Sustainable grazing management in rangelands: Over a century searching for a silver bullet

Abstract

Rangelands represent 91% of the surface devoted to livestock production and a high proportion of them are exposed to some sort of degradation. Considerable research interest has been centered in the effect of grazing strategies on different indicators of rangeland sustainability (e.g., vegetation dynamics, soil properties, livestock productivity and grazing distribution). Considering the large amount of experimental evidence collected during a century of range science, a quantitative study assessing the performance of grazing schemes is timely and necessary. Therefore, we assessed the performance of grazing strategies on sustainability indicators worldwide, considering rangeland type (i.e., grasslands, shrublands, woodlands and forests) and other management variables (e.g., livestock type, grazing level, paddock sizes, precipitation) through a meta-analysis using experimental publications. Our results show that complete destocking does not improve soil or vegetation in comparison to grazed systems, but it could have less negative impacts if it is applied on woodlands, deserts and forests, particularly in areas of higher precipitation. Even though continuous grazing was thought as detrimental, we only observed negative impacts on vegetation on woodlands or under heavy grazing levels. Moreover, continuous grazing is less likely to impact negatively on livestock productivity in forest ranges. Also, it can maintain grazing distribution (except in woodland ranges) when applied for shorter periods of time. For multi-paddock schemes, we observed that rotational grazing is less likely to impact negatively on vegetation under moderate grazing levels, while Savory grazing method is more likely to show negative impacts on livestock productivity (particularly when applied for short time periods). Although many grazing schemes are applied worldwide, their effects can be very different in different range types. Here we provide a quantitative assessment of under which scenarios the different strategies can have negative, positive or neutral outcomes on rangelands. In addition, other management decisions, such as grazing intensity, livestock type and the length of the application period, together with environmental factors such as precipitation level, showed to be key to prevent negative impacts of grazing schemes on rangeland sustainability. Considering that the length of the application periods was very influential for many grazing schemes and indicators, we believe this is highlighting the need for more adaptive grazing strategies with more flexible decisions to allow rangeland sustainability. Finally, we found important information gaps, particularly related to potential interactions with livestock type, alternative rest periods length in rotational schemes, and notably about socio-economic factors. Filling these gaps could lead to more integrative range science and management.