- Email: [email protected]
Something to chew on
BOOK REVIEWS Recently, there can have been few ecological conferences where GIS papers were not presented. Despite this burgeoning interest, however, GIS has gained something of a reputation as being no more than a sophisticated and time-consuming tool for making pretty pictures. GIS can, of course, be timeconsuming, and it is beyond question extremely good for making pretty pictures. However, the important message for ecologists is that GIS can also provide far-ranging and generic insights into many of the great contemporary and historical ecological themes. The spatial element of spatial ecology will include investigations of scale effects, and GIS is a useful tool for studying these problems. But beyond this, GIS can also be used to investigate diversity, dynamics, structure, stability and patterns within ecological systems, and as such will undoubtedly gain many new advocates as time goes by. As someone who has worked with GIS applied to ecological problems, I am keen to communicate to ecologists the need to see beyond the myth of the pretty picture. A new book on the subject is therefore always eagerly anticipated. Carol Johnston’s Geographic Information Systems in Ecology provides a contemporary review of ecological GIS literature and attempts to set the use of GIS into a wider ecological context. However, the main problem in communicating the GIS message to ecologists is how to tread the difficult line between the general and the specific. On the one hand, for example, how do you describe a GIS method to answer a specific ecological question without getting bogged down in operational terminology? On the other hand, how do you describe important aspects of GIS methodology without losing the specific ecological context where the particular operation would be of use? An example of this problem comes early in the book, in a section on ‘why ecologists should be interested in GIS’. Unfortunately, this single paragraph, which could have provided a large, central and generic theme for the book, is merely a short list of rather unconnected questions that have a GIS operation associated with them. Another example is highlighted in a section describing ‘FRAGSTATS’3. This is a suite of GIS compatible programs, capable of generating a wide variety of patch and landscape indices. The author rightly states that this is a basic GIS operation. What is not made clear, however, is that the use of FRAGSTATS is far from a basic ecological operation. In other words, the GIS software will do whatever you tell it to do with your data but, before this, there needs to be a considerable amount of thought put into the structure and limitations of the data set and the specific ecological questions being addressed. One of the other major problems with a methodological book, is deciding how the perceived audience will acquire the conceptual foundation of the central theme, and I TREE vol. 13, no. 10 October 1998
was left with the impression that this book sits rather uneasily between description and prescription. To really comprehend the usefulness of GIS, an ecologist needs to be able to start from the position of his or her own subject area and work towards a number of GIS solutions. This can be extremely difficult to encompass in a single book, given the breadth of current ecological themes. The author has chosen to title each chapter as a GIS operation, and the book is therefore rather inverted in its approach. GIS operations are described comprehensively, but a better approach to convert the ecologists to the GIS cause might have been to focus on ecological problems chapter by chapter and then indicate which GIS operations are helpful in tackling them. Nevertheless, the book may be of some use in introducing GIS to ecologists, and those reading it might begin to regard GIS as more than just a pretty face!
Mark O’Connell Dept of Biological Sciences, University of Durham, South Road, Durham, UK DH1 3LE (m.j.o’[email protected])
References 1 Tilman, D. and Kareiva, P. (1998) Spatial Ecology. The Role of Space in Population Dynamics and Interspecific Interactions, Princeton University Press 2 Environmental Systems Research Institute (1990) Understanding GIS, ESRI 3 McGarigal, K. and Marks, B.J. (1994) Fragstats: Spatial Pattern Analysis Program for Quantifying Landscape Structure, Oregon State University
Something to chew on Foraging for Survival: Yearling Baboons in Africa by Stuart A. Altmann University of Chicago Press, 1998. $70.00 hbk (xii + 536 pages) ISBN 0 226 01595 5
A
little over 20 years ago, I remember listening to Stuart Altmann present the bare bones of an optimization model for baboon diets. His research programme, he said, was to measure the fitness consequences of optimal diet choice. A leading primatologist next to me shook his head and muttered that it just didn’t make sense to invest 25 years of one’s research career on a project that might not yield any results. This book is the final curtain call on that 25 years. The nub of Foraging for Survival is a set of linear optimization models that defines the optimal diet that maximizes specific nutrient intakes while minimizing the ingestion
