for National Geographic News
Habitat destruction and climate change are making migrations increasingly difficult for many species, but it's not too late to bring these visually spectacular and environmentally critical mass movements back, according to a new study.
Migrations are one of the animal kingdom's most widespread phenomena.
They are seasonal tests of endurance, collective journeys often taken at great costs by birds, whales, land mammals, insects, and other creatures that are wired to roam.
Scientists estimate that one-third to half of all animals—and even some microorganisms—migrate during part of their lives.
"Even slime molds migrate," said study co-author Martin Wikelski, a zoologist at the Max Planck Institute in Germany and a National Geographic Emerging Explorer. Wikelski's study appeared last week in the journal PLoS Biology.
According to scientists, human actions are threatening many migrations. Habitat destruction, the creation of obstacles such as dams and fences, overexploitation of natural resources, and climate change are combining to make migrations increasingly difficult for many species.
Global warming, for example, is changing flowering times and other natural cycles, driving many birds and insects to move their ranges or arrive before or after their food sources have emerged.
Many of the planets great migrations have already vanished. The sight of vast bison herds roaming North America's Great Plains or multitudes of passenger pigeons darkening the skies as they migrated from Canada to the southeastern U.S. are things of the past.
Not Too Late
By increasing public awareness of the plight of migratory animals and committing to the preservation not only of individual species but also their way of life, many migrations can still be saved, write Wikelski and study co-author David Wilcove of Princeton University.
The authors argue that migrations should be saved, if not for the sheer awe that seeing millions of animals moving with one purpose elicits, then for their ecological importance.
Migrating songbirds, for example, snack on plant-eating insects that might otherwise destroy crops or forests during their layovers.
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