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

2009 February 4

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?

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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21 Responses leave one →
  1. Lina-EPA permalink*
    February 4, 2009

    Dr. Bagley, we were just posing having a parallel discusion on the Coquis-EPA blog. See comments at:
    Care to join the discussion? Any thoughts on invasive species and evolution protection?

  2. Mark B permalink
    February 5, 2009

    Hi Lina. The question of invasive species and what to do about them was on my mind when I wrote this post about biological integrity.

    I think, ultimately, my post was about my problems with the word ‘integrity’. It is a human value-laden term and our (current) values can be at odds with the requirements for long-term biological sustainability.

    For the most part, we do not value invasive species and generally consider an ecosystems that contains them to be worse off (have less intrity) than ecosystems that do not. But the fact that the invasive species was able to establish in the first place suggests that the ecosystem was not operating at highest efficiency before being invaded.

    From the perspective of ecosystem functioning, I think the question of whether invasive spcecies are good or bad hinges on whether the short-term success of the invader translates into greater or lower biological productivity and sustainability. And that brings me full circle to the question of human values and ethics- just what is it that we want to sustain? Biological processes or biological structure? Our tendency as conservation-minded people is to want to sustain biological structure that we are familiar with. Ethically, therefore, we see invasives as bad. But in the (very) long term, our innate desire to preserve structure rather than sustain processes could be counter to ecosystem sustainability goals.

    At the very least, we ought to be aware of this conflict.

  3. Dr. D permalink
    February 5, 2009

    First let me just say thanks to Mark for his thought provoking blog!

    I agree that conservation-minded people will want to maintain biological structure because it is familiar (and tangible). What’s interesting though is the preservation of structure assumes we fully understand all the nuances of the structure and can make the “right” or “correct” decisions in terms of ecosystem management/restoration/conservation/preservation. When you add the presence of our friend uncertainty into the equation it makes the integrity issue that much more complex and interesting.

    Our assumption is that the successful introduction of an invasive species indicates a less than optimal ecological efficiency (and I realize that there is data to support this). This assumption basically implies there is an optimal threshold or hard line above or below which efficiency is impacted by the addition or subtraction of a species. What about cases where ecosystems survived even with the removal of a species (e.g., the Chestnut blight)? True these examples may be more limited yet uncertainty remains and how do we factor in this uncertainty when it comes to these important decisions?

    Given that species interactions are so complex can we ever be truly confident that we are making the right long-term choice whether we choose to sustain processes or structure?

  4. Lina-EPA permalink*
    February 9, 2009

    So, sustainability aside–when you introduce an invasive–does everything boil down to survival of the fittest?

  5. estraka permalink
    February 10, 2009

    This is a great question that many invasional and conservation biologists ask all the time. Lina poses a great question: once a species becomes invasive (usually beyond control) does it then boil down to whoever is best at gathering resources the rightful heir? Here in Hawaii, we are considered the invasive capital of the US- we have more introduced species than native ones, and many of the introduced are invasive or has the potential to become invasive through facilitative actions. Island ecosystems are also much more susceptible to invasions and its effects are more prominent. Many of our worse invasive species, especially plants, disrupts entire ecosystem processes. Psidium cattlenium creates monoculture stands where no other vegetation can grow under, so thick that a person cannot walk through- killing native and non-native vegetation in the process and disrupts our watershed systems. Some of Hawaii’s native flora and fauna are so specialized that the loss of one equals the loss of the other. Does this mean that the years in which these species evolved is moot once a new species enters the scene? Like many indigenous cultures, do we say if you can’t adapt then you cannot exist?
    Also, if we say that invasive species are only in the eyes of the beholder, wouldn’t that also mean that having less water (we rely on our watersheds for drinking water) is also arbitrary?

  6. Ken permalink
    February 11, 2009

    Mark, thanks for initiating the blog and for inviting me to participate.

    In response to “…the capacity of the community of organisms within an ecosystem to continue to evolve so that it can optimize the sustainable transformation of solar energy and nutrients into biological matter. Isn’t it this optimization process that really describes biological integrity?”: I agree communities change to optimize available energy and nutrients but that does not necessarily result in systems that we typically consider as having high biological integrity. For example, consider a stream that drains a local water treatment facility. The channel is choked with 2 species (tubificids and blood chironomids), the community has “evolved” such that it can take advantage of the high nutrients and labile organic matter available (ie., subsidized by human waste). This community is more optimal in the current environment than the one that likely occurred there before the waste water plant was put into place. The previous community likely could not survive periodic depressions in oxygen or peaks of ammonia and compete with current dominants, let alone process elevated levels of nutrients and organic matter as efficiently as the tubifids and chironomids. And unless people quit sending waste to the plant, this subsidy supporting the 2 species community is sustainable.

