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What Is a Healthy Ecosystem?

2008 April 23

About the author: Dr. Robert Lackey is a 27-year veteran senior scientist in EPA’s Office of Research and Development’s Corvallis, Oregon research laboratory.

Bob LackeyVery young children have a habit of asking innocent, but thorny questions. My grandson, however, has reached an age where innocence no longer passes for an excuse for his questions; he knows enough now that his questions reflect the traits of a budding intellectual troublemaker.

A case in point: here is my answer to his question about the increasingly popular term: ecosystem health.

“Grandpa, in school today in my science class, we talked about healthy ecosystems. My teacher says that when we are not feeling well, we go to a doctor to find out how to get healthy. If I have a sick ecosystem, she says that I should go to a scientist find out how to make the ecosystem healthy. Dad says you are a scientist, so what is a healthy ecosystem?”

It is a good question and one that I, as a research scientist who has worked on such issues for over 40 years, should be able to answer with ease.

This seemingly straightforward question, however, does not have a simple answer. Further, the answer requires a clear understanding of the proper role of science in a democracy (PDF) (7 pp., 39K) Link to EPA's External Link Disclaimer.

First, how is a person to recognize a healthy ecosystem? Many might identify the healthiest ecosystems as those that are pristine. But what is the pristine state of an ecosystem? Is it the condition of North America prior to alterations caused by European immigrants, say 1491? Or perhaps it is the condition of the land sometime well after the arrival of immigrants who came by way of the Bering land bridge, say 1,000 years ago? Or maybe it is the state of North America prior to the arrival of any humans, say more than 15,000 years ago?

Ultimately it is a policy decision (PDF) (16 pp., 173K) Link to EPA's External Link Disclaimer that will specify the desired state of an ecosystem. It is a choice, a preference, a goal.

Scientists can provide options, alternatives, and possibilities, but ultimately in a democracy it is society that chooses from among the possible goals (PDF) (6 pp., 157K) Link to EPA's External Link Disclaimer.

A malarial infested swamp in its natural state could be defined as a healthy ecosystem, as could the same land converted to an intensively managed rice paddy. Neither the swamp nor the rice paddy can be seen as a “healthy” ecosystem except through the lens of a person’s values or policy goals.

Once the desired state of an ecosystem is specified by someone, or by society overall through laws and regulation, scientists can determine how close we are to achieving that goal. They might even offer some approaches that might better achieve the goal. Ultimately, though, it is society (PDF) (5 pp., 21K) Link to EPA's External Link Disclaimer that defines the goal, not scientists. One person’s sick ecosystem is another person’s healthy ecosystem.

So the answer to my grandson’s provocative question is that human health is not an appropriate metaphor for ecosystem health. There is no inherently “healthy” state of ecosystems except when viewed from the perspective of societal values.

Pristine ecosystems (wilderness watersheds, Antarctica, uninhabited tundra) are certainly very different than highly altered ecosystems (farms, city parks, harbors) but neither a pristine ecosystem nor a highly altered ecosystem is scientifically better or worse — just different.

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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17 Responses leave one →
  1. Sue Hecht permalink
    April 23, 2008

    Nice job explaining it in simple, straight forward terms. I like it.

  2. Patraig permalink
    April 23, 2008

    Very thought provoking, and I must say I agree. An ecosystem is what it is without needing to be valued and labeled by humanity. I would also add to this my own observation, that there seems to be a widely held view that somehow humans are ‘alien’ to our environment and ecosystems, instead of being part of it. I contend that humans are a part of the ecosystem, rather than ‘just’ an external force affecting the environment. Granted humans can and have made tremendous changes to our environment, many of which I would label as harmful, but other species do things that have been labeled as harmful to the ecosystems. (E.g: ‘Invasive’ species of plans and animals) I recently saw on National Geographic Channel the show Aftermath: Population Zero. This program explores the likely consequences to the world, if all of a sudden, people disappeared. Although somewhat speculative, the point I derived from it, is that in a matter of several hundred years, the earth would shrug off the vast majority of all evidence that humanity was ever here. What’s more, the changes we’ve made that have ‘put the earth out of balance’ would heal. Very interesting how the macro ecosystem we call earth, can shrug off the changes made by man in a relatively short amount of time.

  3. Joe F. permalink
    April 24, 2008

    Nice to have such a nuanced explanation from someone from the EPA. Much of the conversation around the environment is couched in very black and white, moralistic tones. It’s a great point, that society decides on ecological value.

