Bayesian Belief Networks as a tool for evidence-based conservation management

Effective conservation management is dependent on accessing and integrating different forms of evidence regarding the potential impacts of management interventions. Here, we explore the application of Bayesian Belief Networks (BBN), which are graphical models that incorporate probabilistic relationships among variables of interest, to evidence-based conservation management. We consider four case studies, namely: (i) impacts of deer grazing on saltmarsh vegetation; (ii) impacts of burning on upland bog vegetation; (iii) control of the invasive exotic plant Rhododendron ponticum; and (iv) management of lowland heathland by burning. Each of these themes is currently a significant conservation issue in the UK, and yet the potential outcomes of management interventions are poorly understood. Through these examples, we demonstrate that BBNs can be used to integrate and explore evidence from a variety of sources, including expert opinion and quantitative results from research investigations. Incorporation of such information in BBNs enables different sources of evidence to be compared, the potential impacts of management interventions to be explored and management trade-offs to be identified. BBNs also offer a highly visual tool for communicating the uncertainty associated with potential management outcomes to conservation practitioners, and they can also be readily updated as new evidence becomes available. Based on these features, we suggest that BBNs have outstanding potential for supporting evidence-based approaches to conservation management.     

Spatially combining wood production and recreation with biodiversity conservation

Pine plantations established on former heathland are common throughout Western Europe and North America. Such areas can continue to support high biodiversity values of the former heathlands in the more open areas, while simultaneously delivering ecosystem services such as wood production and recreation in the forested areas. Spatially optimizing wood harvest and recreation without threatening the biodiversity values, however, is challenging. Demand for woody biomass is increasing but other pressures on biodiversity including climate change, habitat fragmentation and air pollution are intensifying too. Strategies to spatially optimize different ecosystem services with biodiversity conservation are still underexplored in the research literature. Here we explore optimization scenarios for advancing ecosystem stewardship in a pine plantation in Belgium. Point observations of seven key indicator species were used to estimate habitat suitability using generalized linear models. Based on the habitat suitability and species’ characteristics, the spatially-explicit conservation value of different forested and open patches was determined with the help of a spatially-explicit conservation planning tool. Recreational pressure was quantified by interviewing forest managers and with automated trail counters. The impact of wood production and recreation on the conservation of the indicator species was evaluated. We found trade-offs between biodiversity conservation and both wood production and recreation, but were able to present a final scenario that combines biodiversity conservation with a restricted impact on both services. This case study illustrates that innovative forest management planning can achieve better integration of the delivery of different forest ecosystem services such as wood production and recreation with biodiversity conservation.     

Conservation planning with insects at three different spatial scales

Deciding which areas to protect, and where to manage and how, are no easy tasks. Many protected areas were established opportunistically under strong political and economic constraints, which may have resulted in inefficient and ineffective conservation. Systematic conservation planning has helped us move from ad-hoc decisions to a quantitative and transparent decision-making process, identifying conservation priorities that achieve explicit objectives in a cost-efficient manner. Here we use Finnish butterflies to illustrate different modeling approaches to address three different types of situations in conservation planning at three different spatial scales. First, we employ species distribution models at the national scale to construct a conservation priority map for 91 species at the resolution of 10×10  km. Species distribution models interpolate sparse occurrence data to infer variation in habitat suitability and to predict species responses to habitat loss, management actions and climate change. Second, at the regional scale we select the optimal management plan to protect a set of habitat specialist species. And third, at the landscape scale, we use a metapopulation approach to manage a network of habitat patches for long-term persistence of a single butterfly species. These different modeling approaches illustrate trade-offs between complexity and tractability and between generality and precision. General correlation-based models are helpful to set priorities for multiple species at large spatial scales. More specific management questions at smaller scales require further data and more complex models. The vast numbers of insect species with diverse ecologies provide a source of information that has remained little used in systematic conservation planning.     

