It was perhaps Sigmund Freud who provided some further insight into the scale and importance of emerging issues. Freud observed, "humanity has in the course of time had to endure from the hands of science two great outrages upon its naive self love. The first when it realized that our earth was not the center of the universe but only a speck in a world system of magnitude barely conceivable and the second was when biological research robbed man if his particular privilege of having been specially created and relegated him to a descent from the animal world" (Gould, 1977). In hindcast, the degree of uncertainty, at the time, associated with each of these outrages might possibly be equated to the uncertainty of the climate change debate, today. But more importantly, what would be the consequences if climate change were, in fact, the "third outrage" on humanity?
The Intergovernmental Panel on Climate Change (IPCC, 1996) concluded "the balance of evidence ... suggests a discernible human influence on global climate." The most recent IPCC assessment (2001) suggests "there is new and stronger evidence that most of the warming observed over the past 50 yr is attributable to human activities." We know from past experiences that weather and climate have a powerful influence on biological and human environments and that today's forests are the culmination of a long evolution within a climate envelope containing many natural fluctuations and extremes. The conclusion by the IPCC is alarming with the result that today's forests will be maladapted to future climate and its many variabilities and extremes. This projected magnitude of climate change, especially the anticipated rate of change because of human influences on the climate system, is beyond our current level of knowledge and adaptation mindset. This "outrage" imposed by humanity on the climate system will require a significant paradigm shift and new levels of knowledge for forest managers. However, knowing the anticipated future climate scenarios, continuing population demands, and emission increases, forest managers can begin an adaptation process to design the forests of the future to satisfy a multiplicity of needs, products and services.
The Earth's climate is not static. Shifts between climate states have occurred not only repeatedly but also often abruptly in the past (Charles, 1998). Gedalof and Smith (1998) highlight these step-like climate shifts using western North America tree-ring evidence, such as mountain hemlock (Tsuga mertensiana), where climate variability is largely a function of the winter size and position of the Aleutian low-pressure system. Interannual climate variability in this system is largely a response to El Nino/southern oscillation (ENSO) related teleconnections and interdecadal climate variability are driven by the Pacific Decadal Oscillation (PDO). The PDO is distinct in that it does not appear to be an oscillatory system, as the name implies, but rather switches between states abruptly, in step-like time periods. There is strong evidence suggesting that the North Pacific underwent a massive reorganisation following the winter of 1976 with significant repercussions in fisheries, water resources, forestry, agriculture and other areas of natural resources management in western Canada (Ebbesmeyer et al., 1990). The tree-ring studies by Gedalof and Smith (1999) show that annual radial growth of mountain hemlock is sensitive to the types of climate variability associated with the North Pacific-Ocean-Atmosphere system. The climate shift of 1976 may mark a return to greater interdecadal variability. Under climate change, is it expected that future changes will perform in a similar abrupt fashion, or gradual or both?
Forest biodiversity, at all taxa levels, has become increasingly important and other traditional forest issues, such as growth and yield have evolved, for example, into detailed modelling of global carbon sinks and sources under climate change. It is the human expectation of the roles performed by trees, woodlots and forests, managed or unmanaged, that makes it difficult to set global targets for biodiversity conservation, tourism, industrial, natural, environmental, social and spiritual services, to name a few. Values are diverse and the incremental costs of conservation and national benefits are sometimes difficult to articulate. Regardless, the changing climate affects all of these processes either directly or indirectly, nothing is stationary, and abrupt climate shifts are expected to occur in the future.
Why should adaptation to climate change and variability be considered? Responses to global warming are popularly considered to be mainly in terms of mitigation with the aim of reducing human generated greenhouse gas emissions. However, adaptation is also a main part of the response set. Pro-active adaptation actions, especially the many benefits, are needed for several reasons, principally because human-induced climatic change appears unavoidable, regardless of the mitigation actions to slow the speed of global warming.
Characteristics of systems related to adaptation are identified in several literature streams, including disciplines in both the natural and socio-economic sciences. These include concepts, such as resilience, sensitivity, tolerance, thresholds, critical levels, susceptibility, vulnerability, adaptability, adaptive capacity, coping range, flexibility, size (individual or collective) and part of the forest ecosystem (e.g. human, plant, animal, water, soil, air). Several of these are described in Smithers and Smit (1997). Any new operative word will need to focus much more on enhancing the "resourcefulness" of the forest estate, specifically, the interlinkages between forest ecosystems, species and genetics and the changing atmosphere.
It is important to collectively understand, develop adaptation options, design and manage forests, enhance the benefits, and reduce the dangers of climate variability and climate change (Wheaton and MacIver, 1999). For example, the recent IPCC Special Report "The Regional Impacts of Climate Change: An Assessment of Vulnerability" (Watson et al., 1998) addresses the vital question: what is "the degree to which human conditions and the natural environment are vulnerable to the potential effects of climate change?" The degree of vulnerability indicates the amount of adaptation that is required within the context of our history, infrastructure, and changing technologies.
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