5.2 Current sensitivity, vulnerability and adaptive capacity to climate
5.2.1 Current sensitivity
The inter-annual, monthly and daily distribution of climate variables (e.g., temperature, radiation, precipitation, water vapour pressure in the air and wind speed) affects a number of physical, chemical and biological processes that drive the productivity of agricultural, forestry and fisheries systems. The latitudinal distribution of crop, pasture and forest species is a function of the current climatic and atmospheric conditions, as well as of photoperiod (e.g., Leff et al., 2004). Total seasonal precipitation as well as its pattern of variability (Olesen and Bindi, 2002) are both of major importance for agricultural, pastoral and forestry systems.
Crops exhibit threshold responses to their climatic environment, which affect their growth, development and yield (Porter and Semenov, 2005). Yield-damaging climate thresholds that span periods of just a few days for cereals and fruit trees include absolute temperature levels linked to particular developmental stages that condition the formation of reproductive organs, such as seeds and fruits (Wheeler et al., 2000; Wollenweber et al., 2003). This means that yield damage estimates from coupled crop–climate models need to have a temporal resolution of no more than a few days and to include detailed phenology (Porter and Semenov, 2005). Short-term natural extremes, such as storms and floods, interannual and decadal climate variations, as well as large-scale circulation changes, such as the El Niño Southern Oscillation (ENSO), all have important effects on crop, pasture and forest production (Tubiello, 2005). For example, El Niño-like conditions increase the probability of farm incomes falling below their long-term median by 75% across most of Australia’s cropping regions, with impacts on gross domestic product (GDP) ranging from 0.75 to 1.6% (O’Meagher, 2005). Recently the winter North Atlantic Oscillation (NAO) has been shown to correlate with the following summer’s climate, leading to sunnier and drier weather during wheat grain growth and ripening in the UK and, hence, to better wheat grain quality (Atkinson et al., 2005); but these same conditions reduced summer growth of grasslands through increased drought effects (Kettlewell et al., 2006).
The recent heatwave in Europe (see Box 5.1) and drought in Africa (see Table 5.1) illustrate the potentially large effects of local and/or regional climate variability on crops and livestock.
Box 5.1. European heatwave impact
on the agricultural sector
Europe experienced a particularly extreme climate event during the summer of 2003, with temperatures up to 6°C above long-term means, and precipitation deficits up to 300 mm (see Trenberth et al., 2007). A record drop in crop yield of 36% occurred in Italy for maize grown in the Po valley, where extremely high temperatures prevailed (Ciais et al., 2005). In France, compared to 2002, the maize grain crop was reduced by 30% and fruit harvests declined by 25%. Winter crops (wheat) had nearly achieved maturity by the time of the heatwave and therefore suffered less yield reduction (21% decline in France) than summer crops (e.g., maize, fruit trees and vines) undergoing maximum foliar development (Ciais et al., 2005). Forage production was reduced on average by 30% in France and hay and silage stocks for winter were partly used during the summer (COPA COGECA, 2003b). Wine production in Europe was the lowest in 10 years (COPA COGECA, 2003a). The (uninsured) economic losses for the agriculture sector in the European Union were estimated at ¤13 billion, with largest losses in France (¤4 billion) (Sénat, 2004).
Table 5.1. Quantified impacts of selected African droughts on livestock, 1981 to 1999.
|Date ||Location ||Mortality and species ||Source |
20% of national herd
FAO, 1984, cited in Toulmin, 1986
62% of national cattle herd
Ethiopia (Borana Plateau)
45-90% of calves, 45% of cows, 22% of mature males
28% of cattle
18% of sheep and goats
Surtech, 1993, cited in Barton
and Morton, 2001
42% of cattle
Desta and Coppock, 2002
22% of cattle
41% of goats and sheep
Devereux and Tapscott, 1995
Greater Horn of Africa
(average of nine pastoral areas)
20% of cattle
20% of sheep and goats
Ndikumana et al., 2000
46% of cattle
41% of sheep and goats
Ndikumana et al., 2000
62% of cattle
Shibru, 2001, cited in Desta and Coppock, 2002