Troy Merrill - Academia.edu (original) (raw)

Papers by Troy Merrill

Ursus, Apr 1, 2004

We used a broad-scale model based on observations of grizzly bears (Ursus arctos) or their sign, ... more We used a broad-scale model based on observations of grizzly bears (Ursus arctos) or their sign, calibrated to reported putative death rate, to appraise current habitat conditions in the Cabinet-Yaak region of Montana. Habitat capability (i.e., potential grizzly bear densities) and regional human population sizes had the greatest effects in this model. We predicted the effects of (1) human population increases (+150% anticipated by 2023), (2) changes in lethality of humans (i.e., the probability that a human would kill a bear given an encounter), and (3) differences in the ratio of unknown to known bear deaths on the extent and location of potential source areas. We predicted densities of 1.0 and 2.1 grizzly bears/100 km2 with and without human impacts, respectively. Under our baseline scenario (3% sustainable mortality and 1:1 ratio of unknown to known bear deaths), we predicted that 2 source areas totaling 9,156 km2 and potentially supporting 123 bears occurred in our study area. With projected human population increases, potential source areas and bear populations declined by 33% and 45%, respectively. A spatially uniform increase of 1% in annual death rate (as a surrogate for increased human lethality) reduced potential source areas and bear numbers by 41% and 36%. Source areas and bear numbers declined by 39% and 34% if the ratio of unknown to known grizzly bear deaths was 2:1 versus 1:1. We obtained the best match with current population estimates (about 35 bears) assuming a 2:1 ratio of unknown to known deaths and a very low sustainable death rate of 2%. This implies either high levels of illegal human-caused mortality and low birth and recruitment rates or a population smaller than currently estimated. We conclude that human numbers and human lethality will likely govern the fate of grizzly bears in this region.

Conservation Biology, 1996

Large carnivores need large areas of relatively wild habitat, which makes their conservation chal... more Large carnivores need large areas of relatively wild habitat, which makes their conservation challenging. These species play important ecological roles and in some cases may qualify as keystone species. Although the ability of carnivores to control prey numbers varies according to many factors and often is effective only in the short term, the indirect effects of carnivores on community structure and diversity can be great. Perhaps just as important is the role of carnivores as umbrella species (i.e., species whose habitat area requirements encompass the habitats of many other species). Conservation areas large enough to support populations of large carnivores are likely to include many other species and natural communities, especially in regions such as the Rocky Mountains of Canada and the United States that have relatively low endemism. For example, a plan for recovery of grizzly bears (Ursus arctos) proposed by Shaffer (1992) covers, in part, 34% of the state of Idaho (compared to 8% covered by a U.S. Fish and Wildlife Service proposal) and would capture 10% or more of the statewide ranges of 71% of the mammal species, 67% of the birds, 61% of the am-phibian& but only 27% of the reptiles native to Idaho. Two-thirds (67%) of the vegetation types in Idaho would have 10% or more of their statewide area included in the Shaffer plan. The U.S. Fish and Wildlife Service recovery zones provide a much poorer umbrella. The umbrella functions of large carnivores are expected to be poorer in regions with high endemism. The application of metapopulation concepts to large carnivore conservation has led to proposals for regional reserve networks composed of wilderness core areas, multipleuse buffer zones, and some form of connectivity. The exceptional vagiltty of most large carnivores makes such networks feasible in a region with low human population density, such as the Rocky Mountains, but mortality risks still need to be addressed. Roads are a major threat to carnivore recovery because of barrier effects, vehicle collisions, and increased accessibility of wild areas to poachers. Development, especially for tourism, is also becoming a threat in many parts of the region. Biologia de la Conservaci6n y Conservacion de Carnivoros en las Montafias Rocallosas Resumen: Los carn#voros mayores requieren de extensas dreas de hdbitat relativamente natural, lo cual hace de su conservaci6n un reto. Estas especies juegan un papel ecol6gico importante y pueden, en algunos casos, ser consideradas como especies clave. Aunque la capacidad de los carnivoros para controlar la abundancia de sus presas varia en funci6n de numerosos factores y a menudo solo es a corto plazo, los efectos indirectos de los carnivoros sobre la estructura y diversldad de la comunldad pueden ser grandes. Posiblemente igual importancia tiene el papel de los carniivoros como especies sombriila (i.e., especies cuyos requerimientos de extensi6n del hdbitat comprenden los hdbitats de muchas otras especies). Es probable que dreas de con-servaci6n suficientemente grandes para mantener poblaciones de carnivoros mayores incluyan muchas otras especies y comunidades naturales, especialmente en regiones con endemismo relativamente bajo, tal como las Monta~as Rocallosas. Por ejemplo, un plan de recuperaci6n de osos pardos (UrSus arctos) propuesto por Schaffer (1992) abarca, en parte, el 34% del estado de Idaho (comparado con el 8% del Servicio de Pesca

