Tag Archives: conservation ecology

Is Community Ecology Impossible?

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John Lawton writing in 1999 about general laws in ecological studies stated:

“…. ecological patterns and the laws, rules and mechanisms that underpin them are contingent on the organisms involved, and their environment…. The contingency [due to different species’ attributes] becomes overwhelmingly complicated at intermediate scales, characteristic of community ecology, where there are a large number of case histories, and very little other than weak, fuzzy generalizations….. To discover general patterns, laws and rules in nature, ecology may need to pay less attention to the ‘middle ground’ of community ecology, relying less on reductionism and experimental manipulation, but increasing research efforts into macroecology.” (Lawton 1999, page 177)

There are two generalizations here to consider: first that macroecology is the way forward, and second that community ecology is a difficult area that can lead only to fuzzy generalizations. I will leave the macroecology issue to later, and concentrate on the idea that community ecology can never develop general laws.

The last 15 years of ecological research has partly justified Lawton’s skepticism because progress in community ecology has largely rested on local studies and local generalizations. One illustration of the difficulty of devising generalities is the controversy over the intermediate disturbance hypothesis (Schwilk, Keeley & Bond 1997; Wilkinson 1999; Fox 2013a; Fox 2013b; Kershaw & Mallik 2013; Sheil & Burslem 2013). In their recent review Kershaw and Mallik (2013) concluded that confirmation of the intermediate disturbance hypothesis for all studies was around 20%. For terrestrial ecosystems only, support was about 50%. What should we do with hypotheses that fail as often as succeed? That is perhaps a key question in community ecology. Kershaw and Mallik (2013) adopt the approach that states that the intermediate disturbance hypothesis will apply only to grassland communities of moderate productivity. The details here are not important, the strategy of limiting a supposedly general hypothesis to a small set of communities is critical. We are back to the issue of generality. It is certainly progress to set limits on particular hypotheses, but it does leave the land managers hanging. Kershaw and Mallik (2013) state that the rationale for current forest harvesting models in the boreal forest relies on the intermediate disturbance hypothesis being correct for this ecosystem. Does this matter or not? I am not sure.

Prins and Gordon (2014) evaluated a whole series of hypotheses that represented the conventional wisdom in community ecology and concluded that much of what is accepted as well supported community ecological theory has only limited support. If this is accepted (and Simberloff (2014) does not accept it) we are left in an era of chaos in which practical ecosystem management has few clear models for how to proceed unless studies are available at the local level.

Should we conclude that community ecology is impossible? Certainly not, but it may be much more difficult than our simple models suggest, and the results of studies may be more local in application than our current general overarching theories like the intermediate disturbance hypothesis.

The devil is in the details again, and the most successful community ecological studies have essentially been population ecology studies writ large for the major species in the community. Evolution rears its ugly head to confound generalization. There is not, for example, a generalized large mammal predator in every community, and the species of predators that have evolved on different continents do not all follow the same ecological rules. Ecology may be more local than we would like to believe. Perhaps Lawton (1999) was right about community ecology.

Fox, J.W. (2013a) The intermediate disturbance hypothesis is broadly defined, substantive issues are key: a reply to Sheil and Burslem. Trends in Ecology & Evolution, 28, 572-573.

Fox, J.W. (2013b) The intermediate disturbance hypothesis should be abandoned. Trends in Ecology & Evolution, 28, 86-92.

Kershaw, H.M. & Mallik, A.U. (2013) Predicting plant diversity response to disturbance: Applicability of the Intermediate Disturbance Hypothesis and Mass Ratio Hypothesis. Critical Reviews in Plant Sciences, 32, 383-395.

Lawton, J.H. (1999) Are there general laws in ecology? Oikos, 84, 177-192.

Prins, H.H.T. & Gordon, I.J. (eds.) (2014) Invasion Biology and Ecological Theory: Insights from a Continent in Transformation.  Cambridge University Press, Cambridge. 540 pp.

