Communicating the value of ecology
TL;DR: It is predicted that applied ecology will continue as a vital tool in detecting ecological problems and informing environmental management, and will emerge also as an arena for advancing the fundamental nature of the discipline.
Abstract: Summary
1. Environmental change and impact continue to create a major need for the application of ecology. We attempted to ascertain whether authors in the Journal of Applied Ecology made relevant contributions at appropriate spatio-temporal scales to the problems that result.
2. A review of 84 papers published in the Journal during 1999 indicated that all carried information of direct value in environmental management, and 46% made explicit management recommendations.
3. The techniques used most frequently by applied ecologists were correlational (48% of all papers; including ordination) or anova-style comparisons between replicated locations that were either purposely manipulated or contrasted on a priori criteria (38%). Models (13%), laboratory experiments, mark–recapture studies and observational work – involving for example stable isotopes – also figured. This breadth reveals how classical and novel approaches in ecology are brought to bear on real environmental problems. The journal continues to publicise innovative new techniques with applied relevance.
4. In keeping with the widespread use of correlation and a priori contrasts, 34% of published studies in 1999 involved time scales exceeding >5–10 years. Similarly, 40% of studies approached problems in large, regional contexts. Applied ecologists are clearly providing leadership in developing methods to tackle challenging questions at spatio-temporal scales beyond the capabilities of manipulative ecological experiments. We will augment this area of the Journal's work with a special issue on large-scale processes in 2000.
5. Only 20% of the papers published explicitly state clearly testable hypotheses, but nearly all state clear aims or questions being addressed.
6. Overwhelmingly, papers approach applied ecology by seeking to assess the effects of anthropogenic factors on ecological systems, and a minority assess the effects of organisms on human activity. Few studies, by contrast, use anthropogenic impacts to test or develop ecological theory. We suggest this is an area ripe for development.
7. Points 2, 3 and 4 above demonstrate how the Journal of Applied Ecology communicates the value and utility of ecology to society at large. We prompt leading ecologists to maintain their involvement with the application of ecology to problem solving. We urge authors to emphasize further the generic value in their work. We predict that applied ecology will continue as a vital tool in detecting ecological problems and informing environmental management. It will emerge also as an arena for advancing the fundamental nature of our discipline.
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TL;DR: In this article, the authors used a logistic regression with real data from 34 families of aquatic invertebrates in 180 Himalayan streams to evaluate the performance of presence and absence models.
Abstract: • 1. Models for predicting the distribution of organisms from environmental data are widespread in ecology and conservation biology. Their performance is invariably evaluated from the percentage success at predicting occurrence at test locations.
• 2. Using logistic regression with real data from 34 families of aquatic invertebrates in 180 Himalayan streams, we illustrate how this widespread measure of predictive accuracy is affected systematically by the prevalence (i.e. the frequency of occurrence) of the target organism. Many evaluations of presence–absence models by ecologists are inherently misleading.
• 3. With the same invertebrate models, we examined alternative performance measures used in remote sensing and medical diagnostics. We particularly explored receiver-operating characteristic (ROC) plots, from which were derived (i) the area under each curve (AUC), considered an effective indicator of model performance independent of the threshold probability at which the presence of the target organism is accepted, and (ii) optimized probability thresholds that maximize the percentage of true absences and presences that are correctly identified. We also evaluated Cohen's kappa, a measure of the proportion of all possible cases of presence or absence that are predicted correctly after accounting for chance effects.
• 4. AUC measures from ROC plots were independent of prevalence, but highly significantly correlated with the much more easily computed kappa. Moreover, when applied in predictive mode to test data, models with thresholds optimized by ROC erroneously overestimated true occurrence among scarcer organisms, often those of greatest conservation interest. We advocate caution in using ROC methods to optimize thresholds required for real prediction.
• 5. Our strongest recommendation is that ecologists reduce their reliance on prediction success as a performance measure in presence–absence modelling. Cohen's kappa provides a simple, effective, standardized and appropriate statistic for evaluating or comparing presence–absence models, even those based on different statistical algorithms. None of the performance measures we examined tests the statistical significance of predictive accuracy, and we identify this as a priority area for research and development.
1,687 citations
Cites background from "Communicating the value of ecology"
...The potential applications are many (Table 1), particularly at large spatial scales ( Ormerod, Pienkowski & Watkinson 1999; Caldow & Racey 2000)....
