and citizens worry about new invasive species that move into our
woodlands and waterways. The so-called invaders become more common as
world trade helps transport living organisms from one place on the
planet to another, and as climate change impels many species to seek
more hospitable environments.
But are new-comers actually alien, and is their arrival necessarily trouble?
Asian carp that can grow three feet long and weigh up to 100 pounds can frighten passengers in a canoe. Catfish farmers in the American south imported these fish from Asia in the 1970s to filter and clean their ponds. A Time story by Bryan Walsh explains
how the carp multiplied exponentially, escaped from the ponds, and
began devouring the plankton that supports the bottom layers of the food
chain in rivers. Wildlife experts speculate there maybe millions of
them in the Illinois River alone. They leap out of the water, and have injured some boaters. Government
officials and commercial and sports fishermen are worried they may
escape into the Great Lakes, where they could wreak havoc with the
ecosystems, literally starving trout and other fish. Attempts are
underway to build electric barriers blocking their entry.
A National Geographic story by Susan McGrath describes non-native reptiles lurking in the Everglades, and the unfamiliar snakehead fish, also called "frankenfish," that have alarmed people who have seen them in Maryland waterways. One of the best known non-native plants is the Kudzu vine, brought
from Japan in the late 1800s, now are estimated to cover more than
seven million acres in the south. The woody vines can grow as much as a
foot a day, covering anything in their path, including cars, buildings
and telephone polls. They literally suffocate other plants with their
heavy foliage. But during the first half of the twentieth
century, their cultivation was promoted for forage, ground cover, and
preventing soil erosion.
an anthropologist who explores the relationships among people, animals
and things, writes that "just as America is a nation built by
immigrants, our natural landscape is a shifting mosaic of plant and
animal life." In his New York Times story "Mother Nature's Melting Pot," Raffles says that like people, other living organisms travel in ways we can't always know or control, arrive unannounced and change each other and their environments. He
says some immigrant plants and animals help keep the environment
strong, and some native species are harmful.For instance, he says zebra muscles, Caspian
Sea natives believed to have reached U.S. waterways by ballast from
ocean vessels, can increase small fish populations by improving water quality (pdf). The honeybee was introduced to the Americas from Europe in the 1600s and became indispensable for agriculture. What's native and what's alien? Increased intermingling and recombining may blur the distinction. The kudzu vine flourished because the climate of the southern states was so hospitable to it. The population of the native mountain pine beetle (pdf) has skyrocketed to disastrous effect, largely because of climate change, to which ironically, its numbers contribute.
his thoughtful piece, Raffles, who is himself an immigrant, suggests
that our non-native plants and animals deserve thoughtful, inclusive
evaluation that considers the importance of healthy diversity in our
shifting and dynamic living environments.