sustainability Review Prosopis Species—An Invasive Species and a Potential Source of Browse for Livestock in Semi-Arid Areas of South Africa Khuliso Emmanuel Ravhuhali 1,2, * , Humbelani Silas Mudau 1,2 , Bethwell Moyo 3 , Onke Hawu 1,2, * and Ntokozo Happy Msiza 1,2   Citation: Ravhuhali, K.E.; Mudau, H.S.; Moyo, B.; Hawu, O.; Msiza, N.H. Prosopis Species—An Invasive Species and a Potential Source of Browse for Livestock in Semi-Arid Areas of South Africa. Sustainability 2021, 13, 7369. https://doi.org/10.3390/ su13137369 Academic Editor: Carl Ronald Carroll Received: 8 May 2021 Accepted: 15 June 2021 Published: 1 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Animal Science, School of Agricultural Sciences, Faculty of Natural and Agricultural Sciences, North-West University, Mmabatho 2735, South Africa; mudausilas@gmail.com (H.S.M.); happy.msiza@yahoo.com (N.H.M.) 2 Food Security and Safety Niche Area, Faculty of Natural and Agricultural Sciences, North-West University, Mmabatho 2735, South Africa 3 Department of Animal Production, Fort Cox Agriculture and Forestry Training Institute, Middledrift 5685, South Africa; bethwellm@gmail.com * Correspondence: ravhuhalike@gmail.com (K.E.R.); onkehawu97@gmail.com (O.H.) Abstract: Globally, there have been differing views on whether the proliferation of invasive species will be of benefit as a livestock feed source or it will have detrimental effects on the ecosystem. The infestation of invasive plants such as Prosopis species does not only affect the groundwater levels but also threatens the grazing capacity and species richness of most of the semi-arid areas around South Africa. Though Prosopis is invasive, it is however of good nutritive value and can serve as an alternative source of protein and minerals for livestock during the dry season. Bush encroachment by browsable invasive species can be controlled through biological methods by using organisms such as livestock. The utilisation of Prosopis through browse benefits livestock production and at the same time reduces its spread, thereby preventing possible environmental harm that may arise. Although several studies have been carried out globally on the assessment of the Prosopis species’ nutritive value and also on the threat of this invasive species to the environment, there is a need to update the state of knowledge on this species, particularly in the context of the semi-arid areas of South Africa where the dry season is characterised by less herbage of poor quality. It is therefore critical to understand whether Prosopis is a beneficial invader, or a detriment that needs to be eradicated. This review will contribute knowledge towards finding practical solutions to controlling Prosopis species and whether utilising Prosopis as a feed source will limit its spread and result in a vegetation structure where Prosopis becomes part of the ecosystem with limited detrimental impact. This means that the several components of the species such as nutritive value and the negative impact associated with this plant species along with the means to control its spreading must be well understood to recognise the plant species’ vital contribution to the ecosystem. Keywords: Prosopis species; livestock; nutritive value; invasive species; environment; semi-arid 1. Introduction In South Africa over the past half-century, various species of deciduous, leguminous thorn tree species have been introduced for various purposes, such as timber, firewood, bark for tannins, medicines, windbreaks, edible products for humans, and fodder for animals [1,2]. These trees include Acacia mearnsii, Opuntia ficus-indica, and Prosopis species. The genus Prosopis has several species and hybrids, and in South Africa, the dominant ones are Prosopis glandulosa (Honey mesquite) and Prosopis velutina (Velvet mesquite) [3]. The Prosopis species were initially introduced to South Africa from South, Central, and North America in the late 1880s, mainly to provide fodder (pods in drought years), shade for livestock, windbreak, wood for fuel, timber for furniture, and a nectar source for honey pro- duction [4–7]. The plant was of great value to all stakeholders until the 1960s [8,9], before its Sustainability 2021, 13, 7369. https://doi.org/10.3390/su13137369 https://www.mdpi.com/journal/sustainability