Global Decline (global + decline)

Distribution by Scientific Domains


Selected Abstracts


Remarkable Amphibian Biomass and Abundance in an Isolated Wetland: Implications for Wetland Conservation

CONSERVATION BIOLOGY, Issue 5 2006
J. WHITFIELD GIBBONS
biodiversidad; declinación de anfibios; recuperación de humedales sequía; uso de suelo Abstract:,Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts for the past 54 years. We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.), to sample all amphibians for 1 year following a prolonged drought. Despite intensive agricultural use of the land surrounding Ellenton Bay prior to 1951, we documented 24 species and remarkably high numbers and biomass of juvenile amphibians (>360,000 individuals; >1,400 kg) produced during one breeding season. Anurans (17 species) were more abundant than salamanders (7 species), comprising 96.4% of individual captures. Most (95.9%) of the amphibian biomass came from 232095 individuals of a single species of anuran (southern leopard frog[Rana sphenocephala]). Our results revealed the resilience of an amphibian community to natural stressors and historical habitat alteration and the potential magnitude of biomass and energy transfer from isolated wetlands to surrounding terrestrial habitat. We attributed the postdrought success of amphibians to a combination of adult longevity (often >5 years), a reduction in predator abundance, and an abundance of larval food resources. Likewise, the increase of forest cover around Ellenton Bay from <20% in 1951 to >60% in 2001 probably contributed to the long-term persistence of amphibians at this site. Our findings provide an optimistic counterpoint to the issue of the global decline of biological diversity by demonstrating that conservation efforts can mitigate historical habitat degradation. Resumen:,A pesar de la pérdida de hábitats de humedales y las declinaciones asociadas de poblaciones de anfibios, se han realizado pocos intentos para traducir las pérdidas de humedales en pérdidas mensurables en los ecosistemas. Estimamos la productividad potencial de la comunidad de anfibios que se afectaría por la pérdida de un humedal aislado que ha estado protegido de los impactos industriales, agrícolas y urbanos durante los últimos 54 años. Utilizamos un cerco de desvío en la Bahía Ellentonn, un humedal dulceacuícola de 10 ha en el Río Savannah, cerca de Aiken, Carolina del Sur (E.U.A.), para muestrear todos los anfibios durante 1 año después de una sequía prolongada. A pesar del intensivo uso agrícola del suelo alrededor de la Bahía Ellenton antes de 1951, documentamos 24 especies y números y biomasa de anfibios juveniles notablemente altos (>360,000 individuos; >1,400 kg) en una temporada reproductiva. Los anuros (17 especies) fueron más abundantes que las salamandras (7 especies), y comprendieron 96.4% de las capturas individuales. La mayor parte (95.9%) de la biomasa provino de 232095 individuos de una sola especie de anuro (Rana sphenocephala). Nuestros resultados revelaron que la resiliencia de la comunidad de anfibios a los estresantes naturales y a la alteración histórica del hábitat y la magnitud potencial de la transferencia de biomasa y energía desde los humedales aislados hacia el hábitat terrestre circundante. Atribuimos el éxito post-sequía de los anfibios a una combinación de longevidad de adultos (a menudo > 5 años), la reducción de la abundancia de depredadores y la abundancia de recursos alimenticios para las larvas. Asimismo, el incremento de la cobertura forestal alrededor de la Bahía Ellerton de < 20% en 1951 a > 60% en 2001 probablemente contribuyó a la persistencia de los anfibios a largo plazo en este sitio. Nuestros hallazgos proporcionan un contrapunto optimista al tema de la declinación global de la diversidad biológica al demostrar que los esfuerzos de conservación pueden mitigar a la degradación histórica del hábitat. [source]


Fishing out marine parasites?

