Tag Archives: wildlife management

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 the Use of “Density-dependent” in the Ecological Literature

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The words ‘density-dependent’ or ‘density dependence’ appear very frequently in the ecological literature, and I write this blog in a plea to never use these words unless you have a very strong definition attached to them. If you have a spare day, count how many times these words appear in a single recent issue of Ecology or the Journal of Animal Ecology and you will get a dose of my dismay. In the Web of Science a search for these words in a general ecology context gives about 1300 papers using these words since 2010, or approximately 1 paper per day.

There is an extensive literature on what density dependence means. In the modeling world, the definition is simple and can be found in every introductory ecology textbook. But it is the usage of the words ‘density-dependence’ in the real world that I want to discuss in this blog.

The concept can be quite meaningless, as Murray (1982) pointed out so many years ago. At its most modest extreme, it only says that, sooner or later, something happens when a population gets too large. Everyone could agree with that simple definition. But if you want to understand or manage population changes, you will need something much more specific. More specific might mean to plot a regression of some demographic variable with population density on the X axis. As Don Strong (1986) pointed out long ago a more typical result is density-vagueness. So if and when you write about a density-dependent relationship, at least determine how well the data fit a straight or curved line, and if the correlation coefficient is 0.3 or less you should get concerned that density has little to do with your demographic variable. If you wish to understand population dynamics, you will need to understand mechanisms and population density is not a mechanism.

Often the term density-dependent is used as a shorthand to indicate that some measured variable such as the amount of item X in the diet is related to population density. In most of these cases it is more appropriate to say that item X is statistically related to population density, and avoid all the baggage associated with the original term. Too often statements are made about mortality process X being ‘inversely density dependent’ or ‘directly density dependent’ with no data that supports such a strong conclusion.

So if there is a simple message here it is only that when you write ‘density-dependent’ in your manuscript, see if is related to the population regulation concept or if it is a simple statistical statement that is better described in simple statistical language. In both cases evaluate the strength of the evidence.

Ecology is plagued with imprecise words that can mean almost anything if they are not specified clearly, so statements about ‘biodiversity’, ‘ecosystems’, ‘resilience’, ‘diversity’, ‘metapopulations’, and ‘competition’ are fine to use so long as you indicate exactly what the operational meaning of the word entails. ‘Density-dependence’ is one of these slippery words best avoided unless you have some clear mechanism or process in mind.

Murray, B.G., Jr. (1982) On the meaning of density dependence. Oecologia, 53, 370-373.

Strong, D.R. (1986) Density-vague population change. Trends in Ecology and Evolution, 1, 39-42.

The Anatomy of an Ecological Controversy – Dingos and Conservation in Australia

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Conservation is a most contentious discipline, partly because it is ecology plus a moral stance. As such you might compare it to discussions about religious truths in the last several centuries but it is a discussion among scientists who accept the priority of scientific evidence. In Australia for the past few years there has been much discussion of the role of the dingo in protecting biodiversity via mesopredator release of foxes and cats (Allen et al. 2013; Colman et al. 2014; Hayward and Marlow 2014; Letnic et al. 2011, and many more papers). I do not propose here to declare a winner in this controversy but I want to dissect it as an example of an ecological issue with so many dimensions it could continue for a long time.

Dingos in Australia are viewed like wolves in North America – the ultimate enemy that must be reduced or eradicated if possible. When in doubt about what to do, killing dingos or wolves has become the first commandment of wildlife management and conservation. The ecologist would like to know, given this socially determined goal, what are the ecological consequences of reduction or eradication of dingos or wolves. How do we determine that?