  4. Kirk Rensmeyer permalink
    April 24, 2008

    I’m interested in what you actually told your granddaughter..I have a couple of grandkids that usually ask what you least expect!

    I agree that scientists must maintain objectivity and avoid “normative science”. I also think this objectivity adds to a scientist’s skill set for dealing with really complex and “wicked” problems. One metaphor I was thinking about today was the canary in the coal mine. I would be interested in your thoughts on this. I was thinking that for a given ecosystem scientists probably have the best expertise to identify/find the canary, establish whether it is dead or not or establish whether there is a single canary to consider. Granting that the term ecosystem health is pretty subjective, this is how I would view a scientific approach. Kirk

  5. Mike Gearheard permalink
    April 24, 2008

    Hi Bob,

    I’m having some trouble with your overall premise that the answer to the question is a function of society’s judgement about what they want the ecosystem to be. That system of judgements will necessarily be based on our worldview, our value system. It is that value system that brings us the managed environment we live with today in much of our country. Are the rivers in the Northwest just there for our use? Is their value, and their ‘health’ what we determine it to be based on what value it has to us? One could argue — as Lichatowich does in Salmon Without Rivers — that it is this tendency to see our ecosystems in terms of what value they have for us that has resulted in the extermination or near extermination of salmon in our rivers. The problem is that the predominant values of our modern society reflect our view of the natural environment as something that exists to do our bidding. I read (perhaps misread?) your answer as furthering that notion.

    The Clean Water Act says we are to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” To me that implies that these ecosystems have integrity (and health) without it having to be defined by us. That integrity is integral to the natural system, even if it is a swamp. Maybe in the future our values might evolve and we will be more skilled at managing our environment. In that case, your premise that our society defines the goals (and the health) of ecosystems might produce a more sustainable environmental condition.

    Better yet, native cultures in our area like to say that they are not managing the natural environment, but rather are borrowing it from their grandchildren. If our definition of a healthy ecosystem is one that will be healthy for our grandchildren and their grandchildren, and if we are wise enough today be be able to define it, then I would be more comfortable with your answer.

  6. Tony Grover permalink
    April 25, 2008

    Bob, Mike & others,
    It is nice to hear from friends and acquaintences on such an interesting topic. You both are leading me to conclude there seems tobe a bit of a conflation of ideas: healthy ecosystem. Ecosystems are. They exist independent of any human value judgement placed on them. An ecosystem can have non valued qualities such as expanding, contracting, diverse, simple, steady stae, punctuated. The notion of ‘healthy’ is as both Bob and Mike have said, up to human society. If we, as a fractious society, could reach an imaginary ‘consensus’ about ecosystem ‘health’ today, it would have a shelf life only as long as society could hold that thought.

    I am attracted to the idea of identifying and working to preserve those threads of the ecosystem that seem likely to have the most value for society in the future. It is not our job to stop all change or extinction — afterall, the history of life on earth is a long tale of gradual and disasterous change with nearly all species headed to extinction. Of course no ecosystem thread can sustain itself, but we rapidly run out of reliable scientific understanding of how the threads of an ecosystem are interconnected.

    All this leads me to conclude that ‘healthy’ can be defined as a mix data, hypotheses, degree of penetration into society of the hypotheses, and acts of blind faith. So let’s get on with what we can do about preserving important threads of the ecosystem around us, but not beat ourselves up too badly when we discover the little lump of grey matter in our skulls did not get everything just right.

  7. Steve Jordan permalink
    April 25, 2008

    Congratulations for stating this issue so clearly. The flip side of your comment is that society and policy makers need to do a better job of setting goals (quantitative, time-bound) for ecosystems so scientists know what to measure. “More fish” or “healthier ecosystems” are not suitable goals. Scientists do have a role in goal-setting, i.e. to inform policy not about what is good or bad, but what is possible and measurable.

  8. Bob Lackey permalink
    April 25, 2008

    OK, here is a brief elaboration on my thoughts about normative science and its use — and misuse — by scientists (and others) in influencing public policy.

    Effectively solving any of the major ecological policy issues facing society today requires providing an array of scientific information to decision makers. The ability of scientists (and scientific information) to inform constructively ecological policy deliberations is diminished when what is offered as “science” is inculcated with policy preferences (the definition of normative science).