Local scale prioritization of cost-efficient protection within the National Park Thy

This study applied MARXAN to identify cost-efficient areas for biodiversity protection, within the Thy National Park in Denmark. Public authorities have requested a more systematic approach to managing public land, which identifies cost-effective solutions and potential trade-offs between economic cost and biodiversity benefits. The aim of this study was to support the local management staff in setting conservation targets and prioritizing their management efforts. This was addressed through the creation of two primary scenarios: i) applying uniform conservation targets to all biodiversity features, and ii) heterogeneous targets addressing various degrees of conservation importance. Four sub-scenarios were established for each primary scenario to investigate the implications of various conservation targets on conservation cost. Local data on red-listed species and habitat types were used to assess biodiversity benefits. Detailed cost estimates of required conservation actions were included. The results indicated that scenarios with uniform conservation targets provided more flexible networks of protected areas but contributed less to target achievement and a smaller share of selected planning units overlapped with current protected areas. Applying heterogeneous targets based on threat status resulted in a higher degree of target achievement and compactness, but provided less flexible networks. However, these networks may be more suitable for efficient management due to a higher level of clustering and spatial overlap with threatened species distributions.     

Habitat suitability modelling and implications for management of roan antelopes in Kenya

The roan antelope is locally endangered in Kenya with <50 individuals remaining in Ruma National Park (RNP). An understanding of the habitat requirements is essential to formulate habitat management strategies for species recovery. This study identifies habitat and management features affecting roan distribution in different seasons using information‐theoretic and multimodel inference (MMI) techniques. MMI averaged models were coupled with GIS data to develop habitat suitability maps. Results showed that roan habitat suitability is determined by different factors in different seasons but overall habitat was more important than management. Best predictors of roan incidence were wooded grassland, open grassland and water points. Water was more significant in the dry season whilst vegetation burned status, slope, soil type, distances to snares, park fence and security gates were important predictors at other seasons. Receiver operating characteristic (ROC) plots confirmed that the models fitted well to the data (AUC>0.9). Sustainable conservation of roans in RNP can be achieved via long‐term habitat management including prescribed burning and construction of more water points and short‐term urgent solutions to key management issues, especially control of poaching.     

A small mammal’s map: identifying and improving the large-scale and cross-border habitat connectivity for the hazel dormouse <Emphasis Type="Italic">Muscardinus avellanarius</Emphasis> in a fragmented agricultural landscape

Fragmentation and habitat loss pose major threats to global biodiversity. Especially forest dwelling species with small ranges and high habitat specialisation are affected by ongoing land use change. Building projects for infrastructural purposes, expanding settlements, and extensive agricultural areas are assumed to have a high impact on these species. The European Habitat’s Directive aims to conserve and restore habitat networks to lower these impacts. We propose that the idea of securing habitat networks for protected species should be incorporated within large scale landscape planning e.g. by modelling and improving corridors for umbrella species. Within a Danish-German project we developed a model demonstrating potential connecting corridors for Muscardinus avellanarius, a specialised forest dwelling rodent species with low dispersal ability. We used presence data and eco-geographical variables to find a data based time-efficient procedure which may be applied also in other species for future landscape planning. The habitat suitability model shows that the hazel dormouse occupies a narrow niche with highly suitable habitats comprising edge habitats. It indicates the preference of forest patches, linear structures and networks of the mentioned habitats. Along with connectivity the diversity of suitable habitats diversity is the major factor predicting hazel dormouse presence. For conservation management, we calculated habitat corridors and highlight sections with missing connections. This allowed us to accentuate regions of high management interest. The results represent the foundation not only for this cross-border conservation project, but also for long-term dormouse conservation on a federal-state level.     

A predictive diagnostic model for wild sheep (Ovis orientalis) habitat suitability in Iran

Wild sheep (Ovis orientalis) as the true ancestor of domestic sheep (Ovis aries) is currently listed as vulnerable (VU) by IUCN. Effective conservation of this species requires collecting all available ecological knowledge into a single framework that could be used for management decision making. Use of Bayesian Belief Networks for such purposes have been advocated over recent decades as this approach can integrate different sources of knowledge and perform comprehensive analyses. We built a decision support tool using BBN to assist in habitat management of wild sheep populations throughout the species’ geographical range. The behaviour of the model was tested using scenario and sensitivity analysis. Habitat security, food and water suitability, and thermal cover were recognised as the main habitat variables determining wild sheep habitat suitability. Integrating the complex interactions between variables, the model can be applied for both diagnostic and predictive analyses answering “what if” and “how” questions. This approach can assist wildlife conservationists for building similar models for other poorly-studied threatened species.     

