Humans responsible for wiping out world's mass migrations

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Washington, June 2 (ANI): A new research has indicated that human activities have played a large part in wiping out the world's mass migrations.

The researchers determined that all of the world's large-scale terrestrial migrations have been severely reduced and a quarter of the migrating species are suspected to no longer migrate at all because of human changes to the landscape.

"Conservation science has done a poor job in understanding how migrations work, and as a result many migrations have gone extinct," said Grant Harris of the Center for Biodiversity and Conservation at the American Museum of Natural History.

"Fencing, for example, blocks migratory routes and reduces migrant's access to forage and water. Migrations can then stop, or be shortened, and animal numbers plummet."

Migrations of large-bodied herbivores (also called ungulates) occur when animals search for higher quality or more abundant food. Ecologically, there are two primary drivers of food availability.

In temperate regions of the world, higher-quality food shifts predictably as the seasons change, and animals respond by moving along well-established routes.

For savannah ecosystems, rain and fire allow higher-quality food to grow. This is a less predictable change that animals must track across expansive landscapes.

Human activity now prevents large groups of ungulates from following their food.

Fencing, farming, and water restrictions have changed the landscape and over-harvesting of the animals themselves has played a role in reducing the number of migrants.

To assess the impact of human activity on migrations throughout the world, Harris and his co-authors gathered information on all 24 species of large (over 20 kilograms) ungulates known for their mass migrations.

Animals included in the study, for example, range over Arctic tundra (Caribou), Eurasian steppes and plateaus (Chiru and Saiga), North American plains (bison and elk), and African savannahs (zebra and wildebeests).

All 24 species in the current study lost migration routes and were reduced in number of individuals.

Similar changes are found on other continents when human activity limits the ability of species to move to new patches of food.

"If we are going to conserve migrations and species, we need to identify what needs to be done: where migrations remain, how far animals move, their habitat needs and location, threats, and the knowledge gaps needed to be filled," said co-author Joel Berger of the Wildlife Conservation Society and the University of Montana. (ANI)

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