The experimentalist suggests doing a removal experiment (or conversely a re-introduction experiment) so we have ecosystems with and without dingos (Newsome et al. 2015). This would have to be carried out on a large scale dependent on the home range size of the dingo and for a number of years so that the benefits or the costs of the removal would be clear. Here is the first hurdle, this kind of experiment cannot be done, and only a quasi-experiment is possible by finding areas that have dingos and others that do not have any (or a reduced population) and comparing ecosystems. This decision immediately introduces 5 problems:

  1. The areas with- and without- the dingo are not comparable in many respects. Areas with dingos for example may be national parks placed in the mountains or in areas that humans cannot use for agriculture, while areas with dingo control are in fertile agricultural landscapes with farming subsidies.
  2. Even given areas with and without dingos there is the problem of validating the usual dingo reduction carried out by poison baits or shooting. This is an important methodological issue.
  3. One has to census the mesopredators, in Australia foxes and cats, with further methodological issues of how to achieve that with accuracy.
  4. In addition one has to census the smaller vertebrates presumed to be possibly affected by the mesopredator offtake.
  5. Finally one has to do this for several years, possibly 5-10 years, particularly in variable environments, and in several pairs of areas chosen to represent the range of ecosystems of interest.

All in all this is a formidable research program, and one that has been carried out in part by the researchers working on dingos. And we owe them our congratulations for their hard work. The major part of the current controversy has been how one measures population abundance of all the species involved. The larger the organism, paradoxically the more difficult and expensive the methods of estimating abundance. Indirect measures, often from predator tracks in sand plots, are forced on researchers because of a lack of funding and the landscape scale of the problem. The essence of the problem is that tracks in sand or mud measure both abundance and activity. If movements increase in the breeding season, tracks may indicate activity more than abundance. If old roads are the main sampling sites, the measurements are not a random sample of the landscape.

This monumental sampling headache can be eliminated by the bold stroke of concluding with Nimmo et al. (2015) and Stephens et al. (2015) that indirect measures of abundance are sufficient for guiding actions in conservation management. They may be, they may not be, and we fall back into the ecological dilemma that different ecosystems may give different answers. And the background question is what level of accuracy do you need in your study? We are all in a hurry now and want action for conservation. If you need to know only whether you have “few” or “many” dingos or tigers in your area, indirect methods may well serve the purpose. We are rushing now into the “Era of the Camera” in wildlife management because the cost is low and the volume of data is large. Camera ecology may be sufficient for occupancy questions, but may not be enough for demographic analysis without detailed studies.

The moral issue that emerges from this particular dingo controversy is similar to the one that bedevils wolf control in North America and Eurasia – should we remove large predators from ecosystems? The ecologist’s job is to determine the biodiversity costs and benefits of such actions. But in the end we are moral beings as well as ecologists, and for the record, not the scientific record but the moral one, I think it is poor policy to remove dingos, wolves, and all large predators from ecosystems. Society however seems to disagree.

 

Allen, B.L., Allen, L.R., Engeman, R.M., and Leung, L.K.P. 2013. Intraguild relationships between sympatric predators exposed to lethal control: predator manipulation experiments. Frontiers in Zoology 10(39): 1-18. doi:10.1186/1742-9994-10-39.

Colman, N.J., Gordon, C.E., Crowther, M.S., and Letnic, M. 2014. Lethal control of an apex predator has unintended cascading effects on forest mammal assemblages. Proceedings of the Royal Society of London, Series B 281(1803): 20133094. doi:DOI: 10.1098/rspb.2013.3094.

Hayward, M.W., and Marlow, N. 2014. Will dingoes really conserve wildlife and can our methods tell? Journal of Applied Ecology 51(4): 835-838. doi:10.1111/1365-2664.12250.

Letnic, M., Greenville, A., Denny, E., Dickman, C.R., Tischler, M., Gordon, C., and Koch, F. 2011. Does a top predator suppress the abundance of an invasive mesopredator at a continental scale? Global Ecology and Biogeography 20(2): 343-353. doi:10.1111/j.1466-8238.2010.00600.x.

Newsome, T.M., et al. (2015) Resolving the value of the dingo in ecological restoration. Restoration Ecology, 23 (in press). doi: 10.1111/rec.12186

Nimmo, D.G., Watson, S.J., Forsyth, D.M., and Bradshaw, C.J.A. 2015. Dingoes can help conserve wildlife and our methods can tell. Journal of Applied Ecology 52. (in press, 27 Jan. 2015). doi:10.1111/1365-2664.12369.