Integrating GIS and expert judgment in a multi-criteria analysis to map and develop a habitat suitability index: A case study of large mammals on the Malayan Peninsula

Many habitat patches in tropical landscapes have become less suitable for wildlife due to an increase in anthropogenic disturbances. An index of habitat suitability based on the ecological factors that collectively determine the suitability of an organism's habitat is important for conservation planning. However, a widely accepted and comprehensive multi-criteria habitat suitability index for umbrella species is still lacking, particularly in areas where information related to the biology and ecology of the species of interest is not available. Therefore we develop preliminary habitat maps and measure the degree of habitat suitability for large mammals, focusing on four umbrella species in the State of Selangor, Peninsular Malaysia: Panthera tigris jacksoni (Malayan tiger), Tapirus indicus (Malayan tapir), Helarctos malayanus malayanus (Malayan sun bear), and Rusa unicolor cambojensis (sambar deer). The former two are endangered and the latter two are vulnerable according to the IUCN Red List. The suitability of habitat patches for each species was measured across the entire study area as well as in nine wildlife protected areas by integrating GIS data and expert opinion. Expert opinions were used as the source of information regarding the stresses faced by the species because there was insufficient information available from ground surveys.We developed an index and maps of habitat suitability for each species, which were then integrated to represent a combined index (ranging from 0 to 27) and spatially explicit maps of the area's habitat suitability for large mammals. The average large mammal habitat suitability index value of the State of Selangor (9) indicates that many habitat patches have become unsuitable for such species. Of the nine wildlife protected areas, Fraser's Hill (22), Sungai Dusun (22), and Bukit Kutu (21) are very suitable; Klang Gate (20) and Templers Park (17) are suitable; and the remaining four are unsuitable for large mammals. We assume that this preliminary habitat suitability index and mapping are useful for conservation planning of wildlife habitats at both landscape and regional scales, as well as providing an initial foundation for revision by future research with significant new information.     

Applying species distribution modelling to improving conservation based decisions: a gap analysis of Trinidad and Tobago’s endemic vascular plants

For the successful conservation of a species, habitat loss and fragmentation must be controlled through a protected area network that adequately covers its habitat. Here the suitable habitats of all of Trinidad and Tobago’s endemic plant species are determined and used to perform a gap analysis of a proposed protected area network. Data from a recently completed botanical survey, the WorldClim 2 environmental parameters, and a range of other sources were used to determine the habitat of each species using the species distribution model MaxEnt. Modelled habitat suitability for each species was combined and used to create maps showing endemic richness, weighted endemism and corrected weighted endemism, and to rank areas by conservation value using Zonation. The coverage of the proposed protected area network and a land use map were overlaid on these modelled distributions. We identified data limitations which meant that more than half of the 66 endemic species could not be modelled with confidence. For the remaining species, we found that the proposed protected area network contains just 13?±?7% of the total modelled habitat of the endemic species. For eight endemic species?>?25% of the suitable habitat is degraded. Model analysis indicated that elevation and temperature seasonality are the most important drivers of endemism. Based on a gap analysis the inclusion of high elevation areas of Trinidad’s Northern Range in the proposed protected area network would expand the coverage to include?>?25% of the total modelled habitat of the endemic species, thus greatly increasing the long-term sustainability of the endemic species populations.     

Assessment of Habitat Fragmentation and Corridors for an Isolated Subspecies of the Sichuan Golden Snub-Nosed Monkey, <Emphasis Type="Italic">Rhinopithecus roxellana hubeiensis</Emphasis>

Understanding habitat quality and landscape connectivity and exploring corridors connecting habitat patches are crucial for conservation, particularly for species distributed among isolated populations. The Sichuan golden snub-nosed monkey, Rhinopithecus roxellana, is an Endangered primate species endemic to mountainous forests in China. Its easternmost distribution lies in the Shennongjia area, which harbors an isolated subspecies, R. roxellana hubeiensis. Unfortunately, it has experienced significant habitat loss, fragmentation, and dramatic population decline in recent decades, primarily due to increased human disturbance. To quantify habitat quality, identify suitable habitat patches, and detect possible linkages among these patches for R. roxellana hubeiensis, we conducted habitat suitability assessments and landscape connectivity analyses in the Shennongjia area based on a set of environmental factors. We created a habitat quality model and a movement cost surface for the Shennongjia area based on a habitat suitability index, graph theory, expert knowledge, field experience, and information from the literature. Our results show that suitable habitat for R. roxellana hubeiensis in Shennongjia is fragmented and limited, and that this is particularly true for highly suitable habitats. We detected six core habitat patches and six least-cost paths and corridors. Our study does not provide accurate distributions of the monkeys and their habitat use. However, it identifies the most feasible and traversable habitats and corridors, which should be conservation priorities for this subspecies, and provides valuable guidance for reevaluating habitat conservation plans.     

