Impact of climate change on forage resources and factors influencing pastoral responses in semi-arid areas of South Sudan
Onono, Francis Alex
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The greatest challenge of pastoralists living in arid and semi-arid areas is inadequate forage resource availability. Climate variability affects temporal and spatial distribution of these forage resources, indirectly affecting livestock production and pastoral livelihoods. The aim of the study was to assess climate trends and its effects on forage availability, quantify temporal and spatial changes in distribution of forage resources, and establish factors influencing pastoral coping and adaptation strategies to climate and forage variability in Kapoeta, South Sudan. To assess trends and the rate of change in rainfall and temperature, Mann-Kendall test and Sen’s Slope respectively were used. Projected rainfall and temperature trends (2021-2050) was determined using the Norwegian Earth System Model (NorESM1) under Representative Concentration Pathways (RCP) 4.5 and 8.5. Supervised and unsupervised classification was used to determine the temporal and spatial distribution of grasslands, shrubs and thickets. Normalized Difference Vegetation Index (NDVI) was used to indicate the quality and quantity of forage resources. A cross-sectional household survey of pastoralists was conducted using structured and semi-structured questions and logistic regression was run to establish factors influencing their decisions to cope and adapt to climate and forage variability. The results showed a significant (P=0.05) decrease in annual rain days at a rate of 1.4 day per year between 1984 and 2016, but no significant (P=0.615) decline was observed in annual rainfall amount in the same period. The monthly rainfall patterns shifted from unimodal pattern (1984–1995) to bimodal (2006–2015). The average projected (2021-2050) annual rainfall amount under RCP4.5 and RCP8.5 will be similar to that observed between 1984 and 2016, but most rainfall will be received between September and December with unimodal pattern. There was a significant (P<0.05) increase in maximum annual temperature at a rate of 0.061 degree Celsius per year (1984-2016) and projected annual temperature will increase at the rate of 0.028 degree Celsius and 0.016 degree Celsius per year (2021-2050) under RCP4.5 and RCP8.5. Temporally, the area covered by grassland, and shrubs and thickets reduced by 3353.07 Km2 (9.17 percent) and 614.30 Km2 (1.68 percent) from 1984 to 2016. Spatially, grasses, thickets and shrubs decreased in the South-Western and Eastern part of Kapoeta in 2016 compared to 2000. In addition, the biomass of grass, shrubs and thickets as indicated by NDVI was more distributed throughout the year in 2016 compared to 1984. In the survey, 63 percent of the pastoralists had observed climate change and 66 percent of these used migration to cope with climate and forage variability. The majority (40 percent) adapted by changing from rearing cattle to sheep and goats. Migration was significantly influenced by distance to water points in dry season, and pasture conservation methods used, while changing livestock species was significantly influenced by family grazing land owned and accessed (P<0.05). The historical (1984-2016) changes in climate and forage resources notwithstanding the increase in temperature and rainfall amount between 2021 and 2050, indicate that forage resources, and pastoral responses will be determined by land tenure systems. These historical and future changes in climate call for sustainable use and management of current natural forage resources to maintain or improve livestock production as a livelihood.