http://www.sciencedaily.com/releases/2008/07/080728215330.htm
Is It Too Late To Save The Great Migrations?
ScienceDaily (July 28, 2008) — Long gone are the days when hundreds of
thousands of bison grazed the Great Plains, millions of passenger
pigeons darkened the skies while migrating to and from their breeding
grounds, and some 12.5 trillion Rocky Mountain locusts crowded an area
exceeding the size of California.
The subject of great migrations—lost and still to be saved—is explored
in two new articles published in the journal PLoS Biology.
In the first article, "Going, Going, Gone: Is Animal Migration
Disappearing?" David S. Wilcove and Martin Wikelski describe the
threats facing "one of nature's most visible and widespread
phenomena," a behavior found in animals as diverse as whales and
warblers, dragonflies and salamanders. Many of the most spectacular
migrations have disappeared or experienced steep declines due to human
behavior, the authors lament. With so much left to learn about the
biological mechanisms underlying the world's migrations, Wilcove,
author of "No Way Home: The Decline of the World's Great Animal
Migrations," argues that conserving this spectacular phenomenon is
critical to efforts to understand it.
What is being lost with the disappearance of these great migrations?
We are left only to wonder what early explorers experienced as they
watched "infinite multitudes" of birds soar overhead, but the authors
make the case that even more important, we stand to lose the
ecological properties and services associated with animals that
migrate in huge numbers. "Protecting the abundance of migrants is the
key to protecting the ecological importance of migration," they argue.
Consider that prior to European settlement, 160-226 million kilograms
of salmon migrated each year up the rivers of Washington, Idaho,
Oregon, and California. Today, after decades of dam construction,
overfishing, water withdrawals for irrigation, logging, and streamside
grazing by livestock, the total biomass of spawning salmon in the
Pacific Northwest is now estimated to be only 12-14 million kilograms.
How does this shortfall affect the ecology of the surrounding
landscape? No one knows.
In the second article, "Protecting Migration Corridors: Challenges and
Optimism for Mongolian Saiga," Joel Berger, Julie Young, and Kim
Murray Berger highlight the challenges of protecting a population of
migratory saiga—a critically endangered antelope—in western Mongolia.
Saiga numbers have dropped more than 95%, from greater than 1,000,000
to less than 50,000 in the past 20 years, with just two
subpopulations, totaling approximately 5,000 individuals.
To piece together the saiga's migratory route, the authors outfitted
females with global positioning system collars. They identified three
key bottlenecks along the migratory corridor, created by natural
(e.g., a lake) and anthropogenic (e.g., a town) barriers. Berger et
al. predict that the antelopes face an increasingly difficult and
dangerous journey ahead, as the region's human population increases in
size and affluence—leading to increased vehicle traffic—a trend that
will surely place additional pressure on these endangered animals.
Efforts are under way to expand the boundaries of the Sharga Nature
Reserve, where one of the subpopulations live, to protect the
migratory corridor. The scientific community has an important role to
play by providing data to identify potential threats, Berger et al.
argue. "Ultimately, however, it is only through dialogue with vested
interests that recommendations to reduce threats can be implemented.
Protecting corridors will necessitate addressing difficult issues, but
baseline data provide opportunities to engage in these discussions
before situations become dire."
Whether we can preserve the awe-inspiring beauty and wonder of great
migrations ultimately depends on us, Wilcove and Wikelski argue. "If
we are successful, it will be because governments and individuals have
learned to act proactively and cooperatively to address environmental
problems, and because we have created an international network of
protected areas that is capable of sustaining much of the planet's
natural diversity."
Journal reference:
Wilcove et al. Going, Going, Gone: Is Animal Migration Disappearing.
PLoS Biology, 2008; 6 (7): e188 DOI:
10.1371/journal.pbio.0060188==============================www.birding-aus.org
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