ECOLOGY LETTERS, Issue 6 2010
Impacts of fishing on rates of parasitism in the ocean
Ecology Letters (2010) 13: 761,775 Abstract Among anthropogenic effects on the ocean, fishing is one of the most pervasive and extends deepest into the past. Because fishing reduces the density of fish (reducing transmission efficiency of directly transmitted parasites), selectively removes large fish (which tend to carry more parasites than small fish), and reduces food web complexity (reducing transmission efficiency of trophically transmitted parasites), the removal of fish from the world's oceans over the course of hundreds of years may be driving a long-term, global decline in fish parasites. There has been growing recognition in recent years that parasites are a critical part of biodiversity and that their loss could substantially alter ecosystem function. Such a loss may be among the last major ecological effects of industrial fishing to be recognized by scientists. [source]


Mining and sustainable development: considerations for minerals supply

NATURAL RESOURCES FORUM, Issue 4 2001
Ian B. Lambert
Abstract Sustainable development involves meeting the needs of human societies while maintaining viable biological and physical Earth systems. The needs include minerals: metals, fuels, industrial and construction materials. There will continue to be considerable demand for virgin mineral resources, even if levels of recycling and efficiency of use are optimal, and rates of population growth and globalisation decrease significantly. This article aims to stimulate debate on strategic issues for minerals supply. While the world has considerable stocks of mineral resources overall, international considerations of the environmental and social aspects of sustainable development are beginning to result in limitations on where mining will be conducted and what types of deposits will be mined. Current and emerging trends favour large mines in parts of the world where mining can be conducted within acceptable limits of environmental and social impact. Finding new deposits that meet such criteria will be all the more challenging given a disturbing global decline in the rate of discovery of major economic resources over the last decade, and the decreasing land area available for exploration and mining. To attract responsible exploration and mining, governments of mining nations will need to provide: regional-scale geo-scientific datasets as required to attract and guide future generations of exploration; resource access through multiple and sequential land use regimes, and frameworks for dealing with indigenous peoples' issues; and arrangements for consideration of mining proposals and regulation of mines that ensure responsible management of environmental and social issues. The minerals industry will need to continue to pursue advances in technologies for exploration, mining, processing, waste management and rehabilitation, and in public reporting of environmental and social performance. [source]


Identifying the origins of fishing gear ingested by seabirds: a novel multivariate approach

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2010
Cindy Ridley
Abstract 1.The global decline of albatrosses (Diomedidae: Procellariiformes) is thought to have occurred largely as a direct result of fishery-related mortality. Albatrosses and other large petrels interact with fisheries in several ways, including scavenging used bait and discarded offal, which may contain hooks. 2.Hooks that are ingested by breeding birds are often fed to chicks which subsequently regurgitate them shortly before fledging. 3.In this study a series of mathematical (cladistic, cluster and principal components) analyses are applied to a sample of 241 items of fishing gear (hook, snood and hook/snood unit) collected from seabird nest sites on Bird Island, South Georgia, and 44 reference gear items provided by four South Atlantic regional fisheries. 4.The five separate analyses failed to assign most gear to a particular fishery or to identify any consistent annual trends. The homogeneous nature of the material, which was largely derived from the same manufacturers, meant that gear origin could not be determined. This suggests that hooks found at seabird colonies in this, and potentially other regions, will be of limited use in identifying offending fisheries, unless operators are obliged to deploy gear with unique marks in the future. 5.Nevertheless, it is suggested that this approach should work effectively where birds interact with a range of fisheries targeting different species using variable gear. This study therefore represents an innovative approach to the characterization of lost fishing gear with potentially widespread application. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Freshwater mussel abundance predicts biodiversity in UK lowland rivers

