Earth & Sky

Links:

Thomas, C. D. et al. ““Extinction risk from climate change.”“:http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v427/n6970/full/nature02121_fs.html Nature 427, 145-148 (2004) 4pp.

BBC News, “Climate risk “to million species”“:http://news.bbc.co.uk/1/hi/sci/tech/3375447.stm (Jan. 7, 2004)

Center for Applied Biodiversity Science at Conservation International – Climate Change

Complete transcript from the ““Global Warming”“:http://www.washingtonpost.com/ac2/wp-dyn?pagename=article&node=&contentId=A4375-2004Jan9&notFound=true live chat on washingtonpost.com, featuring Dr. Lee Hannah of CABS (January 12, 2004)

Author’s Notes:

We interviewed the two U.S. authors of the nineteen authors for the Nature paper. They are Dr. Lee Hannah and Dr. A.P. Townsend. We also interviewed Dr. John Harte, a respected scientist not involved with the study.

Highlights from Dr. Lee Hannah’s Interview:

Every species depends on a certain range of climate for its survival. These ecological niche models are excellent predictors. For example, researchers have predicted the current spread of many invasive species by using these models.

To estimate extinction risk from climate change modeled climate requirements for individual species and then extrapolated from present-day climate to predicted future climate to see what the new range of a species would be. We used established/accepted global climate models (also known as general circulation models) to project future climate scenarios. We plug the future climate projections back into the ranges for each species, and see what happens to the expected range in the future.

This is the first time scientists have estimated extinction risk from climate change for such a large number of species, from all over the world. More will follow.

If these areas are representative of Earth’s species in general, then we have a lot of reason to be concerned, worldwide. We are getting similar results for species and areas all over the globe-different taxonomies, habitats, geographies etc., and we are getting the same results. This suggests that this is a close enough representation of what will happen to all species and areas. Furthermore, the models we used all give similar results. The choice of which model to use is not a big issue.

We may have underestimated extinction risk. We only looked at risk until 2050. We expect even more loss after 2050. Climate change is expected to accelerate over the century. From 2050-21oo we expect even more extinction risk.

What can people do if they are concerned? These results are not inevitable. They are based on climate models that assume no changes in greenhouse gas emissions or reductions in carbon in the atmosphere. Two things we can do are: 1) Improve parks, refuges, and conservation areas so that species have places to migrate as climate shifts. 2). MOST important, CURB climate change itself. Without this, it won’t make much difference whether we improve parks and conservation areas. All these improvements would be swamped if climate change were unabated. *So, get policy makers to make a serious commitment to a shift in energy sources, away from the greenhouse gas emissions of petroleum to clean, renewable energy sources. *And reduce personal emissions as much as possible.

Biologists are major stakeholders and it is within our expertise to comment on policy.

Some people might wonder why species would be at risk of extinction if they survived the last ice age. The expected changes in climate go far outside the envelope of the past few million years-including ice ages. Furthermore, we expect a warming, not a cooling. There is no place left to go as climate warms-even mountaintops won’t be as cool and will run out of room for species to shelter from the heat.

Finally, we are not looking at a “natural” planet anymore. Species run into human land use everywhere. Land use and climate are not independent. Land use is a huge barrier to species migration.

Highlights from Dr. A.P. Townsend’s Interview:

This (the Science report) was a study of studies. Labs from around the world used ecological niche modeling to predict what will happen to present-day species distribution as the climate warms into the future.

Biological species follow simple and accessible rules about where they are found and not found. These models are very predictive-every species obeys these rules within their native range. We can use these rules to predict what will happen if a species invades a new range.

We can also use these rules/models to predict what will happen to a species range as the climate warms 50 years into the future.

A large percentage of species are going to see serious declines if climate warms. By reducing the expected warming, we expect fewer species to be at risk of extinction. In other words, by curbing climate change, we can save a large percentage of species from extinction.

This decline in species is a very serious concern. There are at least three levels to this concern:

1) Aesthetic/ethical: Humans are here on Earth with a natural heritage and a chunk of that will be gone by the end of this generation. This is a damning view even if nothing is relevant to human well being. Loosing it is still serious-it represents millions of years of evolutionary experience.

2) With any reorganization of natural systems, we can expect serious reorganization of how ecosystems function. Natural systems are highly integrated and we can expect cascading affects, and can only guess at what these might be. We will be sitting back and watching it unfold.

3) Human-related support systems will be affected in known and unknown ways. For example, can’t we just keep growing corn and other food crops and not worry about whether other species are going extinct? Corn doesn’t grow in the absence of other species. It needs pollinators, soil biota, and simply doesn’t grow in a vacuum. What’s more, pest species are likely to be affected in positive ways by climate warming (e.g. the cockroaches of the world). This may have substantial impacts on human food production.

Even if we signed the Kyoto Protocol tomorrow, we’d still have a bad time to get through. This situation is totally unprecedented in the history of all life on Earth.

One current example: Monarchs are in deep trouble due to climate change. They overwinter in Mexico in cool, dry forests. Right now those forests are not so dry anymore. They are experiencing increasing levels of precipitation. Because of this, in recent episodes, 50% of monarchs in the two largest colonies have died (frozen due to the moisture), with millions of butterflies on the ground. These events continue to unfold.

What can people do? Make it clear to your congressmen and senators that this is very important. The EPA must shift its regulations, and this should be done in an international context.

It is irresponsible as a scientist, not to think about the (public) implications of the science that you do. Scientists offer dependable, serious quantitative results. We, the public, need to consider whether we really want to rely on petroleum in the future.

Highlights from Dr. John Harte’s Interview:

My overall take on this study is that it is a very useful analysis. The general conclusion is correct-a large fraction of species is in jeopardy if global warming proceeds. This work adds yet another reason for why we (humans) need to take action to reduce global warming in the future-including working for new energy policies.

My major concern with this study is that it underestimates the scope of the problem. They make a key assumption: that the adaptation of species to climates is uniform across the species range. But I suspect in reality that populations within a species are differentially adapted to climate (e.g. the southern limit versus the northern limit). The study constructs a climate envelope that the species exists within, and assumes that all members of the species have the same envelope.

But imagine an individual in the middle of its range, the climate warms, and it is still in the predicted climate envelope. However, the individuals in the south, are shunted out of the climate envelope. If you suppose that every population is adapted to a narrower climate envelope within the range then all the individuals within that narrower range would be stressed by changes to the envelope. Data are not available yet on narrower within-species adaptations to climate – We don’t know enough about general differences between populations within a species.

There is a strong likelihood that this is actually a very important affect.

The overall conclusion is the same. There will be a large affect on species diversity with global warming. We need to take action now to reduce the risk of species loss. This is yet another example of a likely huge impact of global warming on the planet, others including sea level rise, changes in food production, and affects on ecosystems.

The risk of species loss due to warming is comparable to the risks of species loss due to habitat loss, or perhaps even bigger.

It’s important for future research to focus on the damage from the loss of this diversity. How will species collapse affect human well being, natural ecosystems, and other variables?

The following people were interviewed for today’s program. Our thanks to:

Dr. Lee Hannah
Co-Leader, CABS/TNC Climate Change Initiative Climate Change Program
CABS Conservation International
Washington, DC

A. Townsend Peterson, Ph.D.
Associate Professor
Department of Ecology and Evolutionary Biology
Curator of Ornithology
Natural History Museum and Biodiversity Research Center
The University of Kansas
Lawrence, Kansas

Dr. John Harte
Professor Energy and Resources Group
University of California
Berkeley, CA