Conservation Science Blog

New research relevant to conservation in western North America

The Conservation Science Blog is intended to bring new and relevant research to the attention of conservation scientists, and facilitate discussion on how to apply this science to further conservation goals in western North America.

New paper and software for detecting dispersal barriers and restoring habitat connectivity

An interesting new paper by Brad McRae and colleagues has been published in the journal PLoS One. Entitled “Where to Restore Ecological Connectivity? Detecting Barriers and Quantifying Restoration Benefits” (download link), the research uses techniques to identify connectivity barriers that are similar to those used in microchip design, where simulated voltage levels reveal areas with strong voltage gradients where electrical connectivity must be enhanced. Software to implement the method is freely available (download link).

Posted in Endangered species management |

Do top predators increase the amount of carbon stored in ecosystems?

In a new paper in the journal Frontiers in Ecology and the Environment, Chris Wilmers and colleagues examine how much carbon is stored (in the form of kelp) in North Pacific coastal ecosystems which either have or lack sea otters. In the absence of sea otters, sea urchin populations increase and graze kelp forest to form urchin barrens. Wilmers’ results suggest that sea otters can substantially alter ecosystem carbon budgets through their indirect effects on plants. They hypothesize that predators can strongly influence the carbon cycle in general and atmospheric carbon dioxide through top-down forcing and trophic cascades. Although the authors caution that the extent to which these effects can be extrapolated across species and global ecosystems remains to be determined, they suggest that, because predators exert strong indirect effects on plants in many ecosystems, these effects might appreciably influence the concentration of atmospheric carbon. The effects of trophic cascades on carbon flux and storage also have an economic dimension, given that the value of increased kelp carbon standing stock due to sea otters would be valued at between 205 and 408 million dollars on world markets for carbon credits.

The authors suggest that the degree to which predator effects in other ecosystems would substantially influence atmospheric carbon dioxide concentration will depend on three factors: the overall influence of predators on autotrophs through trophic cascades across global ecosystems; food chain length and the resulting degree to which the trophic cascades have a positive or negative influence on associated plant populations; and the standing plant biomass and NPP for each particular ecosystem. They propose that we should expect predators in food webs with odd numbers of trophic levels to reduce atmospheric carbon (via increased sequestration by plants), while predators in food webs with even numbers of trophic levels might increase atmospheric carbon. They conclude “This influence alone complicates the assessment of predator effects on carbon in aquatic systems because food chain length varies considerably among aquatic systems. Large predators in most terrestrial ecosystems occupy the third trophic level, thus implying a more consistent sequestering effect of predators on C for the terrestrial realm. However, terrestrial ecosystems are rife with other complexities such as predator interference, omnivory, and defended plant tissue that make it difficult to form general conclusions about the magnitude of such effects.”

This new study is important in focusing attention on the ecosystem effects of predator restoration. However, proposals to monetize the effects of predator-prey dynamics on ecosystem carbon storage raise ethical questions. For example, although in parts of the developed world, ungulates are superabundant due to predator removal, in other regions, ungulate abundance and distribution has been reduced below historic levels by over-exploitation. Would recovery of these prey populations be opposed due to the effects on carbon storage?

Figure from Wilmers et al. 2012. When occurring at ecologically effective densities, sea otters reduce sea urchins, resulting in large kelp standing stocks and high net primary productivity (NPP). (b) When sea otters are absent, urchins decimate kelp stands, resulting in small kelp standing stocks and low NPP.

Posted in Climate change, Endangered species management |

Grizzly bears as surrogates for balancing trade-offs between fisheries and ecosystem services

A new paper in PLoS Biology by Levi and colleagues (here) describes a new approach for assessing trade-offs between economic and ecological goals in “Ecosystem Based Management” (EBM). The paper concludes:
“Commercial fisheries that harvest salmon for human consumption can end up diverting nutrients that would normally be directed to terrestrial and aquatic ecosystems. We examined this problem for Pacific salmon fisheries by using grizzly bears as indicators of salmon ecosystem function. Bear densities vary enormously depending on salmon availability, and by leaving uneaten salmon carcass remains beside spawning streams, bears play an important role in dispersing marine nutrients to plants, invertebrates, and other wildlife. By relating the number of spawning fish to bear diet and density, we developed a model to quantify ‘‘ecosystem-harvest’’ tradeoffs; i.e., how bear density changes with the amount of fish harvested (fishery yields). We estimated this tradeoff between yields and bear density for six sockeye salmon stocks in Alaska and British Columbia (BC) across a range of management options that varied the number of salmon allowed to escape from the fishery. Our model shows that bear densities will increase substantially with more spawning fish at all sites. Notably, in most study systems, fishery yields are also expected to increase as the number of spawning fish increases. There is one exception, however, in the Fraser River (BC), where bears are threatened and sockeye salmon are nearly the only species of salmon available. Here, releasing more salmon to spawn would result in lower fishery yields. To resolve such conflicts in this and other systems, we propose a generalizable ecosystem-based fisheries management framework, which allows decision-makers (such as fisheries managers and conservation scientists) to evaluate different allocation options between fisheries and other ecosystem recipients.”

In a news story from California (here), the study’s authors suggest that their conclusions are also relevant to areas where grizzly bears are extinct: “Levi argues that having more salmon in streams would also have economic benefits from better wildlife viewing opportunities. Increased salmon abundance would surely help California’s bald eagles. More salmon would be a boon to the state’s recovering eagle population. More salmon would also increase black bear populations, he says, which is good for both hunters and wildlife observers.”

Posted in Endangered species management |

Comprehensive analysis of wolf genome suggests new conservation priorities

Sorry I haven’t had time to post recently (did you know there’s an entire blog devoted to that topic?), but today I hope to get caught up on a few new papers that shed light on topical conservation issues such as wolf recovery.

Bridget vonHoldt and colleagues have performed the most comprehensive assessment to date on genetic diversity in the wolf. Genotyping arrays developed for dogs, that assay 48,000 areas on the genome, were applied to determine relatedness among the world’s wolves. In contrast, just a few years ago such genetic assessments could examine perhaps dozens of fragments of the genome.

The results suggested several conclusions that are relevant to wolf conservation: Read more

Posted in Endangered species management |

New research on threats to biodiversity from climate change

In a recent article, the New York Times drew attention to three new papers on the threat to biodiversity from climate change.

Multitude of Species Face Climate Threat

“Over the past 540 million years, life on Earth has passed through five great mass extinctions. In each of those catastrophes, an estimated 75 percent or more of all species disappeared in a few million years or less.
For decades, scientists have warned that humans may be ushering in a sixth mass extinction, and recently a group of scientists at the University of California, Berkeley, tested the hypothesis. They applied new statistical methods to a new generation of fossil databases. As they reported last month in the journal Nature, the current rate of extinctions is far above normal. If endangered species continue to disappear, we will indeed experience a sixth extinction, over just the next few centuries or millennia. Read more

Posted in Climate change, Endangered species management |

The Impact of Conservation on the Status of the World’s Vertebrates

A new study published in the journal Science shows the number of vertebrate species that are threatened worldwide is increasing, but that conservation activities are mitigating these losses. However, the (many) authors conclude that conservation efforts may not be sufficient to offset the main drivers of biodiversity loss. The full article can be found here.

Posted in Endangered species management |

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