|
News | |
|
|
|
|
Construction Methods of the Ancient Inca Offer Sustainable Lessons
|
9/1/2010 4:31:19 PM
|
Civil engineers and other researchers working under a $90,000 National Science Foundation grant are studying the Great Inca Road of South America for clues to help modern society build roads, bridges and other infrastructure that last longer and have a less harmful impact on the environment.
|
|
|
|
|
Surge Busters Delivering in New Orleans
|
9/1/2010 4:31:19 PM
|
The U.S. Army Corps of Engineers’ $14.6-billion drive to bring New Orleans’ hurricane defenses to 100-year levels of protection by June 2011 could fundamentally change the way U.S. civil-works projects are funded and delivered, project leaders say.
|
|
|
|
Are Wolves Saving Yellowstone's Aspen Trees from Elk?
|
9/3/2010 10:15:52 AM OC_Web@usgs.gov (Office of Communications Web Group)
|
LARAMIE, Wy. — Previous research has claimed that the reintroduction of wolves to Yellowstone National Park in 1995 is helping restore quaking aspen in risky areas where wolves prowl. But apparently elk hungry for winter food had a different idea.
They didn’t know they were supposed to be responding to a “landscape of fear.”
According to a study set to be published this week in Ecology, a journal of the Ecological Society of America, the fear of wolf predation may not be discouraging elk from eating aspen trees after all.
Previous thinking went like this: Aspen are not regenerating well in Yellowstone National Park. Elk eat young aspen. But wolves eat elk. Elk will learn to avoid high-risk areas that wolves frequent. Plants in those areas – such as aspen – will then get a chance to grow big enough so that elk cannot kill them. Eventually, an entire habitat is restored because of a landscape of fear.
Over the last 15 years, the reintroduction of wolves in Yellowstone was heralded as a great success, not only because it reestablished the species, but also because wolves were expected to help restore a healthier ecosystem through such cascading indirect effects on other species.
But this recent study led by Matthew Kauffman, a U.S. Geological Survey scientist, suggests that aspen are not benefitting from the landscape of fear created by wolves, and that claims of an ecosystem-wide recovery of aspen are premature.
“This study not only confirms that elk are responsible for the decline of aspen in Yellowstone beginning in the 1890s, but also that none of the aspen groves studied after wolf restoration appear to be regenerating, even in areas risky to elk,” said Kauffman.
Because the fear of wolves does not appear to be benefiting aspen, the authors conclude that if the Northern Range elk population does not continue to decline -- their numbers are 40 percent of what they were before wolves -- many of Yellowstone’s aspen stands are unlikely to recover. “A landscape-level aspen recovery is likely only to occur if wolves, in combination with other predators and climate factors, further reduce the elk population,” Kauffman said.
Predators play an important role in ecosystems, said Kauffman, and can influence plants by altering how many herbivores there are (by eating the herbivores) or by changing the behavior of herbivores (deterring them from areas where predators lurk). He adds, however, that considerable scientific debate exists regarding the importance of these two ways in which predators influence their prey. And this is especially true for large carnivores.
To complicate matters, predators use different hunting strategies – there is the sit-and-wait strategy (as with a spider in a web, or a rattlesnake waiting for a mouse to leave its burrow) and the more active, go get ’em strategy (think cheetahs and wolves). “So, given that it takes a lot of energy to avoid a predator – energy that could be used to stave off winter starvation – we wanted to find out whether the prey of active-hunting predators such as wolves demonstrated risk-induced changes in areas where they foraged for food,” Kauffman said.
To do this, the authors analyzed tree rings to discern when, in the last century, aspen stands stopped regenerating, examined whether aspen stands have begun to regenerate now that wolves have been reintroduced to the park and tested whether any differences in aspen regeneration were occurring in areas considered safe or risky for foraging elk. They used a landscape-wide risk map of elk killed by wolves over the first 10 years of wolf recovery. Finally, the authors experimentally fenced in young aspen suckers to compare the protection afforded to them by wolves versus that of a physical barrier that prevented elk browsing.
“The results were surprising and have led us to refute several previous claims regarding interactions among wolves, elk and aspen in Yellowstone,” Kauffman said.
The tree rings showed that the period when aspen failed to regenerate (1892 to 1956) lasted more than 60 years, spanning periods with and without wolves by several decades. “We concluded from this that the failure of aspen to regenerate was caused by an increase in the number of elk following the disappearance of wolves in the 1920s rather than by a rapid behavioral shift to more browsing on aspen once wolves were gone from the park,” said Kauffman.