Schwilk, D.W., Keeley, J.E. & Bond, W.J. (1997) The intermediate disturbance hypothesis does not explain fire and diversity pattern in fynbos. Plant Ecology, 132, 77-84.

Sheil, D. & Burslem, D.F.R.P. (2013) Defining and defending Connell’s intermediate disturbance hypothesis: a response to Fox. Trends in Ecology & Evolution, 28, 571-572.

Simberloff, D. (2014) Book Review: Herbert H. T. Prins and Iain J. Gordon (eds.): Invasion biology and ecological theory. Insights from a continent in transformation. Biological Invasions, 16, 2757-2759.

Wilkinson, D.M. (1999) The disturbing history of intermediate disturbance. Oikos, 84, 145-147.

On Repeatability in Ecology

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One of the elementary lessons of statistics is that every measurement must be repeatable so that differences or changes in some ecological variable can be interpreted with respect to some ecological or environmental mechanism. So if we count 40 elephants in one year and count 80 in the following year, we know that population abundance has changed and we do not have to consider the possibility that the repeatability of our counting method is so poor that 40 and 80 could refer to the same population size. Both precision and bias come into the discussion at this point. Much of the elaboration of ecological methods involves the attempt to improve the precision of methods such as those for estimating abundance or species richness. There is less discussion of the problem of bias.

The repeatability that is most crucial in forging a solid science is that associated with experiments. We should not simply do an important experiment in a single place and then assume the results apply world-wide. Of course we do this, but we should always remember that this is a gigantic leap of faith. Ecologists are often not willing to repeat critical experiments, in contrast to scientists in chemistry or molecular biology. Part of this reluctance is understandable because the costs associated with many important field experiments is large and funding committees must then judge whether to repeat the old or fund the new. But if we do not repeat the old, we never can discover the limits to our hypotheses or generalizations. Given a limited amount of money, experimental designs often limit the potential generality of the conclusions. Should you have 2 or 4 or 6 replicates? Should you have more replicates and fewer treatment sites or levels of manipulation? When we can, we try one way and then another to see if we get similar results.

A looming issue now is climate change which means that the ecosystem studied in 1980 is possibly rather different than the one you now study in 2014, or the place someone manipulated in 1970 is not the same community you manipulated this year. The worst case scenario would be to find out that you have to do the same experiment every ten years to check if the whole response system has changed. Impossible with current funding levels. How can we develop a robust set of generalizations or ‘theories’ in ecology if the world is changing so that the food webs we so carefully described have now broken down? I am not sure what the answers are to these difficult questions.

And then you pile evolution into this mix and wonder if organisms can change like Donelson et al.’s (2012) tropical reef fish, so that climate changes might be less significant than we currently think, at least for some species. The frustration that ecologists now face over these issues with respect to ecosystem management boils over in many verbal discussions like those on “novel ecosystems” (Hobbs et al. 2014, Aronson et al. 2014) that can be viewed as critical decisions about how to think about environmental change or a discussion about angels on pinheads.

Underlying all of this is the global issue of repeatability, and whether our current perceptions of how to manage ecosystems is sufficiently reliable to sidestep the adaptive management scenarios that seem so useful in theory (Conroy et al. 2011) but are at present rare in practice (Keith et al. 2011). The need for action in conservation biology seems to trump the need for repeatability to test the generalizations on which we base our management recommendations. This need is apparent in all our sciences that affect humans directly. In agriculture we release new varieties of crops with minimal long term studies of their effects on the ecosystem, or we introduce new methods such as no till agriculture without adequate studies of its impacts on soil structure and pest species. This kind of hubris does guarantee long term employment in mitigating adverse consequences, but is perhaps not an optimal way to proceed in environmental management. We cannot follow the Hippocratic Oath in applied ecology because all our management actions create winners and losers, and ‘harm’ then becomes an opinion about how we designate ‘winners’ and ‘losers’. Using social science is one way out of this dilemma, but history gives sparse support for the idea of ‘expert’ opinion for good environmental action.

