Long-term Ecological Research Reveals Causes and Consequences of Environmental Change
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As global temperatures rise, the most threatened ecosystems are those that depend on a season of snow and ice, scientists from the National Science Foundation (NSF) Long Term Ecological Research (LTER) Network have found.
"The vulnerability of cool, wet areas to climate change is striking," says scientist Julia Jones of Oregon State University and the H.J. Andrews LTER site in Oregon.
Jones is the lead author of a paper in the April issue of the journal BioScience; the issue features results from more than 30 years of long-term ecological research.
In semi-arid regions like the Southwestern United States, mountain snowpacks are the dominant source of water for human consumption and irrigation.
Research by Jones and colleagues shows that as average temperatures increase in these snowy ecosystems, a significant amount of stream water is lost to the atmosphere.
The study involves more than 30 years of data from 19 forested watersheds across the country. All the study sites provide water to major agricultural areas and to medium and large cities.
But, like many long-term studies, this one revealed a surprise; water flow only decreased in the research sites with winter snow and ice.
"Streams in dry forested ecosystems seem more resilient to warming," says Jones. "These ecosystems conserve more water as the climate warms, keeping streamflow within expected bounds."
A range of factors can affect watersheds, from human influence past and present, to El Niño climate oscillations.
"Long-term records are finally long enough to begin to separate the effects of each," Jones says.
"This research shows both the vulnerability and resilience of headwater streams. Such nuanced insights are crucial to effective management of public water supplies."
Surprising and transformative results are common in the NSF LTER network, which comprises 26 sites in North America, Puerto Rico, the island of Moorea and Antarctica.
The network has amassed more than 30 years of data on environmental recovery and change.
In contrast to most research of this type, which span only a few years, LTER studies are sustained over decades, documenting gradual changes and long-term variability that often cannot be revealed by short-term studies.
"Each additional year of LTER data helps us to better understand how ecosystems respond to environmental change," says Scott Collins, an ecologist at the University of New Mexico and principal investigator at the Sevilleta LTER site in New Mexico.
"Such understanding provides valuable information for federal agencies, land managers and legislators who want to develop responsible policies to deal with a rapidly changing world."
The results reveal that the LTER network's diversity of long-term research approaches--including detailed observations and experiments, environmental gradient studies and complex simulation models--can contribute to new solutions in an era of unprecedented environmental change.
"How can we evaluate the ability of natural ecosystems to sustain critical ecological processes and the human societies that depend on them?" asks Saran Twombly, NSF LTER program director.
"LTER research demonstrates the unique and powerful insights that emerge from long-term studies and the analysis of long-term data," she says. "The results reach beyond scientists to engage the public and decision makers."
In addition to deciphering ecosystem-level clues, LTER research can identify the biological winners and losers in a changing climate.
"The cryosphere, or the part of the Earth affected by snow and ice, has been shrinking," says scientist Andrew Fountain of Portland State University in Oregon and the McMurdo Dry Valleys LTER site.
"Populations of microbes, plants and animals that depend on snow and ice will decrease if they are unable to migrate. But life that finds the cryosphere too hostile should expand."
In shallower snow, he explains, animals such as white-tailed deer, mule deer, elk and caribou expend less energy and can more easily escape predators.
"One species' loss can be another species' gain," says Fountain.
The retrospective look at the LTER network comes at a time when institutions charged with stewarding the nation's environmental health are increasingly being challenged to provide a basis for their decision making.
An article by scientist Charles Driscoll of New York's Syracuse University and the Hubbard Brook LTER site in New Hampshire shows that LTER research has contributed to important decisions over the past decade, including state and regional forest and watershed management policies.
"LTER datasets and experiments help inform local- to national-scale decisions on climate change, pollution, fire, land conversion and other pressing environmental challenges," says Driscoll. "This creates a crucial bridge between the scientific community and society."
Demand for natural resources is increasing with the global human population, which the United Nations projects will reach at least 9 billion by 2050.
Long-term ecosystem data can help researchers simulate a region's future based on a range of possible human actions.
"For example, how might forest ecosystems change if more people begin to use wood to heat their homes?" asks Jonathan Thompson of the Smithsonian Conservation Biology Institute in Front Royal, Va., and the Harvard Forest LTER site in Massachusetts. Thompson is the lead author of a paper in the volume.
Each year, some 2,000 scientists and students carry out more than 200 large-scale LTER field experiments to find new answers.
The resulting datasets are freely and publicly available online.
"LTER sites are providing transformative information about the causes and consequences of climate and environmental changes to ecosystems," says David Garrison, NSF program director for coastal and ocean LTER sites.
"They are some of our best hopes for providing the sound scientific underpinnings needed to guide policy for the challenges of future environmental change."