Surveys of current conditions indicated that aspen in study stands exposed to elk browsing were not growing to heights necessary to make them invulnerable to elk. The only places where suckers survived to reach a height sufficient to avoid browsing were in the fenced-in areas. In addition, aspen stands identified as risky from the predation risk map were browsed just as often as aspen growing in less risky areas.
“This work is consistent with much of what researchers have learned from studying wolves and elk in Yellowstone,” Kauffman said. “Elk certainly respond behaviorally to the predation risk posed by wolves, but those small alterations to feeding and moving across the landscape don’t seem to add up to long-term benefits for aspen growing in areas risky to elk.”
The paper, Are wolves saving Yellowstone’s aspen? A landscape-level test of a behaviorally mediated trophic cascade, will be published online in Ecology this week. Co-authors on the study are Matthew Kauffman (USGS), Jedediah Brodie (University of Montana) and Erik Jules (Humboldt State University).
The Ecological Society of America is the world’s largest professional organization of ecologists, representing 10,000 scientists in the United States and around the globe. Since its founding in 1915, ESA has promoted the responsible application of ecological principles to the solution of environmental problems through ESA reports, journals, research, and expert testimony to Congress. Visit the ESA website.

|
|
|
Climate Change Implicated in Decline of Horseshoe Crabs
|
9/3/2010 10:15:52 AM OC_Web@usgs.gov (Office of Communications Web Group)
|
LEETOWN, W. Va. — A distinct decline in horseshoe crab numbers has occurred that parallels climate change associated with the end of the last Ice Age, according to a study that used genomics to assess historical trends in population sizes.
The new research also indicates that horseshoe crabs numbers may continue to decline in the future because of predicted climate change, said Tim King, a scientist with the U.S. Geological Survey and a lead author on the new study published in Molecular Ecology.
While the current decline in horseshoe crabs is attributed in great part to overharvest for fishing bait and for the pharmaceutical industry, the new research indicates that climate change also appears to have historically played a role in altering the numbers of successfully reproducing horseshoe crabs. More importantly, said King, predicted future climate change, with its accompanying sea-level rise and water temperature fluctuations, may well limit horseshoe crab distribution and interbreeding, resulting in distributional changes and localized and regional population declines, such as happened after the last Ice Age.
“Using genetic variation, we determined the trends between past and present population sizes of horseshoe crabs and found that a clear decline in the number of horseshoe crabs has occurred that parallels climate change associated with the end of the last Ice Age,” said King.
The research substantiated recent significant declines in all areas where horseshoe crabs occur along the West Atlantic Coast from Maine to Florida and the eastern Gulf of Mexico, with the possible exception of a distinct population along the Yucatan Peninsula of Mexico
These findings, combined with the results of a 2005 study by King and colleagues, have important implications for the welfare of wildlife that rely on nutrient-rich horseshoe crab eggs for food each spring.
For example, Atlantic loggerhead sea turtles, which used to feed mainly on adult horseshoe crabs and blue crabs in Chesapeake Bay, already have been forced to find other less suitable sources of food, perhaps contributing to declines in Virginia’s sea turtle abundance. Additionally, horseshoe crab eggs are an important source of food for millions of migrating shorebirds. This is particularly true for the red knot, an at-risk shorebird that uses horseshoe crab eggs at Delaware Bay to refuel during its marathon migration of some 10,000 miles. Since the late 1990s, both horseshoe crabs and red knot populations in the Delaware Bay area have declined, although census numbers for horseshoe crabs have increased incrementally recently.
“Population size decreases of these ancient mariners have implications beyond the obvious,” King said. “Genetic diversity is the most fundamental level of biodiversity, providing the raw material for evolutionary processes to act upon and affording populations the opportunity to adapt to their surroundings. For this reason, the low effective population sizes indicated in the new study give one pause.”
These studies should help conservation managers make better-informed decisions about protecting horseshoe crabs and other species with a similar evolutionary history. For example, the 2005 study indicated males moved between bays but females did not, suggesting management efforts may best be targeted at local populations instead of regional ones since an absence of enough females may result in local extinctions.
“Consequently, harvest limitations on females in populations with low numbers may be a useful management strategy, as well as relocating females from adjacent bays to help restore certain populations,” King said. “Both studies highlight the importance of considering both climatic change and other human-caused factors such as overharvest in understanding the population dynamics of this and other species.”
