Climate Change: Concepts and Impacts
Climate changes include the changes in the seasonal and/or annual temperature, regional rainfall rates, drier conditions risk, and increasing emissions of the atmospheric greenhouse gas concentrations.
Any change in climate is seriously affecting the natural environment and human activities, including agriculture, and it alters the global energy budget. Abundant scientific literature indicates a consensus understanding of such issues (Anwar et al., 2015; Sudmeyer et al., 2016). Accordingly, it is prudent to contemplate and plan for recognition of the global ambitions to limit the climate change’s negative externalities on food sector production performances (Qureshi et al., 2013).
Climate change impacts include economic pressures and opportunities related to increasing human populations and changing human dietary preferences, increased input costs and energy prices, competing land-use pressures and economic policy-related pressures. The impacts of climate change on agricultural productivity will vary regionally and by enterprise, with some regions and enterprises benefiting and some not. Changing rainfall, temperature, carbon dioxide (CO2) and other climatic variables will affect average crop and pasture productivity, quality and nutrient cycling, pest and disease activity, livestock production and reproductive rates. Whereas increased CO2 concentrations will improve the efficiency of plant use of water, increased temperature could be both beneficial harmful depending on season and location (Barros, et al., 2014).
Rainfed Agriculture is Globally the Dominant System
The world’s land and water resources are finite and under pressure from a growing population. Global figures about the shares of land and water used by agriculture versus non-agricultural sectors show major regional variations and a series of locally important imbalances on demand and supply. The growing recognition of the need to meet environmental requirements has generated further intensified competition (Moeller, 2009; Oliver, 2010).
Rainfed agriculture is the predominant agricultural production system worldwide. Of the current 1600 million ha of world cultivated area, about 80 percent are rainfed. Rainfed agriculture produces about 60 percent of global crop output in a wide variety of production systems. The most productive systems are concentrated in temperate zones of Europe, followed by North America, and rainfed systems in the subtropics and humid tropics. Rainfed cropping in highland areas and the dry tropics tends to be relatively low yielding and is often associated with subsistence farming systems. Evidence from farms worldwide shows that less than 30 percent of rainfall is used by plants in the process of biomass production. The rest evaporates into the atmosphere, percolates to groundwater or contributes to river runoff (Abrahams, et. al., 2012).
The extent of rainfed area has not grown in recent years, due to the replacement of some land too degraded for further cropping by lands newly converted from forests and grasslands to arable farming. This process of land degradation and abandonment, and the development of new lands in replacement, is particularly characteristic of low-input, low-management farming systems, or cultivation on steep slopes. However, data on these farming systems are sparse, because some of these lands may not be permanently degraded but may be brought back into cultivation after long fallow. Therefore, it is difficult to estimate the areas involved, (Ali, et. al., 2012).