On the role of anthropogenic climate change in the emerging food crisis in southern Africa in the 2019–2020 growing season

Anthropogenic climate change likely influences the beginning of 2020 growing season's water deficit in parts of southern Africa, with severe consequences to food security. The failure of early (October–December) rains, amidst a multiyear drought, has raised concerns of a potential emerging food security crisis in parts of southern Africa, with an estimated 45 million people at risk of severe food insecurity (WFP (World Food Programme), 2019). Here, we evaluate recent climate data to assess the possible role of anthropogenic climate change (ACC) in the emerging crisis in this region spanning southern Mozambique, Zimbabwe, and central and western Zambia (Figure 1a). This region is among the most drought prone in Africa (Ujeneza & Abiodun, 2015), with much of the population dependent on small-scale, rain-fed farming systems, and was identified over a decade ago as a priority hotspot for ACC adaptation to avoid severe food security impacts (Lobell et al., 2008). Observations in the region indicate a nonsignificant downward long-term rainfall trend and a strong upward air temperature trend particularly in the post-1970 period (Figure 1b,c). Two measures of drought, the standardized precipitation index (SPI; McKee, Doesken, & Kleist, 1993) and standardized precipitation evapotranspiration index (SPEI; Vicente-Serrano, Beguería, & López-Moreno, 2010), both indicate strong water deficits for January 2020 (Figure 1d,e; Table 1). If rainfall and evapotranspiration are considered, the January 2020 conditions are unprecedented in the last 70 years. Drought in this region is often related to the occurrence of El Niño events in the tropical Pacific (Funk et al., 2016), although January 2020 is lacking any such event (IRI (International Research Institute for Climate and Society), 2020). The current drought measures are stronger than those experienced during the 2015–2016 El Niño that had severe implications to the agricultural productivity (FAO (Food and Agriculture Organization), IFAD, UNICEF, WFP, & WHO, 2017). Index Data SPI (pSPI)a GPCC rainfall SPEI (pSPEI)a GPCC rainfall and GHCN-CAMS air temperature Probability ratio: p2020/p1901 (5%–95% CI)b GPCC rainfall Detecting an anthropogenic contribution to a rainfall deficit-driven drought is challenging due to low signal to noise ratio (National Academies of Sciences, Engineering, and Medicine, 2016). Attributing agricultural drought is further complicated by the plant physiological responses to environmental factors including CO2 concentrations. While Funk et al. (2016) concluded that ACC affected the severity of the 2015–2016 El Niño-related drought causing a 24% decrease in rainfall, relevance to a 2019–2020 season lacking an El Niño event is unclear. Application of the observation-based event attribution methodology of Van Oldenborgh (2007) used in earlier drought studies (e.g., Otto et al., 2018) suggests an increased probability of the rainfall deficit event, but the effect is not detectable in statistical sense (Table 1). However, comparison of the SPI and SPEI indicates that the January 2020 conditions are much more exceptional when considering the effects of both rainfall and potential evapotranspiration (PET; used by the SPEI) rather than just rainfall (used by the SPI; Table 1). Since air temperature (and thus likely PET) shows a strong ACC-linked trend (Figure 1; Stone & Hansen, 2016), the effect of ACC on water availability may be much stronger than for rainfall. Although any crisis such as the current food situation in southern Africa is driven by multiple factors, including adverse macroeconomic conditions and suboptimal agricultural policies, as our analyses suggest, ACC stresses can play a role. A more detailed study is needed to accurately determine the contribution of ACC to this specific event. The current crisis likely requires immediate humanitarian response but also rehighlights the need for more proactive efforts to identify agricultural vulnerability and rapidly develop adaptation mechanisms to increase and protect food security amidst ongoing and predicted changes in regional climate and a growing population.

openalex: W3008401183 mag: 3008401183