Almost philosophical question about controlling a pest/plague?

Question

Once in a math congress someone presented a paper on a mathematical model used to predict the impact of certain measures that could be taken in order to control some pest/plague. A guy in the audience interrupted the speaker and asked why not to "kill them all"(referring to the specimens of the pest/plague) and put a stop to the problem. The speaker observed that we were thinking that kind of things because almost all of us were mathematicians and so we were not aware that it would be a big problem to do that. From my point of view, he was suggesting that "the right way to control a plague is not to kill them all" is a standard, uncontroversial fact that all biologists would agree. My question is about this last point. Is that a scientific thesis or an ideological one? I mean, do biologists have theories that allow them to know that the "right" way to control a plague is not to kill every specimen of the species? Why is it the case that we can assure that exterminating a species is necessarily going to affect, directly or not, humankind? Is it a matter of chance and, as we are not completely certain of what may happen after exterminating the species, then we don't want to take a risk? Thanks! And feel free to edit tags :)

Answer 1

If you asked me to name a theory, I could not. But pest management is at least as old as agriculture. The considerations for how extreme a solution to apply to a pest problem are numerous.

Start with how serious a problem it really is. Are we talking not spraying DDT and accepting a few brown spots on our apples? Side benefits are maintaining almost every other strand in the food web: other bugs not causing any harm, amphibians and reptiles that eat them, and birds and mammals too. Or do we have large carnivores running through city streets, an immediate danger to all humans and domestic animals in the vicinity?

Next, consider the financial impact. How much will this cost? Who is paying for all this? Those directly concerned, the State, the Feds? Wall Street, the prime and the election cycle come into play here.

Then consider whether or not it is possible to get an LD100 (100% lethal dose) without destroying more than just your target pest. Collateral damage is a major worry (refer back to the DDT example).

As an Ecologist and Environmental Scientist, the first thing that I teach my students is that in this business, EVERYTHING THAT YOU DO OR DO NOT DO, MATTERS. Chaos Theory, the Butterfly Effect, is the place where our sciences meet. Eliminating a species will change the balance, what comes to take its place is unknown, usually until it is too late.

So I suppose it is more pragmatic than philosophical/ideological. We would try to get the best results with the least cost, least damage, least effort, least resistance.