Conservation and Climate Change: the Challenges Ahead

Abstract

Climatic changes in the distant past were driven by natural causes, such as variations in the Earth’s orbit or the carbon dioxide (CO2) content of the atmosphere. Today, and even more so in the future, climatic changes have another driver as well: human activities (IPCC 1996). The natural greenhouse effect from clouds, water vapor, and CO2, primarily, is responsible for some 33◦ C of surface warming. Human use of the atmosphere to dump gaseous wastes adds to the natural greenhouse gases and is typically projected to result in a global warming of about 1.5◦–6◦ C in the next century (IPCC 2001a). This range— especially if beyond 1–2◦ C—could result in ecologically significant changes (Thomas et al., 2004), which is why climatic considerations are fundamental in the discussion of conservation strategies for the twenty-first century. The transition from extensive glaciations of the Ice Age to more hospitable landscapes of the Holocene took from 5,000 to 10,000 years, during which time the average global temperature increased 5–7◦ C and the sea level rose some 100 m. Thus, we estimate that over the last 20,000 years, the natural rates of warming on a sustained global basis are about 0.5◦–1.5◦ C/thousand years. There is, however, evidence amassing of regional, rapid (i.e., abrupt nonlinear) changes as well (e.g., Schneider 2004 provides an overview). Both the slower and more rapid changes radically influenced where species lived and their extinction rates. Climate change was a potential contributor—along with hunting and other human activities—to the extinctions of woolly mammoths, saber tooth cats, and enormous salamanders. During the last Ice Age, most of Canada was under ice. Pollen cores indicate that as the ice receded, boreal trees moved northward “chasing” the ice cap (i.e., moving with the warming temperature). But did the species within the boreal tree community shift in lock-step with the trees?