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TL;DR: This work used 12 criteria that should be fulfilled by an "ideal" biomonitoring tool, addressing the rationale, implementation, and performance of a method, and suggested that societies and governments prioritize how these criteria should be ranked.
Abstract: ▪ Abstract Aquatic insects and other benthic invertebrates are the most widely used organisms in freshwater biomonitoring of human impact. Because of the high monetary investment in freshwater management, decisions are often based on biomonitoring results, and a critical and comparative review of different approaches is required. We used 12 criteria that should be fulfilled by an “ideal” biomonitoring tool, addressing the rationale, implementation, and performance of a method. After illustrating how the century-old but still widely used Saprobian system does not meet these criteria, we apply them to nine recent approaches that range from the suborganismal to the ecosystem level. Although significant progress has been made in the field, no recent approach meets all 12 criteria. Given that the use of biomonitoring information has important financial consequences, we suggest that societies and governments prioritize how these criteria should be ranked.
814 citations
Cites methods from "Communicating the value of ecology"
...PERFORMANCE OF THE IDEAL BIOMONITORING TOOL Current budgets for environmental management are used to execute policy and legislation across large geographic units (37, 96, 101)....
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TL;DR: In this paper, the authors analyzed the causes of shrub encroachment in the lowveld savanna of north-eastern Swaziland, southern Africa, and highlighted management regimes that can be used to reduce or prevent it.
Abstract: Summary
1
Shrub encroachment has been widely observed in savanna regions. This study analysed the causes of shrub encroachment in the lowveld savanna of north-eastern Swaziland, southern Africa, and highlighted management regimes that can be used to reduce or prevent it.
2
The rates and dynamics of shrub encroachment were quantified for the period 1947–90 using aerial photographs, and for 1997 using a ground survey. Five similar areas with different land-use histories were compared to investigate the relative importance of fire, herbivory, rainfall, soil type and shrub density in driving shrub dynamics.
3
In the study area as a whole, shrub cover increased from a mean of 2% in 1947 to 31% in 1990. Dichrostachys cinerea accounted for most of the increase in cover, contributing 81% to total shrub cover during 1997. Shrub cover was strongly correlated with shrub density and weakly negatively correlated with tree cover.
4
Shrub encroachment varied across land-use fence lines. The key determinants of shrub dynamics were grazing, through its negative effect on fire frequency and an interaction between drought frequency and high shrub cover. Browsing pressure had a significant but minor impact on dynamics, while soil type had no significant effect. High grazing pressures through their effect on fire frequency were critical throughout the study period in promoting shrub encroachment, while the interaction between drought and high shrub cover produced declines in the later stages. Browsing had an impact on encroachment only in the early stages.
5
Frequent fires, facilitated by low grazing pressures, were capable of preventing shrub encroachment. When coupled with drought, frequent fires could reduce high shrub densities.
6
As cover and density were strongly correlated, it can be inferred from the negative correlation between change in cover (density) and initial cover (density) that the rate of shrub encroachment was cover (density)-dependent and that there was a shrub equilibrium of 40% cover, approximating to 2400 plants ha−1. Shrub population growth was driven by events (fire, drought) as well as continuous agents (density dependence, mean browsing and grazing pressure).
7
Bush encroachment can be reversed by a combination of management (frequent fires) and climatic events (drought). The implications for savanna management are discussed.
769 citations
TL;DR: In this article, the authors presented predictive models for great bustards in central Spain based on readily available advanced very high resolution radiometer (AVHRR) satellite imagery combined with mapped features in the form of geographic information system (GIS) data layers.
Abstract: Summary 1. Many species are adversely affected by human activities at large spatial scales and their conservation requires detailed information on distributions. Intensive ground surveys cannot keep pace with the rate of land-use change over large areas and new methods are needed for regional-scale mapping. 2. We present predictive models for great bustards in central Spain based on readily available advanced very high resolution radiometer (AVHRR) satellite imagery combined with mapped features in the form of geographic information system (GIS) data layers. As AVHRR imagery is coarse-grained, we used a 12-month time series to improve the definition of habitat types. The GIS data comprised measures of proximity to features likely to cause disturbance and a digital terrain model to allow for preference for certain topographies. 3. We used logistic regression to model the above data, including an autologistic term to account for spatial autocorrelation. The results from models were combined using Bayesian integration, and model performance was assessed using receiver operating characteristics plots. 4. Sites occupied by bustards had significantly lower densities of roads, buildings, railways and rivers than randomly selected survey points. Bustards also occurred within a narrower range of elevations and at locations with significantly less variable terrain. 5. Logistic regression analysis showed that roads, buildings, rivers and terrain all contributed significantly to the difference between occupied and random sites. The Bayesian integrated probability model showed an excellent agreement with the original census data and predicted suitable areas not presently occupied. 6. The great bustard’s distribution is highly fragmented and vacant habitat patches may occur for a variety of reasons, including the species’ very strong fidelity to traditional sites through conspecific attraction. This may limit recolonization of previously occupied sites. 7. We conclude that AVHRR satellite imagery and GIS data sets have potential to map distributions at large spatial scales and could be applied to other species. While models based on imagery alone can provide accurate predictions of bustard habitats at some spatial scales, terrain and human influence are also significant predictors and are needed for finer scale modelling.
