Tag Archives: ecosystem dynamics

Ecological Alternative Facts

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It has become necessary to revise my recent ecological thinking about the principles of ecology along the lines now required in the New World Order. I list here the thirteen cardinal principles of the new ecology 2017:

  1. Population growth is unlimited and is no longer subject to regulation.
  2. Communities undergo succession to the final equilibrium state of the 1%.
  3. Communities and ecosystems are resilient to any and all disturbances and operate best when challenged most strongly, for example with oil spills.
  4. Resources are never limiting under any conditions for the 1% and heavy exploitation helps them to trickle down readily to assist the other 99%.
  5. Overexploiting populations is good for the global ecosystem because it gets rid of the species that are wimps.
  6. Mixing of faunas and floras have been shown over the last 300 years to contribute to the increasing ecological health of Earth.
  7. Recycling is unnecessary in view of recent advances in mining technology.
  8. Carbon dioxide is a valuable resource for plants and we must increase its contribution to atmospheric chemistry.
  9. Climate change is common and advantageous since it occurs from night to day, and has always been with us for many millions of years.
  10. Evolution maximizes wisdom and foresight, especially in mammals.
  11. Conservation of less fit species is an affront to alternative natural laws that were recognized during the 18th century and are now mathematically defined in the new synthetic theory of economic and ecological fitness.
  12. Scientific experiments are no longer necessary because we have computers and technological superiority.
  13. Truth in science is no longer necessary and must be balanced against equally valid post-truth beliefs.

The old ecology, now superseded, was illustrated in Krebs (2016), and is already out of date. Recommendations for other alternative ecological facts will be welcome. Please use the comments.

Krebs, C.J. (2016) Why Ecology Matters. University of Chicago Press, Chicago. 208 pp.

Fishery Models and Ecological Understanding

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Anyone interested in population dynamics, fisheries management, or ecological understanding in general will be interested to read the exchanges in Science, 23 April 2016 on the problem of understanding stock changes in the northern cod (Gadus morhua) fishery in the Gulf of Maine. I think this exchange is important to read because it illustrates two general problems with ecological science – how to understand ecological changes with incomplete data, and how to extrapolate what is happening into taking some management action.

What we have here are sets of experts promoting a management view and others contradicting the suggested view. There is no question but that ecologists have made much progress in understanding both marine and freshwater fisheries. Probably the total number of person-years of research on marine fishes like the northern cod would dwarf that on all other ecological studies combined. Yet we are still arguing about fundamental processes in major marine fisheries. You will remember that the northern cod in particular was one of the largest fisheries in the world when it began to be exploited in the 16th century, and by the 1990s it was driven to about 1% of its prior abundance, almost to the status of a threatened species.

Pershing et al. (2015) suggested, based on data on a rise in sea surface temperature in the Gulf of Maine, that cod mortality had increased with temperature and this was causing the fishery management model to overestimate the allowable catch. Palmer et al. (2016) and Swain et al. (2016) disputed their conclusions, and Pershing et al. (2016) responded. The details are in these papers and I do not pretend to know whose views are closest to be correct.

But I’m interested in two facts. First, Science clearly thought this controversy was important and worth publishing, even in the face of a 99% rejection rate for all submissions to that journal. Second, it illustrates that ecology faces a lot of questions when it makes conclusions that natural resource managers should act upon. Perhaps it is akin to medicine in being controversial, even though it is all supposed to be evidence based. It is hard to imagine physical scientists or engineers arguing so publically over the design of a bridge or a hydroelectric dam. Why is it that ecologists so often spend time arguing with one another over this or that theory or research finding? If we admit that our conclusions about the world’s ecosystems are so meager and uncertain, does it mean we have a very long way to go before we can claim to be a hard science? We would hope not but what is the evidence?

One problem so well illustrated here in these papers is the difficulty of measuring the parameters of change in marine fish populations and then tying these estimates to models that are predictive of changes required for management actions. The combination of less than precise data and models that are overly precise in their assumptions could be a deadly combination in the ecological management of natural resources.

Palmer, M.C., Deroba, J.J., Legault, C.M., and Brooks, E.N. 2016. Comment on “Slow adaptation in the face of rapid warming leads to collapse of the Gulf of Maine cod fishery”. Science 352(6284): 423-423. doi:10.1126/science.aad9674.

Pershing, A.J., Alexander, M.A., Hernandez, C.M., Kerr, L.A., Le Bris, A., Mills, K.E., Nye, J.A., Record, N.R., Scannell, H.A., Scott, J.D., Sherwood, G.D., and Thomas, A.C. 2016. Response to Comments on “Slow adaptation in the face of rapid warming leads to collapse of the Gulf of Maine cod fishery”. Science 352(6284): 423-423. doi:10.1126/science.aae0463.

Pershing, A.J., Alexander, M.A., Hernandez, C.M., Kerr, L.A., Le Bris, A., Mills, K.E., Nye, J.A., Record, N.R., Scannell, H.A., Scott, J.D., Sherwood, G.D., and Thomas, A.C. 2015. Slow adaptation in the face of rapid warming leads to collapse of the Gulf of Maine cod fishery. Science 350(6262): 809-812. doi:10.1126/science.aac9819.