Reptiles Under the Conservation Umbrella of the Greater Sage-Grouse

In conservation paradigms, management actions for umbrella species also benefit co-occurring species because of overlapping ranges and similar habitat associations. The greater sage-grouse (Centrocercus urophasianus) is an umbrella species because it occurs across vast sagebrush ecosystems of western North America and is the recipient of extensive habitat conservation and restoration efforts that might benefit sympatric species. Biologists' understanding of how non-target species might benefit from sage-grouse conservation is, however, limited. Reptiles, in particular, are of interest in this regard because of their relatively high diversity in shrublands and grasslands where sage-grouse are found. Using spatial overlap of species distributions, land cover similarity statistics, and a literature review, we quantified which reptile species may benefit from the protection of intact sage-grouse habitat and which may be affected by recent (since about 1990) habitat restoration actions targeting sage-grouse. Of 190 reptile species in the United States and Canadian provinces where greater sage-grouse occur, 70 (37%) occur within the range of the bird. Of these 70 species, about a third (11 snake and 11 lizard species) have >10% of their distribution area within the sage-grouse range. Land cover similarity indices revealed that 14 of the 22 species (8 snake and 6 lizard species) had relatively similar land cover associations to those of sage-grouse, suggesting greater potential to be protected under the sage-grouse conservation umbrella and greater potential to be affected, either positively or negatively, by habitat management actions intended for sage-grouse. Conversely, the remaining 8 species are less likely to be protected because of less overlap with sage-grouse habitat and thus uncertain effects of sage-grouse habitat management actions. Our analyses of treatment databases indicated that from 1990 to 2014 there were at least 6,400 treatments implemented on public land that covered approximately 4 million ha within the range of the sage-grouse and, of that, >1.5 million ha were intended to at least partially benefit sage-grouse. Whereas our results suggest that conservation of intact sagebrush vegetation communities could benefit ≥14 reptiles, a greater number than previously estimated, additional research on each species' response to habitat restoration actions is needed to assess broader claims of multi-taxa benefits when it comes to manipulative sage-grouse habitat management. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.     

Old concepts,new challenges: adapting landscape-scale conservation to the twenty-first century

Landscape-scale approaches to conservation stem largely from the classic ideas of reserve design: encouraging bigger and more sites, enhancing connectivity among sites, and improving habitat quality. Trade-offs are imposed between these four strategies by the limited resources and opportunities available for conservation programmes, including the establishment and management of protected areas, and wildlife-friendly farming and forestry. Although debate regarding trade-offs between the size, number, connectivity and quality of protected areas was prevalent in the 1970–1990s, the implications of the same trade-offs for ongoing conservation responses to threats from accelerating environmental change have rarely been addressed. Here, we reassess the implications of reserve design theory for landscape-scale conservation, and present a blueprint to help practitioners to prioritise among the four strategies. We consider the new perspectives placed on landscape-scale conservation programmes by twenty-first century pressures including climate change, invasive species and the need to marry food security with biodiversity conservation. A framework of the situations under which available theory and evidence recommend that each of the four strategies be prioritized is provided, seeking to increase the clarity required for urgent conservation decision-making.     

The Use of Habitat Models in Conservation of Rare and Endangered Leafhopper Species (Hemiptera,Auchenorrhyncha)

For conservation of Auchenorrhyncha species, knowledge of their habitat requirements is essential. However, for most species there is no ‘quantitative’ knowledge that would allow e.g. spatially explicit predictions. Such predictions can be made by habitat models, which quantify the relationship between the environment and the occurrence of species. In two plot-based case studies – the endangered leafhopper Verdanus bensoni in mountainous grasslands and four endangered Auchenorrhyncha in urban brownfields – we used habitat models to quantify the habitat requirements of these five species and to exemplify their use for creating habitat suitability maps. In the first case study, the multivariate model showed that occurrence probabilities of the leafhopper V. bensoni increase with both decreasing nitrogen indicator values and decreasing tree cover. On urban brownfields, successional age was a driving factor for species’ occurrence. Site age largely determines a range of vegetation characteristics, which, in multivariate models, often replaced the variable age. Internal validation showed the robustness of all models. The models allow predictions of habitat quality under different management regimes (e.g. response to fertilization or abandonment for V. bensoni or to different turnover rates on brownfield sites). We discuss the application of habitat models in the conservation of Auchenorrhyncha, especially the use of habitat suitability maps.     