of toxins. Altmann considers five models that use different maximization criteria (daily energy intake, daily protein intake, daily feeding time, and energy or protein intake per unit feeding time), with a long list of constraint functions (including gut fill, daily minima for water, mineral, lipid and fibre intake, daily maxima for 15 cation intakes plus feeding time and energy and protein intake rates, as well as seasonal availability for 50 principal foods). The optimal diets predicted by these models are then compared with the actual diets of 11 yearlings sampled over a 40-week age span during 1975–1976. In the final analysis, none of the models is especially good at predicting the diets of the infants, but a number of important conclusions arise from the exercise nonetheless. First, maximizing energy intake and maximizing intake rate are not the same thing: although most optimal foraging models assume that they are, they actually represent incompatible goals. Second, maximizing energy intake rate often leads to absurd conclusions (and marked apparent underachievement by the animals). Third (and perhaps especially useful for field ecologists), satisfying protein and energy intakes always satisfies the animal’s requirements for all micronutrients. Finally, one of the likely reasons why the models fail to predict the infants’ actual diets is that they all ignore (and this seems a remarkable omission) search time and handling time. Green acacia pods fail the optimal diet test, for example, because they contain an antitrypsin factor that makes the seeds bitter – yet baboons of all ages gorge themselves on them. The likely reason for this is that, despite the adverse consequences of overeating (and I have the dubious honour of appearing in the book as an unnamed experimental subject responsible for unveiling this fact by eating too many half-cooked beans one day and being violently ill as a result), the green beans are easier to chew than the dry ones and they are easier to find on the ground beneath the parent trees when still in their pods. Although none of the 11 infants came close to achieving an optimal diet (the best was 16% below optimal energy-maximizing intake), some startling results emerge from the long-term demographic data. A combination of energy shortfall and protein surplus at the age of 12 months predicts (with correlation coefficients in the order of 0.90) a female’s reproductive lifespan, the number of infants she produces over a lifetime and the number of surviving offspring. Quite why this should be remains unclear, although it almost certainly has to do with the impact of juvenile diets on longevity, rather than on birth rates. Although the sample size is small, all the infants that failed to survive to reproductive maturity had an energy shortfall below 70% of the optimum intake and a protein surplus below 60% of the optimum intake.
Copyright © 1998, Elsevier Science Ltd. All rights reserved. 0169-5347/98/$19.00
423
BOOK REVIEWS Interestingly, in this respect, milk energy intake and protein surplus directly predict the amount of time individual yearlings spend playing. Aside from a very detailed appendix listing macro- and micronutrient requirements for baboons (extracted with not a little difficulty from a diffuse and often imperfect literature), this book is perhaps most notable for the meticulous and, at times, overbearing detail with which it treats its questions. At the end of it all, one is left wondering whether, given the sources of sampling error that field biologists have to contend with, the kind of precision of sampling and statistical analysis espoused by Altmann is really worth the effort. Perhaps the time spent on these analytical details could have been more usefully used exploring other aspects of the later lives of this cohort of yearlings. That having been said, this book is a worthwhile contribution to our understanding of baboon ecology.
Robin Dunbar Population Biology Research Group, School of Biological Sciences, Nicholson Building, University of Liverpool, Liverpool, UK L69 3BX ([email protected])
The lessons of palaeoecology re-taught Terrestrial Ecosystems in Changing Environments by Herman H. Shugart Cambridge University Press (Cambridge Studies in Ecology), 1998. £75.00 hbk, £27.95 pbk (xiv + 537 pages) ISBN 0 521 56342 9 / 0 521 56523 5
P
alaeoecologists have long been aware that environmental change is the rule, rather than the exception. Communities of organisms do not exist in a state of long-term equilibrium with a stable environment – the so-called ‘balance of nature’ – but rather are constantly changing as they respond to their constantly changing environment1,2. Whether there ever is equilibrium between the two is a matter of debate; what is certain is that any tendency that communities may have towards an equilibrium with their environment is towards a dynamic equilibrium. In contrast to palaeoecologists, most ecologists – at least until quite recently – have taken as a paradigm the long-term stability of communities and their equilibrium with a stable environment, or else their successional tendency towards a condition that will be in such equilibrium. This has led to the development of complex theories relating to the
424