Swain, D.P., Benoît, H.P., Cox, S.P., and Cadigan, N.G. 2016. Comment on “Slow adaptation in the face of rapid warming leads to collapse of the Gulf of Maine cod fishery”. Science 352(6284): 423-423. doi:10.1126/science.aad9346.

On Critical Questions in Biodiversity and Conservation Ecology

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Biodiversity can be a vague concept with so many measurement variants to make one wonder what it is exactly, and how to incorporate ideas about biodiversity into scientific hypotheses. Even if we take the simplest concept of species richness as the operational measure, many questions arise about the importance of the rare species that make up most of the biodiversity but so little of the biomass. How can we proceed to a better understanding of this nebulous ecological concept that we continually put before the public as needing their attention?

Biodiversity conservation relies on community and ecosystem ecology for guidance on how to advance scientific understanding. A recent paper by Turkington and Harrower (2016) articulates this very clearly by laying out 7 general questions for analyzing community structure for conservation of biodiversity. As such these questions are a general model for community and ecosystem ecology approaches that are needed in this century. Thus it would pay to look at these 7 questions more closely and to read this new paper. Here is the list of 7 questions from the paper:

  1. How are natural communities structured?
  2. How does biodiversity determine the function of ecosystems?
  3. How does the loss of biodiversity alter the stability of ecosystems?
  4. How does the loss of biodiversity alter the integrity of ecosystems?
  5. Diversity and species composition
  6. How does the loss of species determine the ability of ecosystems to respond to disturbances?
  7. How does food web complexity and productivity influence the relative strength of trophic interactions and how do changes in trophic structure influence ecosystem function?

Turkington and Harrower (2016) note that each of these 7 questions can be asked in at least 5 different contexts in the biodiversity hotspots of China:

  1. How do the observed responses change across the 28 vegetation types in China?
  2. How do the observed responses change from the low productivity grasslands of the Qinghai Plateau to higher productivity grasslands in other parts of China?
  3. How do the observed responses change along a gradient in the intensity of human use or degradation?
  4. How long should an experiment be conducted given that the immediate results are seldom indicative of longer-term outcomes?
  5. How does the scale of the experiment influence treatment responses?

There are major problems in all of this as Turkington and Harrower (2016) and Bruelheide et al. (2014) have discussed. The first problem is to determine what the community is or what the bounds of an ecosystem are. This is a trivial issue according to community and ecosystem ecologists, and all one does is draw a circle around the particular area of interest for your study. But two points remain. Populations, communities, and ecosystems are open systems with no clear boundaries. In population ecology we can master this problem by analyses of movements and dispersal of individuals. On a short time scale plants in communities are fixed in position while their associated animals move on species-specific scales. Communities and ecosystems are not a unit but vary continuously in space and time, making their analysis difficult. The species present on 50 m2 are not the same as those on another plot 100 m or 1000 m away even if the vegetation types are labeled the same. So we replicate plots within what we define to be our community. If you are studying plant dynamics, you can experimentally place all plant species selected in defined plots in a pre-arranged configuration for your planting experiments, but you cannot do this with animals except in microcosms. All experiments are place specific, and if you consider climate change on a 100 year time scale, they are also time specific. We can hope that generality is strong and our conclusions will apply in 100 years but we do not know this now.

But we can do manipulative experiments, as these authors strongly recommend, and that brings a whole new set of problems, outlined for example in Bruelheide et al. (2014, Table 1, page 78) for a forestry experiment in southern China. Decisions about how many tree species to manipulate in what size of plots and what planting density to use are all potentially critical to the conclusions we reach. But it is the time frame of hypothesis testing that is the great unknown. All these studies must be long-term but whether this is 10 years or 50 years can only be found out in retrospect. Is it better to have, for example, forestry experiments around the world carried out with identical protocols, or to adopt a laissez faire approach with different designs since we have no idea yet of what design is best for answering these broad questions.

I suspect that this outline of the broad questions given in Turkington and Harrower (2016) is at least a 100 year agenda, and we need to be concerned how we can carry this forward in a world where funding of research questions has a 3 or 5 year time frame. The only possible way forward, until we win the Lottery, is for all researchers to carry out short term experiments on very specific hypotheses within this framework. So every graduate student thesis in experimental community and ecosystem ecology is important to achieving the goals outlined in these papers. Even if this 100 year time frame is optimistic and achievable, we can progress on a shorter time scale by a series of detailed experiments on small parts of the community or ecosystem at hand. I note that some of these broad questions listed above have been around for more than 50 years without being answered. If we redefine our objectives more precisely and do the kinds of experiments that these authors suggest we can move forward, not with the solution of grand ideas as much as with detailed experimental data on very precise questions about our chosen community. In this way we keep the long-range goal posts in view but concentrate on short-term manipulative experiments that are place and time specific.

