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NEWS TIPS FROM THE April 2002 ISSUE OF CONSERVATION BIOLOGY the journal of the Society for Conservation Biology
FOR IMMEDIATE RELEASEPlease mention Conservation Biology as the source of these items:
PDFs of these papers are available to the media; contact Robin Meadows robin@nasw.org Images are provided by the researchers; please contact them directly for more information. To register for media access to the TOC and our expert directory: http://www.conbio.org/scb/information/media/ For more information about the Society for Conservation Biology: http://conservationbiology.org
CLIMATE CHANGE LINKED TO MIGRATORY BIRD DECREASEBiologists believe that climate change is affecting living things worldwide, and the latest evidence suggests that warmer winters may mean fewer migratory birds. New research shows that as winter temperatures have risen in central Europe, the number of migratory birds has dropped. Ultimately, this may also decrease the number of migratory bird species there. "We predict that with increasing winter temperatures...the number of long-distance migratory bird species should decline," say Nicole Lemoine and Katrin Boehning-Gaese of Johannes Gutenberg University in Mainz, Germany, in the April issue of Conservation Biology. The Earth's surface temperature has increased by about a degree F since 1860, and is expected to increase by as much as 10 degrees F more over the next century. Already, climate change is affecting plants and animals in many parts of the world: for instance, plants in Europe have a longer growing season, a North American marmot has a shorter hibernation period, and some migratory birds in Europe are starting to breed earlier. Climate change could also affect the abundance and diversity of birds. The idea is that warmer winters could increase the survival of birds that live in an area year-round, which could give migratory birds more competition for resources such as food and nest sites when they return to breed in the spring - and that in turn could decrease the total number of migratory birds as well as the number of species. To see if climate change affects the abundance and diversity of migratory birds, Lemoine and Boehning-Gaese analyzed existing bird census and climate data for the Lake Constance region of central Europe, which includes parts of Germany, Austria and Switzerland. The researchers determined the number of land bird species and the abundance of each species during two recent census periods (1980-81 and 1990-92). The researchers considered 300 species of land birds and divided them into three categories: residents, short-distance migrants (those that migrate an average of roughly 600 to 1,200 miles) and long-distance migrants (those that migrate more than 2,200 miles). There were 122, 80 and 108 species in each category, respectively. While climate change did not affect resident or short-distance migratory birds, Lemoine and Boehning-Gaese found that it did affect the long-distance migrants. Between the two census periods, winters got warmer and the abundance of long-distant migrants decreased. Specifically, the average temperature of the coldest month increased more than four degrees F, and the abundance of long-distance migratory birds decreased by a fifth. Ultimately, warmer winters will probably also decrease the number of long-distance migratory bird species in Central Europe, say the researchers. In addition, the birds' migratory behavior will probably evolve. The migratory behavior of bird populations can change in only a few generations, and several populations of wrens, skylarks and other short-distance migrants have stopped migrating in the last 20 years. CONTACT: Nicole Lemoine (+49-6131-392-3950, lemoine@oekologie.biologie.uni-mainz.de)
WEBSITES: Bird Migration and Climate Change
European Science Foundation Workshop: Bird migration in relation to climatic change
RIPARIAN BIRDS CAN REBOUND AFTER COWS ARE GONEThe southwest U.S. has lost more than four-fifths of its riparian habitat and one of the biggest reasons is livestock, which can graze and trample stream-side plants to death. New research shows that the damage can sometimes be reversed: birds rebounded quickly after cows were removed from the riparian area along an Arizona river. "The speed, magnitude and extent of the recovery were surprising and suggest that even severely degraded systems can recover quickly, at least in some cases, after cattle removal," say David Krueper, who did this work while at the U.S. Bureau of Land Management in Sierra Vista, Arizona, and is now at the U.S. Fish and Wildlife Service in Albuquerque, New Mexico; Jonathan Bart of the U.S. Geological Service in Boise, Idaho; and Terrell Rich of the U.S. Fish and Wildlife Service in Boise, Idaho, in the April issue of Conservation Biology. Many animals in the arid southwest depend on riparian habitat for its water and lush plants. In Arizona and New Mexico, most vertebrates use riparian areas during at least part of their lives; and throughout the western U.S., the diversity of breeding birds is higher in riparian areas than in all the other types of habitat combined. To help determine how well grazed riparian areas can recover after cows are removed, Krueper and his colleagues monitored the diversity and abundance of 61 bird species in the San Pedro Riparian National Conservation Area in southeastern Arizona, which is 43 miles long and roughly 2-5 miles wide. Every year, 5-10 million songbirds migrate along the San Pedro River. The researchers monitored birds during the breeding seasons of five years (two before and three after the cows were removed) in three types of plant communities (riparian, mesquite grassland and Chihuahuan desert-scrub). They also determined the density of vegetation at the peak of summer growth several times over the course of the study. Krueper and his colleagues found that removing the cows dramatically increased the vegetation in the study area: the density of native plants (such as grasses, cottonwoods and willows) increased 4-6 times in the riparian and mesquite grassland communities.
