Predictions of Climate Change and its Impact on Crop Productivity

In the first section of the book, chapters by Lobell and Burke (Chapter 3) and Jarvis et al. (Chapter 2) address predictions of climate change over the next 30+ years and their likely biological and economic consequences

© CAB International 2010. Climate Change and Crop Production (ed. M.P. Reynolds)

in the context of crop productivity. Their main points are summarized as follows.

Developing countries will be affected most for three reasons: (i) climate change will have its most negative effects in tropical and subtropical regions; (ii) most of the predicted population growth to 2030 will occur in the developing world (United Nations Population Division DoEaSA, 2009); and (iii) more than half of the overall work force in the developing world is involved in agriculture (FAO, 2005).

While anthropogenic effects on climate have been apparent for several decades, modelling future climate change is not an exact science due to the complexity and incomplete understanding of atmospheric processes. None the less, there is broad agreement that, in addition to increased temperatures (see Plate 1), climate change will bring about regionally dependent increases or decreases in rainfall (see Plate 2), an increase in cloud cover and increases in sea level. Extreme climate events will also increase in intensity or frequency, such as higher maximum temperatures, more intense precipitation events, increased risk and duration of drought, and increased peak wind intensities of cyclones. Predictions in sea level rise indicate that this will continue for centuries after temperatures stabilize, causing flooding of coastal lands and salini-zation of soils and subsurface water in coastal regions.

Models of crop response to climate change mainly consider temperature, soil moisture and increased carbon dioxide. However, many other processes not easily incorporated into models could potentially have significant effects including: pests and diseases, brief exposures of crops to very high temperatures, elevated ozone, loss of irrigation water, and increase in inter-annual climate variability associated with monsoons and phenomena like El Niño. The model outputs, while encompassing a wide range of potential outcomes, tend to have the following in common:

• The yield potential of staple foods will decline in most production environments and commodity prices will rise.

• While projections for a few countries with northerly latitudes indicate net positive impacts of climate change, projections for most developing countries are negative.

• Only 'best-case' scenarios predict no net effect of climate change on global cereal yields by 2030 but predictions beyond that time frame are much more pessimistic.

On a more positive note, Lobell and Burke (Chapter 3) also state that an important factor in terms of maintaining productivity in the face of climate change will be the way farmers adapt their cropping systems: for example by diversifying when faced by increased risk, or by adopting new technologies derived from centrally planned efforts, such as cultivars bred to resist biotic and abiotic stresses as well as improved and more sustainable cropping practices that permit the genetic potential of new cultivars to be realized. These issues are addressed in subsequent chapters.

0 0

Post a comment