This will not be easy. Birds are probably the best studied group of animals on Earth, and we now have many species that are changing in abundance dramatically over large spatial scales (e.g. http://www.stateofcanadasbirds.org/ ). I am sobered by asking avian ecologists why a particular species is declining or dramatically increasing. I never get a good answer, typically only a generally plausible idea, a hand waving explanation based on correlations that are not measured or well understood. Species recovery plans are often based on hunches rather than good data, with few of the key experiments of the type requested by Turkington and Harrower (2016). At the moment the world is changing rather faster than our understanding of these ecological interactions that tie species together in communities and ecosystems. We are walking when we need to be running, and even the Red Queen is not keeping up.

Bruelheide, H. et al. 2014. Designing forest biodiversity experiments: general considerations illustrated by a new large experiment in subtropical China. Methods in Ecology and Evolution, 5, 74-89. doi: 10.1111/2041-210X.12126

Turkington, R. & Harrower, W.L. 2016. An experimental approach to addressing ecological questions related to the conservation of plant biodiversity in China. Plant Diversity, 38, 1-10. Available at: http://journal.kib.ac.cn/EN/volumn/current.shtml

The Volkswagen Syndrome and Ecological Science

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We have all been hearing the reports that Volkswagen fixed diesel cars by some engineering trick to show low levels of pollution, while the actual pollution produced on the road is 10-100 times higher than the laboratory predicted pollution levels. I wonder if this is an analogous situation to what we have in ecology when we compare laboratory studies and conclusions to real-world situations.

The push in ecology has always been to simplify the system first by creating models full of assumptions, and then by laboratory experiments that are greatly oversimplified compared with the real world. There are very good reasons to try to do this, since the real world is rather complicated, but I wonder if we should call a partial moratorium on such research by conducting a review of how far we have been led astray by both simple models and simple laboratory population, community and ecosystem studies in microcosms and mesocosms. I can almost hear the screams coming up that of course this is not possible since graduate students must complete a degree in 2 or 3 years, and postdocs must do something in 2 years. If this is our main justification for models and microcosms, that is fair enough but we ought to be explicit about stating that and then evaluate how much we have been misled by such oversimplification.

Let me try to be clear about this problem. It is an empirical question of whether or not studies in laboratory or field microcosms can give us reliable generalizations for much more extensive communities and ecosystems that are not in some sense space limited or time limited. I have a personal view on this question, heavily influenced by studies of small mammal populations in microcosms. But my experience may be atypical of the rest of natural systems, and this is an empirical question, not one on which we can simply state our opinions.

If the world is much more complex than our current understanding of it, we must conclude that an extensive list of climate change papers should be moved to the fiction section of our libraries. If we assume equilibrial dynamics in our communities and ecosystems, we fly in violation of almost all long term studies of populations, communities, and ecosystems. The problem lies in the space and time vision of our science. Our studies are too short to show even a good representation of dynamics over a 100 year time scale, and the problems of landscape ecology highlight that what we see in patch A may be greatly influenced by whether patches B and C are close by or not. We see this darkly in a few small studies but are compelled to believe that such landscape effects are unusual or atypical. This may in fact be the case, but we need much more work to see if it is rare or common. And the broader issue is what use do we as ecologists have for ecological predictions that cannot be tested without data for the next 100 years?

Are all our grand generalizations of ecology falling by the wayside without us noticing it? Prins and Gordon (2014) in their overview seem to feel that the real world is poorly reflected in many of our beloved theories. I think this is a reflection of the Volkswagen Syndrome, of the failure to appreciate that the laboratory in its simplicity is so far removed from real world community and ecosystem dynamics that we ought to start over to build an ecological edifice of generalizations or rules with a strong appreciation of the limited validity of most generalizations until much more research has been done. The complications of the real world can be ignored in the search for simplicity, but one has to do this with the realization that predictions that flow from faulty generalizations can harm our science. We ecologists have very much research yet to do to establish secure generalizations that lead to reliable predictions.

Prins, H.H.T. & Gordon, I.J. (2014) Invasion Biology and Ecological Theory: Insights from a Continent in Transformation. Cambridge University Press, Cambridge. 540 pp. ISBN 9781107035812.

In Praise of Long Term Studies

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I have been fortunate this week to have had a tour of the Konza Prairie Long Term Ecological Research (LTER) site in central Kansas. Kansas State University has run this LTER site for about the last 30 years with support from the National Science Foundation (NSF) of the USA. Whoever set up this program in NSF so many years ago deserves the praise of all ecologists for their foresight, and the staff of KSU who have managed the Konza site should be given our highest congratulations for their research plan and their hard work.

The tall grass prairie used to occupy much of the central part of the temperate zone of North America from Canada to Texas. There is almost none of it left, in Kansas about 1% of the original area with the rest given over to agriculture and grazing. The practical person sees this as progress through the lens of dollar bills, the ecologist sees it as a biodiversity catastrophe. The big questions for the tall-grass prairie are clear and apply to many ecosystems: What keeps this community going? Is it fire or grazing or both in some combination? If fire is too frequent, what are the consequences for the plant community of tall-grass prairie, not to mention the aquatic community of fishes in the streams and rivers? How can shrub and tree encroachment be prevented? All of these questions are under investigation, and the answers are clear in general but uncertain in many details about effects on particular species of birds or forbs.

