Abstract
Analysis and interpretation of future climate change impacts on a particular crop, require a number of different models and datasets. Such datasets often operate at vastly disparate spatial scales. Mechanistic crop models, for example, classically operate at a site-specific, point location, for which soil and climate must be described in great detail. Future climate scenarios however, are obtained from various Global Climate Models (GCMs) at a very coarse resolution – typically gridded to 300 km or more. In order to be useful at a local level they need to be downscaled to a spatial scale useful for local analysis. Weather monitoring station locations in the province are irregularly distributed – much denser in the fruit and vine areas than in the extensive wheat areas. The Western Cape Province is a highly diverse region with regard to geology, topography, climatic influences and the resulting agricultural systems and practices. Future climate change therefore, is likely to have different impacts in different zones of the province where wheat is produced. To address this heterogeneity, the province was divided into 21 distinct response zones for modelling purposes. Geographic Information Systems (GIS) play a key role in addressing the spatial complexities - facilitating issues such as weighted average zonation, aggregation (or disaggregation) of spatial components, local parameterisation of crop models through interpolation, integration of ancillary data such as satellite imagery within the modelling framework and finally in the spatial analysis and display of modelled scenarios. This paper uses a recent climate impact study in the Western Cape to demonstrate the role of GIS in the assessment of expected climate change impacts on dryland wheat agriculture.
Highlights
A number of studies, both international and local have indicated that South Africa and in particular the Western Cape, is expected to become warmer and probably drier (Niang et al, 2014; WCDoA and WCDEA&DP, 2016)
Considerable work has been done in recent years in assessing the potential impacts of climate change on the local climate through the application of downscaling techniques to Global Climate Models (GCMs)
The report indicated a strong likelihood of warming, reduced rainfall in the western parts of the province, with increased frequency and intensity of extreme events towards mid-21st century, based on modelling undertaken by Hewitson and colleagues at the Climate Systems Analysis Group (CSAG) at the University of Cape Town
Summary
A number of studies, both international and local have indicated that South Africa and in particular the Western Cape, is expected to become warmer and probably drier (Niang et al, 2014; WCDoA and WCDEA&DP, 2016). The Western Cape is a highly diverse region with regard to topography, soil types and climate This variability dictates the need for either subtle or distinct differences in farming systems and practices in different sub-regions. This is evident upon examination of the wide range of agricultural activities in the 80 relatively homogeneous farming areas (RHFAs) in the Western Cape (One World Sustainable Investments, 2007). A variety of crop models exist and have particular strengths and weaknesses, in the context of spatial applications (Nagamani et al, 2017) Such models are increasingly used to test the impacts of expected climate change at a detailed physiological level.
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