Environmental Management, 1995

/ Legally designated wilderness areas are acknowledged to be an important element in strategies t... more / Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in the United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious. Criteria for establishment have typically been associated with opportunity and aesthetic and experiential values. Biological data have not normally played a major role in guiding wilderness establishment. We present four wilderness allocation options for those public lands considered suitable for wilderness designation in Idaho. These options cover the span of choices presently available to wilderness planners in the state and range from not establishing any new wilderness areas to the inclusion of all suitable lands in wilderness. All options are evaluated using spatial biological data from the National Biological Survey's Gap Analysis Project. A conservation strategy that would protect a minimum of 10% of the area occupied by each of 113 native vegetation types and at a minimum 10% of the distribution of each of 368 vertebrate species was evaluated for each option. Only the inclusion of all suitable lands in wilderness, creating a system of 5.1 million ha came close to achieving these goals, protecting 65% of the vegetation types and 56% of the vertebrate species. We feel this approach, which allows planners to evaluate the ecological merits of proposed wilderness units along with other values, can provide a means to resolve the impasse over additional wilderness designation in Idaho.

There have been many attempts to classify geographic areas into zones of similar characteristics.... more There have been many attempts to classify geographic areas into zones of similar characteristics. Recent focus has been on ecoregions. We examined how well the boundaries of the most commonly used ecoregion classi®cations for the US matched the boundaries of existing vegetation cover mapped at three levels of classi®cation, ®ne, mid-and coarse scale. We analyzed ecoregions in Idaho, Oregon and Washington. The results were similar among the two ecoregion classi®cations. For both ecoregion delineations and all three vegetation classi®cations, the patterns of existing vegetation did not correspond well with the patterns of ecoregions. Most vegetation types had a small proportion of their total area in a given ecoregion. There was also no dominance by one or more vegetation types in any ecoregion and contrary to our hypothesis, the level of congruence of vegetation patterns with ecoregion boundaries decreased as the level of classi®cation became more general. The implications of these ®...

Conservation Biology, 2002

We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribili... more We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribilis) in 1850 and their extirpation during 1850-1920 and 1920-1970 in the contiguous United States. We used autologistic regression to describe relations between grizzly bear range in 1850, 1920, and 1970 and potential explanatory factors specified for a comprehensive grid of cells, each 900 km 2 in size. We also related persistence, 1920-1970, to range size and shape. Grizzly bear range in 1850 was positively related to occurrence in mountainous ecoregions and the ranges of oaks (Quercus spp.), piñon pines (Pinus edulis and P. monophylla), whitebark pine (P. albicaulis), and bison (Bos bison) and negatively related to occurrence in prairie and hot desert ecoregions. Relations with salmon (Oncorynchus spp.) range and human factors were complex. Persistence of grizzly bear range, 1850-1970, was positively related to occurrence in the Rocky Mountains, whitebark pine range, and local size of grizzly bear range at the beginning of each period, and negatively related to number of humans and the ranges of bison, salmon, and piñon pines. We speculate that foods affected persistence primarily by influencing the frequency of contact between humans and bears. With respect to current conservation, grizzly bears survived from 1920 to 1970 most often where ranges at the beginning of this period were either larger than 20,000 km 2 or larger than 7,000 km 2 but with a ratio of perimeter to area of Ͻ 2. Without reductions in human lethality after 1970, there would have been no chance that core grizzly bear range would be as extensive as it is now. Although grizzly bear range in the Yellowstone region is currently the most robust of any to potential future increases in human lethality, bears in this region are threatened by the loss of whitebark pine.