It strikes me that ecology very much needs more LTER programs. To my knowledge Canada and Australia have nothing like this LTER program that NSF funds. We need to ask why this is, and whether this money could be used much better for other kinds of ecological research. To my mind ecology is unique among the hard sciences in requiring long term studies, and this is because the ecological world is not an equilibrial system in the way we thought 50 years ago. Environments change, species geographical ranges change, climate varies, and all of this on top of the major human impacts on the Earth. So we need to ask questions like why is the tall grass prairie so susceptible to shrub and tree encroachment now when it apparently was not this way 200 years ago? Or why are polar bears now threatened in Hudson’s Bay when they thrived there for the last 1000 or more years? The simple answer is that the ecosystem has changed, but the ecologist wants to know how and why, so that we have some idea if these changes can be managed.

By contrast with ecological systems, physics and chemistry deal with equilibrial systems. So nobody now would investigate whether the laws of gravitation have changed in the last 30 years, and you would be laughed out of the room by physical scientists for even asking such a question and trying to get a research grant to answer this question. Continuous system change is what makes ecology among the most difficult of the hard sciences. Understanding the ecosystem dynamics of the tall-grass prairie might have been simpler 200 years ago, but is now complicated by landscape alteration by agriculture, nitrogen deposition from air pollution, the introduction of weeds from overseas, and the loss of large herbivores like bison.

Long-term studies always lead us back to the question of when we can quit such studies. There are two aspects of this issue. One is scientific, and that question is relatively easy to answer – stop when you find there are no important questions left to pursue. But this means we must have some mental image of what ‘important’ questions are (itself another issue needing continuous discussion). Scientists typically answer this question with their intuition, but not everyone’s intuition is identical. The other aspect leads us into the monitoring question – should we monitor ecosystems? The irony of this question is that we monitor the weather, and we do so because we do not know the future. So the same justification can be made for ecosystem monitoring which should be as much a part of our science as weather monitoring, human health monitoring, or stock market monitoring are to our daily lives. The next level of discussion, once we agree that monitoring is necessary, is how much money should go into ecological monitoring? The current answer in general seems to be only a little, so we stumble on with too few LTER sites and inadequate knowledge of where we are headed, like cars driving at night with weak headlights. We should do better.

A few of the 186 papers listed in the Web of Science since 2010 that include reference to Konza Prairie data:

Raynor, E.J., Joern, A. & Briggs, J.M. (2014) Bison foraging responds to fire frequency in nutritionally heterogeneous grassland. Ecology, 96, 1586-1597. doi: 10.1890/14-2027.1

Sandercock, B.K., Alfaro-Barrios, M., Casey, A.E., Johnson, T.N. & Mong, T.W. (2015) Effects of grazing and prescribed fire on resource selection and nest survival of upland sandpipers in an experimental landscape. Landscape Ecology, 30, 325-337. doi: 10.1007/s10980-014-0133-9

Ungerer, M.C., Weitekamp, C.A., Joern, A., Towne, G. & Briggs, J.M. (2013) Genetic variation and mating success in managed American plains bison. Journal of Heredity, 104, 182-191. doi: 10.1093/jhered/ess095

Veach, A.M., Dodds, W.K. & Skibbe, A. (2014) Fire and grazing influences on rates of riparian woody plant expansion along grassland streams. PLoS ONE, 9, e106922. doi: 10.1371/journal.pone.0106922

On Tipping Points and Regime Shifts in Ecosystems

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A new important paper raises red flags about our preoccupation with tipping points, alternative stable states and regime shifts (I’ll call them collectively sharp transitions) in ecosystems (Capon et al. 2015). I do not usually call attention to papers but this paper and a previous review (Mac Nally et al. 2014) seem to me to be critical for how we think about ecosystem changes in both aquatic and terrestrial ecosystems.

Consider an oversimplified example of how a sharp transition might work. Suppose we dumped fertilizer into a temperate clear-water lake. The clear water soon turns into pea soup with a new batch of algal species, a clear shift in the ecosystem, and this change is not good for many of the invertebrates or fish that were living there. Now suppose we stop dumping fertilizer into the lake. In time, and this could be a few years, the lake can either go back to its original state of clear water or it could remain as a pea soup lake for a very long time even though the pressure of added fertilizer was stopped. This second outcome would be a sharp transition, “you cannot go back from here” and the question for ecologists is how often does this happen? Clearly the answer is of great interest to natural resource managers and restoration ecologists.

The history of this idea for me was from the 1970s at UBC when Buzz Holling and Carl Walters were modelling the spruce budworm outbreak problem in eastern Canadian coniferous forests. They produced a model with a manifold surface that tipped the budworm from a regime of high abundance to one of low abundance (Holling 1973). We were all suitably amazed and began to wonder if this kind of thinking might be helpful in understanding snowshoe hare population cycles and lemming cycles. The evidence was very thin for the spruce budworm, but the model was fascinating. Then by the 1980s the bandwagon started to roll, and alternative stable states and regime change seemed to be everywhere. Many ideas about ecosystem change got entangled with sharp transition, and the following two reviews help to unravel them.

