Archive | January, 2012

Beyond Climate Envelopes

Most portrayals of the effects of climate change on wildlife and ecosystems is that species will simply shift towards the poles or upslope to follow the climate conditions they have evolved with as the earth warms.  But species are much more complicated than that.

One of the biggest hurdles in climate studies involves the complexity of species and habitats.  No species or habitat exists on its own; rather, an unknown number of interactions is constantly happening, and in turn affecting the status of said species or habitats.  Competition for food and habitat and displacement of species are among those interactions.  Consequently, when one wants to study a species or habitat response to a certain factor, it is important to consider those interactions as much as possible, seeing that they play a significant role in the possible outcome.

The state of the art in climate-species models for many years has been the climate-envelope model. which describes the climate variables such as temperature, humidity, and precipitation, among others, which characterize the conditions under which a species is found.  Once the climate-envelope of a species or habitat has been modeled, you can then project where that climate-envelope will exist under future climate scenarios and you assume that is an approximation for where species will need to go to survive.  However, these types of models have been traditionally taken into account the effect of the modeled conditions on other species that ultimately will be interacting with the species or system of focus and affecting its future.

A new study, however, is one of the first to include species interactions and dispersal abilities under the modeled climate scenarios, therefore portraying a much more accurate view of what the future will likely hold for a species, habitat, or ecosystem.  This is particularly important in the estimation of species extinction rates, since new distributions of species due to climate change might lead to interactions never before seen, as well as to the loss of others, and species might find themselves under conditions that were nonexistent before.  When shifting its range to a more suitable climate, a species may encounter others that are strong competitors and that will prevent its establishment, and in the event of no other suitable climate – or better dispersal abilities – lead to its eventual extinction due not to lack of available habitat, but rather lack of available living conditions.

The main findings of the paper are that climate change will strongly affect communities where “species have narrow niches, low mean dispersal rates,” and large differences in dispersal ability between species.  The authors reached those findings by simulating a 40-species community undergoing 4⁰C change over 100 years.  During the simulations, species were exposed to different thermal ranges and were assigned different dispersal rates and temperature tolerances, and their predicted distribution shifts tracking climate change determined future competitive interactions.  Interactions could be with species better adapted to the novel climate in a new area (due to their assigned thermal range and temperature tolerances), with species that had been in the new area before the new species arrival, or could be new interactions in the original distribution area due to the loss of one of more species that could not track climate change.  Those interactions, together with loss of thermal range for survival, were in turn used to predict extinctions.

In natural communities species will always have different dispersal abilities.  The rates of dispersal played a vital role in the simulations, as they would determine which species would be able to track climate change, and which would have the probability of facing competition.  Without dispersal variation, the model predicted a 98% extinction rate when species did not disperse.  That figure is lower (74%) when species have low dispersal levels and cannot track their optimal thermal range, and is lowest (13%-24%) when species have a high dispersal level and are able to track their thermal optima.

Variation in dispersal rates determined contractions and expansions in distribution, and those in turn determined what interactions occurred and which were lost due to climate change.  Competition for suitable habitat within a species temperature tolerance was the main interaction modeled, and the authors found that without competition, actually very few species would become extinct, independently of their dispersal rates.  Competition usually increases extinctions risks due to reduced fitness (species get stressed and don’t do as well when competing with others) and abundance (species numbers get reduced due to direct or indirect mortality because of competition), and climate change increases those risks because species are under added stress.  More new competitive interactions with consequent extinctions were observed when species had different dispersal rates, because good and poor dispersers would have more probability of interacting.  The study also found that competition reduced range expansions and slowed climate tracking, but interestingly, under low dispersal rates, it was sometimes to some species advantage: because the ones that could not disperse well would become extinct, the remaining species could better track climate change under less competition.

Finally, the authors state that climate change is an important factor adding to competition – in the absence of the competition, the effects of the climate change are predicted to be less severe for many species.  This is an important study for the understanding of how climate change can affect species, which can provide better guidance to the process of climate adaptation and related conservation strategies.

Posted in Climate Change0 Comments

Mining threatens important habitat on the Coronado National Forest

Mining threatens important habitat on the Coronado National Forest

Ocelot (photo: USFWS)

(Written with help from Matt Clark and Heather Murray.)

Defenders of Wildlife, along with a diverse set of partner groups, submitted comments this week on the Rosemont Mine proposal on the Coronado National Forest in Arizona.  The proposed open pit mine, just southeast of Tucson, would have a direct impact on 4,500 acres of the Santa Rita Mountain range, as well as impacts that would radiate far beyond the project’s footprint.