Stephens, P.A., Pettorelli, N., Barlow, J., Whittingham, M.J., and Cadotte, M.W. 2015. Management by proxy? The use of indices in applied ecology. Journal of Applied Ecology 52(1): 1-6. doi:10.1111/1365-2664.12383.

On Adaptive Management

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I was fortunate to be on the sidelines at UBC in the 1970s when Carl Walters, Ray Hilborn, and Buzz Holling developed and refined the ideas of adaptive management. Working mostly in a fisheries context in which management is both possible and essential, they developed a new paradigm of how to proceed in the management of natural resources to reduce or avoid the mistakes of the past (Walters & Hilborn 1978). Somehow it was one of those times in science where everything worked because these three ecologists were a near perfect fit to one another, full of new ideas and inspired guesses about how to put their ideas into action. Many other scientists joined in, and Holling (1978) put this collaboration together in a book that can still be downloaded from the website of the International Institute for Applied Systems Analysis (IASA) in Vienna:
(http://www.iiasa.ac.at/publication/more_XB-78-103.php

Adaptive management became the new paradigm, now taken up with gusto by many natural resources and conservation agencies (Westgate, Likens & Lindenmayer 2013). Adaptive management can be carried out in two different ways. Passive adaptive management involves having a model of the system being managed and manipulating it in a series of ways that improve the model fit over time. Active adaptive management takes several different models and uses different management manipulations to decide which model best describes how the system operates. Both approaches intend to reduce the uncertainty about how the system works so as to define the limits of management options.

The message was (as they argued) nothing more than common sense, to learn by doing. But common sense is uncommonly used, as we see too often even in the 21st century. Adaptive management became very popular in the 1990s, but while many took up the banner of adaptive management, relatively few cases have been successfully completed (Walters 2007; Westgate, Likens & Lindenmayer 2013). There are many different reasons for this (discussed well in these two papers), not the least of which is the communication gap between research scientists and resource managers. Research scientists typically wish to test an ecological hypothesis by a management manipulation, but the resource manager may not be able to use this particular management manipulation in practice because it costs too much. To be useful in the real world any management experiment needs to have careful, long-term monitoring to map its outcome, and management agencies do not often have the opportunity to carry out extensive monitoring. The underlying cause then is mainly financial, and resource agencies rarely have an adequate budget to cover the important wildlife and fisheries issues they are supposed to manage.

If anything, reading this ‘old’ literature should remind ecologists that the problems discussed are inherent in management and will not go away as we move into the era of climate change. Let me stop with a few of the guideposts from Holling’s book:

Treat assessment as an ongoing process…
Remember that uncertainties are inherent…
Involve decision makers early in the analysis…
Establish a degree of belief for each of your alternative models…
Avoid facile and narcotic compression of indicators such as cost/benefit ratios that are generally inappropriate for environmental problems….

And probably remind yourself that there can be wisdom in the elders….

The take-home message for me in re-reading these older papers on adaptive management is that it is similar to the problem we have with models in ecology. We can produce simple models or in this case solutions to management problems on paper, but getting them to work properly in the real world where social viewpoints, political power, and scientific information collide is extremely difficult. This is no reason to stop doing the best science and to try to weld it into management agencies. But it is easier said than done.

Holling, C.S. (1978) Adaptive Environmental Assessment and Management. John Wiley and Sons, Chichester, UK.

Walters, C.J. (2007) Is adaptive management helping to solve fisheries problems? Ambio, 36, 304-307.

Walters, C.J. & Hilborn, R. (1978) Ecological optimization and adaptive management. Annual Review of Ecology and Systematics, 9, 157-188.

Westgate, M.J., Likens, G.E. & Lindenmayer, D.B. (2013) Adaptive management of biological systems: A review. Biological Conservation, 158, 128-139.

Wildlife Management Dilemmas

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The science of wildlife management has moved from the good old days of worrying only about deer and ducks to the broader issues of conservation management of all species. But it operates in an impossible squeeze between human activities and wildlife responses. One key problem is the incremental creep of land use decisions. If we log half of the forest surely there is plenty left there for the wildlife to thrive, or so many people believe. So a central dilemma is habitat loss. The simple approach using ‘cow arithmetic’ says that if you have a farm one-third the size of what you have now, you will be able to have only one-third the number of cows. So habitat loss is critical but there seems to be no way of stopping it as long as the human population continues to expand.

