Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact firstname.lastname@example.org with any questions.
A global mass extinction of amphibians is well under way, driven both by habitat loss and by environmental changes. As amphibian communities in Central America are being decimated by chytrid disease, scientists are working to fashion an emergency response. They are also sending out an urgent warning about what the loss of these environmentally sensitive species may portend.
The Sonoran pronghorn, one of five pronghorn subspecies, may be the most endangered large mammal in the United States. Once ranging more widely, today they are found in the United States only on protected lands in southwestern Arizona. Captive breeding programs and desert enhancements are starting to revive Sonoran pronghorn numbers.
We compared long-term change in two lake districts, one in a forested rural setting and the other in an urbanizing agricultural region, using lakes as sentinel ecosystems. Human population growth and land-use change are important drivers of ecosystem change in both regions. Biotic changes such as habitat loss, species invasions, and poorer fishing were prevalent in the rural region, and lake hydrology and biogeochemistry responded to climate trends and landscape position. Similar biotic changes occurred in the urbanizing agricultural region, where human-caused changes in hydrology and biogeochemistry had conspicuous effects. Feedbacks among ecosystem dynamics, human uses, economics, social dynamics, and policy and practice are fundamental to understanding change in these lake districts. Sustained support for interdisciplinary collaboration is essential to build understanding of regional change.
Estimating carbon (C) balance in erosional and depositional landscapes is complicated by the effects of soil redistribution on both net primary productivity (NPP) and decomposition. Recent studies are contradictory as to whether soil erosion does or does not constitute a C sink. Here we clarify the conceptual basis for how erosion can constitute a C sink. Specifically, the criterion for an erosional C sink is that dynamic replacement of eroded C, and reduced decomposition rates in depositional sites, must together more than compensate for erosional losses. This criterion is in fact met in many erosional settings, and thus erosion and deposition can make a net positive contribution to C sequestration. We show that, in a cultivated Mississippi watershed and a coastal California watershed, the magnitude of the erosion-induced C sink is likely to be on the order of 1% of NPP and 16% of eroded C. Although soil erosion has serious environmental impacts, the annual erosion-induced C sink offsets up to 10% of the global fossil fuel emissions of carbon dioxide for 2005.
No species in the eastern United States better exemplifies a ubiquitous yet subordinate tree than does blackgum (Nyssa sylvatica). What enables blackgum to grow nearly everywhere, but almost always at very low densities? It is the longest-lived hardwood species in the eastern United States, with a maximum age that can exceed 650 years. It is inherently slow growing, which most likely explains its great longevity and high shade tolerance; it is also one of the few tree species that are fire resistant as well as shade tolerant. Blackgum can grow in bottomlands or at xeric sites, being tolerant of both flooding and drought. Despite these ecologically beneficial attributes—and the fact that early loggers systematically avoided blackgum because of its tendency to rot—this slow-growing tree is rarely dominant. Blackgum has so far simply persisted as a marginal species. The future of blackgum is uncertain, however, because of the opposing forces of global warming and increased competition from other tree species. This article synthesizes a broad range of ecological studies that relate to the unique behavior of blackgum as a consummate subordinate, something that is poorly understood for this and other similar species in the ecology literature.
The abundance of birds recorded in the North American Breeding Bird Survey decreased by up to 18 percent between 1966 and 2005. The abundance of US and Canadian resident species decreased by 30 percent, and that of migrants within the United States and Canada decreased by 19 percent. By contrast, Neotropical migrants increased by up to 20 percent. Land-cover changes in northern latitudes therefore seem more consequential for bird populations than those occurring in Neotropical habitats. Lower abundances were most marked for resident breeding birds that used open, edge, and wetland habitats, the environments most affected by human disturbances—particularly urban sprawl—in northern latitudes. The abundance of resident and migrant forest-dwelling birds increased (although trends varied from species to species), with the increases seeming to follow the 20th-century expansion of forest area in northern latitudes, rather than the loss of Neotropical forests. The geographic footprint of changes in bird abundance linked to habitat changes in North America may thus be extending southward, with negative effects on birds that use open habitats and positive effects on forest birds.