The first of these two chapters focuses on invasives and all the bad press they get. Marris claims that invasives are judged as detrimental before they are able to truly show their worth. She names a few cases where invasive species have been responsible for serious ecological and economic costs, but then goes on to tell stories of how invasive species have a bad name for only those few incidents. Many foreign species, she says, are incapable of actually causing extinctions and that they actually increase diversity in some cases. She uses researcher Sax’s study of increased diversity on islands as an example. Of course, she has to admit that this was on a per island basis and that global diversity was actually decreasing. The example only serves to show that extinctions cause by invasive species is rare — a statistic we might expect… Surely Marris is exaggerating when she suggests that everyone thinks invasives kill off native species as if they have genocidal intent in their genes. She goes on to other cases where the distinction between native and non-native species is blurred, and it is therefore difficult to say who is the invasive and who belongs. This is a good point that I like, because it speaks a lot about how humans organize reality into labels that are not necessarily efficient or logical. Is the familiar always the same as the native? Do animals that have lived in one place for a time have a “right” to that land, or “belong” there? These are questions that need more appreciation and reflection.
The next chapter, about “novel ecosystems”, discusses situations where exotic plants are introduced and then left to their own will. Marris’ argument is that these can sometimes bring better conditions to the ecosystem, more efficient nutrient cycling, faster growth, etc. The condition is sometimes, since she admits that “these new system likely do spell out homogenization and extinction, in some places.” While it may be the case that some species can be safely added to an ecosystem like her example of mangoes, she is right to say it “sometimes” works, and not even venture “the majority of times”. Even if a species becomes invasive and the population booms, she says, they become controlled with passing time. However, she does not and cannot claim this happens all the time. While species like the zebra water mussel and Canadian water weed have faded as pests, she forgets that there still exist examples like kudzu and rabbits in Austrailia that spell serious ecological and economic trouble. Not to mention that it may take decades to wait for nature to clean up the mistake, during which time the invasive species will already have wrought enough damage. This may not the most fitting example, but the Irish potato blight comes to mind and the negative impact that potato mold had on people was temporary but intense. The ecologists Marris so makes fun of are simply operating on a “better safe than sorry” mode. In the end of the chapter, Marris mentions that much of the world is already a “novel ecosystem” by her definition, which is true. man’s touch has been that widespread. I agree that these should be studied and offer much new knowledge for us, but I am still not comfortable with the idea of going out and creating these new “novel ecosystems” as our experiments.