Of the 135 papers reviewed by Capon et al. (2015) very few showed good evidence of alternative stable states in freshwater ecosystems. They highlighted the use and potential misuse of ecological theory in trying to predict future ecosystem trajectories by managers, and emphasized the need of a detailed analysis of the mechanisms causing ecosystem change. In a similar paper for estuaries and near inshore marine ecosystems, Mac Nally et al. (2014) showed that of 376 papers that suggested sharp transitions, only 8 seemed to have sufficient data to satisfy the criteria needed to conclude that a transition had occurred and was linkable to an identifiable pressure. Most of the changes described in these studies are examples of gradual ecosystem changes rather than a dramatic shift; indeed, the timescale against which changes are assessed is critical. As always the devil is in the details.

All of this is to recognize that strong ecosystem changes do occur in response to human actions but they are not often sharp transitions that are closely linked to human actions, as far as we can tell now. And the general message is clearly to increase rigor in our ecological publications, and to carry out the long-term studies that provide a background of natural variation in ecosystems so that we have a ruler to measure human induced changes. Reviews such as these two papers go a long way to helping ecologists lift our game.

Perhaps it is best to end with part of the abstract in Capon et al. (2015):

“We found limited understanding of the subtleties of the relevant theoretical concepts and encountered few mechanistic studies that investigated or identified cause-and-effect relationships between ecological responses and nominal pressures. Our results mirror those of reviews for estuarine, nearshore and marine aquatic ecosystems, demonstrating that although the concepts of regime shifts and alternative stable states have become prominent in the scientific and management literature, their empirical underpinning is weak outside of a specific environmental setting. The application of these concepts in future research and management applications should include evidence on the mechanistic links between pressures and consequent ecological change. Explicit consideration should also be given to whether observed temporal dynamics represent variation along a continuum rather than categorically different states.”

 

Capon, S.J., Lynch, A.J.J., Bond, N., Chessman, B.C., Davis, J., Davidson, N., Finlayson, M., Gell, P.A., Hohnberg, D., Humphrey, C., Kingsford, R.T., Nielsen, D., Thomson, J.R., Ward, K., and Mac Nally, R. 2015. Regime shifts, thresholds and multiple stable states in freshwater ecosystems; a critical appraisal of the evidence. Science of The Total Environment 517(0): in press. doi:10.1016/j.scitotenv.2015.02.045.

Holling, C.S. 1973. Resilience and stability of ecological systems. Annual Review of Ecology and Systematics 4: 1-23. doi:10.1146/annurev.es.04.110173.000245.

Mac Nally, R., Albano, C., and Fleishman, E. 2014. A scrutiny of the evidence for pressure-induced state shifts in estuarine and nearshore ecosystems. Austral Ecology 39: 898-906. doi:10.1111/aec.12162.

Ecosystem Science to the Rescue

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What can ecologists do to become useful in the mess that is currently the 21st Century? In Australia we have a set of guidelines now available as “Foundations for the Future: A Long Term Plan for Australian Ecosystem Science” (http://www.ecosystemscienceplan.org.au ) It is a useful overall plan in many respects and the only question I wish to discuss here is how we ecologists come to such plans and whether or not they are realistic.

We should begin by treating this plan as an excellent example of political ecology – a well presented, glossy brochure, with punch lines carved out and highlighted so that newspaper reporters and sympathetic politicians can present sound bites on air or in Parliament. One example: “Healthy ecosystems are the cornerstone of our social and economic wellbeing”. No arguments there.

Six key directions are indicated:

  1. Delivering maximum impact for Australia: Enhancing relationships between scientists and end-users
  2. Supporting long-term research
  3. Enabling ecosystem surveillance
  4. Making the most of data resources
  5. Inspiring a generation: Empowering the public with knowledge and opportunities
  6. Facilitating coordination, collaboration and leadership

Most ecologists would agree with all 6 key directions, but perhaps only 2 and 3 are scientific goals that are key to research planning. Everyone supports 2, but how do we achieve this without adequate funding? Similarly 3 is an admirable direction but how is it to be accomplished? Could we argue that most ecologists have been trying to achieve these 6 goals for 75 years, and particularly goals 2 and 3 for at least 35 years?

As a snapshot of the importance of ecosystem science, the example of the Great Barrier Reef is presented, and in particular understanding reef condition and its changes over time.

“Australia’s Great Barrier Reef is one of the seven wonders of the natural world, an Australian icon that makes an economic contribution of over $5 billion annually. Ongoing monitoring of the reef and its condition by ecosystem scientists plays a vital role in understanding pressures and informing the development of management strategies. Annual surveys to measure coral cover across the Great Barrier Reef since 1985 have built the world’s most extensive time series data on reef condition across 214 reefs. Researchers have used this long-term data to assess patterns of change and to determine the causes of change.”

