Scientists have said that the most threatened systems due to increasing global warming are those that depend on a season of snow and ice.
The finding results from more than 30 years of Long Term Ecological Research (LTER), a program of the National Science Foundation (NSF).
"The vulnerability of cool, wet areas to climate change is striking," said Julia Jones, a lead author of the study.
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 her colleagues showed 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 thirty years of data from 19 forested watersheds across the country. All of 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. These ecosystems conserve more water as the climate warms, keeping streamflow within expected bounds," Jones explained.
A range of factors can impact watersheds, from human influence past and present, to El Nino climate oscillations.
"Long-term records are finally long enough to begin to separate the effects of each. This research shows both the vulnerability and resilience of headwater streams. Such nuanced insights are crucial to effective management of public water supplies," Jones pointed out.
Surprising and transformative results are common in LTER, 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 grant-funded research, which spans only a few years, LTER studies are often sustained over decades, documenting gradual changes and long-term variability that often cannot be revealed by short-term studies.
Scott Collins, Chair of the LTER Executive Board, observes that "each additional year of LTER data helps us to better understand how ecosystems respond to environmental change. 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."
In addition to deciphering ecosystem-level clues, LTER research can identify the biological winners and losers in a changing climate.
According to Andrew Fountain, lead author of another LTER study, "The cryosphere, or the part of the earth affected by snow and ice, has been shrinking. The populations of microbes, plants, and animals that depend on the snow and ice will decrease if they are unable to migrate to new areas with ice. But life that previously found the cryosphere too hostile should expand."
In shallower snow, he explained, 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," said Fountain.
The study appeared in the April issue of the journal BioScience.