To solve this problem we set up parks and reserves. That will please most of the botanists because if you have a plant species you are concerned about, you need set aside only a few hectares of land to keep it safe. This approach is at the core of wildlife management’s dilemma. You keep the plant species but lose the ecosystem. Certainly you can keep many of the small insects in a few hectares, so you protect not only the plant species but more of the biota. But you will lose all the birds and the larger species that need much larger areas of habitat. One of the defining moments in wildlife management and conservation ecology occurred when several ecologists recognized that even large national parks were not large enough for the charismatic megafauna.

Maybe we can rescue it all with metapopulations, islands of good habitat close enough to each other to permit dispersal. That will work in some cases and is a useful addition to the management arsenal of tools. But then we have to cope with additional problems – introduced pests and diseases that we may or may not be able to control, and global problems of air and water pollution that respect no neat geographic boundaries.

We cannot control species interactions so if we tinker with one aspect of the ecosystem, we find unintended consequences in another aspect of the ecosystem that we did not expect. We brought rabbits to Australia and to many islands with dire consequences no one seemed to anticipate. We also brought rats and pigs to island inadvertently with many well documented problems for bird and plants. We take predators away from ecosystems and then complain to the government that there are too may deer or Canada geese.

So part of the dilemma of wildlife management in the 21st century is that we do XYZ and then only later ask ecologists whether it was a good idea or not to do XYZ. Decisions are made by governments, companies, farmers, or city dwellers to change some element of the ecosystem without anyone asking a wildlife manager or an ecologist what the consequences might be. We love cats so we pass laws that prohibit managers from culling wild cats and only allow them to sterilize and release them. We love horses so we do the same. So wildlife management decisions are driven not by ecological studies and recommendations but by public demands and weak politicians. Wildlife management is thus a social science, with all the dilemmas generated when one part of society wishes to harvest seals and one part demands protection for seals.

Wildlife management has always been handicapped by the hunters and fishers who know everything about what management should be practiced. There is no need to have any professional training to decide management goals, management actions, and funding preferences for many of these people. I suppose we should at least be grateful that the same approach is not applied in medical science.

Wildlife management has always been a low priority activity, underfunded and moved more by political whims than by science. This is not at all the fault of all the excellent wildlife and fishery scientists who try their best to protect and manage our ecosystems. It is a victim of the constraints of making decisions on the spot about long term issues without the time or money to investigate the science necessary for knowledge of the consequences of our actions. The world changes slowly and if our memory is on the time span of 1-3 years, we are not on ecosystem time.

Much action must be spent on trying to restore ecosystems damaged by human activities. Restoration ecology recognizes that it is really partial restoration ecology because we cannot get back to the starting point. None of this is terribly new to ecologists or wildlife managers but it is good to keep it in mind as we get lost in the details of our daily chores.

Humans are destroying the earth in their quest for wealth, and simultaneously producing the problems of poverty and obesity. Led by politicians who do not lead and who do not seem to know what the problems of the Earth are, we keep a positive view of the scientific progress we generate, enjoy the existing beauty of biodiversity, and hope that the future will somehow cope with the changes we have set in motion.

“Humans, including ecologists, have a peculiar fascination with attempting to correct one ecological mistake with another, rather than removing the source of the problem”.   (Schindler 1997, p. 4)

 

Estes, J.A. et al. 2011. Trophic downgrading of Planet Earth. Science 333:301-306.

Likens, G.E. 2010. The role of science in decision making: does evidence-based science drive environmental policy? Frontiers in Ecology and the Environment 8:e1-e9.

Newmark, W.D. 1985. Legal and biotic boundaries of Western North American National Parks: A problem of congruence. Biological Conservation 33:197-208.

Pauly, D. 1995. Anecdotes and the shifting baseline syndrome of fisheries. Trends in Ecology and Evolution 10:430.

Schindler, D. W. 1997. Liming to restore acidified lakes and streams: a typical approach to restoring damaged ecosystems? Restoration Ecology 5:1-6.