The paper they cite (De’ath et al. 2012) shows a coral cover decline on the Great Barrier Reef of 50% over 27 years, with three main causes: cyclones (48% of total), crown-of-thorns starfish (43%) and coral bleaching (10%). From a management perspective, controlling the starfish would help recovery but only on the assumption that the climate is held stable lest cyclones and bleaching increase in future. It is not clear at all to me how ecosystem science can assist reef recovery, and we have in this case another good example of excellent ecological understanding with near-zero ability to rectify the main causes of reef degradation – climate change and water pollution.

The long-term plan presented in this report suggests many useful activities by which ecosystem studies could be more integrated. Exactly which ecosystem studies should be considered high priority are left for future considerations, as is the critical question of who will do these studies. Given that many of the originators of this ecosystem plan are from universities, one worries whether universities have the resources or the time frame or the mandate to accomplish all these goals which are essentially government services. With many governments backing out of serious ecosystem research because of budget cuts, the immediate future does not look good. Nearly 10 years ago Sutherland et al. (2006) gathered together a list of 100 ecological questions of high policy relevance for the United Kingdom. We should now go back to see if these became a blueprint for success or not.

De’ath, G., Fabricius, K.E., Sweatman, H., and Puotinen, M. (2012). The 27–year decline of coral cover on the Great Barrier Reef and its causes. Proceedings of the National Academy of Sciences 109(44): 17995-17999. doi:10.1073/pnas.1208909109.

Sutherland, W.J., et al. (2006). The identification of 100 ecological questions of high policy relevance in the UK. Journal of Applied Ecology 43(4): 617-627. doi: 10.1111/j.1365-2664.2006.01188.x

 

The Naïve Ecologist

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I confess to being a member of the Naïve Ecologist Society. I began research when Zoology and Botany Departments typically consisted of a great mix of scientists working at different levels of biological organization from cells and molecules to ecosystems. As far as I can remember no one thought that it was our job to save the Earth or even a part of it. Our job was to do good science to help understand the processes we see in front of us. Physiologists studied ion transfer in the gills of fish, and muscle energetics, geneticists tried to unravel the genetics of protozoa, and developmental biologists tried to understand the embryology and endocrinology of sex determination. We thought that it was the universities’ job to do excellent teaching and research, and the government’s job to take care of the society and to protect and enhance our natural environment.

Now time warp about 40-50 years later. As far as I can see the molecular and cellular physiologists and geneticists are doing the same thing now as they did then. The tools of course are much improved, their knowledge base has vastly expanded, and modern genetic technology has provided insights into how things work that no one could have imagined long ago. But still (in my experience) if you talk to these sub-organismal biologists in general they will still not tell you they are trying to save the Earth by doing science. They will certainly twist and turn to convince the granting agencies that their work is critical to solving all the problems of humanity, but everyone knows that this is fluff and will be immediately tossed off when the money is delivered. But somehow at the present time it has become the job of the ecologist to save the Earth from human destruction. There is no time left to do pure ecological research to try to find out how ecosystems work and how species interact. We must have answers now to all the pressing questions of conservation biology, and if you wish to get funding for your research you had best try to bend your goals to the solution of climate change, ecosystem services, adaptation, and evolution in the days ahead. There is no time to think and study and observe, we must know now what to do. So we build models of unknown validity and speculate with little data about plans to save the Earth based on untested theory. No other postgraduate student or scientist in a university will operate under this imperative.

This would not be a serious problem if we had a better division between more basic ecologists in universities and more applied ecologists in government labs. Some of this division still exists in some countries, but in many cases governments have cut applied ecology research programs to save money and have turned their applied ecologists into paper pushers assigned to stamp approval on environmental impact statements they have no time or resources to evaluate. So a partial solution to this problem would be to fund more applied ecology positions in government with the resources and regulatory authority to protect as much ecological integrity as possible. State of the Environment glossy brochures are not a substitute for ecological information on environmental impacts, and when you read them carefully you can begin to appreciate how little is truly known about the state of our planet.

I enjoy listening to science programs on the radio as it provides a tiny window into what the radio stations think we need to know about science in action. Science broadcasters usually concentrate on the physical sciences because since they have the big money, they must be very important, then on the space sciences, since no one wants to think about how things are on earth, and finally on behavioural ecology, nice stories that warm our hearts about how bees and birds and orchids make a living. The overall mantra is relatively simple: avoid population ecology lest you have to think about the problems of eternal growth and the human population, and avoid community and ecosystem ecology lest you have to provide more bad news about collapsing coral reefs and the impacts of climate change. Keep the Pablum flowing and hope that the Hadron Collider will save us all.

There is a certain irony is the vast expenditures now being used in medicine to make sure humans live a few more years versus the tiny expenditures being given to environmental science to check on the state of natural world. If the human population collapses in the near future, it will not be because they have not made enough progress in medicine to make us all live to be 95 instead of 85. It will be more likely be due to the inability to appreciate the twin juggernauts of overpopulation and pollution that will render the globe a less nice place for us. By that time the gated communities of Los Angeles will be passé and we will be looking for someone to blame.

Are Birds of Any Consequence?

