background metal concentrations are a “moving target.”
A study on the subject was published in the journal Environmental Science and Technology. Other collaborators include Andrew Manning and Philip Verplanck of USGS. The data analyzed for the study came from INSTAAR, the USGS and the U.S. Environmental Protection Agency.