The Interplay between Climate Variability and Density Dependence in the Population Viability of Chinook Salmon

Abstract:  The viability of populations is influenced by driving forces such as density dependence and climate variability, but most population viability analyses (PVAs) ignore these factors because of data limitations. Additionally, simplified PVAs produce limited measures of population viability such as annual population growth rate (λ) or extinction risk. Here we developed a "mechanistic" PVA of threatened Chinook salmon ( Oncorhynchus tshawytscha ) in which, based on 40 years of detailed data, we related freshwater recruitment of juveniles to density of spawners, and third-year survival in the ocean to monthly indices of broad-scale ocean and climate conditions. Including climate variability in the model produced important effects: estimated population viability was very sensitive to assumptions of future climate conditions and the autocorrelation contained in the climate signal increased mean population abundance while increasing probability of quasi extinction. Because of the presence of density dependence in the model, however, we could not distinguish among alternative climate scenarios through mean λ values, emphasizing the importance of considering multiple measures to elucidate population viability. Our sensitivity analyses demonstrated that the importance of particular parameters varied across models and depended on which viability measure was the response variable. The density-dependent parameter associated with freshwater recruitment was consistently the most important, regardless of viability measure, suggesting that increasing juvenile carrying capacity is important for recovery.     

Effects of Alternative Cotton Agriculture on Avian and Arthropod Populations

Abstract:  Among the major agricultural crops in the southeastern United States, cotton ( Gossypium hirsutum L.) generally provides the least suitable habitat for most early successional songbirds. Newer cropping approaches, such as use of conservation tillage and stripcover cropping, offer hope for improving the ecological value of cotton fields. We examined the effects of clover stripcover cropping with conservation tillage versus conventionally grown cotton with either conventional or conservation tillage on avian and arthropod species composition and field use in east-central Georgia. Stripcover fields had higher bird densities and biomass and higher relative abundance of arthropods than both conservation tillage and conventional fields. During migration and breeding periods, total bird densities on stripcover fields were 2–6 times and 7–20 times greater than on conservation and conventional fields, respectively. Abundance and biomass for epigeal arthropods were also greatest on stripcover fields during much of the breeding season. Although the clover treatment attracted the highest avian and arthropod densities, conservation fields still provided more wildlife and agronomic benefits than conventional management. Our findings suggest that both conservation tillage and stripcropping systems will improve conditions for birds in cotton, with stripcropped fields providing superior habitat. The reduction of inputs possible with the clover system could allow farmers to lower costs associated with conventional cotton production by $282–317/ha. This reduction of input, coupled with similar or possibly increased yield over conventional systems makes stripcover cropping not only a good choice for reducing negative impacts on wildlife and surrounding ecosystems, but also an economically desirable one.     

The Ecological Future of the North American Bison: Conceiving Long-Term, Large-Scale Conservation of Wildlife

Abstract:  Many wide-ranging mammal species have experienced significant declines over the last 200 years; restoring these species will require long-term, large-scale recovery efforts. We highlight 5 attributes of a recent range-wide vision-setting exercise for ecological recovery of the North American bison ( Bison bison ) that are broadly applicable to other species and restoration targets. The result of the exercise, the "Vermejo Statement" on bison restoration, is explicitly (1) large scale, (2) long term, (3) inclusive, (4) fulfilling of different values, and (5) ambitious. It reads, in part, "Over the next century, the ecological recovery of the North American bison will occur when multiple large herds move freely across extensive landscapes within all major habitats of their historic range, interacting in ecologically significant ways with the fullest possible set of other native species, and inspiring, sustaining and connecting human cultures." We refined the vision into a scorecard that illustrates how individual bison herds can contribute to the vision. We also developed a set of maps and analyzed the current and potential future distributions of bison on the basis of expert assessment. Although more than 500,000 bison exist in North America today, we estimated they occupy <1% of their historical range and in no place express the full range of ecological and social values of previous times. By formulating an inclusive, affirmative, and specific vision through consultation with a wide range of stakeholders, we hope to provide a foundation for conservation of bison, and other wide-ranging species, over the next 100 years.     

