As the planet warms, species are shifting where, when, and how they thrive, forcing many to migrate to cooler climates and higher elevations. Studies have suggested that this reshuffling is the biggest in about 25,000 years, with the planet’s entire species being slowly redistributed.
Vegetation and precipitation are affected and, in turn, affect the movement of both birds and mammals as springtime arrives earlier in many parts of the world and even shrubs and trees are seeding northward. Using fifty years of bird-banding, scientists have pulled records from over 38 million songbirds proving that their migration has been getting earlier and earlier in recent decades. American robins, for example, migrate 12 days earlier than in 1994. And, of course, it is not birds alone. Europe’s purple emperor butterfly moved more than 125 miles in a single decade. And, these flying creatures are lucky enough not to be impeded by fences.
This is also true for marine species. But, they face, a slightly different challenge. As the oceans warm their migration is also shifting — with mollusks, Atlantic cod, mackerel, haddock, penguins, and plankton all on the move — some south and some north as they escape equatorial waters to get nearer to the poles in both hemispheres. A global analysis of more than 300 marine species observed that: “Marine species distributions are limited by cold temperatures towards the poles and high temperatures towards the equator. Warming seas would lead each species to increase in abundance at the poleward side of its range, as the warmer climate made the habitat more agreeable. Each species would decline in abundance at the equatorward side of its range, as temperatures become too warm to survive.”
For birds and certain mammals, there’s at least a chance that they can follow their ideal habitat as it shifts toward the poles or into higher altitudes. For reptiles and plants, it’s less likely or slower. And for those species already at the poles—like the ones living in the Arctic — there’s nowhere further north to go.