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The end of migrations: wildlife's greatest spectacle is critically endangered Jeremy Hance, mongabay.com July 28, 2008 Why abundance matters: the conservation of migrations would preserve important ecosystem services
Fast-forward to today and the humpback whale population is less than 2 percent of its estimated historic population, from 1.5 million behemoths to 20,000. Only 350,000 bison are left out of a population that may have reached 100 million; their percentage remaining is not even a whole number. The saiga antelope has dropped 95 percent in twenty years, from a million individuals to 50,000. But the passenger pigeon proves the most drastic, going from one of the world's most populous bird to extinct in a few decades. These examples illustrate a common occurrence: the phenomenon of mass-migration is going the way of the passenger pigeon. From whales and sea turtles to insects and song-birds, from hoofed mammals to the predators that track them, massive migrations are declining worldwide. In an essay in PLoS Biology, scientists David S. Wilcove and Marin Wikelski discuss the ramifications of these losses in abundance and the importance of new conservation attention on the beleaguered migrants.
Although no one knows exactly how each migration affects its ecosystem, the authors believe that the diminishing of such migrations drastically alters the productivity of an ecosystem, challenging its ability to provide essential services. For example, the authors illustrate that salmon "by migrating upstream, spawning, and dying, transfer nutrients from the ocean to the rivers. A portion of the nutrients is delivered in the form of feces, sperm, and eggs from the living fish; much more comes from the decaying carcasses of the adults. Phosphorus and nitrogen from salmon carcasses enhance the growth of phytoplankton and zooplankton in the rivers, which provide food for smaller fish, including young salmon." However, the Northwestern rivers of America, receive only about 6-7 percent of the nutrients they once did due to a drastic decline in the migratory population of salmon. Fewer nutrients ultimately lead to less salmon in the next generation and less biomass altogether.
Preserving thousands to millions of individuals will not be easy. The scientists write that saving these migrations will pose "unique scientific and social challenges". How does one approach preserving abundance, rather than settling for simple existence? The writers believe that protecting migrations will require action on the local, national, and global level. Those in power will have to change their mindset and protect a species before its population declines.
The authors believe it will be well worth the energy and sacrifices required, considering the ecological services provided by these massive movements, the scientific importance of studying the mechanisms behind such migrations, and the perfect wonder of such spectacles. Such migrations are a kind of culmination of Nature's potential—once so prevalent across the world, now only surviving in a few aberrant places. Some great migrations do remain. Butterflies still cross international boundaries in astounding numbers. Every May, over a million wildebeests travel across the African plains, providing food for many of the Africa's large predators, from lions to hyenas to crocodiles. Caribou still migrate in the thousands across the Arctic tundra. And only a year ago an unknown migration was observed in the Southern Sudan, with over a million antelopes, including the white-eared kob, the tiang, and the mongalla gazelle. Conservationist and adventurer, Michael Fay, said of the discovery: "This could represent the biggest migration of large mammals on Earth. I have never seen wildlife in such numbers, not even when flying over the mass migrations of the Serengeti."
Wilcove DS, Wikelski M (2008) Going, going, gone: Is animal migration disappearing? PLoS Biol 6(7): e188. doi:10.1371/journal.pbio.0060188
Tags: whales africa endangered species insects wildlife mammals birds animal behavior ecology in-situ conservation animals Fish biodiversity conservation featured environment jeremy hance green News index | RSS | News Feed | Twitter | Home Advertisements: Organic Apparel from Patagonia | Insect-repelling clothing
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