Critique: Daniel Simberloff's "Introduced Species: The Threat to Biodiversity & What We Can Be Done"

Insisting that the introduction of non-native species causes disastrous effects to our planet's ecosystems, Daniel Simberloff (2000) argues that "more attention must be paid to the problem and devising a solution before the cost is more than we can bear." Simberloff, who is the Nancy Gore Hunger professor of environmental studies at the University of Tennessee, argues that "keeping potentially damaging invaders out is the most cost-effective way to deal with introduced species" (2000) and he offers several technologies that can be used to help deal with the problem.

There is no doubt that introduced species have caused havoc in many areas of the world, one area being the Galapagos Islands, an isolated archipelago about six hundred miles off the coast of Ecuador in the Eastern Pacific. For instance, the Galapagos Tortoise has taken a beating from many introduced species which are infesting the islands, species like feral goats, blackberries, donkeys, cats, and dogs. According to James Hider of Puerto Ayora, "Donkeys trample their nests, dogs, pigs, rats, and ants eat their eggs, cats kill their young" (2005). As Hider says, "the islands have become victims of their own success as a tourist destination, despite the hefty cost of getting there" (2005). There is no doubt that "introductions of nonindigenous organisms can be both a boon and a bane to society" (Ewel et al., 1999).

There is no doubt that introduced species cause a host of problems in various locations around the globe. Daniel Simberloff points out that non-native species are a serious threat to our environment because they a) can change an entire habitat, placing ecosystems at risk, b) crowd out or replace native species that are beneficial to a habitat, and c) damage human enterprise, such as fisheries, costing the economy millions of dollars (2000). He provides facts that prove how much of a negative effect non-native species can have on the environment. It is clear that something needs to be done about this problem. Simberloff does a good job of offering several technologies to help control the invasive species problem, and he wisely points out that "no method is a magic bullet, each can have drawbacks if misused, and each has failed when used against certain invaders, but each also has successes to its credit" (2000).

Simberloff's plan for combating the invasive species problem is reasonable for the most part. However, he fails to cite instances in which some non-native species have had positive effects on the economy. For instance, a coconut palm that originally originated in Malaysia is now found in tropical areas all over the globe and it "provides a host of products that support subsistence economies on Pacific atolls, agroindustries in the Philippines, and international tourism in the Caribbean" (Ewel et al., 1999). Sure, non-native species can and have damaged human enterprise, as was the case when "the accidental introduction of the blight-causing fungus Cryophonectria parasitica from Asia led to the loss of the economically important American chestnut tree from the deciduous forests of the eastern United States" (Ewel et al., 1999). It may very well be that, as Simberloff points out, "through damage to agriculture, forestry, fisheries, and other human enterprises, introduced species inflict an enormous economic cost, estimated at $137 billion per year to the U.S. economy alone" (2000). However, as seen is from the example mentioned previously, there are some non-native species such as the coconut palm from Malaysia that play a huge role in supporting the economies of several countries.

Another problem with Simberloff's argument is that he doesn't mention all of the other causes of the extinction of native species. He does mention disease, pollution, harvest, and habitat destruction, but he forgets another main cause: a change in the climate. This is significant because climate may play a major role in the extinction of native species. According to a report from the WWF website, blue whales are under threat because the krill population is under threat. According to the report ("Climate Change," 2001), the reason for this is that the sea ice is disappearing as a result of rising temperatures and this would decrease the number of algae present. This is bad since krill feed on the algae. Krill makes up a large portion of the blue whale's diet, so less krill means there would be starving whales. This could be traced back to the change in climate.

Simberloff is right when he says that the introduction of invasive species can have disastrous effects on the environment and he gives several good ideas that can be used to combat the problem. However, he should not overlook the benefits that certain non-native species can provide. Even though non-native species may inflict a serious economic cost to some areas of the world, they also have positive effects on the economy of other areas. An invasive species may have more negative effects in one area of the world than it does in another. We have quite a challenge figuring out a way to eliminate the harmful effects of invasive species without eliminating the positive effects.

Sources:

Simberloff, D. (2000, December). Introduced Species: The Threat to Biodiversity & What Can Be Done. American Institute of Biological Sciences. Retrieved March 21, 2006, from http://www.actionbioscience.org/biodiversity/simberloff.html

Hider, J. (2005). This Glorious Fellow is Facing Extinction. Who is to Blame? The Times (United Kingdom). Retrieved March 21, 2006, from Academic Search Premier database.

Climate Change Threatens Blue Whales. (2001). Retrieved March 21, 2006, from http://www.greenpeace.org.uk/blog/climate/melting-ice-threatens-blue-whales-food-supply

Ewel, J. et al. (1999). Deliberate Introductions of Species: Research Needs. Bioscience, 49, 619. Retrieved March 21, 2006, from Academic Search Premier database.