465 citations
Cites background from "Communicating the value of ecology"
...Large-scale studies continue to pose major challenges in applied ecology and model development may provide ecological insight at scales where manipulation is not possible ( Ormerod, Pienkowski & Watkinson 1999; Caldow & Racey 2000)....
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TL;DR: This measure for the functional composition of invertebrate communities provides a first unified European baseline for future stream and river management: it was stable in the most natural but otherwise very different running water types across Europe, it safely indicated human impact, and it could potentially discriminate specific types of human disturbances.
248 citations
Cites background from "Communicating the value of ecology"
...In addition, such research would be a collective response of applied ecologists to the challenge to examine, at large scales, models and hypotheses being derived from theory (Ormerod et al. 1999)....
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...A major challenge for applied ecologists is to examine, at large scales, models and hypotheses that are derived from theory (Ormerod et al. 1999)....
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References
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TL;DR: The second volume in a series on terrestrial and marine comparisons focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern was published by Levin et al..
Abstract: This book is the second of two volumes in a series on terrestrial and marine comparisons, focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern (Levin et al. 1993). The issue of the relationships among pattern, scale, and patchiness has been framed forcefully in John Steele’s writings of two decades (e.g., Steele 1978). There is no pattern without an observational frame. In the words of Nietzsche, “There are no facts… only interpretations.”
5,833 citations
TL;DR: It is argued that ecology has numerous laws in this sense of the word, in the form of widespread, repeatable patterns in nature, but hardly any laws that are universally true.
Abstract: The dictionary definition of a law is: "Generalized formulation based on a series of events or processes observed to recur regularly under certain conditions; a widely observable tendency". I argue that ecology has numerous laws in this sense of the word, in the form of widespread, repeatable patterns in nature, but hardly any laws that are universally true. Typically, in other words, ecological patterns and the laws, rules and mechanisms that underpin them are contingent on the organisms involved, and their environment. This contingency is manageable at a relatively simple level of ecological organisation (for example the population dynamics of single and small numbers of species), and re-emerges also in a manageable form in large sets of species, over large spatial scales, or over long time periods, in the form of detail-free statistical patterns - recently called 'macroecology'. The contingency becomes overwhelmingly complicated at intermediate scales, characteristic of community ecology, where there are a large number of case histories, and very little other than weak, fuzzy generalisations. These arguments are illustrated by focusing on examples of typical studies in community ecology, and by way of contrast, on the macroecological relationship that emerges between local species richness and the size of the regional pool of species. The emergent pattern illustrated by local vs regional richness plots is extremely simple, despite the vast number of contingent processes and interactions involved in its generation. To discover general patterns, laws and rules in nature, ecology may need to pay less attention to the 'middle ground' of community ecology, relying less on reductionism and experimental manipulation, but increasing research efforts into macroecology.
1,349 citations
TL;DR: The emerging discipline of restoration ecology as mentioned in this paper provides a powerful suite of tools for speeding the recovery of degraded lands, and provides a crucial complement to the establishment of nature reserves as a way of increasing land for the preservation of biodiversity.
Abstract: Conversion of natural habitats into agricultural and industrial landscapes, and ultimately into degraded land, is the major impact of humans on the natural environment, posing a great threat to biodiversity. The emerging discipline of restoration ecology provides a powerful suite of tools for speeding the recovery of degraded lands. In doing so, restoration ecology provides a crucial complement to the establishment of nature reserves as a way of increasing land for the preservation of biodiversity. An integrated understanding of how human population growth and changes in agricultural practice interact with natural recovery processes and restoration ecology provides some hope for the future of the environment.