Conservation Biology, 2002

We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribili... more We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribilis) in 1850 and their extirpation during 1850-1920 and 1920-1970 in the contiguous United States. We used autologistic regression to describe relations between grizzly bear range in 1850, 1920, and 1970 and potential explanatory factors specified for a comprehensive grid of cells, each 900 km 2 in size. We also related persistence, 1920-1970, to range size and shape. Grizzly bear range in 1850 was positively related to occurrence in mountainous ecoregions and the ranges of oaks (Quercus spp.), piñon pines (Pinus edulis and P. monophylla), whitebark pine (P. albicaulis), and bison (Bos bison) and negatively related to occurrence in prairie and hot desert ecoregions. Relations with salmon (Oncorynchus spp.) range and human factors were complex. Persistence of grizzly bear range, 1850-1970, was positively related to occurrence in the Rocky Mountains, whitebark pine range, and local size of grizzly bear range at the beginning of each period, and negatively related to number of humans and the ranges of bison, salmon, and piñon pines. We speculate that foods affected persistence primarily by influencing the frequency of contact between humans and bears. With respect to current conservation, grizzly bears survived from 1920 to 1970 most often where ranges at the beginning of this period were either larger than 20,000 km 2 or larger than 7,000 km 2 but with a ratio of perimeter to area of Ͻ 2. Without reductions in human lethality after 1970, there would have been no chance that core grizzly bear range would be as extensive as it is now. Although grizzly bear range in the Yellowstone region is currently the most robust of any to potential future increases in human lethality, bears in this region are threatened by the loss of whitebark pine.

Biological Conservation, 1999

Informed management of large carnivores depends on the timely and useful presentation of relevant... more Informed management of large carnivores depends on the timely and useful presentation of relevant information. We describe an approach to evaluating carnivore habitat that uses pre-existing qualitative and quantitative information on humans and carnivores to generate coarse-scale maps of habitat suitability, habitat productivity, potential reserves, and areas of potential con¯ict. We use information pertinent to the contemplated reintroduction of grizzly bears Ursus arctos horribilis into central Idaho to demonstrate our approach. The approach uses measures of human numbers, their estimated distribution, road and trail access, and abundance and quality of bear foods to create standardized indices that are analogues of death and birth rates, respectively; the ®rst subtracted from the second indicates habitat suitability (HS). We calibrate HS to sightings of grizzly bears in two ecosystems in northern Idaho and develop an empirical model from these same sightings based on piece-wise treatment of the variables contained in HS. Depending on whether the empirical model or HS is used, we estimate that there is 14 800 km 2 of suitable habitat in two blocks or 37 100 km 2 in one block in central Idaho, respectively. Both approaches show suitable habitat in the current Evaluation Area and in an area of southeastern Idaho centered on the Palisades Reservoir. Areas of highly productive habitat are concentrated in northern and western Idaho and in the Palisades area. Future con¯icts between humans and bears are most likely to occur on the western and northern margins of suitable habitat in central Idaho, rather than to the east, where opposition to reintroduction of grizzly bears is currently strongest.

Environmental Management, 1995

Legally designated wilderness areas are acknowledged to be an important element in strategies to ... more Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in the United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious.

Environ Manage, 1995

Legally designated wilderness areas are acknowledged to be an important element in strategies to ... more Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious. Criteria for establishment have typically been associated with opportunity and aesthetic and experiential values. Biological data have not normally played a major role in guiding wilderness establishment. We present four wilderness allocation options for those public lands considered suitable for wilderness designation in Idaho. These options cover the span of choices presently available to wilderness planners in the state and range from not establishing any new wilderness areas to the inclusion of all suitable lands in wilderness. All options are evaluated using spatial biological data from the National Biological Survey's Gap Analysis Project. A conservation strategy that would protect a minimum of 10% of the area occupied by each of 113 native vegetation types and at a minimum 10% of the distribution of each of 368 vertebrate species was evaluated for each option. Only the inclusion of all suitable lands in wilderness, creating a system of 5.1 million ha came close to achieving these goals, protecting 65% of the vegetation types and 56% of the vertebrate species. We feel this approach, which allows planners to evaluate the ecological merits of proposed widerness units along with other values, can provide a means to resolve the impasse over additional wilderness designation in Idaho.