Assessing the Value of the Umbrella‐Species Concept for Conservation Planning with Meta‐Analysis

Abstract: The umbrella‐species concept, which suggests that conservation strategies designed for one species may benefit co‐occurring species, has been promoted as a framework for conservation planning. Nevertheless, there has been considerable variation in the outcome of empirical tests of this concept that has led researchers to question its value, so we used data from 15 published studies in a meta‐analysis to evaluate whether conservation of putative umbrella species also conserves co‐occurring species. We tested the effectiveness of putative umbrella species categorized by taxonomic group, taxonomic similarity to co‐occurring species, body size, generality of resource use, and trophic level to evaluate criteria proposed to guide the selection of umbrella species. We compared species richness and number of individuals (by species and higher taxonomic group) between sites with and without putative umbrella species to test whether more co‐occurring species were present in greater abundances when the area or resource needs of umbrella species were met. Species richness and abundance of co‐occurring species were consistently higher in sites where umbrella species were present than where they were not and for conservation schemes with avian than with mammalian umbrella species. There were no differences in species richness or species abundance with resource generalist or specialist umbrella species or based on taxonomic similarity of umbrella and co‐occurring species. Taxonomic group abundance was higher in across‐taxonomic umbrella species schemes than when umbrella species were of the same taxon as co‐occurring species. Co‐occurring species had similar, or higher, species richness with small‐bodied umbrella species relative to larger‐bodied umbrella species. The only significant difference among umbrella species categorized by trophic level was that species richness was higher with omnivorous than it was with carnivorous avian umbrella species. Our results suggest there is merit to the umbrella‐species concept for conservation, but they do not support the use of the criteria we used to identify umbrella species.     

Physiological and Behavioral Differences in Magellanic Penguin Chicks in Undisturbed and Tourist-Visited Locations of a Colony

Abstract:  Studies examining anthropogenic effects on wildlife typically focus on adults and on behavioral responses rather than the physiological consequences of human disturbances. Here we examined how Magellanic Penguin (  Spheniscus magellanicus ) chicks living in either tourist-visited or undisturbed areas of a breeding colony were affected by human visitation by comparing the baseline and stress-induced levels of corticosterone during three periods of the breeding season. Newly hatched chicks in visited areas had higher corticosterone stress responses than newly hatched chicks in undisturbed areas ( p = 0.007), but baseline levels were similar ( p = 0.61). By 40–50 days of age and around fledging time, both visited and undisturbed chicks showed a robust corticosterone stress response to capture. Tourist-visited chicks did not flee when approached by humans, however, whereas undisturbed chicks fled significantly sooner (i.e., when approached no closer than 9 m; p < 0.0001). Although it is unknown whether Magellanic Penguin chicks raised in visited areas suffer negative consequences from the elevation of the corticosterone stress response at hatching, they do exhibit behavioral habituation to human contact by the time they are ready to fledge. Unlike adults living in tourist areas, however, fledging chicks in visited areas do not have a decreased stress response to capture and restraint. Our results show that the coupling of behavioral and physiological habituation in Magellanic Penguins is complex and life-history context may greatly affect the ability of wildlife to adapt to anthropogenic disturbances.     