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2007
David C. Aldridge
Abstract 1.Indicator taxa are widely used as a valuable tool in the assessment of freshwater biodiversity. However, this approach to identifying sites of conservation priority requires surveyors to possess expert taxonomic knowledge. Furthermore, sorting and microscopic examination of material can present logistical and financial constraints. 2.Comparisons were made between the taxon richness and the density of freshwater mussels (Bivalvia: Unionidae) from 30 sites in seven UK lowland rivers, ranging from ca 3 m to 50 m width and ca 0.5 m to 4 m depth. Where mussels occurred, taxon richness of other invertebrates was strongly correlated with both mussel density and mussel biomass. Overall mussel density was a better predictor of taxon richness than the density of any individual mussel species. 3.It is suggested that this association arises from the ,keystone' role that mussels play in many freshwater ecosystems. Local biota can benefit from the mussels' filtration, excretion, biodeposition and physical presence. 4.Using mussel abundance as a surrogate provides a rapid and straightforward alternative to conventional methods of assessing freshwater biodiversity. No expert knowledge is required and any standardized sampling technique can be used. Freshwater mussels are found throughout the world's lentic and lotic fresh waters and this approach therefore has the potential for widespread utility, especially where rapid comparisons of biodiversity are required between biogeographically similar regions. In addition, the results highlight the ecosystem-level consequences of allowing the global decline of freshwater mussels to remain unchecked. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Short and long term consequences of increases in exotic species richness on water filtration by marine invertebrates

ECOLOGY LETTERS, Issue 8 2009
Jarrett Byrnes
Abstract Although recent research has considered the consequences of global declines in the number of species, less attention has focused on the aggregate effects of regional increases in species richness as a result of human-mediated introductions. Here we examine several potential ecosystem consequences of increasing exotic species diversity of suspension feeding marine invertebrates. First, we experimentally manipulated native and non-native suspension feeder richness and measured its effect on short-term phytoplankton clearance rates. Multispecies communities all performed similarly, regardless of whether they were dominated by natives, exotics, or an even mix of the two. Individual species varied considerably in filtration rates, but non-native species often filtered less than the most similar native. Second, we determined potential changes in integrated function over time by comparing seasonal patterns of recruitment as a proxy for the ability to quickly recover filtration capacity after a disturbance. We found that exotic species have complementary seasonal phenologies both to native species and each other. Our results suggest that the consequences of local increases in species richness due to invasions may be manifest over long (annual to interannual) time scales, even when short term changes in ecosystem function are negligible. [source]


Using probabilistic models to investigate the disappearance of a widespread frog-species complex in high-altitude regions of south-eastern Australia

ANIMAL CONSERVATION, Issue 3 2010
A. J. Hamer
Abstract Amphibian populations have suffered declines and disappearances around the world. It is now recognized that many of the disappearances were the result of infection by the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). Most global declines were first observed in the 1980s. Here, we used information from museum collections, natural-history databases and the literature to quantitatively assess the disappearance of the bell frog species complex (Litoria aurea, Litoria castanea and Litoria raniformis) in high-altitude Tableland regions of the Great Dividing Range, south-eastern Australia. Based on the sighting record, we estimated that Li. castanea disappeared on the Northern Tablelands in 1979, then from the Southern and Central Tablelands in 1984. Estimated dates of disappearance of Li. aurea and Li. raniformis from the Southern and Central Tablelands were 1981 and 1982, respectively. The Northern Tablelands populations of Li. castanea may have been one of the first high-altitude populations of frogs to disappear from Australasia and perhaps one of the first globally. We documented targeted searches of suitable habitat within the historic range of the three species in these Tableland regions since 1985, noting that only one bell frog population was discovered (Li. aurea, Southern Tablelands, 2000). Our Solow equation estimate of the probability of extant populations of bell frogs persisting up to the year 2000 was <0.001, so the rediscovery of Li. aurea was mathematically exceptional. Although the cause of these declines remains unknown, the latitudinal (i.e. north to south) and rapid pattern of disappearance of Li. castanea, and the rapid contraction in the range of Li. aurea and Li. raniformis from high-altitude regions, strongly suggests a pathogen such as Bd was responsible. We recommend further surveys for bell frogs on the Tablelands, as the rediscovery of Li. aurea provides faint hope of finding other extant populations. [source]