Yet Another Empty Forest: Considering the Conservation Value of a Recently Established Tropical Nature Reserve

The primary approach used to conserve tropical biodiversity is in the establishment of protected areas. However, many tropical nature reserves are performing poorly and interventions in the broader landscape may be essential for conserving biodiversity both within reserves and at large. Between October 2010 and 2012, we conducted bird surveys in and around a recently established nature reserve in Xishuangbanna, China. We constructed a checklist of observed species, previously recorded species, and species inferred to have occurred in the area from their distributions and habitat requirements. In addition, we assessed variation in community composition and habitat specificity at a landscape-scale. Despite the fact that the landscape supports a large area of natural forest habitat (~50,000 ha), we estimate that >40% of the bird fauna has been extirpated and abundant evidence suggests hunting is the primary cause. A large proportion (52%) of the bigger birds (>20 cm) were extirpated and for large birds there was a U-shaped relationship between habitat breadth and extirpation probability. Habitat specificity was low and bird communities were dominated by widespread species of limited conservation concern. We question whether extending tropical protected area networks will deliver desired conservation gains, unless much greater effort is channeled into addressing the hunting problem both within existing protected areas and in the broader landscape.     

Habitat suitability of Rhincodon typus in three localities of the Gulf of California: Environmental drivers of seasonal aggregations

The whale shark is an endangered species that usually feeds in coastal areas of highly productive seas such as the Gulf of California, Mexico. This study aims to describe the effect of sea surface temperature, chlorophyll a, bathymetry and slope on the habitat suitability of whale sharks in three important aggregation sites of the Gulf of California. A total of 2396 records of occurrence of whale sharks were obtained from international databases and scientific literature between 1996 and 2018. These records were used for the creation of a species distribution model using MaxEnt for each of the three aggregation sites. The concentration of chlorophyll a explained 71% of the habitat suitability, followed by bathymetry and slope with a combined 17%, and sea surface temperature constituting 10% of the model. Habitat suitability was related to areas where nontargeted fisheries may impact whale sharks through bycatch, entanglement and ship strikes. The implications for the conservation of whale sharks should be considered for management decisions in terms of marine protected areas, fishing refugees or bans, and other regulations regarding fisheries activities.     

Distribution of medium- to large-sized African mammals based on habitat suitability models

The knowledge of the areas inhabited by a species within its distribution range and the connections among patches are critical pieces of information for successful conservation actions. The internal structure of the extent of occurrence (EO) of a species is almost always unknown, even for “well-known” flagship species. We developed a methodology to infer the area of occupancy (AO) within the EO of a species using the limited available data. We present here the results of a three years project funded by European Union to develop high-resolution models of habitat suitability for 281 medium- to large-sized African mammals across the whole continent. The existing literature was reviewed and all data on the geographic distribution and environmental preferences of the selected species were collected. For each species, these data were then expressed in terms of key variables available as GIS layers at a resolution of 1 km² over the entire African continent. The AO of each species was obtained merging the information on the ecological needs of the species and the values of ecological variables over the region identified as EO. The habitat suitability models were evaluated through direct field work in four countries (Morocco, Cameroon, Uganda, Botswana) chosen as representatives of the environmental and species diversity of Africa. More than 81% of models had positive true skill statistics (TSS) values, indicating models performing better than random. Rigorous modeling procedures supported by ad-hoc field evaluation allowed the production of high-resolution habitat suitability models useful for conservation applications.     

Species Distribution Modelling predicts habitat suitability and reduction of suitable habitat under future climatic scenario for Sclerophrys perreti: A critically endangered Nigerian endemic toad

Sclerophrys perreti is a critically endangered Nigerian native frog currently imperilled by human activities. A better understanding of its potential distribution and habitat suitability will aid in conservation; however, such knowledge is limited for S. perreti. Herein, we used a species distribution model (SDM) approach with all known occurrence data (n = 22) from our field surveys and primary literature, and environmental variable predictors (19 bioclimatic variables, elevation and land cover) to elucidate habitat suitability and impact of climate change on this species. The SDM showed that temperature and precipitation were the predictors of habitat suitability for S. perreti with precipitation seasonality as the strongest predictor of habitat suitability. The following variable also had a significant effect on habitat suitability: temperature seasonality, temperature annual range, precipitation of driest month, mean temperature of wettest quarter and isothermality. The model predicted current suitable habitat for S. perreti covering an area of 1,115 km². However, this habitat is predicted to experience 60% reduction by 2050 owing to changes in temperature and precipitation. SDM also showed that suitable habitat exists in south-eastern range of the inselberg with predicted low impact of climate change compared to other ranges. Therefore, this study recommends improved conservation measures through collaborations and stakeholder's meeting with local farmers for the management and protection of S. perreti.     

