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.

SCB seeks a director for the North American Policy Program

The Society for Conservation Biology (SCB) is a global community of conservation professionals with over 4,000 members (resource managers, educators, government and private conservation workers, informed members of the public, and students) dedicated to advancing the science and practice of conserving the Earth’s biological diversity. SCB seeks a North American Policy Director to fill two critical roles: (1) to help prepare and implement the policy process guided by SCB’s strategic plan; and (2) to empower the membership by providing them with the information and skills necessary to influence the policy process themselves. This is a new position. The North American Policy Director is responsible for coordinating all of SCB’s policy activities in the U.S. and Canada. This position requires significant abilities and experience in communications, a broad understanding of SCB’s mission and philosophies, sensitivity to maintaining an objective role for SCB scientists in the policy arena, collaboration with other professional societies and scientists, and a clear vision for SCB’s role in influencing conservation policy and compelling ideas on how to achieve it. For more information see this announcement or this pdf.

New version of the Connectivity Analysis Toolkit (1.3.0) released

The Connectivity Analysis Toolkit is a software interface that provides conservation planners with tools for both linkage mapping and landscape-level ‘centrality’ analysis.

We have just released Version 1.3 with the following changes:
Updated python and python packages, including NetworkX to version 1.8dev.
Updated Hexsim-based functions to Hexsim version 2.5.1, which improves conversion of .asc input files to hxn files.
Added support for locales (e.g., areas in Europe) that use a comma instead of a period as decimal separator.

The free software can be downloaded here.

Does wolf recovery trigger trophic cascades?: New research from Yellowstone, the Great Lakes, and Europe

A lot of media attention continues to be focused on the question of whether and how wolves trigger trophic cascades in ecosystems, by suppression of herbivory by ungulates and consequent release of vegetation and species such as birds that are dependent on the vegetation for their habitat needs. Trophic cascades can be caused by numeric effects (declines in ungulate populations), behavioral effects (prey foraging differently and avoiding areas of high predation risk), or a combination of the two. Behavioral or non-consumptive effects can be linked to numeric effects when altered behavior leads to poorer nutrition and lower pregnancy rates.

This last effect has been proposed as a cause of elk declines in the Greater Yellowstone Ecosystem, but a new paper by Arthur Middleton and coauthors in Ecology Letters challenges that hypothesis, and finds that changes in elk behavior due to encounters with wolves have little effect on elk body fat or pregnancy rate, probably because elk encounter wolves infrequently (about every 9 days) in this area. This leaves open the possibility that wolves are contributing to elk population declines directly via predation. This last point has at times been missed by the media, resulting in headlines such as “wolves not to blame for elk decline”.

Another paper by the same research team found that a factor contributing to elk population declines in Yellowstone National Park was the decline in native cutthroat trout in Yellowstone Lake after nonnative lake trout were introduced. Because spawning cutthroat trout, but not lake trout, form an important food source for grizzly bears, the invasive speceis indirectly caused grizzly bears to shift their diet towards increased predation on elk calves, contributing to a decline in elk that had previously been attributed primarily to wolf predation (figure below).

While most research of wolf-induced trophic cascades has taken place in Yellowstone, two new papers test the trophic cascade hypothesis in the northcentral US and Poland. Both take a correlative approach that compares vegetation in areas with vs. without wolves. In Wisconsin, Ramana Callan and coauthors found that species richness of both forbs and shrubs was significantly higher in areas with high wolf use. This supports the hypothesis that wolves, by reducing the intensity of browsing by white-tailed deer, are reversing the biotic impoverishment of understory plant communities caused by decades of overabundant deer populations. Similar contrasts between areas of high and low wolf use were found by DPJ Kuijper and coauthors in Poland, where browsing intensity of tree saplings was lower inside wolf core areas. At a finer scale within wolf core areas, sites with more coarse-woody debris, which is an impediment to escape from wolf predation, had even lower browsing rates, supporting the conclusion that at least a portion of the effects on vegetation are behaviorally-mediated rather than solely due to lower numbers of ungulates.

From Middleton et al. 2013

From Middleton et al. 2013

Posted in Endangered species management |

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 |

Society for Conservation Biology (SCB) overhauls its website to provide more resources for conservation scientists

The Society for Conservation Biology recently completed a major overhaul of the SCB website.

The new website provides a wealth of information on recent issues in conservation policy. You can access regular updates on conservation policy news by subscribing to the Policy RSS feed.

Other sections of the website provide information on SCB’s regional sections and working groups. The most popular section of the website is the board listing job openings in the field of conservation biology.

Newer Posts ›

‹ Older Posts