increase in the frequency, as well as severity, of tropical storms over the past few decades. Globally, flooding has increased severalfold on all continents except Oceania. More disturbing still is the projection that the changes set in motion will endure well into the next millennium.
The most common point of reference in discussions about global climate change is the rise in average global temperature. Rising temperatures lead to higher rates of evapotranspiration and place greater demands on water resources. A warmer climate causes a more rapid melting of snowpack and glaciers, thus affecting the future water security of high population density areas in central and south Asia. Elevated temperatures are also responsible for more rapid plant maturation and a shortening of the reproductive period, leading to declines in net crop productivity and requiring more land and greater irrigation to realize the same yields as in the past. The focus on this single factor, however, masks the fact that the average global temperature is itself an index of local and regional climatic patterns, such that relatively small changes in the global index implies greater changes in these patterns, with even greater intra-annual impacts on agriculture.
Together, deviations in rainfall, temperature change, and CO2 fertilization effects are among the major factors addressed in large-scale modeling efforts. For the northern latitudes, a slight rise in temperatures and lengthening of the growing season is expected to increase productivity. Over the long term, however, rising temperatures will have negative influence on crop yields. A comparison of modeling scenarios (Easterling and Apps 2005) showed that with temperature changes above 1.5°C, major crops, such as rice and maize, show a distinct downward trend with rising temperature, with relative declines of 30% for rice and 15% for maize over a 3°C increase in temperature. Empirical results suggest even greater sensitivity to ambient temperature change. Rice, maize, and soybean yields have declined between 11-17% with each increase of 1°C in nighttime temperatures (Peng et al. 2004; Lobell and Asner 2003). Figure 23.1 illustrates a projection of combined impacts of climate change on agriculture worldwide.
To feed a global population of over 9 billion by 2050, production of major cereals needs to double. To achieve this, the average annual increase in cereal yields will need to increase by nearly 70%, and this level of growth must be sustained for the next 40 years (World Bank 2008). Over the short term, such increases are easily met. For the long term, this challenge will be far more difficult to meet. Two critical aspects that are not considered in the projections of impacts of climate change on agriculture are (a) the increased frequency of disruptive events (droughts, floods, heat waves) as temperatures rise and (b) the increased variability in rainfall levels (on-set, distribution, overall quantities) as precipitation levels fall. Both will increase the adverse impacts of climate change on agriculture beyond what is already being projected, and, in response, could cause a switch to short-term destructive behaviors (e.g., a massive acceleration of deforestation to open up new lands for food and fuel production). This, in turn, would escalate CO2 emissions and almost ensure that worst-case climate change scenarios occur. It is clear that we must not allow this to happen.
Put into the context of population and economic growth, the access to land, water, and energy will define many political debates in the future. On the whole, development of the bioeconomy will likely be accompanied by the development of biopolitics.
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