‘evolution’ of communities, as well as to hypotheses relating the stability, diversity and complexity of ecosystems. This view of the natural world has also predominated among those seeking to conserve wildlife; very often, change is seen as necessarily negative and conservation management is designed to maintain some illusory stable relationship between a community and its environment. The recent development of concern about the potential impacts on the biosphere of anthropogenic changes to the global environment has resulted in a new branch of ecology that has begun explicitly to address the manner in which ecosystems respond to their changing environment. This new ecology is concerned with scale, and especially with processes that operate over temporal and spatial scales longer and larger than can be addressed by means of conventional ecological monitoring or experimentation. It is also concerned with temporal and spatial heterogeneity of the environment and hence with place and time; in consequence, it has adopted some of the tools of geography, especially geographical information systems. Most fundamentally, however, it uses models as a primary tool for expressing and exploring the relationships between the environment and the components of ecosystems. These models are diverse in character and range from relatively simple, nonmechanistic models based upon observed correlations between organisms and their environment, to complex mechanistic models that simulate fundamental processes within ecosystems. Models also vary in spatial scale from 0.1 ha (such as forest-stand simulation models) to global (such as models of terrestrial vegetation). A third important dimension of variation among so-called ecosystem models relates to the range of processes that they simulate; many models do not address soil processes, whereas they simulate in detail the processes of plant metabolism and leaf gas exchange. Only a minority of models – typically, those that attempt to simulate processes that involve dispersal – have as yet attempted explicitly to represent the spatial heterogeneity of landscapes. In his book, Shugart provides both an excellent and a readable background to the development of the new ecology of environmental change, as well as clear descriptions of the range of models applied by ecologists. He also gives numerous examples of studies that have used such models, and describes how various classes of ecological models are being used to evaluate aspects of global change. As a practitioner in this field, he is ideally suited to write such a text. Shugart does more, however, than simply provide an up-to-date account of the use of models by ecologists in their investigations of ecosystem responses to environmental change. He relates the development of these
Copyright © 1998, Elsevier Science Ltd. All rights reserved. 0169-5347/98/$19.00
models both to much earlier mathematical descriptions of ecological processes and interactions, and to the whole concept of ‘pattern and process’ as developed by Watt3 in his seminal work on plant community dynamics. He also provides a valuable discussion of the development and use of such fundamental ecological concepts as those of the ecosystem and the niche, and relates the topical use of ‘plant functional types’ to much earlier systems of classification based on biogeography and plant form. In short, this book is a stimulating read that many ecologists will find valuable and also will want to recommend their students. It is a useful and timely synthesis that puts the new ecology of global change into its broader context. Given the prevalence among those concerned with the conservation of wildlife and of natural systems of a ‘static’ view of ecosystems, this is also a book that I should want to recommend to students reading courses on conservation, as well as many practising conservationists. The lessons that the new ecology of global change is teaching – albeit lessons that should have been learned from palaeoecology long ago – are fundamental, and their conclusions need to be communicated widely. Unless these conclusions ultimately influence policy makers, then our students may live to see our present models of ecological processes and environmental change validated by mankind’s current experiment with the global system.
Brian Huntley Environmental Research Centre, University of Durham, Dept of Biological Sciences, South Road, Durham, UK DH1 3LE
References 1 West, R.G. (1964) J. Ecol. 52 (Suppl.), 47–57 2 Huntley, B. (1996) Q. Sci. Rev. 15, 591–606 3 Watt, A.S. (1947) J. Ecol. 35, 1–22
Alternative states in shallow lakes Ecology of Shallow Lakes by Marten Scheffer Chapman & Hall (Population and Community Biology Series 22), 1998. £45.00/$79.65 hbk (xx + 357 pages) ISBN 0 412 74920 3
S
hallow lakes have been the focus of substantial research during the past decade. To a large extent, this research stems from the management problems that eutrophication of these lakes has caused in terms of TREE vol. 13, no. 10 October 1998
was left with the impression that this book sits rather uneasily between description and prescription. To really comprehend the usefulness of GIS, an ecologist needs to be able to start from the position of his or her own subject area and work towards a number of GIS solutions. This can be extremely difficult to encompass in a single book, given the breadth of current ecological themes. The author has chosen to title each chapter as a GIS operation, and the book is therefore rather inverted in its approach. GIS operations are described comprehensively, but a better approach to convert the ecologists to the GIS cause might have been to focus on ecological problems chapter by chapter and then indicate which GIS operations are helpful in tackling them. Nevertheless, the book may be of some use in introducing GIS to ecologists, and those reading it might begin to regard GIS as more than just a pretty face!