    I agree that biological integrity should incorporate biological processes, but I think there is a problem with defining it in terms of maximum optimization. When we alter the environment there will always be biological adjustments, but the adjustments are often extirpation, extinction, and homogenization (at higher rates than would occur without strong human influence). Are these processes we should view as characteristic of a systems with high biological integrity? If so, then this would clearly make the CWA at odds with other federal regulations and policies (e.g., ESA). Which may or may not be so unusual.

  7. Lina-EPA permalink*
    February 12, 2009

    So, I have another question–do you think that islands, due to their isolation, are more vulnerable to invasive species? (I have Hawaii and Puerto Rico in mind)

  8. estraka permalink
    February 13, 2009

    The definition of “biological integrity” should always contain the idea of sustainability. The ability to create and use energy should not be the main focus of this term, or even the idea that an ecosystem should be working in peak efficiency. Eutrophication in aquatic and marine habitats increase available nutrients and therefore creates a quick burst of biomass. Many fisheries toyed with the idea, but in the end, the increased number of organisms quickly depleted the amounts of oxygen and therefore, everything reliant on o2 for respiration died out. But, for those moments of high growth, their finite ecoystem was working at peak efficiency- taking advantage of all resources until an important resource was depleted. I see this same idea in terrestrial environment with any organism that increases nutrient loads into the environment to sustain higher biomass than what is sustainable.

  9. estraka permalink
    February 13, 2009

    Another thought that comes to mind while reading this post is how, in Hawaii, we were worried about sustaining our watersheds in the mid 1900’s. Foresters and biologists looked for all kinds of high-growth rate trees to replace native ones that were going through die-backs. The trees they found (albizia, banyan, faya trees) were aerially broadcast across the island and especially in native forests. The overall idea is that we wanted to protect our watershed function. Well, now, half a century later, we realized that by focusing only on ecosystem function at the present, we shot ourselves in the foot. Those trees we selected grew way too fast too and spread so quickly that it took over not only our watersheds, but also our intact native forests. Now, we have another watershed problem- our invasive trees require too much water and therefore our watershed is worse off.
    You probably don’t need this referral but a really good book on invasive species problems is “The Ecology of Invasions by Animals and Plants” by Charles Elton.

  10. Lina-EPA permalink*
    February 17, 2009

    You know, anytime we try to play God to protect a watershed or the environment as a whole, too often we find unintended consequences beyond our control.

    Take the current discussion to introduce a specific species of Asian oyster to the Chesapeake Bay, the nation’s largest estuary. It’s scary. See link below:

  11. estraka permalink
    February 17, 2009

    I agree, Lina. Far too many decisions are based on the present moment and doesn’t look at the future repercussions- mainly because we don’t know what could happen in the future. For example, some common landscape plants have been benign for ages, but suddenly with the introduction of a nitrogen fixing tree (through facilitation), these plants spread into natural areas and become invasive. We have no idea what other plants or animals will be introduced intentionally or unintentionally, as well as not having enough of an idea of how global warming will affect our ecosystems. I think this is a good argument for not introducing plants and animals into new areas- we have no idea how they will interact with every organism in the long-run.

  12. Mark B permalink
    February 18, 2009

    Part of my post had to do with whether biological integrity can be defined objectively, apart from human values. The problem with a definition based on human values is that our values are not uniform in time or space so we could be chasing a moving target.

    For example, introducing a self-sustaining trout population to a previously fishless Sierra stream (perhaps because a waterfall blocked natural colonization) would improve its biological integrity for some people and decrease it for others.

    If we take human values out of the definition, what is left seems to be the capacity of ecosystems to carry on, doing what they do (at a fundamental level, converting energy and nutrients into biomass) without intervention from us. As Ken notes, however, it’s rather distressing to describe ecosystems that do this well as having high “integrity”, particularly if we are talking about a high-biomass algal mat where previously there was a complex biological structure. But this is distressing because of our values.

    The very interesting discussions about invasive species imply a desire to define biological integrity in terms of complexity, uniqueness, biologically stability (low species turnover) and possibly aesthetics. Some of these traits contribute to ecosystem sustainability, but there is clearly a bioethical undertone involved as well.

    So does removal of human values from the definition result in a concept of biological integrity that is simply too bland and uninteresting to protect? I suspect it does. Does anybody have a definition that could withstand the test of time (and regional attitudes and cultural differences)?

  13. Mark B permalink
    February 19, 2009

    responding to my own post, I guess our existing comparative definition of biological integrity (similarity to some ‘reference’ ecosystem that is judged to be functional, balanced, and integrated) would get us there. We just need to learn more about processes, functions, and services so that we can replace comparisons of biological structure with functional comparisons. “Does this ecosystem function at an equivalent level as the reference ecosystem”.

    This does appear to be the path that EPA’s research office is heading towards.