    As with all human activity, the scientific enterprise is not free of values, but values reflected in subtle form as policy preferences should not be permitted to prejudice scientific information. Scientific information becomes “normative” when it contains tacit policy preferences and thus, by extension, promotes particular policy options. There are many examples (ecosystem health, degradation, biological integrity) of normative science confusing the development of sound ecological policy when it operates under the guise of policy neutral science. With its disguised value and preference characteristics, normative science provides little substantive help in reconciling the most divisive elements of ecological policy.

    In my opinion, scientists should play the important role of informing policy discussions with unbiased, understandable scientific information, assessments, and forecasts. To develop sound policy, science is important, helpful, perhaps even essential, but involvement with policy issues by a naive scientist or scientific organization can lead to loss of credibility and perceived independence unless the proper roles of both science and policy are understood and followed.

    Scientific information is central to the successful resolution of important, divisive, and controversial ecological issues. When providing scientific information to the public and decision makers, scientists should play the proper role — the appropriate role — but know and announce when they have stepped out of a scientific role and into the role of political advocate, however subtle that advocacy may be.

  9. D White permalink
    April 28, 2008

    What is a scientist, a policy-maker, a member of society? Sometimes one person can be all three. And sometimes it seems like “society” as the polity that makes decisions in a democracy is actually a rather small subset of the population.

    Is the conduct of science totally incompatible with making decisions for environmental managment? One argument is that when science is mixed with the judgments involved in decision-making then science is weakened because scientists may be perceived as partisan advocates rather than objective observers. But everything that science studies reflects human values and interests. And all facts of science have an origin in human values and, in turn, values reflect how humans observe the world.

    Does a scientist have a duty to society to advocate a position when they believe, based on their scientific knowledge, that not advocating that position can result in harm? To make too sharp a distinction between what a scientist does and what society does can limit potentially valuable and important debate.

    If a scientist does advocate a position, it is certainly reasonable to ask for value judgments to be made explicit, for positions to be subjected to scientific and public debate, for uncertainties in knowledge to be admitted, and for consequences of advocated positions to be assessed.

  10. Hal Michael permalink
    August 15, 2008

    One of the serious problems I see is when agencies, organizations, policy people stifiling meaningful scientific and policy debate. Once an entity determines its direction and sets the “message” it seems to become more difficult to bring in a differing view. The message becomes the “science”. It also seems that we create quasi-religions about old-growth forests, wild fish, and so on without ever having a discussion about the consequences of those choices. What must be given up to have ….fish, trees, lumber, food, water, wolves?

    As a scientist, I have a personal desire to see some fully functional ecosystems supported by spawning salmon. As a member of society, I want to see a fully informed debate, where the science, the economics, and values can be debated.

    As has been said above, the ecosystem IS. What it is allowed to be is what society decides. We need a more open debate.

  11. Kim Mattson permalink
    August 20, 2008

    To address the question of what is a healthy ecosystem, I think it is useful to review the terms ecosystem and even health. Ecosystems seem to be commonly misunderstood. Ecosystems according to how the term has been used by the Odum’s and other ecosystems ecologists can be best thought of as an abstract notion we humans have invented. It represents a notion that nature is organized into energy flow and nutrient cycles leading to trophic structures, populations and ultimately a place where life exists. To the layman, ecosystems are most often (mistakenly) synonymous with nature or landscapes. When in fact, nature or the landscape is better thought of as the “result” of the ecosystem properties. A city is also an abstract notion–it has invisible boundaries, and a set of rules that control how people behave and how cities are constructed. We can see the buildings are built in certain way due to building codes and traffic flows on streets as a result of traffic ordinances and so on. So is nature constructed and organized along what we see as ecosystem principles.

    About health… It makes sense to say a population that is declining in numbers might be less healthy. It really doesn’t make as much sense to say an ecosystem is unhealthy because a population is in decline. The change in the population is likely the result of some change in the ecosystem property (increase in competitor, decrease in resource availability…). Almost always a decline in one population results in an increase in another population. In a case where this doesn’t happen, such as a toxic chemical spill, perhaps one could say the ecosystem is less healthy. But even still in these cases, such as what happened in the Upper Sacramento River over ten years ago, the system typically recovers and populations can even exceed those of the pre-spill years.

    Here are a few measures of what undisturbed ecosystems seem to tend toward: high species diversity, ability to resist population changes, ability to recover from population changes, accumulation of both living and non-living organic matter, and the ability to retain moisture. All of these will act as buffers to resist change and therefore create greater stability. Are these the characteristics that humans might associate with health? I suppose so…most humans are taught to fear change…and rightly so as it could mean their own decline.

  12. Bob Vadas, Jr. permalink
    September 4, 2008

    Below is a revised version of relevant discussions that I’ve previously had with Bob Lackey.