Ursus, Apr 1, 2004

We used a broad-scale model based on observations of grizzly bears (Ursus arctos) or their sign, ... more We used a broad-scale model based on observations of grizzly bears (Ursus arctos) or their sign, calibrated to reported putative death rate, to appraise current habitat conditions in the Cabinet-Yaak region of Montana. Habitat capability (i.e., potential grizzly bear densities) and regional human population sizes had the greatest effects in this model. We predicted the effects of (1) human population increases (+150% anticipated by 2023), (2) changes in lethality of humans (i.e., the probability that a human would kill a bear given an encounter), and (3) differences in the ratio of unknown to known bear deaths on the extent and location of potential source areas. We predicted densities of 1.0 and 2.1 grizzly bears/100 km2 with and without human impacts, respectively. Under our baseline scenario (3% sustainable mortality and 1:1 ratio of unknown to known bear deaths), we predicted that 2 source areas totaling 9,156 km2 and potentially supporting 123 bears occurred in our study area. With projected human population increases, potential source areas and bear populations declined by 33% and 45%, respectively. A spatially uniform increase of 1% in annual death rate (as a surrogate for increased human lethality) reduced potential source areas and bear numbers by 41% and 36%. Source areas and bear numbers declined by 39% and 34% if the ratio of unknown to known grizzly bear deaths was 2:1 versus 1:1. We obtained the best match with current population estimates (about 35 bears) assuming a 2:1 ratio of unknown to known deaths and a very low sustainable death rate of 2%. This implies either high levels of illegal human-caused mortality and low birth and recruitment rates or a population smaller than currently estimated. We conclude that human numbers and human lethality will likely govern the fate of grizzly bears in this region.

Conservation Biology, 1996

Large carnivores need large areas of relatively wild habitat, which makes their conservation chal... more Large carnivores need large areas of relatively wild habitat, which makes their conservation challenging. These species play important ecological roles and in some cases may qualify as keystone species. Although the ability of carnivores to control prey numbers varies according to many factors and often is effective only in the short term, the indirect effects of carnivores on community structure and diversity can be great. Perhaps just as important is the role of carnivores as umbrella species (i.e., species whose habitat area requirements encompass the habitats of many other species). Conservation areas large enough to support populations of large carnivores are likely to include many other species and natural communities, especially in regions such as the Rocky Mountains of Canada and the United States that have relatively low endemism. For example, a plan for recovery of grizzly bears (Ursus arctos) proposed by Shaffer (1992) covers, in part, 34% of the state of Idaho (compared to 8% covered by a U.S. Fish and Wildlife Service proposal) and would capture 10% or more of the statewide ranges of 71% of the mammal species, 67% of the birds, 61% of the am-phibian& but only 27% of the reptiles native to Idaho. Two-thirds (67%) of the vegetation types in Idaho would have 10% or more of their statewide area included in the Shaffer plan. The U.S. Fish and Wildlife Service recovery zones provide a much poorer umbrella. The umbrella functions of large carnivores are expected to be poorer in regions with high endemism. The application of metapopulation concepts to large carnivore conservation has led to proposals for regional reserve networks composed of wilderness core areas, multipleuse buffer zones, and some form of connectivity. The exceptional vagiltty of most large carnivores makes such networks feasible in a region with low human population density, such as the Rocky Mountains, but mortality risks still need to be addressed. Roads are a major threat to carnivore recovery because of barrier effects, vehicle collisions, and increased accessibility of wild areas to poachers. Development, especially for tourism, is also becoming a threat in many parts of the region. Biologia de la Conservaci6n y Conservacion de Carnivoros en las Montafias Rocallosas Resumen: Los carn#voros mayores requieren de extensas dreas de hdbitat relativamente natural, lo cual hace de su conservaci6n un reto. Estas especies juegan un papel ecol6gico importante y pueden, en algunos casos, ser consideradas como especies clave. Aunque la capacidad de los carnivoros para controlar la abundancia de sus presas varia en funci6n de numerosos factores y a menudo solo es a corto plazo, los efectos indirectos de los carnivoros sobre la estructura y diversldad de la comunldad pueden ser grandes. Posiblemente igual importancia tiene el papel de los carniivoros como especies sombriila (i.e., especies cuyos requerimientos de extensi6n del hdbitat comprenden los hdbitats de muchas otras especies). Es probable que dreas de con-servaci6n suficientemente grandes para mantener poblaciones de carnivoros mayores incluyan muchas otras especies y comunidades naturales, especialmente en regiones con endemismo relativamente bajo, tal como las Monta~as Rocallosas. Por ejemplo, un plan de recuperaci6n de osos pardos (UrSus arctos) propuesto por Schaffer (1992) abarca, en parte, el 34% del estado de Idaho (comparado con el 8% del Servicio de Pesca