    This has implications for the invasive species issue though. We may reject invasive species based on structural comparisons but embrace them based on functional comparisons. Hypothetically, if a native species that became extinct is replaced by a functionally similar invasive species, the biological integrity of the ecosystem is increased based on functional considerations.

  14. Lina-EPA permalink*
    February 19, 2009

    So in a hypothetical case, we would be willing to selectively “introduce” a species if “the biological integrity of the ecosystem is increased based on functional considerations.” What happens when, outside the lab, there are unintended consequences in the ecosystem?

  15. Mark B permalink
    February 19, 2009

    Well that’s always the rub, isn’t it? Unintended consequences are, by definition, unpredictable (or at least unpredicted). In my note above, I wasn’t actually advocating introductions though, I was just saying that once an invasion occurs, it is possible to think of the ecosystem as functionally improved if the invader provides some important function that was previously missing.

    This conversation reminds me of the “rewilding” North America article in which several highly-respected conservationists suggested we repopulate North America with exotic megafauna that are functionally equivalent to extinct North American relatives, including elephants, camels and great cats, I think. The idea is that these large animals exerted great control on ecosytem balance and biodiversity, and their re-introduction would restore that balance. Here is the reference:
    Donlan, J., et al. 2005. Re-wilding North America. Nature 436: 913-914

  16. estraka permalink
    February 19, 2009

    One thing missing from your post is that invasive species are more than just another non-native or introduced species, it’s a species that is known to have adverse effects to either native, agricultural or residential communities. Megafauna (at least terrestrial) rarely become invasive and if they do, they can usually be reduced back to manageable levels. I always liked the idea of replacing extinct species with another in the same functional group (though not INVASIVE). Theoretically it should work, but it is rare, if impossible, to find a displaced species that will stay within the limits of the functional group without overlapping with another.

  17. Lina-EPA permalink*
    February 19, 2009

    I was not implying that you were advocating in favor of the introduction of new species. I’m just still concerned by the WP article on possibly introducing an Asian oyster to the Chesapeake.

    I’ts in that context that I express concern about “playing God” in nature even if it’s supposedly for the greater good. My two cents.

  18. Mark B permalink
    February 19, 2009

    Right. I guess I should have said “alien” instead of “invasive” above. I should say thought that it’s hard for me to imagine any successful alien species that doesn’t have some adverse effect on some component of the resident community. There are probably always winners and losers in resident community after an introduction.

  19. fritzi -environmental activist permalink
    February 22, 2009

    I am a private citizen living on Willapa Bay. Spartina Alterniflora was accidentally(perhaps) introduced in the late 1800’s. It was used as packing material for the Virginia Oyster that was going to be used in Washington State. The native oyster had been depleted by over harvesting. Over the next hundred years the spartina grew, largely as a result of sediment disturbances caused by one thing or another. However, in 1990 USFWS, and Monsanto decided that the grass was an invasive that needed to be eradicated. There have been many myths about the destructive capacities of the grass. Although beloved on the East and Gulf Coasts it is despised in the West where the scientists say that none of the conditions, which make the grass desirable on other coasts is relevant to the Pacific Coast. As a result tons of glyphosate and now glyphosate and imazapyr have been poured into the waters to kill this grass which many like myself think was Nature’s gift. And because of its ability to so efficiently sequester CO2 its demise is even more distressing. Spartina certainly performed the same function in Willapa Bay that it does in various Chesapeake and Gulf coast estuaries. So my experience with the invasive/alien species issue has been that it tends to be dominated by arbitrary judgments by humans as to whether its good or bad, should be left alone, or exterminated. And too often the code result for invasive species is let the pesticides flow.
    That is what I find most disturbing about the issue. Lina-EPA’s concern
    was about “playing God” by introducing something to nature. A legitimate concern. But isn’t it also playing God to use poisons to destroy something that even though perhaps of a different origin has naturalized in an ecosystem over a number of years.

  20. estraka permalink
    February 23, 2009

    aloha fritzi,
    Spartina Alterniflora has well-documented negative effects on the west coast environment. Through becoming introduced in an area, they displace native species and spread uncontrollably. They also seem to have either created a new type of “functional group” because the grass is known to take over mudflats, thereby decreasing invertebrate populations that are needed for the local bird populations. I would say such environmental degradation is not arbitrary at all and points to a real problem. I agree with you that chemicals are often overdone and we need to be a lot more responsible, but this species, as well as many other invasive species, are a man-made problem that won’t go away without a man-made solution. Of course, the best solution is by tightening up on what we allow into our local ecosystems.

  21. estraka permalink
    February 25, 2009

    Aloha Mark B,
    At some level, there could be some adverse effect on the environment, but I think most of the alien species that do not become invasive are reliant on humans. A lot of alien species in Hawaii , even if they become naturalized, stay within the limits of residential areas or abandoned grasslands where native species are already displaced.

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