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Extinction Debt (extinction + debt)
Selected AbstractsExtinction debt on oceanic islandsECOGRAPHY, Issue 2 2010Kostas A. Triantis Habitat destruction is the leading cause of species extinctions. However, there is typically a time-lag between the reduction in habitat area and the eventual disappearance of the remnant populations. These "surviving but ultimately doomed" species represent an extinction debt. Calculating the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species,area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands, to calculate realistic and ecologically-adjusted species,area relationships. The results reveal dramatic and hitherto unrecognized levels of extinction debt, as a result of the extensive destruction of the native forest:>95%, in<600,yr. Our estimations suggest that more than half of the extant forest arthropod species, which have evolved in and are dependent on the native forest, might eventually be driven to extinction. Data on species abundances from Graciosa Island, where only a very small patch of secondary native vegetation still exists, as well as the number of species that have not been found in the last 45,yr, despite the extensive sampling effort, offer support to the predictions made. We argue that immediate action to restore and expand native forest habitat is required to avert the loss of numerous endemic species in the near future. [source] Extinction debt in fragmented grasslands: paid or not?JOURNAL OF VEGETATION SCIENCE, Issue 1 2009Sara A.O. Cousins Abstract Fragmentation of grasslands and forests is considered a major threat to biodiversity. In the case of plants, the effect of fragmentation or landscape context is still unclear and published results are divergent. One explanation for this divergence is the slow response of long-lived plants, creating an extinction debt. However, this has not been empirically confirmed. In this study, data were compiled from broad-scale studies of grasslands from throughout the world that relate plant diversity to fragmentation effects. Only seven studies from northern Europe, out of a total 61, gave any information on actual habitat fragmentation in time and space. In landscapes with >10% grassland remaining, present-day species richness was related to past landscape or habitat pattern. In landscapes with <10% grassland remaining, in contrast, plant species richness was more related to contemporary landscape or habitat pattern. Studies from landscapes with >10% grassland remaining supported the concept of an extinction debt, while studies from more fragmented landscapes did not provide any evidence of an extinction debt. In order to make generalisations about historical legacies on species diversity in grasslands it is important to consider a range of highly transformed landscapes, and not only landscapes with a high amount of grassland remaining. [source] Extinction debt on oceanic islandsECOGRAPHY, Issue 2 2010Kostas A. Triantis Habitat destruction is the leading cause of species extinctions. However, there is typically a time-lag between the reduction in habitat area and the eventual disappearance of the remnant populations. These "surviving but ultimately doomed" species represent an extinction debt. Calculating the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species,area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands, to calculate realistic and ecologically-adjusted species,area relationships. The results reveal dramatic and hitherto unrecognized levels of extinction debt, as a result of the extensive destruction of the native forest:>95%, in<600,yr. Our estimations suggest that more than half of the extant forest arthropod species, which have evolved in and are dependent on the native forest, might eventually be driven to extinction. Data on species abundances from Graciosa Island, where only a very small patch of secondary native vegetation still exists, as well as the number of species that have not been found in the last 45,yr, despite the extensive sampling effort, offer support to the predictions made. We argue that immediate action to restore and expand native forest habitat is required to avert the loss of numerous endemic species in the near future. [source] What hope for African primate diversity?AFRICAN JOURNAL OF ECOLOGY, Issue 2 2006Colin A. Chapman Available empirical evidence suggests that many primate populations are increasingly threatened by anthropogenic actions and we present evidence to indicate that Africa is a continent of particular concern in terms of global primate conservation. We review the causes and consequences of decline in primate diversity in Africa and argue that the major causes of decline fall into four interrelated categories: deforestation, bushmeat harvest, disease and climate change. We go on to evaluate the rarity and distribution of species to identify those species that may be particularly vulnerable to threats and examine whether these species share any characteristic traits. Two factors are identified that suggest that our current evaluation of extinction risk may be overly optimistic; evidence suggests that the value of existing forest fragments may have been credited with greater conservation value in supporting primate populations than they actually have and it is clear that the extinction debt from historical deforestation has not being adequately considered. We use this evaluation to suggest what future actions will be advantageous to advance primate conservation in Africa and evaluate some very positive conservation gains that are currently occurring. [source] Floral free fall in the Swiss lowlands: environmental determinants of local plant extinction in a peri-urban landscapeJOURNAL OF ECOLOGY, Issue 4 2007IVANA STEHLIK Summary 1Local floras are being depleted by a host of human activities, including habitat destruction and fragmentation, eutrophication, and the intensification of agriculture. Species with particular ecological demands or life-history attributes are more prone to extinction than species with a broader niche. 