There are two concepts that are central to the problem of pest resistance in agriculture. One is that small organisms with rapid reproduction can adapt to the harshest of stresses in very short amounts of time. This is the basic underpinning to pesticide resistance everywhere. The flip side is that large organisms cannot adapt quickly because they require too much time to produce offspring. As a direct result, large-sized species are more likely to disappear locally when a severe stress occurs.
The reason this is so relevant is because pesticides are a severe stress. We see rapid evolution in response to pesticide stress in small organisms such as insects. And because large organisms, such as the predators of the small organisms, are much slower to evolve, they tend to disappear and then no biological controls are present to keep the pest species at bay.
A major review paper was just published in Science by Scott Carroll, Peter Jorgensen, and colleagues that focused on just this concept. (http://www.sciencemag.org/content/early/2014/09/10/science.1245993) (By the way, when Science gives this much space to a paper, they consider this a topic of the utmost importance and relevance to science and the public.) The overall point of the paper is that pathogens and pests species can adapt fast enough to keep pace with the changes humans impost on the environment, while many others species cannot. Their core concern is that this has major implications for medicine, agriculture, and the long-term stability of the world economy.
Their overall premise is that it all comes down to an understanding of evolutionary biology and such an understanding also provides avenues for developing solutions. In particular, Carroll and Jorgensen et al are proposing a broadly defined field of applied evolutionary biology that can direct our efforts to manipulate the genetic variation in organisms we favor, such as crop plants, and to do battle against the organisms we want to control, such as bacteria and crop pests. Let me say that for their ideas to come to fruition, we MUST assume that humans are part of the environment and have a long evolutionary history as members of the environment. Once we adopt that understanding into modern medicine, we can more rapidly align our living environment with the genetic history we all carry with us. For example, the western diet (described by Michael Pollan), with its very high proportion of processed carbohydrates, is absolutely contrary to the diet of our ancestors. Combine this with a more sedentary lifestyle and lifespans that are more than double what they were 100 years ago, and we have a desperate and growing medical situation with obesity, diabetes, auto-immune diseases, cardio-vascular diseases, cancer, and (yes!) infectious diseases. While Carroll and Jorgensen et al may not say so explicitly, I will: All of these problems of a highly technological, chemically-dependent, and environmentally destructive, urbanized society are linked. But they are not a necessary outcome.
I applaud Carroll and Jorgensen et al for their insights and thorough treatment of this subject and I hope this paper finds its way into the highest reaches of policy development. Of course, their discussion of agriculture and pest resistance is of great interest to me, but I have to voice a warning concerning their advice. While genetically-engineered crops show tremendous promise, it is always over the short term. They are not solutions; they are bandages applied to a growing environmental wound. No matter what solutions biotechnology is able to devise, they do not address the basic evolutionary problem that I address in the Red Queen and that Carroll and Jorgensen et al state in their opening sentences: Small organisms can adapt as fast as we apply selective stress to them. This will not change. There are rules that govern evolutionary biology and we cannot avoid them and we cannot change them.
All biotech “solutions” will ultimately fail because they attempt to stop a process that is the bedrock of biology. That process is evolution by natural selection. However, if we truly understand the process and apply that understanding such that those rules guide human endeavors and our interactions with nature, it may be possible to greatly reduce the growing number of issues we face in medicine and agriculture. For example, we understand that high genetic variation in large populations of insects provides the raw material for withstanding our attempts to eradicate them. We apparently fail to understand that we cannot and will not achieve eradication of pest species with chemicals. On the other hand, we have completely ignored the value of genetic variation for withstanding environmental stress when it comes to our own crops species. Insects win because of genetic variation. Our crops are losing because of the lack of genetic variation and it’s a lack that we have actively encouraged as we developed high-yield and transgenic crops.
Carroll and Jorgensen et al have provided a nice template for framing this discussion, but it is just the starting point. My goal with Chasing the Red Queen is to make clear the rules that govern such a discussion and in a way that’s readable and accessible.