Thursday, April 23, 2009

Must We Choose Between Climate Change and Habitat Preservation?

An Earth Day article in Slate argues that the focus on preventing climate change is harming the more important goal of preserving endangered species and their habitats.

Even if we consider the impact of environmental degradation on humanity, deforestation has a more significant and immediate impact on local weather, water availability, water quality, and soil erosion than does global climate change from greenhouse gases. The roots of trees and native brush hold loose, nutrient-rich topsoils together, slowing erosion and absorbing precipitation. You can see the impact of habitat loss on local climate by poking a stick into the parched soils of the Brazilian cerrado or wandering along the boundary of the expanding Sahel Desert in Africa. Then there's Cherrapunjee, India, once considered the wettest place on Earth—and now facing climbing temperatures and water shortages as the once lush landscape has been denuded.

Only recently have conservationists begun to grasp what a debacle it was to enact climate change legislation in Europe without first putting in place global deforestation treaties. EU policies promoting a market for biofuels triggered the destruction of Indonesian rain forests in favor of palm plantations. Meanwhile, the forestry industry has argued that their monoculture plantations in Asia, Africa, and South America deserve credit as carbon sinks, but the data show that these biological deserts are actually spewing out carbon dioxide. We don't have federal climate change legislation in place in the United States, but the Obama administration is pushing for a carbon tax in the new budget. Conservationists now have an apparent ally in the White House, so let's tell him to slow down and get those forest protections in place before the carbon-conscious spill any more blood.

As evidence, the author cites a paper from PLoS Biology from 2007 that compared climate change and habitat conversion as causes for loss of biodiversity. (I discussed what the results meant for birds at the time.) That paper found that habitat loss alone would cause at least as many extinctions as climate change, and it is likely to contribute to most climate-related extinctions. In the high latitudes, habitat changes are being wrought primarily by warming, but in the temperate zones and tropics, economic development and deforestation drive habitat changes.

Those two trends, deforestation and climate change, can combine in particularly nasty ways so that what appears to be "green" may actually be harmful. When trees are viewed solely as carbon sinks, then any tree will do, regardless of how appropriate it is for the local landscape. The same may well hold true for fantastic schemes such as genetically-modified carbon-eating trees if such things existed. In most cases it is preferable to preserve existing forests than to convert wild lands into tree farms for carbon offsets. Numerous studies have shown that natural habitats fix more carbon than even the best artificial ones.

Yet preserving natural habitats is not what dominates the climate change discourse. Instead we have various carbon offset schemes and alternative energy, which can consist of a bewildering array of options depending on the speaker. By far the worst manifestation of this thoughtless approach appears in alternative energy proposals, especially biofuels. Currently biofuels derive from one of three main sources: corn, sugarcane, or palm oil. All of them are grown in monoculture with substantial chemical inputs, and all of them are replacing more and more natural habitat. Fuel from all such sources requires more energy to produce than it releases in burning. As of this writing cellulosic ethanol remains largely theoretical. Despite the negative energy cycle and its consequences for natural habitats, these biofuels are presented as the answer to climate change and insecure oil supplies.

The goal of saving endangered species need not be set aside to prevent climate change. However, we need to abandon many of the "solutions" offered thus far and adopt ones that preserve and expand natural landscapes.