Friendly Invaders

This short article by Carl Zimmer challenges the common view of invasive species as a threat to biodiversity. The prevailing view is that invasive species outcompete endemic species and drive them to extinction. Zimmer reports the findings of two scientists, Dov Sax, an ecologist from Brown University, and Steven D. Gaines, a biologist from U.C. Santa Barbara. The two published an article in PNAS which documented extinctions of native plant species in New Zealand due to invasive species. Here are the numbers: 2,065 native plants, 22,000 non-native plants, 2,069 of which have naturalized, leading to 3 total extinctions. Sax and Gaines argue that invasive species are not all bad. In fact many times the extinctions they are predicted to cause never actually happen. They say that the increased competition creates a selective pressure that spurs the evolution of greater diversity. Often invasives will hybridize with native plants to form new and wonderful species like the common cordgrass (See awesome picture below).

The two scientists say that often there is more than enough room for invaders and the native species. There is also mention of invasions throughout biological history that have led to increases in biodiversity rather than extinction. They give an example of pacific mussels invading north atlantic mussels. Rather than causing the atlantic mussels to go extinct the two species hybridized forming a new species, thus increasing biodiversity.

Critics of Sax and Gaines, such as Anthony Ricciardi from McGill argue that invasive species are a greater threat than ever due to their rapid spread by humans and the pressure already placed on native species due to climate change. He says that the extinctions could be eminent.

So maybe invasive species aren't so bad....think again. I say invasive species are hurting America. We need to put up a wall to keep out the invasives so that they stop taking niches away from hard working native species. I know what you're thinking, they do the jobs no one else wants, if we didn't have honey bees we'd be pollinating all those flowers ourselves, and no one wants to do that. But that's the kind of laziness that led to this:

THE ASIAN CARP!!!!!!

These fatties can grow up to 3 feet long and weigh 100 pounds. They eat everything in sight (consumptive competition) causing native fish to starve. They are threatening to destroy the $4.5 billion great lakes fishing industry (http://www.glu.org/asiancarp). Not only are they threatening to kill off fish, they are threatening to kill us. Asian carp are easily startled and jump out of the water. One fisherman was witness to the dangers of the fish, "One of our guys got hit in the (groin). It's insane," said Bob Bennington, of Streater, Ill."

http://blog.mlive.com/muskegon_chronicle_extra/2007/08/asian_carp_pose_dire_threat_to.html

It certainly doesn't end with the Asian Carp. There are a number of economically disastrous invasive species. They are costing the US billions of dollars in damage. (http://www.mnn.com/lifestyle/pets-animals/stories/invasive-exotic-animals-costing-us-billions-of-dollars). The USDA keeps a comprehensive list of all invasives, check it out at: http://www.invasivespeciesinfo.gov/