Greenversations

Each week we write about the science behind environmental protection. Previous Science Wednesdays.

About the author: Dr. David Reif is a Statistician in the National Center for Computational Toxicology with the EPA’s Office of Research and Development in Research Triangle Park, NC. He holds degrees in Biology, Statistics, and Human Genetics—giving him an abiding appreciation for the lasting impact of Darwin’s theories.

From an evolutionary perspective, should we be surprised that our bodies sometimes react inappropriately to novel chemicals encountered in the environment? According to the principles of adaptation by natural selection laid out by Darwin, the answer is “not at all.”

Each of us alive today is the product of tens of thousands of years of environmental adaptation. This long evolutionary process allows modern humans to respond appropriately to a remarkable set of naturally-occurring substances.

In contrast, people have had comparatively zero time to figure out how to handle the myriad of man-made chemicals introduced since industrialization. Even at the earliest centers of the Industrial Revolution, we’ve had less than 10 generations to obtain evolutionary solutions to previously unseen combinations of substances. Given that Darwin posited “incomprehensively vast” time periods for natural selection to arrive at workable solutions, he would not be surprised that humans have yet to adapt. Neither should we.

Modern civilization has given us all sorts of incredible tools for fighting diseases, making more efficient use of natural resources, and dealing with identifiably toxic substances. However, along with this progress, we have burdened ourselves with an unquantified volume of synthetic substances to which we are all exposed (to various degrees) on a daily basis. This tension between the needs of modern society versus the volume of new chemicals introduced into the environment puts enormous pressure on our bodies to appropriately respond.

Does that mean we must wait patiently while hoping that natural selection weeds through humanity to settle on appropriate adaptations for continuously shifting environmental conditions? No! Thankfully, a key adaptation of modern society is compassion—meaning that we must explore potential toxic effects of all new chemicals through smart science and careful consideration of relevant ethical, legal, and social consequences. Darwin would be proud.

Each week we write about the science behind environmental protection. Previous Science Wednesdays.

About the author: Dr. Mark Bagley is a research biologist and acting branch chief in EPA’s Office of Research and Development in Cincinnati, OH. Since joining the EPA in 1999, his work has involved application of molecular and population genetic methods to ecological questions.

The Clean Water Act charges EPA with protecting and restoring “biological integrity” to aquatic ecosystems. I’ve been wondering lately what we mean by that. The Agency generally uses a definition that refers to the structural and functional similarity to an undisturbed ecosystem—how those factors compare to what we would expect to find in some ideal system.

But who is to say there is just one path to biological integrity? And can we really ever say we have achieved it?
 
In practice, we evaluate biological integrity by surveying the complexity of an ecosystem, typically taking into account differences among species in their sensitivity to different disturbances. We then compare the species we find to those in ecosystems that have been judged to be minimally impacted.

This approach works reasonably well but reinforces a somewhat static view of biological integrity, since comparisons are based on historical notions of what an optimal structure should look like. There are efforts within EPA to more fully understand and evaluate ecosystem functions. At present, there is a strong emphasis on assessing the value that these functions bring to people in the form of ecosystem services (water quality, fisheries, etc).

I think biological integrity requires maintenance of important biological processes, regardless of their value to human well-being and the make-up of the biological community that provides them. In the natural world, species within communities can change without hugely affecting the overall functioning of the ecosystem.

At longer time scales, as environments change, some turnover of species probably has to occur in order for the system to continue to function at an optimal level. And that makes me think that what we’re really talking about is the capacity of the community of organisms within an ecosystem to continue to evolve so that it can find the best solution to sustainable transformation of solar energy and nutrients into biological matter.

Isn’t it this optimization process that really describes biological integrity? It’s an odd question coming from someone whose training is in evolutionary biology. In my work and that of my colleagues, we almost never talk about evolution or the need to preserve evolutionary processes because it seems well beyond the mandate of the EPA. But I’m not so sure anymore.

Maybe in this, the 200th anniversary of the birth of Charles Darwin, it is time to acknowledge that lasting environmental protection isn’t possible without evolution protection.

What do you think real biological integrity is?