Environmental Management, 1995

/ Legally designated wilderness areas are acknowledged to be an important element in strategies t... more / Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in the United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious. Criteria for establishment have typically been associated with opportunity and aesthetic and experiential values. Biological data have not normally played a major role in guiding wilderness establishment. We present four wilderness allocation options for those public lands considered suitable for wilderness designation in Idaho. These options cover the span of choices presently available to wilderness planners in the state and range from not establishing any new wilderness areas to the inclusion of all suitable lands in wilderness. All options are evaluated using spatial biological data from the National Biological Survey's Gap Analysis Project. A conservation strategy that would protect a minimum of 10% of the area occupied by each of 113 native vegetation types and at a minimum 10% of the distribution of each of 368 vertebrate species was evaluated for each option. Only the inclusion of all suitable lands in wilderness, creating a system of 5.1 million ha came close to achieving these goals, protecting 65% of the vegetation types and 56% of the vertebrate species. We feel this approach, which allows planners to evaluate the ecological merits of proposed wilderness units along with other values, can provide a means to resolve the impasse over additional wilderness designation in Idaho.

There have been many attempts to classify geographic areas into zones of similar characteristics.... more There have been many attempts to classify geographic areas into zones of similar characteristics. Recent focus has been on ecoregions. We examined how well the boundaries of the most commonly used ecoregion classi®cations for the US matched the boundaries of existing vegetation cover mapped at three levels of classi®cation, ®ne, mid-and coarse scale. We analyzed ecoregions in Idaho, Oregon and Washington. The results were similar among the two ecoregion classi®cations. For both ecoregion delineations and all three vegetation classi®cations, the patterns of existing vegetation did not correspond well with the patterns of ecoregions. Most vegetation types had a small proportion of their total area in a given ecoregion. There was also no dominance by one or more vegetation types in any ecoregion and contrary to our hypothesis, the level of congruence of vegetation patterns with ecoregion boundaries decreased as the level of classi®cation became more general. The implications of these ®...

Conservation Biology, 2002

We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribili... more We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribilis) in 1850 and their extirpation during 1850-1920 and 1920-1970 in the contiguous United States. We used autologistic regression to describe relations between grizzly bear range in 1850, 1920, and 1970 and potential explanatory factors specified for a comprehensive grid of cells, each 900 km 2 in size. We also related persistence, 1920-1970, to range size and shape. Grizzly bear range in 1850 was positively related to occurrence in mountainous ecoregions and the ranges of oaks (Quercus spp.), piñon pines (Pinus edulis and P. monophylla), whitebark pine (P. albicaulis), and bison (Bos bison) and negatively related to occurrence in prairie and hot desert ecoregions. Relations with salmon (Oncorynchus spp.) range and human factors were complex. Persistence of grizzly bear range, 1850-1970, was positively related to occurrence in the Rocky Mountains, whitebark pine range, and local size of grizzly bear range at the beginning of each period, and negatively related to number of humans and the ranges of bison, salmon, and piñon pines. We speculate that foods affected persistence primarily by influencing the frequency of contact between humans and bears. With respect to current conservation, grizzly bears survived from 1920 to 1970 most often where ranges at the beginning of this period were either larger than 20,000 km 2 or larger than 7,000 km 2 but with a ratio of perimeter to area of Ͻ 2. Without reductions in human lethality after 1970, there would have been no chance that core grizzly bear range would be as extensive as it is now. Although grizzly bear range in the Yellowstone region is currently the most robust of any to potential future increases in human lethality, bears in this region are threatened by the loss of whitebark pine.

