Natural tree regeneration in agricultural landscapes: the implications of intensification.
Concern about food security is prompting a push to intensify agriculture globally. However, agricultural intensification can inhibit regeneration of vegetation in natural ecosystems. This may jeopardise the persistence of trees in agricultural landscapes and the ecosystem services these treed landscapes offer. Here, we study one of the world's most altered ecosystems - temperate eucalypt woodlands - to explore patterns in natural regeneration of trees, and factors influencing regeneration occurrence, across 300 000 km2 of south-eastern Australia between 2008 and 2014. During this period, we found the proportion of remnants supporting natural regeneration was stable, and that regeneration occurrence was negatively associated with variables coincident with agricultural intensification: continuous livestock grazing by sheep and cattle, increased exotic plant cover, increased natural soil fertility, and lower elevation. These results indicate that intensive agriculture is incompatible with natural regeneration in our study area. Left unaddressed, low levels of regeneration may result in the widespread loss of trees and the ecosystem services they provide in agricultural landscapes. Thus, strategic implementation of land-sparing and land-sharing strategies is required across broad spatial scales to satisfy production and conservation needs. Based on our results, we recommend that land sharing be prioritised where: (1) livestock grazing can be removed or employed intermittently, (2) exotic plants do not dominate the ground layer, and (3) natural soil fertility is low. For locations that are continuously grazed or dominated by exotic plants, a land-sparing strategy may be more appropriate. Here, farmland should be managed to maximise production, and the next generation of trees should be 'moved' to areas where natural regeneration can be supported.