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We all love birds. They are colourful, interesting creatures and they entice many people to a love of nature and then hopefully the conservation of biodiversity. Thus we do not want to get rid of them. A great deal of effort goes into censusing birds and they are often thought of as indicator species of ecosystem health. No one is in favour of ‘Silent Spring’. But let us do a thought experiment.

The question I wish to ask is somewhat different than the important issue of bird conservation: are birds of any consequence to the operational integrity of communities and ecosystems? In the simplest case what would happen, say, to the eastern deciduous forest or the tall grass prairie or the arctic tundra if all the birds in those ecosystems went extinct? Predators that specialize on birds would clearly disappear but I do not know how many bird specialist predators exist. At the same time the parasites of these birds would be gone. But what about the integrity of existing ecosystems?

Can we dismiss the oceans because birds have a negligible effect on oceanic food webs and energy flow? I do not know the answer to this. In forests birds are often thought to keep insect pests of trees under control, but this seems to be unlikely in many systems in which defoliating insects damage trees of many sorts. Perhaps insect outbreaks would increase in frequency if there were no birds. I come away with the image that birds are for the most part of little consequence for terrestrial ecosystems because they are consumers operating at a very low quantitative level. An exception might be tropical forests in which birds are essential pollinators and seed dispersers, but again I am not sure how often they are necessary pollinators or seed dispersers.

All of this speculation is pretty useless, one might argue, because birds are not going to disappear. They may well be reduced in abundance if habitat is lost and habitat loss seems to be a global problem. But there are two aspects of current ecological research that these idle speculations touch on. First, are birds very good model systems for conservation biology? The answer the ecological world seems to have decided is that they are and very much research must be done on birds for this reason. If research time and money is limited, more research on birds means less on other aspects of community and ecosystem dynamics. Should we be concerned about this? Bird research is convenient and sexy, at least in university settings, but is it more of “Nero fiddling while Rome is burning”? One might in fact argue that many birds are the worst possible model system for understanding conservation problems except for those specific to birds. When I was producing a textbook section on population dynamics I tried to find a good solid example of a supposed decline in bird abundance for any species in which the mechanisms of decline were understood. While there are many data on declines, and much hand wringing, there were virtually no examples with hard data on mechanisms except for the vague idea of habitat loss. Maybe mechanisms are unimportant in conservation biology but it seems unlikely that they are superfluous to understanding the larger issues of population dynamics.

The second general question is the converse one of what kinds of organisms should ecologists be concentrating on if we are to make convincing arguments about biodiversity conservation? If changes in community and ecosystem dynamics are looming, so that the future will not look like the past, where should we put our energies to prevent ecosystem collapse? Are insects and invertebrates in general of greater importance that birds or mammals?

Hurlbert (1971, 1997) raised the question of how to determine the general functional importance of a species to a community, and he concluded that the only measure that has been put forward is ‘the sum over all species, of the changes in productivity which would occur on removal of the particular species from the community’. He pointed out that this definition of importance is clear and specific but could never be measured for even a single species in a community for practical reasons. Hurlbert (1997) also recognized that ‘importance’ had now morphed into ‘keystone’ for much of ecology (e.g. Daily et al. 1993), with all the problems associated with the keystone idea. He suggested, as did Walker (1992) that most species are redundant and of little consequence to ecosystem functioning. Much discussion has occurred since these papers and some has morphed into discussions of ‘functional groups’ instead of species. But plant ecologists have in general not addressed the challenges that Hurlbert (1999) asked, and we are far from being able to answer even the hypothetical question in the title of this blog.

Daily, G.C., Ehrlich, P.R., and Haddad, N.M. 1993. Double keystone bird in a keystone species complex. Proceedings of the National Academy of Sciences USA 90(2): 592-594. doi:10.2307/2361101.

Hurlbert, S.H. 1971. The non-concept of species diversity: a critique and alternative parameters. Ecology 52: 577-586.

Hurlbert, S.H. 1997. Functional importance vs. keystoneness: Reformulating some questions in theoretical biocenology. Australian Journal of Ecology 22(4): 369-382.

Walker, B.H. 1992. Biodiversity and ecological redundancy. Conservation Biology 6: 18-23.

The Snowshoe Hare 10-year Cycle – A Cautionary Tale

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We have been working on the ten-year cycle of snowshoe hares (Lepus americanus) in the southwest Yukon since 1975 trying to answer the simple question of what causes these cyclic fluctuations. I think that we now understand the causes of the cyclic dynamics, which is not to say all things are known but the broad picture is complete. But some misunderstanding persists, hence this one page summary. Some biology first.

The snowshoe hare cycle has been known from Canada lynx fur return data for more than 100 years, and of course known to First Nations people much before that. Hares are herbivores of small trees and shrubs, they reproduce at age 1 and rarely live more than 1-2 years. They have 2-4 litters in a summer, with litter size around 4-6. Juvenile losses are high and at best populations increase about three-to-four-fold per year. Almost everything eats them – lynx, coyotes, great-horned owls, goshawks, a long list of predators on the young. Reproduction collapses with rising density and females reduce their output from 4 litters to 2 in the peak and decline phase.