Background on Horseshoe Crabs
Horseshoe crabs are not crabs at all – in fact, they are more closely related to spiders, ticks and scorpions. While historically horseshoe crabs have been used in fertilizer, most horseshoe crab harvest today comes from the fishing industry, which uses the crab as bait, and the pharmaceutical industry, which collects their blood for its clotting properties. While the crabs are returned after their blood is taken, the estimated mortality rate for bled horseshoe crabs can be as high as 30 percent.
The research, Population dynamics of American horseshoe crabs—historic climatic events and recent anthropogenic pressures, was published in the June issue of Molecular Ecology and was authored by Søren Faurby (Aarhus University, Denmark), Tim King, Matthias Obst (University of Gothenburg, Sweden) and others.
The 2005 study, Regional differentiation and sex-biased dispersal among populations of the horseshoe crab (Limulus polyphemus), was published in the Transactions of the American Fisheries Society and authored by Tim King, Mike Eackles Adrian Spidle (USGS) and Jane Brockman (University of Florida).

|
|
|
Many Urban Streams Harmful to Aquatic Life Following Winter Pavement Deicing
|
9/3/2010 10:15:52 AM OC_Web@usgs.gov (Office of Communications Web Group)
|
This USGS report is published in the journal Environmental Science and Technology and is available as a free download online.
The use of salt to deice pavement can leave urban streams toxic to aquatic life, according to a new U.S. Geological Survey study on the influence of winter runoff in northern U.S. cities, with a special focus on eastern Wisconsin and Milwaukee.
More than half of the Milwaukee streams included in this study had samples that were toxic during winter deicing. In eastern and southern Wisconsin, all streams studied had potentially toxic chloride concentrations during winter, with lingering effects into the summer at some streams. Nationally, samples from fifty-five percent of streams studied in 13 northern cities were potentially toxic; twenty-five percent of the streams had samples that exceeded acute water quality criteria.
Toxicity was measured by direct testing of organisms in samples during the local study component; in the regional and the national study components, observed chloride levels were used to assess potential toxicity.
“While winter driving and walking safety are the priority in treating pavements, this study suggests the need for advancements that will reduce salt loads to surface waters without compromising safety,” said Matthew C. Larsen, USGS Associate Director for Water.
“We expected to see elevated chloride levels in streams near northern cities during the winter months,” said Steve Corsi of the USGS Wisconsin Water Science Center. “The surprise was the number of streams exceeding toxic levels and how high the concentrations were,” said Corsi, who led the study.
“This study shows that chloride contamination of urban streams is a problem in many places; it’s not just a Milwaukee problem,” said Corsi.
While road deicing accounts for a significant portion of salt applications, it is not the only source. Salt is also used by many public and private organizations and individuals to deice parking lots, walkways and driveways.
Key Findings:
Nationally: During the winter, samples from fifty-five percent of northern streams in this study had chloride levels that exceeded USEPA chronic water-quality criteria, indicating potential toxicity. Samples from twenty-five percent of the streams exceeded acute water-quality criteria.
Regionally: In eastern and south-central Wisconsin, potential toxicity was found during winter at all urban streams studied, with lingering effects at some streams in the summer.
- During winter, 100 percent of the streams monitored had chloride levels that exceeded the USEPA chronic water quality criteria with fifty-five percent of samples exceeding acute water quality criteria.
- Chloride levels higher than 10,000 milligrams per liter were observed at times during winter deicing periods—much greater than the chronic water-quality criteria of 230 milligrams per liter and the acute criteria of 860 milligrams per liter.
- Chloride levels increased as urbanization percentage in the watershed increased.
Locally: In Milwaukee, more than half of the samples collected from streams during winter deicing periods were toxic.
- Samples from seven of 13 streams collected during 2007 deicing periods were toxic in bioassay tests.
- Chloride levels in 12 out of these 13 streams exceeded USEPA chronic water quality criteria; eight of 13 exceeded acute criteria.
- In long-term testing of one Milwaukee stream between 1997 and 2008, seventy-two percent of 38 samples collected during the winter were toxic in bioassay tests.
The Wisconsin State Laboratory of Hygiene co-authored this study and did the bioassay testing involved. Additionally, this study was conducted in cooperation with the Milwaukee Metropolitan Sewerage District and General Mitchell International Airport.
Other major sources of salt to U.S. waters include wastewater treatment, septic systems, farming operations, and natural sources from geologic deposits. These sources may contribute to chloride levels at individual streams in this study, but the geographic, land-use, and seasonal patterns observed in this study suggest deicing activities as the dominant source. This conclusion is also supported by a USGS study published in 2009 on chloride in groundwater and surface water in the northern U.S.

|
|
|
|
|