The future of tropical forestsWright, S. Joseph
doi: 10.1111/j.1749-6632.2010.05455.xpmid: 20536814
Five anthropogenic drivers–land use change, wood extraction, hunting, atmospheric change, climate change–will largely determine the future of tropical forests. The geographic scope and intensity of these five drivers are in flux. Contemporary land use change includes deforestation (∼64,000 km2 yr−1 for the entire tropical forest biome) and natural forests regenerating on abandoned land (∼21,500 km2 yr−1 with just 29% of the biome evaluated). Commercial logging is shifting rapidly from Southeast Asia to Africa and South America, but local fuelwood consumption continues to constitute 71% of all wood production. Pantropical rates of net deforestation are declining even as secondary and logged forests increasingly replace old‐growth forests. Hunters reduce frugivore, granivore and browser abundances in most forests. This alters seed dispersal, seed and seedling survival, and hence the species composition and spatial template of plant regeneration. Tropical governments have responded to these local threats by protecting 7% of all land for the strict conservation of nature—a commitment that is only matched poleward of 40°S and 70°N. Protected status often fails to stop hunters and is impotent against atmospheric and climate change. There are increasing reports of stark changes in the structure and dynamics of protected tropical forests. Four broad classes of mechanisms might contribute to these changes. Predictions are developed to distinguish among these mechanisms.
Impacts of biofuels on climate change, water use, and land useDelucchi, Mark A.
doi: 10.1111/j.1749-6632.2010.05457.xpmid: 20536815
Governments worldwide are promoting the development of biofuels in order to mitigate the climate impact of using fuels. In this article, I discuss the impacts of biofuels on climate change, water use, and land use. I discuss the overall metric by which these impacts have been measured and then present and discuss estimates of the impacts. In spite of the complexities of the environmental and technological systems that affect climate change, land use, and water use, and the difficulties of constructing useful metrics, it is possible to make some qualitative overall assessments. It is likely that biofuels produced from crops using conventional agricultural practices will not mitigate the impacts of climate change and will exacerbate stresses on water supplies, water quality, and land use, compared with petroleum fuels. Policies should promote the development of sustainable biofuel programs that have very low inputs of fossil fuels and chemicals that rely on rainfall or abundant groundwater, and that use land with little or no economic or ecological value in alternative uses.
Nitrogen enrichment and plant communitiesCleland, Elsa E.; Harpole, W. Stanley
doi: 10.1111/j.1749-6632.2010.05458.xpmid: 20536816
Anthropogenic nitrogen (N) enrichment of many ecosystems throughout the globe has important ramifications for plant communities. Observational and experimental studies frequently find species richness declines with N enrichment, in concert with increasing primary production. Nitrogen enrichment also reorders species composition, including species turnover through gains and losses of species, changes in dominance and rarity, and shifts in the relative abundance of particular functional groups. Nitrogen has traditionally been considered the primary limiting nutrient for plant growth in terrestrial ecosystems, but recent synthetic work suggests that colimitation by phosphorus (P), water, and other resources is widespread, consistent with theoretical predictions. At the same time, disproportionate increases in ecosystem N input are expected to exacerbate limitation by P and other resources. Similarly, synthetic research has pointed out the important role of consumers and pathogens in determining plant community structure, especially with respect to shifting resource availability. We argue here that environmental and biotic contexts, including limitation by multiple resources, herbivores and pathogens, play important roles in our understanding of plant community responses to N enrichment.
