We are just beginning to see birds return to the Columbia Gorge from their southern paradises. At its most basic, migration is the movement of a group of animals from one place to another and, in most cases, back again. Most migration is seasonal when birds return here in the spring and leave in the fall.
While we are most familiar with avian migration, land and sea mammals can roam hundreds of miles, tiny monarch butterflies flitter thousands of miles, spotted frogs hop to ponds to lay eggs, snakes slither to communal den sites in the autumn season, and even jellyfish larvae undertake a journey.
Many animals migrate to avoid harsh winter conditions or to follow available food as the seasons change. Migration can have another important benefit. By allowing animals to escape from habitats where parasites have accumulated and by weeding out infected individuals that are not able to survive the journey, migration can reduce parasite infection in animal populations.
When human-provided food resources allow some animals to forego migration and form resident populations, the consequences can be dire. For one thing, by the time migrants return, resident individuals may already be taking up breeding territories and resources, putting the migrants at a competitive disadvantage. And many of those resident animals the migrants encounter may be infected by parasites.
Placing barriers to species on the move becomes seriously problematic. Dams, barb-wire fences, Border Walls, highways, clearcut logging, and polar waters without ice all unnecessarily prevent animals from reaching their destinations.
The dams result in less fish and a sea lion smorgasbord. Barb-wire fences prevent bison, antelope, and elk from finding home. Highways create deadly hazards for wildlife and people. Clearcuts reduce wildlife diversity and make it kind of hard for tree-nesting species. Ice-free waters bring starving polar bears into northern towns. And a Border Wall would bring additional misery and challenges to desperate migrants.
Migration occurs in the animal realm because resources on Earth fluctuate and the benefits of long distant travel outweigh their costs. Migration occurs in the human realm because politics and power fluctuate and the benefits of long distance travel outweigh their costs. Migration will only work for all if greater commitment is shown to eliminating all forms of exploitation and discrimination that migrants experience and to ensuring that their fundamental human rights are upheld. ~