THIRD WORLD ENERGY OPTIONS AND THE ROLE OF THE SOLAR ENERGY RESEARCH INSTITUTE

Developing countries are now in a position to choose between further commitments to petroleum and development of sustainable solar resources. Many solar options are ready and some are already economically competitive, particularly for use in rural areas where most people in developing countries reside. Third World countries are becoming cautious about imitating industrial nations, and in some cases, are beginning to map out unique strategies based on their indigenous cultures and resources. Transitions to solar technologies will not be made without difficulty, however, as baseline data on energy needs and on availability of renewable forms of energy only marginally exist. This paper presents information on the potential and current status of a range of solar technologies. The United States Solar Energy Research Institute (SERI) is advancing a number of technologies that will have direct impact on life in developing countries; but in addition has established a programme to deal specifically with the use of renewable energy resources in developing countries. Technical development, planning, information compilation, and institution building are fundamental parts of the effort. As a research institute, SERI, in particular, wants to ensure that adequate attention is given to the technical problems associated with the use of renewables in developing countries. Too often, these problems are not recognized as being worthy of scientific attention resulting in the design and installation of less than optimal equipment. The limited resources available require optimal allocation and intelligent application. In addition, SERI manages bilateral assistance programmes with developing countries under the auspices of the US Department of Energy and the US Agency for International Development. Les pays en développement ont maintenant la possibilité de choisir entre un système basé sur le pétrole ou la mise en valeur des ressources solaires potentielles. Plusieurs systèmes de récupération de l'énergie solaire sont utilisables et quelques-uns sont déjà économiquement compétitifs, particulièrement dans les régions rurales où se rencontre la majeure partie de la population des pays en développement. Les pays du Tiers Monde exercent de plus en plus une certaine prudence à imiter les pays industriels et, dans certains cas, commencent à formuler des stratégies basées uniquement sur leurs ressources et cultures propres. Cependant, le passage à l'énergie solaire ne se fera pas sans difficulté étant donné que les données de base sur les besoins énergétiques et sur la disponibilité des formes renouvelables d'énergie sont marginales. Cet article donne des informations sur le potentiel et l'état actuel de toute une gamme de technologies solaires. L'Institut de recherche d'énergie solaire (IRES) des Etats-Unis est en train de promouvoir un certain nombre de technologies qui auront une portée directe sur le mode de vie dans les pays en développement. II a aussi élaboré un programme spécial concernant l'utilisation des ressources énergétiques renouvelables dans les pays en développement. Le développement technique, la planification, le rassemblement de l'information et la mise en place d'institutions représentent des composantes fondamentales de cet effort. En tant qu'institut de recherche, IRES en particulier voudrait s'assurer que les problèmes techniques concernant l'utilisation des énergies renouvelables dans les pays en développement soient étudiés sérieusement. Trop souvent ces problèmes ne sont pas reconnus comme méritant une étude scientifique ce qui entraîne la conception et la construction d'un équipement qui n'est pas le meilleur. Les ressources disponibles étant limitées, elles requièrent une répartition optimale ainsi qu'une utilisation intelligente. De plus, IRES dirige des programmes d'assistance bilatérale avec les pays en développement sous les auspices du Département de l'énergie et de l'Agence pour le développement international des Etats-Unis. Los países en desarrollo están ahora en la posibilidad de escoger entre una mayor dependencia del petróleo y el desarrollo de energía solar. Muchas alternativas de uso de energía solar están disponibles y algunas son economicamente competitivas, especialmente en las zonas rurales donde reside la mayor parte de la población de los países en desarrollo. Los países del tercer mundo están mas cautos en imitar los países industrializados, y en algunos casos, están empezando a establecer estrategias basadas en su cultura autóctona y sus recursos. Sin embargo la transición a la tecnología solar no va a ser fácil puesto que la información básica sobre las necesidades de energía y la disponibilidad de recursos renovables es muy escasa. Este artículo examina el potencial y la situación actual de las tecnologías de aplicación de energía solar. En los Estados Unidos, el Instituto de Investigación de Energía Solar (IIES) esta proponiendo ciertas tecnologías que tendrán impacto directo sobre la vida en los países en desarrollo, adicionalmente ha establecido un programa para tratar especificamente el uso de recursos renovables de energía en países en desarrollo. Desarrollo técnico, planificación, procesamiento de información y organización de instituciones son partes fundamentales de este esfuerzo. EL IIES quiere asegurar que se dé adecuada atención a los problemas técnicos relacionados con el uso de recursos renovables en los países en desarrollo. A menudo estos problemas se consideran como no importantes para ser objeto de investigación científica y como resultado se diseñan e instalan equipos que no son óptimos. Sin embargo los recursos limitados requieren que se hagan asignaciones óptimas de recursos y aplicaciones inteligentes. Además, el IIES administra programas de asistencia bilateral con los países en desarrollo bajo los auspicios del Departamento de Energía y la Agencia para el Desarrollo Internacional de los Estados Unidos de América.     

MAPPING TROPICAL DEFORESTATION IN CENTRAL AFRICA

The NASA Landsat Pathfinder Humid Tropical Deforestation Project was to map deforestation activities in the humid tropics using datasets from both the Landsat TM (Thematic Mapper) and MSS (Multispectral Scanner System). In Central Africa, its effort had been constrained by the availability of cloud-free satellite coverage, especially for the 1970s Landsat MSS imagery. Here, we reported the deforestation rate and its spatial variability in the region using 18 pairs of co-registered Landsat TM imagery from the 1980s to 1990s. Of the total classified area of 416000 km, there were approximately 217000 km² of dense forest and 24000 km² of degraded forest in the 1980s. A total of 1012 km² of forest, including 542 km² of dense forest and 470 km² of degraded forest, were cleared annually with an annual deforestation rate of 0.42%, varying among scenes ranging from 0.03 to 2.72%. Additionally, an average of 0.12% (ranging from 0.01 to 0.77% among scenes) or 257 km² of dense forest was degraded annually. Regression analyses indicated that extensive deforestation occurred in areas with larger forest cover, including dense and degraded forests. Image interpretation also confirmed the hypothesized relationship between deforestation and forest accessibility. The annual clearance of the dense forest was significantly related to the rural population density, and there was a positive relationship between the dense forest degraded during the 1980s–1990s and the degraded forest area in the 1980s.