Mark O’Connell Dept of Biological Sciences, University of Durham, South Road, Durham, UK DH1 3LE (m.j.o’[email protected])
References 1 Tilman, D. and Kareiva, P. (1998) Spatial Ecology. The Role of Space in Population Dynamics and Interspecific Interactions, Princeton University Press 2 Environmental Systems Research Institute (1990) Understanding GIS, ESRI 3 McGarigal, K. and Marks, B.J. (1994) Fragstats: Spatial Pattern Analysis Program for Quantifying Landscape Structure, Oregon State University
Something to chew on Foraging for Survival: Yearling Baboons in Africa by Stuart A. Altmann University of Chicago Press, 1998. $70.00 hbk (xii + 536 pages) ISBN 0 226 01595 5
A
little over 20 years ago, I remember listening to Stuart Altmann present the bare bones of an optimization model for baboon diets. His research programme, he said, was to measure the fitness consequences of optimal diet choice. A leading primatologist next to me shook his head and muttered that it just didn’t make sense to invest 25 years of one’s research career on a project that might not yield any results. This book is the final curtain call on that 25 years. The nub of Foraging for Survival is a set of linear optimization models that defines the optimal diet that maximizes specific nutrient intakes while minimizing the ingestion
of toxins. Altmann considers five models that use different maximization criteria (daily energy intake, daily protein intake, daily feeding time, and energy or protein intake per unit feeding time), with a long list of constraint functions (including gut fill, daily minima for water, mineral, lipid and fibre intake, daily maxima for 15 cation intakes plus feeding time and energy and protein intake rates, as well as seasonal availability for 50 principal foods). The optimal diets predicted by these models are then compared with the actual diets of 11 yearlings sampled over a 40-week age span during 1975–1976. In the final analysis, none of the models is especially good at predicting the diets of the infants, but a number of important conclusions arise from the exercise nonetheless. First, maximizing energy intake and maximizing intake rate are not the same thing: although most optimal foraging models assume that they are, they actually represent incompatible goals. Second, maximizing energy intake rate often leads to absurd conclusions (and marked apparent underachievement by the animals). Third (and perhaps especially useful for field ecologists), satisfying protein and energy intakes always satisfies the animal’s requirements for all micronutrients. Finally, one of the likely reasons why the models fail to predict the infants’ actual diets is that they all ignore (and this seems a remarkable omission) search time and handling time. Green acacia pods fail the optimal diet test, for example, because they contain an antitrypsin factor that makes the seeds bitter – yet baboons of all ages gorge themselves on them. The likely reason for this is that, despite the adverse consequences of overeating (and I have the dubious honour of appearing in the book as an unnamed experimental subject responsible for unveiling this fact by eating too many half-cooked beans one day and being violently ill as a result), the green beans are easier to chew than the dry ones and they are easier to find on the ground beneath the parent trees when still in their pods. Although none of the 11 infants came close to achieving an optimal diet (the best was 16% below optimal energy-maximizing intake), some startling results emerge from the long-term demographic data. A combination of energy shortfall and protein surplus at the age of 12 months predicts (with correlation coefficients in the order of 0.90) a female’s reproductive lifespan, the number of infants she produces over a lifetime and the number of surviving offspring. Quite why this should be remains unclear, although it almost certainly has to do with the impact of juvenile diets on longevity, rather than on birth rates. Although the sample size is small, all the infants that failed to survive to reproductive maturity had an energy shortfall below 70% of the optimum intake and a protein surplus below 60% of the optimum intake.
Copyright © 1998, Elsevier Science Ltd. All rights reserved. 0169-5347/98/$19.00
423
BOOK REVIEWS Interestingly, in this respect, milk energy intake and protein surplus directly predict the amount of time individual yearlings spend playing. Aside from a very detailed appendix listing macro- and micronutrient requirements for baboons (extracted with not a little difficulty from a diffuse and often imperfect literature), this book is perhaps most notable for the meticulous and, at times, overbearing detail with which it treats its questions. At the end of it all, one is left wondering whether, given the sources of sampling error that field biologists have to contend with, the kind of precision of sampling and statistical analysis espoused by Altmann is really worth the effort. Perhaps the time spent on these analytical details could have been more usefully used exploring other aspects of the later lives of this cohort of yearlings. That having been said, this book is a worthwhile contribution to our understanding of baboon ecology.