860 citations
TL;DR: The results support the hypothesis that bumble bees do not necessarily forage close to their nest, and illustrate that studies on a landscape scale are required if the authors are to evaluate bee foraging ranges fully with respect to resource availability.
Abstract: Summary
1. Bumble bees play a vital role in the pollination of many crops and wild flowers, and plans for their conservation require a knowledge of the dynamics and spatial scale of their foraging flights, which are, at present, poorly understood.
2. We investigated the foraging range and constancy of two colonies of bumble bees Bombus terrestris L. on a mixed arable farm using harmonic radar, which has a unique capability to record the trajectories of insects flying at low altitude in the field.
3. Foraging bees were fitted with lightweight radar transponders and tracked as they flew to and from the nest to forage. The resulting tracks gave information on length, direction and straightness of foraging routes. Superimposition onto a map of the foraging landscape allowed interpretation of the bees’ destinations in relation to the spatial distribution of forage.
4. Outward tracks had a mean length of 275·3 ± 18·5 m (n = 65) and a range of 70–631 m, and were often to forage destinations beyond the nearest available forage. Most bees were constant to compass bearing and destination over successive trips, although one bee was tracked apparently switching between forage patches. Both outward and return tracks had a mean straightness ratio of 0·93 ± 0·01 (n = 99). The bees’ ground speeds ranged from 3·0 m s–1 to 15·7 m s–1 (n = 100) in a variety of wind conditions.
5. The results support the hypothesis that bumble bees do not necessarily forage close to their nest, and illustrate that studies on a landscape scale are required if we are to evaluate bee foraging ranges fully with respect to resource availability. Such evaluations are required to underpin assessments of gene flow in bee-pollinated crops and wild flowers. They are also required when making decisions about the management of bees as pollinators and the conservation of bee and plant biodiversity.
491 citations
TL;DR: Results from four field studies show that communities of trap-nesting bees and wasps and their natural enemies are promising bioindicators for ecological change or habitat quality and species richness was closely correlated with that sampled by sweep nets.
Abstract: 1. Results from four field studies show that communities of trap-nesting bees and wasps and their natural enemies are promising bioindicators for ecological change or habitat quality. These small and easy-to-handle communities can be analysed with respect to (i) species richness and related parameters, and (ii) ecological functions or interactions. The communities comprise Hymenoptera (Apidae, Sphecidae, Eumenidae, Pompilidae) and natural enemies belonging to many insect taxa. Traps consisted of 150–200, 15–20-cm long, reed internodes, put into tins or plastic tubes of 13–15 cm diameter; wooden posts with 2–10 of such reed-filled tins were exposed in the target habitat.
2. Species richness and abundance of bees (but not wasps) were closely related to plant species richness of the habitat, a measure of the bees’ food resource. However, availability of nest sites of above-ground nesting species was equally important: meadows with old trees supported greater populations than meadows without trees. A threefold increase in exposed traps resulted in a twofold increase in species.
3. The sensitivity of this bioindicator system profits from the fact that evaluations rely not only on presence/absence data, descriptive population attributes or diversity indices, but also on interactions or ecological functions. Monitoring ecological responses or multitrophic interactions, and their relationship to species diversity, is rarely done but much needed. Ecological functions include (i) the percentage mortality of trap-nesting bees and wasps due to parasitoids and predators, which was correlated with the species richness of these natural enemies; (ii) seed set of allogamous plants due to successful pollination by trap-nesting bees; and (iii) biological control by the predacious wasps.
4. With increasing isolation of fragmented habitats (when traps were exposed in a cleared agricultural landscape), both species richness of natural enemies and percentage mortality (parasitism and predation) declined significantly. In a comparison of habitat types (grasslands and field margins), species richness of the trap-nest community correlated with plant diversity, but percentage mortality, due to parasitism and predation, with field age only. The threshold distance to the nearest habitat was 106–530 m for a 10–50% decrease in mean mortality, and the mortality increased greatly in habitats that were older than 5 years. Accordingly, these studies emphasize the significance of a continuum of old habitat patches for the augmentation of natural enemies.
5. Exposure of standardized traps is an experimental approach with a small, interacting and reproducing community that can be easily characterized by simple parameters. Taxonomy and biology are well known, and quick evaluations can be done using the close correlation between the number of occupied traps and species richness. Species richness of trap-nesting bees and wasps was closely correlated with that sampled by sweep nets. Further criteria of indicator taxa that apply to this system are discussed in the text.
386 citations