Bioaccumulation syndrome: identifying factors that make some stream food webs prone to elevated mercury bioaccumulationWard, Darren M.; Nislow, Keith H.; Folt, Carol L.
doi: 10.1111/j.1749-6632.2010.05456.xpmid: 20536817
Mercury is a ubiquitous contaminant in aquatic ecosystems, posing a significant health risk to humans and wildlife that eat fish. Mercury accumulates in aquatic food webs as methylmercury (MeHg), a particularly toxic and persistent organic mercury compound. While mercury in the environment originates largely from anthropogenic activities, MeHg accumulation in freshwater aquatic food webs is not a simple function of local or regional mercury pollution inputs. Studies show that even sites with similar mercury inputs can produce fish with mercury concentrations ranging over an order of magnitude. While much of the foundational work to identify the drivers of variation in mercury accumulation has focused on freshwater lakes, mercury contamination in stream ecosystems is emerging as an important research area. Here, we review recent research on mercury accumulation in stream‐dwelling organisms. Taking a hierarchical approach, we identify a suite of characteristics of individual consumers, food webs, streams, watersheds, and regions that are consistently associated with elevated MeHg concentrations in stream fish. We delineate a conceptual, mechanistic basis for explaining the ecological processes that underlie this vulnerability to MeHg. Key factors, including suppressed individual growth of consumers, low rates of primary and secondary production, hydrologic connection to methylation sites (e.g., wetlands), heavily forested catchments, and acidification are frequently associated with increased MeHg concentrations in fish across both streams and lakes. Hence, we propose that these interacting factors define a syndrome of characteristics that drive high MeHg production and bioaccumulation rates across these freshwater aquatic ecosystems. Finally, based on an understanding of the ecological drivers of MeHg accumulation, we identify situations when anthropogenic effects and management practices could significantly exacerbate or ameliorate MeHg accumulation in stream fish.
Habitat fragmentation, climate change, and inbreeding in plantsLeimu, Roosa; Vergeer, Philippine; Angeloni, Francesco; Ouborg, N. Joop
doi: 10.1111/j.1749-6632.2010.05450.xpmid: 20536818
Habitat fragmentation and climate change are recognized as major threats to biodiversity. The major challenge for present day plant populations is how to adapt and cope with altered abiotic and biotic environments caused by climate change, when at the same time adaptive and evolutionary potential is decreased as habitat fragmentation reduces genetic variation and increases inbreeding. Although the ecological and evolutionary effects of fragmentation and climate change have been investigated separately, their combined effects remained largely unexplored. In this review, we will discuss the individual and joint effects of habitat fragmentation and climate change on plants and how the abilities and ways in which plants can respond and cope with climate change may be compromised due to habitat fragmentation.
Ecology of hantavirus in a changing worldDearing, M. Denise; Dizney, Laurie
doi: 10.1111/j.1749-6632.2010.05452.xpmid: 20536819
Hantavirus is a genus of virus represented by 45 different species and is hosted by small mammals, predominantly rats and mice. Roughly, half of all hantaviruses cause diseases in humans that vary in morbidity from mild to severe. The natural and anthropogenic changes occurring in the environment appear to be impacting the ecology of hantaviruses and their natural hosts as well as the incidence of hantaviral diseases in humans. Although such studies are limited at this time, there is evidence that natural climate cycles such as El Niño as well as anthropogenic climate change enhance hantavirus prevalence when host population dynamics are driven by food availability. Climate appears to have less of an effect on hantavirus when host populations are controlled by predators. Human alteration to the landscape also appears to enhance hantavirus prevalence when the disturbance regime enriches the environment for the host, for example, agriculture. More long‐term studies on multiple species of hantavirus are needed to accurately predict the outcome of changing environmental conditions on prevalence in hosts as well as disease incidence in humans.
Ecology of avian influenza viruses in a changing worldVandegrift, Kurt J.; Sokolow, Susanne H.; Daszak, Peter; Kilpatrick, A. Marm
doi: 10.1111/j.1749-6632.2010.05451.xpmid: 20536820
Influenza A virus infections result in ∼500,000 human deaths per year and many more sublethal infections. Wild birds are recognized as the ancestral host of influenza A viruses, and avian viruses have contributed genetic material to most human viruses, including subtypes H5N1 and H1N1. Thus, influenza virus transmission in wild and domestic animals and humans is intimately connected. Here we review how anthropogenic change, including human population growth, land use, climate change, globalization of trade, agricultural intensification, and changes in vaccine technology may alter the evolution and transmission of influenza viruses. Evidence suggests that viral transmission in domestic poultry, spillover to other domestic animals, wild birds and humans, and the potential for subsequent pandemic spread, are all increasing. We highlight four areas in need of research: drivers of viral subtype dynamics; ecological and evolutionary determinants of transmissibility and virulence in birds and humans; the impact of changing land use and climate on hosts, viruses, and transmission; and the impact of influenza viruses on wild bird hosts, including their ability to migrate while shedding virus.
