Assessing Climate Threat to Food Crop Production in Ghana

摘要

Agricultural productivity growth holds the key to unlocking agricultural potential including food crops in Ghana. Yield levels for major staple crops are significantly lower than their potential levels. Cassava, maize, sorghum, rice and yam have yieldgaps of 57.5%, 40%, 33.33%, 40% and 38% respectively (MOFA, 2007). Despite recent agricultural growth being driven by land expansion, productivity of major staple crops can be enhanced by closing these crop yield gaps (Breisinger et al.， 2009).However, more recent literature points to the adverse impact of changing climate on crop productivity. A review of climate impact literature of various crops by Knox et al. (2010) indicates that yields of cassava, sorghum, millet and maize will decreasein West Africa through adverse effects of climate change. Warming and drying exacerbate stresses in crop plants, potentially leading to catastrophic yield reductions: It affects water availability for irrigation; it also reduces soil fertility, health and nutrient availabil-ity; and it also increases incidence of pests and diseases and weed competition. Sagoe (2006) used crop simulation to analyze climate change impact on root crops in Ghana and the results indicate reductions in yields of cassava and cocoyam under all projected climate scenarios. Analysis of projected climate change impact in Ghana's initial communication to IPCC also indicates reductions in yields of maize in the transition zone (GEPA, 2001). The aforementioned analyses and other similar studies are based on crop simulation models which show relationship between environmental variables including climate and the growth of crop plants. The effect of climate on crop yield may be more complex than just mere climate-crop plant growth relationship. Other factors can reverse an otherwise positive or negative effect of climate on crop yield. The failure to take into account the role of non-environmental variables denoting farm or farmer characteristics and/or management practices by farmers may undermine the use of crop simulation models in climate research.