The researchers also found that the abundance of birds increased. Of the 61 species studied, 26 increased and 8 decreased in the study area. The birds that increased included several "species of special concern", such as the yellow warbler and summer tanager. Only one of the species that increased (the common raven) also increased elsewhere in the region during the study period, suggesting that the increases were due to getting rid of the cows. Three of the species that declined in the study area (the house sparrow, eastern meadowlark and black-throated sparrow) also declined elsewhere in the region during the study period, suggesting that the decreases were not related to getting rid of the cows. "Our results suggest that removing cattle from riparian areas in the southwestern United States can have profound benefits for breeding birds," say Krueper and his colleagues. CONTACT: David Krueper (505-248-6877, dave_krueper@fws.gov)
PAVING ROADS CAN INCREASE WEED INVASIONSWhile it is well-known that roads can spread invasive weeds, new research shows that some roads are worse than others. In Utah, areas along paved roads were far more likely to be invaded than those along 4-wheel-drive tracks. This suggests that limiting road improvements would help keep out invasive weeds. "Each step of road improvement would appear to convert an increasing area of natural habitat to roadside habitat," say Jonathan Gelbard, who did this work while at Duke University in Durham, North Carolina, and is now at the University of California at Davis, and Jayne Belnap of the U.S. Geological Survey in Moab, Utah, in the April issue of Conservation Biology. Cheatgrass, knapweeds and other non-native plants have invaded nearly 125 million acres of the American West. Roads are a big part of the problem: for instance, vehicles can transport non-native seeds into uninfested areas, and clearing land during road construction gives weed seeds a place to become established. Intuitively, it makes sense that improved roads would spread weeds more than primitive roads because the former have more traffic, more exposed soil and more maintenance such as mowing and herbicide treatments, all of which can favor invasive species. To see if non-native weeds really are more likely to invade along improved roads, Gelbard and Belnap surveyed the plants along 42 roads with varying degrees of improvement (paved, improved surface such as gravel, graded and 4-wheel-drive track) in and around southern Utah's Canyonlands National Park. The researchers determined the cover and number of species of non-native and native plants in two areas: roadside verges (strips along the road), and "interior sites" near but not right next to roads (165 feet from the verge). Gelbard and Belnap found that road improvement greatly increased the cover of non-native plants in roadside verges. Notably, cheatgrass cover was three times greater in verges along paved roads than along 4-wheel-drive tracks (27 vs. 9%). In addition, verges along improved roads were also wider, ranging from about three feet on each side of 4-wheel-drive tracks to 23 feet on each side of paved roads. This means that improving roads can convert natural habitat to non-native weed-infested roadside habitat. "For example, our results suggest that improving 10 km [about 6 miles] of 4-wheel-drive tracks to paved roads converts an average of 12.4 ha [about 30 acres] of interior habitat to roadside [habitat]," say Gelbard and Belnap. The researchers also found that improved roads had more non-native plant cover in interior sites. Again, cheatgrass cover was more than three times greater in interior sites adjacent to paved roads than in those adjacent to 4-wheel-drive tracks (26 vs. 8%). Overall, the cover of non-native plants was more than 50% greater in interior sites adjacent to paved roads than in those adjacent to 4-wheel-drive tracks. In addition, road improvement changed the number of both exotic and of native species in the interior community study plots: the number of exotic species was more than 50% greater and the number of native species was 30% lower. "Our findings suggest that major opportunities remain to prevent exotic [non-native] plant invasions in this semiarid landscape by minimizing the construction of new roads and the improvement of existing roads," say Gelbard and Belnap. CONTACT: Jonathan Gelbard (jlgelbard@ucdavis.edu)
BEST CHANCE TO PROTECT GIANT PANDAS
At only about 1,000 in the wild, China's giant panda is among the most endangered species in the world. But there is still hope if we act fast. The panda's greatest threat is habitat loss and new research identifies high-quality habitat that, if protected, could increase the species' chances of long-term survival. "The current network of nature reserves provides protection for less than half of the pandas' remaining habitat and fails to conserve essential habitat for dispersal," say Colby Loucks and Eric Dinerstein of the World Wildlife Fund-US in Washington DC, and four co-authors in the April issue of Conservation Biology. The giant panda's range has shrunk from the lowland forests of southeast China, northern Vietnam and northern Myanmar to six mountain ranges along China's Tibetan Plateau, where only 24 isolated populations survive today. Now, however, there is a window of opportunity to protect more of the panda's habitat, thanks to two conservation