Aronson, J., Murcia, C., Kattan, G.H., Moreno-Mateos, D., Dixon, K. & Simberloff, D. (2014) The road to confusion is paved with novel ecosystem labels: a reply to Hobbs et al. Trends in Ecology & Evolution, 29, 646-647.

Conroy, M.J., Runge, M.C., Nichols, J.D., Stodola, K.W. & Cooper, R.J. (2011) Conservation in the face of climate change: The roles of alternative models, monitoring, and adaptation in confronting and reducing uncertainty. Biological Conservation, 144, 1204-1213.

Donelson, J.M., Munday, P.L., McCormick, M.I. & Pitcher, C.R. (2012) Rapid transgenerational acclimation of a tropical reef fish to climate change. Nature Climate Change, 2, 30-32.

Hobbs, R.J., Higgs, E.S. & Harris, J.A. (2014) Novel ecosystems: concept or inconvenient reality? A response to Murcia et al. Trends in Ecology & Evolution, 29, 645-646.

Keith, D.A., Martin, T.G., McDonald-Madden, E. & Walters, C. (2011) Uncertainty and adaptive management for biodiversity conservation. Biological Conservation, 144, 1175-1178.

On Political Ecology

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When I give a general lecture now, I typically have to inform the audience that I am talking about scientific ecology not political ecology. What is the difference? Scientific ecology is classical boring science, stating hypotheses, doing experiments or observations to gather the data, testing the idea, and accepting or rejecting it, outlined clearly in many papers (Platt 1963, Wolff and Krebs (2008), and illustrated in this diagram:

Scientific ecology is clearly out-of-date, and no longer ‘cool’ when compared to the new political ecology.

Political ecology is a curious mix of traditional ecology added to the advocacy issue of protecting biodiversity. Political ecology is aimed at convincing society in general and politicians in particular to protect the Earth’s biodiversity. This is a noble cause, and my complaint is only that when we advocate and use scientific ecology in pursuit of a political agenda we should be scientifically rigorous. Yet much of biodiversity science is a mix of belief and evidence, with unsuitable evidence used in support of what is a noble belief. If we believe that the end justifies the means, we would be happy with this. But I am not.

One example will illustrate my frustration with political ecology. Dirzo et al. (2014) in a recent Science paper give an illustration of the effects of removing large animals from an ecosystem. In their Figure 4, page 404, a set of 4 graphs purport to show experimentally what happens when you remove large wildlife species in Kenya, the Kenya Long-term Exclosure Experiment (Young et al. 1997). But this experiment is hopelessly flawed in being carried out on a set of plots of 4 ha, a postage stamp of habitat relative to large mammal movements and ecosystem processes. But the fact that this particular experiment was not properly designed for the questions it is now being used to address is not a problem if this is political ecology rather than scientific ecology. The overall goal of the Dirzo et al. (2014) paper is admirable, but it is achieved by quoting a whole series of questionable extrapolations given in other papers. The counter-argument in conservation biology has always been that we do not have time to do proper research and we must act now. The consequence is the elevation of expert opinion in conservation science to the realm of truth without going through the proper scientific process.

We are left with this prediction from Dirzo et al. (2014):

“Cumulatively, systematic defaunation clearly threatens to fundamentally alter basic ecological functions and is contributing to push us toward global-scale “tipping points” from which we may not be able to return ……. If unchecked, Anthropocene defaunation will become not only a characteristic of the planet’s sixth mass extinction, but also a driver of fundamental global transformations in ecosystem functioning.”

I fear that statements like this are more akin to something like a religion of conservation fundamentalism, while we proclaim to be scientists.

Dirzo, R., Young, H.S., Galetti, M., Ceballos, G., Isaac, N.J.B. & Collen, B. (2014) Defaunation in the Anthropocene. Science, 345, 401-406.

Platt, J.R. (1964) Strong inference. Science, 146, 347-353.

Wolff, J.O. & Krebs, C.J. (2008) Hypothesis testing and the scientific method revisited. Acta Zoologica Sinica, 54, 383-386.

