will be little decrease (at maximum -1% decade-1) in south­ern Europe, and hardly any change over central Europe. In North America trends towards increased temperatures and changes in the frequency of heavy precipitation over most land areas are expected to continue. Furthermore, extreme events are likely to increase in frequency and severity (IPCC, 2007a).
     Warming in NAE will generally lead to a northward expansion of suitable cropping areas, and an increase in the length of the growing season for indeterminate crops (whose growth is determined primarily by environmental conditions e.g., root crops) but a reduction for determinate crops (that develop through a pre-determined set of stages, from germination to ripening e.g., cereals). It is assumed that  about  10-20%   of the increased crop productivity, which has doubled over the last 100 years, may be due to the growth-enhancing effect of CO2. It is unclear whether this will continue and to what extent this fertilization effect will be reduced by combinations of multiple biotic (pests, diseases) and abiotic (drought, heat) stresses. The increase of atmospheric CO2 concentrations may increase water use efficiencies (Roetter and van de Geijn, 1999; IPCC, 2007a). However, the expected frequency of extreme weather (flood­ing and droughts) will possibly offset the potential benefits to Europe (Olesen and Bindi, 2002) as well as to Canada and the United States (Reilly et al., 2003; Easterling et al., 2004; Lemmen and Warren, 2004). Northern Hemisphere snow cover, permafrost and sea-ice extent are projected to decrease further. In some areas, the timing of water avail­ability is expected to change—more precipitation falling as rain in winter, earlier snow-melt and more frequent dry spells in summer (IPCC, 2007a). In regions where crop pro­duction is affected by water shortages, such as in southern Europe, increases in the year-to-year variability of yields in addition to lower mean yields are predicted. Extreme high or low temperatures during crucial stages of plant growth can lead to considerable yield loss. Sea level rise could lead to larger areas being susceptible to flooding and saltwater intrusions with potentially disastrous effects on harvests.
     In NW Europe, climate change may lead to positive ef­fects for agriculture by triggering the introduction of new crop varieties and species, higher crop production and ex­pansion of suitable agricultural land area. However, climate change may have negative effects on infectious diseases of plants (Chancellor and Kubiriba, 2006) and may motivate a demand for different pest management practices and for measures to reduce nitrate leaching and the turnover of soil organic matter (Olesen and Bindi, 2002). Estimated in­creases in water shortages and extreme weather events may result in lower yields (and harvest indices), greater yield variability and a reduction of suitable areas for traditional and region-specific crops. Such effects will most likely ag­gravate the current trends of agriculture intensification in NW Europe and extensification in the Mediterranean and SE parts of Europe.
     In the US and Canada, future climate change is likely to result in agricultural shifts toward higher latitudes and elevations.   Moderate  increases  in  temperature   (1-3° C) along with elevated CO2 and changes in precipitation will have small beneficial impacts on crops such as wheat, maize and cotton. Further warming, however, will probably have

increasingly negative effects (Lemmen and Warren, 2004; Easterling et al., 2004; Stern et al., 2006). Some authors have reported positive crop yield responses to temperature increases of about 2°C, but negative yield responses at in­creases over 4°C. Higher temperatures and warmer winters could reduce winterkill of insects and broaden the range of other temperature-sensitive pathogens (Rosenzweig et al., 2000). It is still not clear whether North American agricul­ture as a whole will be affected negatively or positively by climate change. Part of the reason for this is the difference in assumptions regarding agriculture's adaptation potential. The growth enhancing effects of increasing CO2 concentra­tions (currently around 380 ppm and increasing at an an­nual growth rate of 2 ppm) on crops may mask much of the negative effects of changed temperature and precipita­tion patterns. Agriculture will likely be vulnerable to higher frequency and severity of extreme events—as was demon­strated during the summer 2003 European heat wave that was accompanied by drought and maize yield reductions of 20%, representing the largest yield decline since the 1960s.

How could technological innovations influence the ability of agriculture to mitigate and adapt to climate change?
Although unable to erase uncertainties, technological inno­vations may greatly influence the ability of agriculture to mitigate and adapt to climate change. For Europe, mitiga­tion and adaptation are necessary and complementary for a comprehensive  and coordinated  strategy  (Olesen  and Bindi, 2002; Metzger et al., 2006). Adaptation is an im­portant complement to greenhouse gas mitigation measures and policies. Adaptation to climate variability and change is not a new concept. Managed systems are likely to be more amenable than natural systems, and some regions will face greater obstacles than others. Throughout human history, societies have shown a capacity for adapting—though not always successfully (Lamb, 1995; Diamond, 2005). How­ever, adapting to climate change will not be an easy, cost-free task, and adaptation decisions in one sector (e.g., water resources) might have implications for other sectors. Many of the existing adaptation strategies may be strained by the expected changes in climate, particularly extreme events. Adaptation technologies include changing varieties/species to fit in better with changed thermal and/or hydrological conditions,  changing  irrigation  schedules  and  adjusting nutrient management,  applying water-conservation tech­nologies (such as conservation tillage), altering timing or location of cropping activities, etc. Some of those adapta­tion measures also have mitigative effects—such as applying "zero tillage" practices or using cover/catch crops in spring to reduce leaching and erosion. The provision of appropri­ate enabling environments and policies such as technology and knowledge generation and dissemination mechanisms will also be important considerations  (Easterling et al., 2004; Kabat et al., 2005; Carter, 2007).

Adaptive capacity and sustainability
The essence of sustainable development as defined by the Brundtland Commission (WCED, 1987) is meeting funda­mental human needs while preserving the life support sys­tems of the earth (Kates et al., 2000). Actions directed at