Robin Dunbar Population Biology Research Group, School of Biological Sciences, Nicholson Building, University of Liverpool, Liverpool, UK L69 3BX ([email protected])
The lessons of palaeoecology re-taught Terrestrial Ecosystems in Changing Environments by Herman H. Shugart Cambridge University Press (Cambridge Studies in Ecology), 1998. £75.00 hbk, £27.95 pbk (xiv + 537 pages) ISBN 0 521 56342 9 / 0 521 56523 5
P
alaeoecologists have long been aware that environmental change is the rule, rather than the exception. Communities of organisms do not exist in a state of long-term equilibrium with a stable environment – the so-called ‘balance of nature’ – but rather are constantly changing as they respond to their constantly changing environment1,2. Whether there ever is equilibrium between the two is a matter of debate; what is certain is that any tendency that communities may have towards an equilibrium with their environment is towards a dynamic equilibrium. In contrast to palaeoecologists, most ecologists – at least until quite recently – have taken as a paradigm the long-term stability of communities and their equilibrium with a stable environment, or else their successional tendency towards a condition that will be in such equilibrium. This has led to the development of complex theories relating to the
424
‘evolution’ of communities, as well as to hypotheses relating the stability, diversity and complexity of ecosystems. This view of the natural world has also predominated among those seeking to conserve wildlife; very often, change is seen as necessarily negative and conservation management is designed to maintain some illusory stable relationship between a community and its environment. The recent development of concern about the potential impacts on the biosphere of anthropogenic changes to the global environment has resulted in a new branch of ecology that has begun explicitly to address the manner in which ecosystems respond to their changing environment. This new ecology is concerned with scale, and especially with processes that operate over temporal and spatial scales longer and larger than can be addressed by means of conventional ecological monitoring or experimentation. It is also concerned with temporal and spatial heterogeneity of the environment and hence with place and time; in consequence, it has adopted some of the tools of geography, especially geographical information systems. Most fundamentally, however, it uses models as a primary tool for expressing and exploring the relationships between the environment and the components of ecosystems. These models are diverse in character and range from relatively simple, nonmechanistic models based upon observed correlations between organisms and their environment, to complex mechanistic models that simulate fundamental processes within ecosystems. Models also vary in spatial scale from 0.1 ha (such as forest-stand simulation models) to global (such as models of terrestrial vegetation). A third important dimension of variation among so-called ecosystem models relates to the range of processes that they simulate; many models do not address soil processes, whereas they simulate in detail the processes of plant metabolism and leaf gas exchange. Only a minority of models – typically, those that attempt to simulate processes that involve dispersal – have as yet attempted explicitly to represent the spatial heterogeneity of landscapes. In his book, Shugart provides both an excellent and a readable background to the development of the new ecology of environmental change, as well as clear descriptions of the range of models applied by ecologists. He also gives numerous examples of studies that have used such models, and describes how various classes of ecological models are being used to evaluate aspects of global change. As a practitioner in this field, he is ideally suited to write such a text. Shugart does more, however, than simply provide an up-to-date account of the use of models by ecologists in their investigations of ecosystem responses to environmental change. He relates the development of these
Copyright © 1998, Elsevier Science Ltd. All rights reserved. 0169-5347/98/$19.00
models both to much earlier mathematical descriptions of ecological processes and interactions, and to the whole concept of ‘pattern and process’ as developed by Watt3 in his seminal work on plant community dynamics. He also provides a valuable discussion of the development and use of such fundamental ecological concepts as those of the ecosystem and the niche, and relates the topical use of ‘plant functional types’ to much earlier systems of classification based on biogeography and plant form. In short, this book is a stimulating read that many ecologists will find valuable and also will want to recommend their students. It is a useful and timely synthesis that puts the new ecology of global change into its broader context. Given the prevalence among those concerned with the conservation of wildlife and of natural systems of a ‘static’ view of ecosystems, this is also a book that I should want to recommend to students reading courses on conservation, as well as many practising conservationists. The lessons that the new ecology of global change is teaching – albeit lessons that should have been learned from palaeoecology long ago – are fundamental, and their conclusions need to be communicated widely. Unless these conclusions ultimately influence policy makers, then our students may live to see our present models of ecological processes and environmental change validated by mankind’s current experiment with the global system.
Brian Huntley Environmental Research Centre, University of Durham, Dept of Biological Sciences, South Road, Durham, UK DH1 3LE
References 1 West, R.G. (1964) J. Ecol. 52 (Suppl.), 47–57 2 Huntley, B. (1996) Q. Sci. Rev. 15, 591–606 3 Watt, A.S. (1947) J. Ecol. 35, 1–22
Alternative states in shallow lakes Ecology of Shallow Lakes by Marten Scheffer Chapman & Hall (Population and Community Biology Series 22), 1998. £45.00/$79.65 hbk (xx + 357 pages) ISBN 0 412 74920 3
S
hallow lakes have been the focus of substantial research during the past decade. To a large extent, this research stems from the management problems that eutrophication of these lakes has caused in terms of TREE vol. 13, no. 10 October 1998