Young, T.P., Okello, B.D., Kinyua, D. & Palmer, T.M. (1997) KLEE: A long‐term multi‐species herbivore exclusion experiment in Laikipia, Kenya. African Journal of Range & Forage Science, 14, 94-102.

Should All Ecologists Become Social Scientists or Politicians?

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Two items this week have stirred me to write about the state of ecology. The first was a talk by an eminent biologist, who must remain nameless, about how scientists should operate. All very good, we should be evidence-based, open to falsification of hypotheses, and we should work as best we can to counter media misinformation. He/she talked about the future of biology in optimistic terms and in the entire one hour talk the word ‘biodiversity’ occurred once and the word ‘environment’ once. So my conclusion was that to this eminent biologist ecology was not on the radar as anything very important. We should be principally concerned about improving the health and wealth of humanity, and increasing economic growth.

This got me to thinking about why ecology falls at the bottom of the totem pole of science so that even though we work hard to understand the functioning of nature, ecologists seem to have value only to ourselves rather than to society. Perhaps society as a whole appreciates us for light entertainment about birds and bees, but when ecologists investigate problems and offer solutions they seem to be sidelined rapidly. Perhaps this is because taking care of the biosphere will cost money, and while we happily spend money on cars and new airplanes and guns, we can afford little for the natural world. One possible explanation for this is that many people and most politicians believe that “Mother Nature will take care of herself” at no financial cost.

If this is even partly correct, we need to change society’s view. There are several ways to do this, perhaps most importantly via education, but a more direct way is for ecologists to become social scientists and perhaps politicians. My experience with this recommendation is not terribly good. Social scientists have in my experience accomplished little for all their work on the human foibles of our time. Perhaps going into politics would be useful for our science if anyone wishes to cross that Rubicon, but there are few role models that we can put up.

So we continue in a political world where few ecologists sit in high places to challenge the modern paradigm of economic growth fuelled by non-renewable resources, and many of our national leaders see no human footprint on climatic warming. Short-term thinking is one element of this puzzle for we ecologists who take a longer view of life on Earth, but it must really rankle our paleo-ecologists who take a very long term look at changes in the Earth’s environment.

The second item this week that has encapsulated all of this was the announcement from a developed country that a new institute with over 1000 scientists was to be set up to study molecular biology for the improvement of human health. Now this is a noble cause that I do not wish to cast aspersions on, but it occurred to me that this was possibly a number greater than the total number of ecologists working in Canada or Australia or New Zealand. The numbers are hard to document, but I have not seen anything like this kind of announcement for a new institute that would address any of our many ecological problems. There is money for many things but very little for ecology.

None of this is terribly new but I am puzzled why this is the case. We live in a world of inequality in which the rich squander the wealth of the Earth while the future of the planet seems of little concern. Luckily ecologists are a happy lot once they get a job because they can work in the laboratory or in the field on interesting problems and issues (if they can get the money). And to quote the latest Nature (March 13, 2014, p. 140) “If ecologists want to produce work useful to conservation, they might do better to spend their days sitting quietly in ecosystems with waterproof notebooks and hand lenses, writing everything down.” That will cost little money fortunately.

On Biodiversity Science

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Biodiversity science features heavily in articles in Science and Nature and it is a good idea to look at the accumulated wisdom to date. We can begin with the Cardinale et al. (2012) paper in Nature (“Biodiversity Loss and Its Impact on Humanity”) which gives us six consensus statements:

Consensus statement one: There is now unequivocal evidence that biodiversity loss reduces the efficiency by which ecological communities capture biologically essential resources, produce biomass, decompose and recycle biologically essential nutrients.

Consensus statement two: There is mounting evidence that biodiversity increases the stability of ecosystem functions through time.

Consensus statement three: The impact of biodiversity on any single ecosystem process is nonlinear and saturating, such that change accelerates as biodiversity loss increases.

Consensus statement four: Diverse communities are more productive because they contain key species that have a large influence on productivity, and differences in functional traits among organisms increase total resource capture.

