The main objectives of this manuscript are to report, for a southern African study region, on agricultural impacts assessment under climate variability and change scenarios for rainfed systems to illustrate the regional challenges of climate change and variability in southern Africa. The research uses a selected study area, known as the Pandamatenga Plains, which is located in northern Botswana, and it considers cropping of maize, sorghumand sunflower under rainfed conditions.The specific objectives are: 1) to show real world climate change through the scientific understanding of downscaled climate scenarios; 2) to integrate downscaled climate scenarios with a crop model and adaptation option models, and with agricultural production information; 3) to assess the impact of climate change on crop yield, soil moisture stress, excess runoff etc. in rainfed agricultural systems; 4) to determine the potential for excess moisture enhancement and water harvesting through a modeling study; and finally 5) to recommend adaptation strategies based on modeling evidences.
The southern African region is vulnerable to climate change that causes multiple biophysical, political, and socioeconomic stresses. The stresses remain a major threat to the region’s susceptibility to vulnerability; they restrain the region’s populace adaptive capacity to climate changes and variability. Besides increases in temperature, climate change in sub-Saharan Africa is expected to cause, increases in the incidence of extreme events such as droughts and floods, changes in rainfall intensity,increases in desertification and increased in drought frequencies .Present research confirms that while crops would respond positively to elevated CO2 , the associated impacts of elevated temperatures, altered patterns of precipitation and possibly increased frequency of extreme events, droughts and floods. Taken all else as equal, these events will probably combine to depress crop yields and increase production risks.Expected impacts include shortened or disrupted growing seasons, reductions in the area suitable for agriculture, and declines in agricultural yields in many regions of sub-Saharan Africa . Several studies have already revealed that a combination of increased rainfall variability and increasing ambient air temperatures will cause a significant decline in yields of major staple crops, particularly for maize. In a recent work, Lobel et al. used a data set of more than 20,000 historical maize trials in combination with daily weather data.
It showed that for each degree day spent above 30˚C maize yield was reduced by 1 percent under optimal rain-fed conditions, and by 1.7 percent under drought conditions. In a similar study, maize yield projections in Malawi found a decline of up to 20 percent in the next 50 years. A similar study projected a decline of 10 to 57 percent by 2080 in Zimbabwe, which is mainly due to increased rainfall variability.It is noted that many other factors contribute, but these projections allow to showcase the framework and if business as usual would prevail.Climate change is emphasized as one of the major sources of challenge for food security, and livelihoods making the southern African region vulnerable to a variety of stresses. It is estimated that the livelihoods of nearly 70% of the region which depends on rain-fed agriculture, an activity that is characterized by small-scale,subsistence farms is affected . Due to its largely adverse effects on African agriculture and livelihoods,climate change is expected to have a negative impact on food security. In a recent study, most farmers in Zambia are unable to afford certain alternatives, such as those of agro-forestry or conservation; they face difficulties in accessing markets due to poor road infrastructure, fluctuating market prices, high costs and late deliveries of farming in puts.
Coupled with the low presence of systematic early warning systems in place against natural hazards and disasters, it shows the adaptation capacity of farmers remains limited.Most of the research on climate change impacts related to food in Africa, as evident in IPCC assessments, focuses on changes in crop yields and food production reported climate change impacts on the yield of maize by considering regional model across southern Africa. These authors experimented on several climate change scenarios and examined the sensitivity of maximized yields to shifting of sowing dates as a means of developing adaptation decisions by keeping yields as high as possible.It is reported that with current climate change mitigation policies and related sustainable development practices,global GHG emissions will continue to grow over the next few decades .The various future storylines of GHGemission scenarios are expressed in terms of SRES scenarios. The SRES scenarios, provided in , are grouped into four scenario families that represent alternative development pathways, covering a wide range of demographic, economic and technological driving forces and resulting GHG emissions.The emissions projections are widely used in the assessments of future climate change, as inputs to many recent climate change vulnerability and impact assessments.