Science Wednesday: Thinking of Biological Integrity on Darwin’s Birthday

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.

image of authorThe 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?