Application of system dynamics modelling in evaluating sustainability of low-input ruminant farming systems in Eastern Cape Province, South Africa

•System dynamics modelling evaluated sustainability of low-input ruminant farming.•The evaluation used nine farmer-challenges-derived indicators.•Key indicators were biomass supply, household income and farmer training.•Most indicators were sustainable (27%) and moderately sustainable (46%).•Overall, the low-input ruminant farming system was moderately sustainable. As a complex and dynamic concept that requires understanding from an ecological, economic and socio-cultural perspective, sustainability of agriculture and food systems is currently being strongly promoted by many governments and rural development practitioners. However, advances in monitoring and evaluating the sustainability of low-input ruminant farming are hindered by a lack of tools that simultaneously consider the interrelationships and dynamic behaviour of the different components of the system. Here we report on the application of a system dynamics model to evaluate the sustainability of low-input ruminant farming systems. This draws on nine indicators grouped as ecological; (soil organic matter, water availability and biomass supply), economic; (livestock productivity, labour supply and household income, and social: (farmer training, credence attributes of ruminant grazing systems and gender equality) to describe system behaviour over a ten-year period. The outputs from model simulations were used to compute index values for each of the indicators and the indices were subsequently used to evaluate sustainability of low-input ruminant farming systems. Household income, gender equality and farmer training had the highest sustainability indices whereas, soil organic matter and biomass supply recorded the lowest values. Overall, the low-input ruminant farming system was found to be moderately sustainable.