The effects of anthropogenic global changes on immune functions and disease resistanceMartin, Lynn B.; Hopkins, William A.; Mydlarz, Laura D.; Rohr, Jason R.
doi: 10.1111/j.1749-6632.2010.05454.xpmid: 20536821
Humans are changing the environmental conditions of our planet, and animal immune functions are being affected by these modifications. For instance, a diversity of chemical contaminants is entering ecosystems and modifying immune functions directly or indirectly through altered host–parasite interactions. Also, global temperature changes have caused outbreaks of disease that have decimated and even extirpated some host species, outcomes partially driven via immune alterations. Finally, some invasive species are immunologically distinct or impose stress on native species, factors that may facilitate the establishment of nonnative hosts as well as parasite transmission to native species. Here, we summarize the known and likely effects of pollutants, nonnative species introductions, and increases in ambient temperature on host immune functions and infections. We then identify future directions for research given our sparse knowledge of immune variation in natural populations. In sum, we advocate integrative, multidisciplinary work at diverse spatial and temporal scales to assess and prevent anthropogenic global changes from further compromising animal immune functions.
The role of public information in ecology and conservation: an emphasis on inadvertent social informationBlanchet, Simon; Clobert, Jean; Danchin, Étienne
doi: 10.1111/j.1749-6632.2010.05477.xpmid: 20536822
Public information is an emerging major topic in ecology and evolution. We review the literature about the role of public information in ecology and conservation while mainly focusing on inadvertent social information (ISI), which constitutes a major form of public information. We first define the terms of biological information that we use. We then review the accruing evidence for ISI use in many fitness‐affecting decisions in plants and animals. We generalize concepts of information to encompass interspecific interactions. We then develop how intra‐ and interspecific information flows actually shape ecological and evolutionary dynamics. We then discuss some of the application of adopting an information‐driven approach to ecology and evolution in conservation biology. Our hope is to favor the transfer of knowledge from ecology and evolution to conservation biology. We claim that this is the only way to design efficient conservation actions and illustrate how ignoring concepts of information may lead us to design conservation actions that drive endangered populations toward rather than away from extinction.
The conservation and restoration of wild beesWinfree, Rachael
doi: 10.1111/j.1749-6632.2010.05449.xpmid: 20536823
Bees pollinate most of the world's wild plant species and provide economically valuable pollination services to crops; yet knowledge of bee conservation biology lags far behind other taxa such as vertebrates and plants. There are few long‐term data on bee populations, which makes their conservation status difficult to assess. The best‐studied groups are the genus Bombus (the bumble bees), and bees in the EU generally; both of these are clearly declining. However, it is not known to what extent these groups represent the approximately 20,000 species of bees globally. As is the case for insects in general, bees are underrepresented in conservation planning and protection efforts. For example, only two bee species are on the global IUCN Red List, and no bee is listed under the U.S. Endangered Species Act, even though many bee species are known to be in steep decline or possibly extinct. At present, bee restoration occurs mainly in agricultural contexts, funded by government programs such as agri‐environment schemes (EU) and the Farm Bill (USA). This is a promising approach given that many bee species can use human‐disturbed habitats, and bees provide valuable pollination services to crops. However, agricultural restorations only benefit species that persist in agricultural landscapes, and they are more expensive than preserving natural habitat elsewhere. Furthermore, such restorations benefit bees in only about half of studied cases. More research is greatly needed in many areas of bee conservation, including basic population biology, bee restoration in nonagricultural contexts, and the identification of disturbance‐sensitive bee species.