Permanent removal of livestock grazing in riparian systems benefits native vegetation

Abstract

Livestock grazing in riparian areas has significant impacts on waterway ecosystems. In Australia, livestock grazing is allowed on many public waterway frontages under long-term licences. Many barriers to removing or restricting grazing on riparian areas exist, including concerns that removing grazing from historically grazed sites may favour invasive plant species. We compared vegetation changes at 180 sites along three connected waterways in northern Victoria, Australia that had been extensively grazed by livestock under grazing licences. Some of these sites were permanently protected from grazing by the creation of a new public park and reserve system in 2002. We compared vegetation attributes between sites in the ungrazed reserves, to sites outside reserves that were either recently grazed or ungrazed in 2009. Importantly, we used a sampling design and statistical models that explicitly incorporated the proximity to the waterway to account for known resource and disturbance gradients. Broad site condition assessments that were conducted on the exact same sites prior to reservation provided an indication of pre-treatment condition attributes. Despite no clear evidence of having more or less native vegetation prior to reservation, reserved sites had more native vegetation cover across a range of different life-form types than unreserved sites. Reserved sites also had much less bare ground, and this effect was far greater closer to the waterway margin. Livestock grazing within reserves reduced these perceived benefits for native vegetation and bare ground. However, reserved sites also had a higher cover of exotic graminoids, but not herbs. This study suggests that reservation of stream frontages was beneficial to native vegetation condition within the study systems even if grazing persisted. Livestock grazing was effective at reducing exotic vegetation cover but at the cost of native vegetation and ground condition. Many factors may influence outcomes and we expect these responses to differ in more productive landscapes or in periods with greater rainfall, so quantitative monitoring is advisable. Evaluation of cost-benefit trade-offs for the environment, graziers, and social and cultural objectives will be important to guide reservation decisions. • Livestock grazing increases bare ground and reduces native vegetation cover. • Reservation decreases bare ground and increases native vegetation cover. • Removal of grazing increased exotic vegetation cover. • Bare ground and vegetation cover vary with proximity to a waterway. • Livestock grazing pressure and impacts vary with proximity to a waterway.