The Coronado NF provides vital recovery habitat for rare cats including the elusive jaguar and ocelot.  Last year a jaguar was spotted in the region for the first time in three years. In fact, this male jaguar was sighted roaming in a mountain range directly adjacent to the Santa Ritas, where Rosemont wants to dig its mine.  This come back story for jaguars can only carry on if intact, connected, suitable jaguar habitat is prioritized and protected in the region.  Projects of this size and scale on what is currently undisturbed suitable jaguar habitat give us great pause.

As the project proposal has been developed, some important species surveys needed to determine what wildlife would be impacted have not been completed.  Information related to biological resources has not been made available to the public, and impact analysis of key biological and hydrologic resources in the Rosemont area are lacking.  Similarly, analyses of the project’s potential contribution to climate change are completely inadequate.

As the comment letter states:  “The biological and ecological resources of the Rosemont area are unique and of both national and international significance. Hundreds of rare and regionally endemic species occur in the project area.  Neither the Proposed Action nor the Preferred Alternative . . . identify mitigation that is adequate to protect the Rosemont area’s biological resources.”

Groups highlighted a host of other concerns in the letter, from water quality impacts and water volume use to increased traffic and air pollution.  One key request from all groups is for the Forest Service to do its due diligence and provide a supplemental environmental review that fully analyzes the potential threats and impacts.  We will continue to push for additional information to be gathered and reviewed.

Similar issues have come up in other mining projects on the Coronado NF – major environmental impacts with insufficient review.  In fact, Defenders recently challenged an exploratory mining project in the region that was approved without NEPA review.

Last month, Defenders filed suit against the Forest Service in response to its approval of the Hardshell Minerals Exploration Project – located in the Patagonia Mountains approximately five miles south of the town of Patagonia, AZ – which would allow for the drilling of fifteen exploratory holes in an area known for its pristine natural landscapes and rich biological diversity.  The project as approved would involve around-the-clock drilling seven days a week, increase traffic to and from the area, and create significant noise and light impacts, among others.  Perhaps most alarming is that this mining company started a wildfire that burned almost 400 acres of the Coronado NF while conducting similar activities on their private in-holding adjacent to the proposed project area last May.

Despite the potential effects of this project on threatened and endangered species in the area – including the jaguar, ocelot, Mexican spotted owl, and lesser long-nosed bat – the Forest Service approved this project without NEPA environmental review.  Likewise, the Forest Service failed to consider the fact that two other similar exploration projects are currently proposed within just a few miles of the Hardshell project, greatly expanding the overall footprint of exploratory drilling in this area.  Defenders is concerned about the significant and cumulative environmental impacts of exploratory drilling at multiple sites in this Sky Island mountain range and the broader region.

It might not come as a surprise to learn that Rosemont Copper and Wildcat Silver, the two companies pushing for these mines to be permitted, are not only both Canadian-owned companies, but they also share some of the same board members. We are making sure that these companies follow the letter of the law to avoid undue harm to our precious wildlife, water and natural heritage.

Posted in Imperiled Wildlife, In the Field, National Forests, Public Lands, Southwest0 Comments

New England Cottontail Rabbit (FWS)

Upstream solutions for protecting candidate species

How can we find ways to encourage people to voluntarily conserve candidate species before they are listed under the Endangered Species Act?  Candidate conservation agreements are an existing tool, and we have been helping to develop another one.  That tool differs from candidate conservation agreements in several ways.  Most important is that it involves the U.S. Fish & Wildlife Service issuing “credits” for conservation measures taken to benefit a candidate species before listing.  After listing, those credits would be used to offset “incidental take” to the species.  On balance, the amount of credits issued and used would need to result in a net benefit to the species, as might happen when a person buys more credits than he or she uses.

This new candidate conservation tool would benefit species in several ways.  One is by incentivizing early conservation, which generally reduces the costs and difficulty of species recovery.  Two is by incentivizing habitat management (not only preservation), which the ESA does not require of non-federal landowners and which is needed to conserve and recover many conservation-reliant species.  Three is by reducing or precluding the need to list a candidate species.

Yesterday, we, along with other conservation organizations, submitted a letter to the Fish & Wildlife Service asking for their support in creating field-based projects to demonstrate the use of this new tool, which is sometimes called “pre-compliance mitigation” or “candidate conservation banking” (more memorable names are currently in development).

Posted in Imperiled Wildlife, Paying for Conservation0 Comments


dotWild is the blog of scientists and policy experts at Defenders of Wildlife, a national, nonprofit membership organization dedicated to the protection of all native animals and plants in their natural communities.

www.defenders.org