The Great Migration

343

It’s September and time for the Great Human School Migration to begin. Alarm clocks are buzzing, busses are lining up to ferry children to schools, college students and their parents are trekking to their new fall homes and college towns are swelling after the relative quiet of summer.

This is part of life as we know it. We may not see it as a “migration,” but if  you think about it, “flocks” of humans change their locations for reasons entirely human, following cues that we understand, using routes that have been established, finding food and shelter along those routes, headed to destinations that we find valuable and important to our life cycle.

Now imagine if some of those variables were to change.

What if something happened to block the roads? What if the food was made inedible somehow or the roadside restaurants were replaced with walls and fences? What if the weather conditions made passage impossible? What if any number of things conspired to disrupt, distract or discourage travel? What would happen to this important, life enhancing migration?

Like it or not, this is already happening to many of our fellow migrators on earth, be they mammal, insect, fish or fowl. It’s interesting to understand, and reminds me of our incredible interconnectedness, coupled with the enormous power of individual action.

While we are busy gathering school supplies and packing lunches for our little ones or buying bedding and computers for our college kids, birds, snakes, bats, elk, sheep, frogs, butterflies, deer, salmon, whales and many other creatures are preparing for their personal migrations to find better food, climate, breeding or resting grounds for the winter season.

But while we have Google maps, news reports, traffic updates, and grocery stores, our animal friends are not so lucky.

Their paths are being increasingly blocked by our activities. Mile-long fishing nets have wiped out huge numbers of migrating salmon. Logging huge swathes of forest for timber or agriculture erases food and nesting grounds for traveling birds and butterflies. Fences, roads and invisible political boundaries divert animal migration. 24 hour lighting confuses night flying creatures that may navigate by starlight.

On a larger scale, songbirds flying north to breed in North America depend on finding summer insects, particularly caterpillars, when they arrive after their long journey. However, in some places, caterpillars are emerging earlier than usual in response to rising temperatures. The songbirds, wintering south in Central America, the Caribbean or Africa, don’t know what’s happening up north. And if, as suspected, they take their cue to migrate from increasing day length, they don’t know that the caterpillars were born earlier than expected based on temperature, not sunlight. That’s like running a marathon, coming home expecting a nice dinner and learning that everyone went out.  When the birds arrive, their food has literally moved on. This phenomenon has been associated with a decline in certain species of songbirds, and highlights the complex global interaction of elements required to sustain migration.