The obvious driving factors when Lloyd Keith and his students began working on the hare cycle in Alberta in the 1960s were winter food shortage and predation. When there is a high hare peak, damage to shrubs and small trees is obvious. But it was quite clear in Keith’s studies that the decline phase continued well after the vegetation recovered, and so he postulated a two-factor explanation, winter food shortage followed by high predation losses. He looked for disease and parasite problems in hares but found nothing.

Testing the winter food limitation would appear to be simple but is fraught with problems. Everyone believes that food is an ultimate limiting factor, so that it must be involved in the cyclic dynamics. We began testing food limitation in the mid-1970s and found that one could add natural food or artificial food (rabbit chow) and apparently have no effect on cyclic dynamics. Hares came to the food grids so the density increased by immigration, but the decline started at the same time and at the same rate as on control grids. So what is the role of food?

Our next attempt was to do a factorial experiment adding food, reducing predation, and doing both together. The details are important, replication was never enough for the manipulated treatments, we did it only for 10 years rather than 20 or 30. What we found was that there was an interaction between food addition and mammal predator exclusion so that the combined treatment increased to a much higher density than any single treatment. But this result came with a puzzle. What is the role of food? Hares showed no evidence of malnutrition in the peak or decline, fed hares did not increase their reproductive output. What produced the strong interaction between food addition and predator reduction?

The next breakthrough came when Rudy Boonstra suggested that predator-caused stress might underlie these strange dynamics. Because we could now measure stress with faecal cortisol measures we could test for stress directly in free-ranging hares. The surprise was that this idea worked and Michael Sheriff capped off the stress hypothesis by showing that not only does predator-induced stress reduce reproductive rates, but the stress effect is inherited maternally in the next generation.

The bottom line: the whole dynamics of the snowshoe hare cycle are predator-induced. All the changes in mortality and reproduction are direct and indirect effects of predators chasing and eating hares. The experimental food/predator interaction was mechanistically wrong in targeting food as a major limiting factor.

This of course does not mean that food is irrelevant as an important factor to study in hare cycles. In particular very high peak populations damage shrubs and small trees and we do not yet have the details of how this works out in time. Secondary chemicals are certainly involved here.

Why does all this matter? Two points. First, the hare cycle is often trumpeted as an example of a tri-trophic interaction of food – hares – predators, when in fact it seems to be a simple predator-prey system, as Lotka suggested in 1925. Models of the hare cycle have proliferated over time, and there are far more models of the cycle in existence than there are long-term field studies or field experiments. It is possible to model the hare cycle as a predator-prey oscillation, as a food plant-hare oscillation, as a parasite-hare interaction, as a cosmic particle – hare oscillation, as an intrinsic social – maternal effects interaction, and I have probably missed some other combinations of delayed-density dependent factors that have been discussed. That one can produce a formal mathematical model of the hare cycle does not mean that the chosen factor is the correct one.

The other point I would leave you with is the large amount of field work needed to sort out the mechanisms driving the population dynamics of hares. Ecology is not simple. This enigma of the ten-year cycle has always been a classic example in ecology and perhaps it is now solved. Or perhaps not?

Boonstra, R., D. Hik, G. R. Singleton, and A. Tinnikov. 1998. The impact of predator-induced stress on the snowshoe hare cycle. Ecological Monographs 68:371-394.

Boutin, S., C. J. Krebs, R. Boonstra, M. R. T. Dale, S. J. Hannon, K. Martin, A. R. E. Sinclair, J. N. M. Smith, R. Turkington, M. Blower, A. Byrom, F. I. Doyle, C. Doyle, D. Hik, L. Hofer, A. Hubbs, T. Karels, D. L. Murray, V. Nams, M. O’Donoghue, C. Rohner, and S. Schweiger. 1995. Population changes of the vertebrate community during a snowshoe hare cycle in Canada’s boreal forest. Oikos 74:69-80.

Keith, L. B., and L. A. Windberg. 1978. A demographic analysis of the snowshoe hare cycle. Wildlife Monographs 58:1-70.

Keith, L. B. 1990. Dynamics of snowshoe hare populations. Current Mammalogy 4:119-195.

Krebs, C. J., S. Boutin, R. Boonstra, A. R. E. Sinclair, J. N. M. Smith, M. R. T. Dale, K. Martin, and R. Turkington. 1995. Impact of food and predation on the snowshoe hare cycle. Science 269:1112-1115.

Krebs, C. J., S. Boutin, and R. Boonstra, editors. 2001. Ecosystem Dynamics of the Boreal Forest: the Kluane Project. Oxford University Press, New York.

Sheriff, M. J., C. J. Krebs, and R. Boonstra. 2009. The sensitive hare: sublethal effects of predator stress on reproduction in snowshoe hares. Journal of Animal Ecology 78:1249-1258.

Yan, C., N. C. Stenseth, C. J. Krebs, and Z. Zhang. 2013. Linking climate change to population cycles of hares and lynx. Global Change Biology 19:3263-3271.