When dealing with degraded ecosystems in agricultural landscapes, livestock exclusion is often the first step in restoration. However, the outcomes of fencing are usually varied; it does not guarantee the desired effect. A slow transition to desired states or towards undesirable states could suggest legacy farming poses ecological barriers inhibiting the regeneration of native species. In general, such variability in recovery can be related to site productivity, level of degradation, and soil conditions. In a study by Sims et. al (2018), responses to fencing in terms of divergence from initial states and convergence with targeted states that represent restoration was analyzed in grassy woodlands in Australia. Using a conceptual model, they found little evidence to suggest fencing encourages convergence to reference plots (Figure 1). They found evidence to suggest species composition of fenced plots diverged from unfenced plots, however it was highly variable among sites and unrelated to the time since livestock was excluded.
Thus, this study highlights the importance of site selection, as livestock exclusion may gain the desired effect of returning to an initial state (soil and species compositions) but it isn’t guaranteed. In a broader sense, there is no one-size-fits-all solution to very similar problems, as these are more complex than we think. For example, in a study by Gomez-Aparicio (2009), it was asked whether the benefits of facilitation as a restoration tool varies based on study duration, life-form of the neighbour, and target species. Indeed, herbaceous communities provided more inhibition than facilitation whereas shrub communities were the opposite. So facilitation really does not work in all cases, just like livestock exclusion doesn’t either, and management practices should be site-specific.
Gómez-Aparicio L. The role of plant interactions in the restoration of degraded ecosystems: a meta-analysis across life-forms and ecosystems. Journal of Ecology. 2009;97(6):1202–1214. doi:10.1111/j.1365-2745.2009.01573.x
Sims RJ, Lyons M, Keith DA. Limited evidence of compositional convergence of restored vegetation with reference states after 20 years of livestock exclusion. Austral Ecology. 2019. doi:10.1111/aec.12744