Degree of Threat: High
Comments: USFWS (2010) summarized threats as follows (very slightly modified).
Current and future direct and functional loss of habitat due to residential and road development in all populations is the principal threat to the Gunnison sage-grouse. Other threats from human infrastructure such as fences and powerlines may not individually threaten the Gunnison sage-grouse; however, the cumulative presence of these features, particularly when considered with residential and road development, do constitute a threat to the continued existence of the Gunnison sage-grouse as they collectively contribute to habitat loss and fragmentation. These impacts exacerbate the fragmentation that has already occurred in Gunnison sagegrouse habitat from past agricultural conversion and residential development. Gunnison sage-grouse are sensitive to these forms of habitat fragmentation because they require large areas of contiguous, suitable habitat. Given the increasing human population trends in Gunnison sage-grouse habitat, we expect urban and exurban development and associated roads and infrastructure to continue to expand. Likewise, we expect direct and indirect effects from these activities, including habitat loss, degradation and fragmentation, to increase in sage-grouse habitats.
Invasive species, fire, and climate change may not individually threaten the Gunnison sage-grouse; however, the documented synergy among these factors result in a high likelihood that they will threaten the species in the future. Noxious and invasive plant incursions into sagebrush ecosystems, which are facilitated by human activities and fragmentation, are likely to increase wildfire frequencies, further contributing to direct loss of habitat and fragmentation. Climate change may alter the range of invasive plants, intensifying the proliferation of invasive plants to the point that they become a threat to the species. Recent local climatic moderations may have produced some improved habitat quality (increased forb and grass growth providing enhanced grouse productivity and survival). Habitat conservation efforts have been implemented to benefit local habitat conditions, but they have not cumulatively resulted in local population recoveries because unfragmented sagebrush habitats on the scale required that contain the necessary ecological attributes (e.g., connectivity and landscape context) have been lost. Sagebrush habitats are highly fragmented due to anthropogenic impacts, and in most cases are not resilient enough to return to native vegetative states following disturbance from fire, invasive species, and the effects of climate change. We expect these threats to continue and potentially increase in magnitude in the future.
We found no evidence that the threats summarized above, which contribute to habitat loss, degradation and fragmentation will subside within the foreseeable future. Six populations are extremely small and compromised by existing fragmentation. The one remaining relatively contiguous patch of habitat (Gunnison Basin) for the species is somewhat compromised by existing fragmentation. Based on the current and anticipated habitat threats and their cumulative effects as they contribute to the overall fragmentation of Gunnison sage-grouse habitat, we have determined that habitat-based threats pose a significant threat to the species throughout its range. We find that the present or threatened destruction, modification, or curtailment of Gunnison sage-grouse habitat is a threat to the species future existence.
We believe that existing and continued landscape fragmentation will increase the effects of predation on this species, particularly in the six smaller populations, resulting in a reduction in sage-grouse productivity and abundance in the future. Predation has a strong relationship with anthropogenic factors on the landscape, and human presence on the landscape will continue to increase in the future. We find that predation is a significant threat to the species.
West Nile virus is the only disease that currently presents a potential threat to the Gunnison sage-grouse. While we have no evidence of West Nile virus acting on the Gunnison sage-grouse, because of the virus's presence within the species' range and the continued development of anthropogenic water sources in the area, the virus may pose a future threat to the species. We have determined that disease is not currently a threat to the species. However, we anticipate that West Nile virus will persist within the range of Gunnison sage-grouse indefinitely and will be exacerbated by factors such as climate change that could increase ambient temperatures and the presence of the vector on the landscape.
An examination of regulatory mechanisms for both the Gunnison sagegrouse and sagebrush habitats revealed that while limited mechanisms exist, they are not broad enough in their potential conservation value throughout the species range, and are not being implemented consistent with our current understanding of the species' biology and reaction to disturbances, to be effective at ameliorating threats. This is particularly true on private lands, which comprise 41 percent of the species' extant range and are highly dispersed throughout all populations. Inadequate regulation of grazing practices on public land is occurring in some locations within the species' range. Public land management agencies should continue to improve habitat conditions to be compatible with Gunnison sage-grouse life-history requirements. Some local conservation efforts are effective and should be continued, but to date have occurred on a scale that is too small to remove threats at a range-wide level. Many conservation efforts lacked sufficient monitoring to demonstrate their overall effectiveness in minimizing or eliminating the primary threat of habitat loss, fragmentation, and degradation. Therefore, we find the existing regulatory mechanisms are ineffective at ameliorating habitat-based threats.
Small population size and genetic factors subject at least six of the seven populations to a high risk of extirpation from stochastic events. All populations are currently isolated as documented by low amounts of gene flow. The loss of connectivity and the concomitant isolation of the populations also increase the species' extinction risk. Fitness and population size are strongly correlated, and smaller populations are more subject to environmental and demographic stochasticity. When coupled with mortality stressors related to human activity and significant fluctuations in annual population size, long-term persistence of small populations is always problematic. Given the species' relatively low rate of growth and strong site fidelity, recovery and repopulation of extirpated, or nearly extirpated areas, will be extremely challenging. Translocation of Gunnison sage-grouse is difficult and to date has not been demonstrated to be successful in maintaining and improving population and species viability. Given the limited number of source individuals, sustainable, successful translocation efforts involving large numbers of individuals are unlikely at this time. Recent captive-rearing efforts by the Colorado Division of Wildlife (CDOW) have provided some optimistic results. Nonetheless, even assuming CDOW captive-rearing and tranlocation efforts prove to be successful in the long-term, the existing condition of the habitat throughout the species' range will need to be improved, before captive rearing and translocation can be relied on to maintain population and species viability.
The existing and continuing loss, degradation, and fragmentation of sage-grouse habitat; extremely small population sizes; occupancy of extremely small, isolated, and fragmented sagebrush areas; increased susceptibility to predation; lack of interconnectivity; low genetic diversity; and the potential for catastrophic stochastic (random) events, combined with the inadequacy of existing regulations to manage habitat loss (either direct or functional), endanger all Gunnison sage-grouse populations and the species as a whole. Although some local conservation efforts have been implemented and are effective in small areas, they are not at a scale that is sufficient to ameliorate threats to the species as a whole. Other conservation efforts (such as habitat treatments, establishment of conservation easements, improved grazing practices, additional travel management efforts that benefit Gunnison sage-grouse) are being planned, but there is substantial uncertainty as to whether, where, and when they will be implemented, and whether they will be effective.
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