Considerable progress in the understanding of how global climate change is likely to affect agricultural production and forest resources has been made in recent years. In the recent Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change's (IPCC) Working Group (WG) II (McCarthy et al., 2001), agriculture and forest resources were combined in a chapter with other, less managed, terrestrial and aquatic ecosystems in order to assess their response to climate change. This was intended to facilitate comparison of the impacts of climate change on basic biological and ecological processes across ecosystems (including agro-ecosystems and forest ecosystems) in a consistent manner. However, agro-ecosystems and forest ecosystems are fundamentally different from less managed ecosystems such as wetlands, tundra, and savannas: they produce economically valuable goods and services within a system of clear and enforceable property rights. Such greatly complicates understanding of their response to climate change because of intense human intervention into climate-ecosystem interactions and because responses of these ecosystems to climate change can have direct and immediate economic impacts. Hence, we focus on agriculture and forest resources together in this paper.

The aim of this paper is to distill important insights into the vulnerability, potential impacts, and adaptation prospects of agriculture and forest resources in response to climate change from the IPCC's WGII TAR1. The majority of this paper is drawn from material generated for Chapter 5 of the TAR-WGII. The purpose of that chapter was to review and assess scientific progress in the understanding of how ecosystems (including agroecosystems and forest ecosystems) and their coupled social systems may respond and adapt to climate change, and to provide a global perspective on possible agricultural and forest outcomes. The absence of important research published since 2000 dictates caution in the interpretation of earlier studies, which follow below. We adopt a global perspective and although we recognize the importance of regional and local variation of impacts, we leave detailed discussion of such for others to consider.

We follow a modified version of the State-Pressure-Response model (to include Adaptation) of the Organization for Economic Cooperation and Development (OECD) to report key findings. State refers to the status or condition and future trends in food, fiber, fuel, and fodder systems under current climate conditions. Pressure refers to environmental and social stresses, including those arising from climate change, on such systems. Response refers to the induced changes in these systems arising from the imposed pressures (including climate change). Adaptation refers to the managed changes in ecosystems and deliberate human actions aimed at meeting resource supply needs given the ecosystem responses to climate change. This model disciplines our synthesis of the large amount of research on the consequences of climate change by focusing the review on the following questions: What is the current state of the Earth's agricultural and forest ecosystems and how effectively are we meeting the demands for their goods and services? What major challenges confront the world's food and fiber sectors over the next several decades, whether the climate changes or not? What are the likely biophysical and socioeconomic effects of climate change? What are the prospects for successful adaptation by agricultural and forestry systems to those effects? How vulnerable will those systems be after accounting for the potential for adaptation to alleviate adverse outcomes or take advantage of opportunities?

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