2We used an old herbarium from the municipality of Küsnacht (Swiss lowlands) as a historical record for comparison with contemporary plant diversity. This comparison revealed that 17% to 28% of all vascular plants that occurred between 1839 and 1915 were extinct by 2003. 3Species of different habitats and life-forms had significantly different rates of extinction: wetlands, disturbed sites and meadows lost most species, whereas forests and rocky habitats were least affected; aquatics and annuals were most prone to extinction, geophytes and hemicryptophytes were intermediate, and phanerophytes and chamaephytes were least affected. 4Species adapted to nutrient-poor soils suffered highest extinction in all habitats, indicating that eutrophication poses an urgent threat to species diversity. Light and soil moisture requirements also had significant effects on extinction, but the direction of the effect varied by habitat. 5When species were grouped into IUCN categories of the red list of Switzerland, the rank order of the observed extinction matched the red list assignment. 6Because many of the remaining species had high estimated extinction probabilities and because extinction is often delayed (extinction debt), a substantial part of the remaining flora of Küsnacht is likely to go extinct in the near future. This will increase the dominance of the common species that already comprise 81% of the local flora. 7The rates and patterns of extinction in Küsnacht are probably representative of surrounding Swiss lowlands and peri-urban landscapes in most developed countries. Studies such as ours can serve as a call for action and form a basis for future monitoring of biodiversity. [source] Extinction debt in fragmented grasslands: paid or not?JOURNAL OF VEGETATION SCIENCE, Issue 1 2009Sara A.O. Cousins Abstract Fragmentation of grasslands and forests is considered a major threat to biodiversity. In the case of plants, the effect of fragmentation or landscape context is still unclear and published results are divergent. One explanation for this divergence is the slow response of long-lived plants, creating an extinction debt. However, this has not been empirically confirmed. In this study, data were compiled from broad-scale studies of grasslands from throughout the world that relate plant diversity to fragmentation effects. Only seven studies from northern Europe, out of a total 61, gave any information on actual habitat fragmentation in time and space. In landscapes with >10% grassland remaining, present-day species richness was related to past landscape or habitat pattern. In landscapes with <10% grassland remaining, in contrast, plant species richness was more related to contemporary landscape or habitat pattern. Studies from landscapes with >10% grassland remaining supported the concept of an extinction debt, while studies from more fragmented landscapes did not provide any evidence of an extinction debt. In order to make generalisations about historical legacies on species diversity in grasslands it is important to consider a range of highly transformed landscapes, and not only landscapes with a high amount of grassland remaining. [source] Changing climate and historic-woodland structure interact to control species diversity of the ,Lobarion' epiphyte community in ScotlandJOURNAL OF VEGETATION SCIENCE, Issue 5 2007Christopher J. Ellis Abstract Question: How will changing climate and habitat structure interact to control the species diversity of lichen epiphytes? Location: Scotland. Method: Species richness (=diversity) of the epiphyte lichen community known as Lobarion (named after Lobaria pulmonaria) was quantified for 94 Populus tremula stands across Scotland, and compared in a predictive model to seven climate variables and eight measures of woodland structure. An optimum model was selected and used to project Lobarion diversity over the geographic range of the study area, based on IPCC climate change scenarios and hypothetical shifts in woodland structure. Results: Species diversity of the Lobarion community was best explained by three climate variables: (1) average annual temperature; (2) autumn and winter precipitation; in combination with (3) historic-woodland extent. Projections indicate a positive effect of predicted climate change on Lobarion diversity, consistent with the physiological traits of cyanobac-terial lichens comprising the Lobarion. However, the general response to climate is modified significantly by the effect on diversity of historic-woodland extent. Conclusions: Historic-woodland extent may exert an important control over local climate, as well as impacting upon the metapopulation dynamics of species in the Lobarion. In particular, a temporal delay in the response of Lobarion species to changed woodland structure is critical to our understanding of future climate change effects. Future Lobarion diversity (e.g. in the 2050s) may depend upon the interaction of contemporary climate (e.g. 2050s climate) and historic habitat structure (e.g. 1950s woodland extent). This is supported by previous observations for an extinction debt amongst lichen epiphytes, but suggests an extension of simple climate-response models is necessary, before their wider application to lichen epiphyte diversity. [source] | ||||||||||