Consensus statement five: Loss of diversity across trophic levels has the potential to influence ecosystem functions even more strongly than diversity loss within trophic levels.

Consensus statement six: Functional traits of organisms have large impacts on the magnitude of ecosystem functions, which give rise to a wide range of plausible impacts of extinction on ecosystem function.

followed by four emerging trends:

Emerging trend one: The impacts of diversity loss on ecological processes might be sufficiently large to rival the impacts of many other global drivers of environmental change.

Emerging trend two: Diversity effects grow stronger with time, and may increase at larger spatial scales.

Emerging trend three: Maintaining multiple ecosystem processes at multiple places and time requires higher levels of biodiversity than does a single process at a single place and time.

Emerging trend four: The ecological consequences of biodiversity loss can be predicted from evolutionary history.

I encourage you to read this paper and consider how well it describes a blueprint of past and future research on biodiversity. Here I offer a few thoughts on why I think it consists of a set of worrisome generalizations.

First of all every biologist would like to think that biodiversity is important. But we should consider what the equivalent statement might be for chemistry – chemicals are important. Surely this is both true and of little use, since we can never define scientifically the word ‘important’. Biodiversity is so broadly defined as to be a rather poor noun to use in scientific statements unless it is strictly defined. But you can take any kind of biodiversity measure – species number (richness) for example, and you might find that species X is a terrible weed that is not desirable for farmers but is beautiful in your home garden or useful food for butterflies. Malaria-carrying mosquitoes are not particularly desirable members of the local biological community. But let us all agree that biodiversity is important because it is an ethical belief but not a scientific statement as it stands.

If we look at the consensus statements as scientific hypotheses (I note the word ‘hypothesis’ appears only once in this article), we can ask how you could test them and what the alternative hypotheses would be. For consensus 1 for example, what would be the result of finding a community that increased productivity if certain species were lost from the system? This finding would not be viewed as contrary to consensus one because it would be said that the increased productivity was not done efficiently. It is probably best to assume these statements are not hypotheses to be tested.

As we work our way through the consensus statements, we find they are filled with weasel words that are useful in eliminating contrary evidence. Thus for consensus statement 2 we can stop at biodiversity (many definitions) and then stability (perhaps 70 different metrics) and finally ecosystem functions (of which there are many) and time (weeks?, years?, centuries?). The consensus which sounds so solid is empirically rather empty as any guide to the world.

I am left with many questions. Could not all of these consensus statements have been written 30 years ago? All of them have contrary instances that could be given from the literature, if the terms were rigorously defined. But this many not matter. Let us concede that these generalizations may be right 90% of the time. The bottom line is that we should conserve biodiversity. But this is what everybody has been saying for decades so we are no farther ahead.

The singular problem that concerns me the most is that these kinds of consensus statements are of little use to the land manager or the wildlife manager or the politician who has to make applied decisions at the local level. If we wish to arrest the decline of a particular songbird, what is the utility of these kind of statements? I have concluded that these kinds of papers about biodiversity are a kind of pablum for conservation ecologists to show that Nature and Science really are concerned about conservation issues while at the same time they devote 97% of their issues to the technological fixes that will ‘solve’ all the problems conservation biologists continually point out. As such these kinds of papers are useful statements for political ecology.

The four emerging trends are themselves worthy of another blog. They are vague ideas expressing beliefs that cannot be considered scientific hypotheses without rigorous definitions, and in their present form are almost quasi-religious statements of belief. How they might ever be tested is unclear. I particularly enjoyed the fourth emerging trend since I think that one of the evolutionary laws is that evolutionary history is exactly that – history – not a predictive map of future changes. There is a certain irony of our time that some of the world’s most prestigious evolutionary biologists are anti-religion while biodiversity scientists are trying hard to set up a new religion of biodiversity beliefs.

Cardinale, B. J.et al. 2012. Biodiversity loss and its impact on humanity. Nature 486:59-67.