Conservation Biology, 2002

We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribili... more We investigated factors associated with the distribution of grizzly bears (Ursus arctos horribilis) in 1850 and their extirpation during 1850-1920 and 1920-1970 in the contiguous United States. We used autologistic regression to describe relations between grizzly bear range in 1850, 1920, and 1970 and potential explanatory factors specified for a comprehensive grid of cells, each 900 km 2 in size. We also related persistence, 1920-1970, to range size and shape. Grizzly bear range in 1850 was positively related to occurrence in mountainous ecoregions and the ranges of oaks (Quercus spp.), piñon pines (Pinus edulis and P. monophylla), whitebark pine (P. albicaulis), and bison (Bos bison) and negatively related to occurrence in prairie and hot desert ecoregions. Relations with salmon (Oncorynchus spp.) range and human factors were complex. Persistence of grizzly bear range, 1850-1970, was positively related to occurrence in the Rocky Mountains, whitebark pine range, and local size of grizzly bear range at the beginning of each period, and negatively related to number of humans and the ranges of bison, salmon, and piñon pines. We speculate that foods affected persistence primarily by influencing the frequency of contact between humans and bears. With respect to current conservation, grizzly bears survived from 1920 to 1970 most often where ranges at the beginning of this period were either larger than 20,000 km 2 or larger than 7,000 km 2 but with a ratio of perimeter to area of Ͻ 2. Without reductions in human lethality after 1970, there would have been no chance that core grizzly bear range would be as extensive as it is now. Although grizzly bear range in the Yellowstone region is currently the most robust of any to potential future increases in human lethality, bears in this region are threatened by the loss of whitebark pine.

Biological Conservation, 1999

Informed management of large carnivores depends on the timely and useful presentation of relevant... more Informed management of large carnivores depends on the timely and useful presentation of relevant information. We describe an approach to evaluating carnivore habitat that uses pre-existing qualitative and quantitative information on humans and carnivores to generate coarse-scale maps of habitat suitability, habitat productivity, potential reserves, and areas of potential con¯ict. We use information pertinent to the contemplated reintroduction of grizzly bears Ursus arctos horribilis into central Idaho to demonstrate our approach. The approach uses measures of human numbers, their estimated distribution, road and trail access, and abundance and quality of bear foods to create standardized indices that are analogues of death and birth rates, respectively; the ®rst subtracted from the second indicates habitat suitability (HS). We calibrate HS to sightings of grizzly bears in two ecosystems in northern Idaho and develop an empirical model from these same sightings based on piece-wise treatment of the variables contained in HS. Depending on whether the empirical model or HS is used, we estimate that there is 14 800 km 2 of suitable habitat in two blocks or 37 100 km 2 in one block in central Idaho, respectively. Both approaches show suitable habitat in the current Evaluation Area and in an area of southeastern Idaho centered on the Palisades Reservoir. Areas of highly productive habitat are concentrated in northern and western Idaho and in the Palisades area. Future con¯icts between humans and bears are most likely to occur on the western and northern margins of suitable habitat in central Idaho, rather than to the east, where opposition to reintroduction of grizzly bears is currently strongest.

Environmental Management, 1995

Legally designated wilderness areas are acknowledged to be an important element in strategies to ... more Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in the United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious.

Environ Manage, 1995

Legally designated wilderness areas are acknowledged to be an important element in strategies to ... more Legally designated wilderness areas are acknowledged to be an important element in strategies to conserve biological diversity in United States. However, because of the restrictions on consumptive uses in wilderness, their establishment is normally contentious. Criteria for establishment have typically been associated with opportunity and aesthetic and experiential values. Biological data have not normally played a major role in guiding wilderness establishment. We present four wilderness allocation options for those public lands considered suitable for wilderness designation in Idaho. These options cover the span of choices presently available to wilderness planners in the state and range from not establishing any new wilderness areas to the inclusion of all suitable lands in wilderness. All options are evaluated using spatial biological data from the National Biological Survey's Gap Analysis Project. A conservation strategy that would protect a minimum of 10% of the area occupied by each of 113 native vegetation types and at a minimum 10% of the distribution of each of 368 vertebrate species was evaluated for each option. Only the inclusion of all suitable lands in wilderness, creating a system of 5.1 million ha came close to achieving these goals, protecting 65% of the vegetation types and 56% of the vertebrate species. We feel this approach, which allows planners to evaluate the ecological merits of proposed widerness units along with other values, can provide a means to resolve the impasse over additional wilderness designation in Idaho.