Browsing by Subject "Threatened species"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Open Access Can the Endangered Species Act Keep the Polar Bear (Ursus maritimus) Out of Hot Water?(2007-05) Bolen, Ellen E.On December 27, 2006 the Fish and Wildlife Service (FWS) announced their support for listing the polar bear (Ursus maritimus) as a threatened species under the Endangered Species Act (ESA). The polar bear met two of the five listing criteria: (1) decline of the population throughout all or part of its range; and (2) lack of adequate regulatory mechanisms. The notice identified global climate change as the primary cause for population decline. FWS concluded that current laws are adequate to protect the polar bear from short-term direct impacts, but the listing under the ESA is needed to address impacts from climate change; a long-term, indirect threat. The polar bear is the first proposed listing with such diffuse and poorly defined harms. Given the nature of this threat, can the ESA protect the polar bear from global climate change? To answer this question I examined case studies of other species listed, past implementation of the ESA, and the establishment of proximate causation. I also reviewed how Section seven of the ESA might be implemented to address global climate change. The ESA is successful when ‘takers’ can be readily identified, and when the harms are easily managed. ‘Takes’ due to global warming are difficult to identify due to the number of emitters and differentiating between natural and anthropogenic sources. Additionally, it will be difficult to establish the proximate causation needed to assess harms. I conclude that it is unlikely that the listing alone will be able to save the polar bear.Item Open Access The size of savannah Africa: A lion's (Panthera leo) view(Biodiversity and Conservation, 2013-01-01) Riggio, Jason; Jacobson, Andrew; Dollar, Luke; Bauer, Hans; Becker, Matt; Dickman, Amy; Funston, Paul; Groom, Rosemary; Henschel, Philipp; de Iongh, Hans; Lichtenfeld, Laly; Pimm, StuartWe define African savannahs as being those areas that receive between 300 and 1,500 mm of rain annually. This broad definition encompasses a variety of habitats. Thus defined, savannahs comprise 13.5 million km2 and encompass most of the present range of the African lion (Panthera leo). Dense human populations and extensive conversion of land to human use preclude use by lions. Using high-resolution satellite imagery and human population density data we define lion areas, places that likely have resident lion populations. In 1960, 11.9 million km2 of these savannahs had fewer than 25 people per km2. The comparable area shrank to 9.7 million km2 by 2000. Areas of savannah Africa with few people have shrunk considerably in the last 50 years and human population projections suggest they will likely shrink significantly in the next 40. The current extent of free-ranging lion populations is 3.4 million km2 or about 25 % of savannah area. Habitats across this area are fragmented; all available data indicate that between 32,000 and 35,000 free-ranging lions live in 67 lion areas. Although these numbers are similar to previous estimates, they are geographically more comprehensive. There is abundant evidence of widespread declines and local extinctions. Under the criteria we outline, ten lion areas qualify as lion strongholds: four in East Africa and six in Southern Africa. Approximately 24,000 lions are in strongholds, with an additional 4,000 in potential ones. However, over 6,000 lions are in populations of doubtful long-term viability. Lion populations in West and Central Africa are acutely threatened with many recent, local extinctions even in nominally protected areas. © 2012 The Author(s).Item Open Access Use of Site Occupancy Modeling to Delineate a Jaguar Corridor in Southern Belize(2010-04-28T20:08:08Z) Petracca, Lisanne S.This analysis, a component of Panthera's Jaguar Corridor Initiative, incorporated 184 interviews with local hunters and farmers in a site occupancy framework to determine the likelihood of jaguar and jaguar prey occupancy in 90 16-km2 grid cells in the Toledo District of southern Belize. This output was compared with that of Maxent, a presence-only species distribution modeling technique, to determine if both approaches led to similar conclusions. Site occupancy analysis revealed that jaguar occupancy was associated with percent daily chance of seeing armadillo, higher elevation, and proximity to protected areas and forest cover. Prey species analysis revealed that likelihood of white-lipped peccary (Pecari tajacu) occupancy was associated with greater forest cover and proximity to protected areas and water/wetlands; collared peccary (Tayassu pecari) occupancy with greater forest cover and proximity to agriculture and settlements; red brocket deer (Mazama americana) occupancy with greater forest cover, proximity to agriculture, and higher elevation; and armadillo (Dasypus novemcinctus) occupancy with greater agricultural area, lower elevation, and greater distance from water/wetland. Site occupancy models were unable to be fitted for the paca (Agouti paca) and white-tailed deer (Odocoileus virginianus) populations. Following the weighting of jaguar output to 2.0 and prey species output to 1.0, total Psi (probability of occupancy) was calculated for each of the 90 grid cells. Cells with the maximum possible Psi value (meaning that the jaguar and all modeled prey species were present) were identified, and the final cells were chosen from this subset based on having relatively low future threat. These cells were cross-checked with Maxent output to ensure that the corridor contained areas of high habitat suitability. The proposed corridor extends along the eastern flank of the Toledo District and connects Sarstoon-Temash National Park with the protected areas of local NGOs TIDE (Toledo Institute for Development and Environment) and YCT (Ya’axche Conservation Trust). The analysis concludes with recommendations and concerns specific to the communities that fall within the corridor.