    Indeed, his publications and the above discussion collectively make the point about keeping the analytical focus below the ecosystem level. Indeed, I like the IBI (index of biotic integrity) focus on assemblages and smaller biological scales, so environmental management at larger scales (but perhaps below the ecosystem level) seems reasonable. At least biodiversity is now treated more carefully by IBI analyses, in that overly low or high alpha (local) biodiversity (the latter via exotic invasions) is considered to be a red flag for biotic-integrity problems. Low beta (across-site) diversity, however, is likely indicative of biological homogenization, as exotic species come to dominate different locations with different native-fish assemblages.

    Hence, although I agree that ‘ecosystem health’ is a dubious concept, I would resolve the issue by focusing on biotic (ecosystem) integrity as IBI researchers have done. I don’t think it’s wrong to use natural ecosystems as benchmarks for restoration, because human impacts can best be measured by examining deviations away from natural conditions (as measured by genetic, population, assemblage, community, and/or ecosystem-level parameters). That does involve good science. And although I have my reservations about implementation of the IBI, I think that Jim Karr and colleagues have made a strong case that this type of biomonitoring approach is a useful way to proceed. I do work with several watershed groups that are interested in seeing things restored towards more-natural conditions, so such an approach is both ecology- and policy-relevant. Such ecosystems are often more ecologically sustainable, given that hatchery- and agriculturally based ecosystems require much human impact to maintain. Not interfering with evolutionary processes makes sense, given Aldo Leopold’s emphasis on saving all parts of the natural ecosystem to maintain it. But I agree that normative science involves value judgments in defining ecological baselines, such that scientists enter the policy arena (as they should be encouraged to do) when they focus on ecosystem health and consider degraded habitats with exotic-species invasions and reduced native biodiversity to be undesirable.

  13. Bob Vadas, Jr. permalink
    September 8, 2008

    Let me add further information from my past discussions with Bob Lackey.

    When I argue for restoring natural conditions, I do so using the argument that sustainability will be enhanced (i.e., less dependence on hatchery stocking), with the added hope that we may bring coho back into the interior-Columbia River drainage so that it can spawn in the wild again (as in now happening in several tributaries). Restoring riparian and flow conditions should increase these odds, particularly because coho and other salmonids like off-channel habitats that often get destroyed by humans. I’m not uncomfortable with stating this as a desirable management objective for achieving federal-ESA requirements.

    Even after reading Bob’s ‘BioScience’ paper on ecosystem health, I’m still not totally clear on the best way to avoid misuse of ecosystem issues in policy discussions, especially given the explicitness of federal-ESA requirements for the work that I now do. This is pragmatic restoration at a biological scale well below the erudite ecosystem level, but with potential ecosystem implications (e.g., nutrient restoration via coho carcasses). To suggest that coho restoration isn’t desirable unless the public approves it (as implied in http://blog.epa.gov/blog/2008/07/30/science-wednesday-does-the-public-expect-too-much-from-science) is too relativistic for me; we may need to help convince them via education.

  14. Diana Kuest permalink
    May 8, 2009

    Science and the good practice of it, is the “rudder” that steers the ship of good life and living for all concerned on this earth. I would hope that this science practice is given to the schools of our country along with willing information and education to all classrooms. Each year that it is not a part of good practice, is a year that is lost to our youth. I hope that information and education is ongoing and a committment from every agency that has taken the responsibility of this awareness.

  15. Bob Vadas, Jr. permalink
    March 31, 2010

    After listening to Lackey’s 2010 telephone interview that further knocks normative science, I have to disagree when he says that scientists shouldn’t judge whether the increasing human-population growth is “bad”. We certainly know that it’ll make salmon restoration that much tougher, not to mention the sundry other environmental and social problems that come with increasing urbanization like traffic, smog, greenhouse gases, violent crime, communicable diseases, etc. Hence, Lackey’s prescription is much like religion, i.e., thou shalt not do this or else you’ll get judged harshly. I also disagree with Lackey that normative science is a big reason that the public distrusts scientists; rather, we’re often the messengers that bring bad news to conservative, religious people who don’t want to believe in evolution or global warming. Scientists need to think and act positively to achieve environmental benefits, not engage in self-loathing from the ivory tower.

  16. unknown permalink
    November 11, 2013

    you did not answer the question the answer is a healthy ecosystem needs living and nonliving things in it. I get ur a scientist and all but I don’t think ur answer really helped anyone asking the question

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