policies recently adopted by the Chinese government to help control flooding. First, under the National Forest Conservation Program, logging is banned in natural forests until 2010; and second, the Grain-to-Green policy is restoring forests on steep agricultural lands. These policies "have the potential to protect and restore panda habitat across the panda's entire range," say Loucks, Dinerstein and their colleagues. Giant pandas need both high- and low-elevation forests as well as dispersal corridors. They need both types of forest because each supplies their primary food during part of the year: during the summer, pandas eat a kind of bamboo that grows at high elevations; and during the rest of the year, they eat another kind that grows at low elevations. To help identify unprotected areas that are critical to the giant pandas' survival, Loucks, Dinerstein and their colleagues mapped the extent and quality of their habitat in China's Qinling Mountains, which have about a fifth of the remaining wild population. The researchers used satellite images and other existing data to determine the extent of remaining natural forest that could support pandas, and divided it into core and secondary habitat. The former has both of the bamboo species that pandas depend on, while the latter only has one of them. Loucks, Dinerstein and their colleagues calculated that the Qinling Mountains have nearly 900 square miles of forest that could support pandas. While nearly 700 square miles of this is core habitat, it is fragmented into four parts and less than half of it is protected by the existing network of nature reserves. The researchers identified five unprotected areas totalling about 400 square miles that should be added to the existing reserves: three core areas and two linkage zones, which would let pandas get from one core area to another. Next, the researchers call for identifying unprotected giant panda habitat in the other five mountain ranges where the species still survives. "Most are so remote that there are no people or infrastructure development there," says Dinerstein, which increases the chances of saving the pandas. Loucks' co-authors are: Lu Zhi, who did this work while at the World Wide Fund for Nature-China in Beijing and is now at the Critical Ecosystem Partnership Fund in Beijing; and Wang Dajun, Fu Dali and Wang Hao of the Giant Panda Conservation and Research Center in Beijing, China. CONTACT: Colby Loucks (202-778-9671, colby.loucks@wwfus.org)
WEBSITE: WWF Endangered Species: Pandas
ROCK CLIMBING DECREASES BIODIVERSITY
When rock climbers are clinging to a cliff face, the health of the ecosystem is probably the last thing on their minds. But new research shows that rock climbing cuts snail diversity in half in the Canadian Niagara Escarpment, adding to the growing body of evidence that some cliffs should be off limits to climbers. "Our work suggests that rock climbing has significant negative effects on all aspects of the snail community on cliffs," say Jeffery Nekola of the University of Wisconsin in Green Bay, and Michele McMillan and Douglas Larson of the University of Guelph in Canada in the April issue of Conservation Biology. This study builds on the researchers' previous work showing that rock climbing can decrease the diversity and abundance of plants and lichens on cliffs. The Niagara Escarpment is a series of limestone cliffs that extends from Ontario, Canada, to Michigan, Wisconsin, Illinois and Iowa. Noted for having eastern white cedar trees that are nearly 1,000 years old, the Escarpment is also a hotspot of snail diversity, with about half of the 80-odd land snail species found in Ontario. Most of the snails found in the Escarpment are known as "minute" snails because they are less than a tenth of an inch across. They live inside soil and many graze on the algae that grows on the cliffs. Nekola and his colleagues compared the diversity and abundance of snails in climbed and unclimbed cliffs along a two-mile section of the Niagara Escarpment near Milton, Ontario. They studied snail shells in soil collected from three parts of the cliffs: the top edge, the cliff face and the base. Altogether, the researchers found 40 species of snails and more than 14,000 intact shells. The results showed that climbed cliffs had less snail diversity and abundance. Climbed cliffs had only half as many snail species (about 5 vs. 10 per cup of soil, respectively) and only about a fifth as many snails (roughly 15 vs. 78 per cup of soil, respectively) as unclimbed cliffs.
How could rock climbing harm snails on cliffs? They live mostly in ledges and cracks along the cliffs' vertical surfaces and these are also the parts that rock climbers use for hand and foot holds. Rock climbers gouge out the soil where the snails live, either incidentally or on purpose. To help protect snails and other species on cliffs, Nekola and his colleagues recommend limiting new rock climbing routes along the Niagara Escarpment. "Allowing climbing to expand to new areas is equivalent to giving up on our ability to protect this vertical wilderness," says Larson. The researchers also recommend similar protections for the many other cliffs around the world that are also snail hotspots. CONTACT: Jeffery Nekola (902-456-2937, nekolaj@uwgb.edu)
WEBSITE: University of Guelph Cliff Ecology Research Group
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