Category Archives: Climate change

A new paper in the journal Science by Raquel Garcia and coauthors provides one of the first comprehensive reviews of how different aspects of climate change are projected to differentially affect the regions of the earth, and what those contrasts imply for biodiversity. Their findings suggest that while polar climates are projected to warm and shrink in area, the tropics will see the emergence of novel climatic conditions and undergo local changes in average climates beyond past variability. The review outlines a conceptual framework for classification of climate change metrics according to the types of threat and opportunity they are likely to impose on biodiversity, which can assist in planning to enhance climate resilience and adaptation potential.

Figure 3 from Garcia et al. 2014.

A perceptive new paper by Dan Doak and colleagues in the journal TREE (link) critiques the “New Conservation Science” (NCS). NCS is a trend by some scientists and environmental NGOs to prioritize human-centered goals such as ecosystem services, and view as outdated efforts to protect biodiversity for its own sake. The authors conclude that the  movement towards NCS is driven by values rather than science:

Despite claims that NCS approaches are supported
by biological and social science, NCS has limited
support from either. Rather, the shift in motivations and
goals associated with NCS appear to arise largely from a
belief system holding that the needs and wants of
humans should be prioritized over any intrinsic or inherent
rights and values of nature.

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.

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. Continue reading →

The Connectivity Analysis Toolkit is a software interface that provides conservation planners with newly-developed tools for both linkage mapping and landscape-level ‘centrality’ analysis. Centrality refers to a group of landscape metrics that rank the importance of sites as gatekeepers for flow across a landscape network. The Toolkit allows users to develop and compare three contrasting centrality metrics based on input data representing habitat suitability or permeability, in order to determine which areas, across the landscape as a whole, would be priorities for conservation measures that might facilitate connectivity and dispersal. The Toolkit also allows application of these approaches to the more common question of mapping the best habitat linkages between a source and a target patch. The software is freely available at www.connectivitytools.org (a link is also posted on this blog site). A detailed manual included in the download gives more background on the methods, and may also be useful to those who are not GIS modelers but are interested in conservation planning. Although this blog has a purposely limited audience, we plan to make the software broadly available, so please feel free to distribute this information and the location of the download website to anyone who may be interested.

Conservation planners increasingly seek to consider both biodiversity process and pattern in reserve design. However, in part due to computational limitations, most current reserve design tools remained focused on either 1) the selection of sites that capture elements of biodiversity pattern but ignore connectivity, or 2) connectivity mapping methods that have key limitations, such as the need to identify in advance the source and target of linkages. We have developed a software ‘toolkit’ that combines several new connectivity analysis and mapping methods. These methods provide a means to quantitatively incorporate connectivity within the planning process, while overcoming some of the limitations of previous linkage mapping methods. We hope to release the software for beta testing in August-September 2010. If you would like to be informed of the availability of the beta release, please go to the
Beta release registration page