Introduction
Temperate grasslands once covered almost 9 million km2, which is equivalent to about 8% of the earth’s surface (IUCN, 2013). They include the Prairies of North America, the Pampas of South America, the South African Veldts, the Tussock grasslands of Australia and New Zealand, and the Steppes of Eurasia (Table 1). These biomes are often species rich (Faber-Langendoen & Josse, 2010), providing natural habitat for many plants, animals and soil biota. In addition, these grasslands offer invaluable ecosystem services such as high-quality forage for herbivores (Boval & Dixon, 2012), harbour pollinators for crops and native species (Bendel et al ., 2019), provide significant levels of carbon sequestration (Ezeet al ., 2018), and are places for many recreational and cultural activities (Gomez-Limon & de Lucio, 1995). They also afford many other environment stabilizing services, such as soil erosion control and mitigation of flood waters (Sankaran & Anderson, 2009).
Given the significance and contribution of this ecosystem, they’re currently one of the most altered ecosystems in the world (Suttieet al ., 2005), warranting immediate action to restore these beneficial services. Estimates suggest that 70% of these ecosystems were altered or degraded before 1950, and a further 14% by 1990 (Hassanet al ., 2005). This decline in ecosystem health is directly attributed to rapid population growth and subsequent urban expansion (Williams et al ., 2005), as well as the concomitant conversion of these fertile ecological systems into sites for agriculture, particularly for cropping systems and livestock grazing (Martin et al ., 2005; Prober et al ., 2005; Bartolome et al ., 2009; Sankaran & Anderson, 2009). While increased protection of the remaining intact system is critical, it is not enough to ensure the future resilience and functionality of these systems. Therefore, this paper reviews restoration methods, both active and passive, that reduce invasive plant biomass within global degraded temperate grasslands to promote the return of natives and subsequent ecosystem functionality at a landscape scale.