Saturday, June 09, 2012

A MODERN TALE OF BIOGEOGRAPHY

If you've ever taken a science or biology class, you have most likely heard the term biogeography, which is the geographic distribution of plants and animals on the planet. The typical, and classic, tales of biogeography ask the question about how plants and animals got to remote ocean islands. The study of animals on the Galapagos Islands is a particular favorite in this genre. We learn that insects, snakes, birds, even small mammals clinging to floating debris, like trees or mats of vegetation, might arrive on some distant shore by sheer chance. And of course, we also know that humans have transported many plants and animals on their ships and left them on foreign shores.

A story in the Portland, Oregon newspaper today is about a dock that washed ashore on a beach in Newport, Oregon. The concrete dock, measuring 66 by 19 by 7 feet tall, has been traced to Misawa, Japan where it was ripped from its moorings during the devastating March 11, 2011 tsunami. The dock is one of the largest pieces of debris that has recently started washing ashore on beaches of the eastern Pacific from Alaska to Oregon.

Fish and wildlife biologists in Newport worked quickly to scrape and burn living plants and animals off the dock shortly after it washed ashore. The goal was to eradicate these organisms common in Japanese waters that could become invasive species on this side of the ocean where many of them are not found.

I think this is an exercise in futility, because many thousands of floating objects, large and small, have traveled across the ocean from Japan to the west coast of North America following the tsunami, and most of these will have attached organisms. I am certain that biologists will be studying the effects of this biogeographic event for many years to come; in fact, I think careers will be built around it.

This event also begs a question I've always had: what is a native vs. non-native species? Scientists who study species migrations and origins have pondered this question. I remember one conversation with a colleague in this field who was part of a group that determined that a number of the "native" zooplankton species in San Francisco Bay were actually invaders from Asian waters centuries ago. So how long does a species need to live in an area before it is considered "native?"

Plants and animals have probably reached our shores from origins in Asia many times. A devastating storm or tsunami can result in trees, floating marine algae, and other natural objects being released into the ocean currents, carrying with them attached or clinging organisms. These "invasions" don't make the news, but they are a constant. Certainly the tsunami in Japan last year was a very major event that released huge numbers of organisms into the conveyor belt of currents that flow west to east across the north Pacific.

Biogeographic processes: a natural form of globalism.

It's a small world after all.

No comments:

Twitter