Monthly Archives: July 2011

A new paper in Science by Jim Estes and colleagues reviews contemporary findings on the consequences of removing large apex consumers (e.g., top predators) from nature—a process they term trophic downgrading.
The authors highlight the ecological theory that predicts trophic downgrading, consider why these effects have been difficult to observe, and summarize the key empirical evidence for trophic downgrading. The paper concludes Continue reading →

A new paper by Maclean and Wilson in the journal PNAS compares threat of extinction, as documented by IUCN Red List data on recent changes in population and range size, with that predicted by previous studies that used models to predict the potential effects of climate change on extinction. The study is the most comprehensive to date in terms of examining data for a wide range of species worldwide. Observed extinction probabilities were similar to those predicted by models. The authors conclude that climate change: Continue reading →

A new study by Scott Nielsen, a researcher from the University of Alberta, examines whether conservation of important habitat for grizzly bears can also help achieve broader biodiversity goals. The paper is part of a special issue of the British Columbia Journal of Ecosystems Management. This issue of JEM also contains several articles describing other facets of the recently-completed ecoregional plan for BC’s Central Interior region. The plan, which covers a large portion of the province, is one the most comprehensive conservation planning examples from BC to date, integrating data on vegetation, terrestrial focal species, aquatic biodiversity, and other conservation foci.
The Nielsen study compared the distribution of predicted source and sink habitats for grizzly bears with areas found to be highly “irreplaceable” for achieving protection of other biodiversity features. The author concludes that “protection of grizzly bear source habitats across different bear density classes does provide a reasonable umbrella effect or shortcut for protection of other important conservation features in grizzly bear range.” However, Nielsen cautions that “If the highest density source habitats for grizzly bears were used for targeting future conservation areas, important areas of high biodiversity value for low-elevation plains between the mountain ranges would therefore be overlooked. This is particularly evident for the extirpated grizzly bear habitats in the Fraser Basin, where comparisons with grizzly bear habitats were not assessed yet contained noticeable areas of highly irreplaceable habitat (Loos 2011). This research therefore suggests that if grizzly bears are used as a focal surrogate species for conservation planning, source-like habitats across the range of bear density classes should be considered, as well as the extent of the analysis, to acknowledge that at larger extents the extirpated habitats common to low elevations will be overlooked, and yet are critical to the conservation of threatened biodiversity.”

The journal issue can be downloaded here.