South African Cropland Dust Emission Risks: Physical Thresholds, Environmental and Socio-Economic Patterns

Thematic Focus:
Agriculture, Biodiversity and Sustainability
Involved Countries:
Switzerland, Botswana, Namibia, South Africa

Dust emission is a growing issue affecting soil mass losses, ecosystem services, public health, and climate change. Understanding dust emission dynamics originating from farming in drylands is crucial not only to prepare and respond to the aforementioned impacts, but also to secure food production in the best possible conditions using marginal lands, a resource becoming increasingly scarce.

Southern African dust sources have been well documented, feature some of the world’s dustiest regions, and disperse dust throughout the subcontinent and beyond. The west coast of South Africa produces dust from coastal pans, river valleys, and deltas in both the Namib and Northern Cape regions. Mine tailings in and around Johannesburg (Gauteng Province) are among the most studied dust sources in South Africa due to systematic monitoring efforts and immediate impact on nearby urban air quality. However, few studies have drawn attention to dust originating from South Africa’s extensive farmland. These areas appear to be most productive in early summer at the onset of the rainy season as part of cold pool outflows from convective storms over the Free State and Northern Cape.

Such ground level events have gone unmonitored due to their association with cloud and rain events. These associations are different from most other dust events that produce elongated plumes during the clear winter months, particularly in Namibia and Botswana, and disperse throughout the region. Nevertheless, the use of Meteosat MSG clearly suggests that southern African events are not infrequent and not insignificant in extent.

Exposed agricultural lands are thus important dust sources in South Africa, and the supply of fine dust material may be even more pronounced during drought cycles. Such events represent a loss of soil mass at the site of origin, but also impact ecosystem services further afield and, potentially, contribute to climate change. Microbial and chemical contaminants transported by dust from cropland add to the public health concerns with dust originating from farms and reaching urban areas.

The research questions of the proposed four-year project thus are: (i) what are the environmental thresholds for generation of dust (wind, soil moisture soil crust) in relation to farmland management and, (ii) to what extent do farmland dust sources impact ecosystem services, public health and, potentially, climate.

This research aims to fill this knowledge gap by using a holistic and interdisciplinary approach spanning geomorphology, land management, and microbiomics. A Swiss-South African partnership of four institutions (University of Basel, Agricultural Research Council, University of Cape Town, and University of Pretoria), which encompasses the necessary expertise, has been formed. They have divided activities and methods into four work packages. The results of these will be synthetised in a fifth one, leading to publication of holistic scientific contributions on South African cropland dust emissions, identification of farmland management best practices, and informing policy.