Twice a year, tens of thousands of animal species around the world respond to the changing seasons by setting out on long journeys that we call migration.
There's incredible diversity in the form migration takes for different species — and even for different populations of the same species. For some of the world's smallest and slowest migrators, a journey of a few kilometers takes weeks to complete. Others travel thousands of kilometers, guided by instinct and environmental cues.
The reasons animals migrate are equally as diverse, but often include seasonally plentiful food, fewer parasites and diseases, and relative safety from predators.
But climate change is contributing to rapid erosion of migration benefits. Not all species respond to changes the same way, or at the same time — and that threatens to disrupt the functioning of complex ecosystems. Species that once rarely occupied the same habitat at the same time may now be facing increased competition for resources, as their stays in shared seasonal habitat increasingly overlap. Predators may experience prey shortages as their migrations fall out of sync with prey animals' life cycles.
We have lived with the notion that northern breeding grounds represent safe harbors for migratory animals. On the contrary, numerous Arctic and North temperate sites may now represent ecological traps or even worse degraded environments for diverse migratory animals, including shorebirds, caribou or butterflies.
Dr. Vojtěch KubelkaUniversity of South Bohemia in České Budějovice, Department of Zoology and Centre for Polar Ecology
Most troublingly, migration is such an ingrained instinct that species that undertake it may continue making the dangerous trip year after year, even when doing so would reduce their odds of survival.
By understanding why animals migrate, how they find their way, and how they know when it's time to go, scientists can better predict how they'll respond to climate change. With better predictions, researchers hope to anticipate which species will need the most help to survive, and what kind of help they need while there's still time to make a difference.
Whether by sea, by sky or by land, learning more about these miraculous journeys is key to safeguarding the creatures who make them.
The Earth is a complex ecosystem—changes in migration profitability affect populations of migrating animals which precipitate in alterations of species composition, trophic food webs as well as the whole ecosystem functioning. These patterns are particularly threatening for migratory animals as large numbers of those species are already negatively affected outside the breeding period, at their stopover sites and wintering grounds—and many have formerly relied on the northern latitudes to provide [relatively] safe breeding grounds.
Professor Tamás SzékelyProfessor of Biodiversity at the University of Bath, Honorary Professor at the University of Debrecen, and visiting Professor at Beijing Normal University and Sun Yat-Sen University