Assessing the effectiveness of protected areas: paradoxes call for pluralism in evaluating conservation performance

Aim  To highlight and examine apparent paradoxes in assessing the effectiveness of different forms of land-use for biodiversity conservation.
Location  Tanzania.
Methods  We compare and contrast the findings of two recent and seemingly conflicting studies on the effectiveness of conservation protection strategies in Tanzania. We evaluate these studies in the context of a wider body of evidence relating to the problem of determining protected area performance.
Results  We highlight the importance of landscape-scale management approaches for biodiversity conservation; establishing clear management and monitoring objectives in advance; the interrelation between the choice of target species and the appropriate spatial scale over which to measure their fate; and differences between snapshot and longitudinal scales in assessing the effectiveness of conservation strategies.
Main conclusions  Protected area assessments should not promote an isolated focus on particular conservation targets or methods of monitoring and evaluating the effectiveness of conservation strategies. Instead we argue for a more pluralistic approach to evaluating conservation performance that can help to reveal where potential synergies in tackling different objectives exist, and clarifying the trade-offs when they do not.     

Assessing habitat suitability for tiger in the fragmented Terai Arc Landscape of India and Nepal

Tiger Panthera tigris populations have declined dramatically in the Terai Arc Landscape (TAL; India and Nepal), and remaining populations are highly fragmented and endangered. As part of a research program to aid tiger management by identifying critical areas for conservation, we aimed to 1) identify the factors which affect the distribution of tigers in the TAL; 2) explore the role of spatial scale in habitat selection; 3) map potentially suitable habitats; and 4) assess the quality of potential corridors linking suitable habitats. We used an approach based on presence and pseudo‐absence data, combining ecological niche factor analysis and generalized linear models. We used an information‐theoretic approach to compare our data on tiger presence with different hypotheses on tiger habitat selection (i.e. protective habitat, prey species, human disturbance), and spatial scales. All hypotheses yielded models with high prediction accuracy (>79%). The most parsimonious model included variables characterizing habitat suitability of the 2 main prey species. More detailed assessment of potentially suitable areas using an extended source‐sink approach suggested that most of the habitats outside the protected areas were attractive sink‐like habitats (i.e. they suffered high levels of human disturbance in otherwise good habitats). Overall, 24% (ca 18 500 km²) of the study area was predicted as suitable (probability cut‐off p>0.5), approximately 7% of which is under protection. Our models showed that protecting the remaining concentrations of tigers requires focusing management efforts on specific areas outside the currently protected areas. These are characterized by good natural suitability; however, they suffer from a high level of human disturbance. Our models underscore the importance of minimizing human disturbances in these areas to avoid that they act as attractive sinks but act as corridors between existing subpopulations.     

A framework for assessing the biodiversity and fishery aspects of marine reserves

1.  Resource management agencies are often charged with managing natural resources for economic and social goals, while also protecting and conserving biodiversity and ecosystem function. However, this may not always be possible. Ecosystem-based management is frequently suggested as a way to achieve multiple objectives in resource management and requires that trade-offs among conflicting objectives be identified and an effective means to utilize these trade-offs developed.
2.  We examine the relationship between area and species richness in a diverse assemblage of fishes along the US West Coast and then use parameters from this relationship as input for a model that considers trade-offs between fisheries yield and the number of species protected by different management strategies.
3.  The species–area relationship ( S  =  cA ^z ) for fishes along the US Pacific coast is well described by the relationship S  =   16·18 A ^0·226.
4.  There are nearly linear trade-offs between diversity and yield when fishing effort is low. However, the trade-offs become nonlinear as fishing effort increases and imposing MPAs increases both the conservation and fisheries value of the system when the system is overfished.
5.   Synthesis and applications . Solving conflicts between fisheries and conservation requires attention as to how conservation benefits accrue as fishing effort is reduced. However, scientists often lack quantitative information about the trade-offs inherent in human activities such as fisheries. The approach we develop here can begin to help frame the questions to be posed and evaluate the likely consequences of different management options.