Effect of reserve protection level and governance on tree cover loss and gain

Abstract

Terrestrial protected areas are essential for biodiversity conservation, yet it is not fully understood when and how different types of protected areas are most effective in achieving specific conservation objectives. We assessed the impact of reserves on tree cover loss and gain through a case study in Tasmania, Australia. We considered varying protection levels (strict, where human activities are restricted, and multiple use) and governance types (public and private). We used a counterfactual matching approach to compare tree cover loss and gain between reserves and matched unprotected areas from 2004 to 2021. We accounted for forest policy changes, environmental covariates, and human pressures to reduce placement bias. We also characterized reserves by size, governance, management, and vegetation and compared covariates inside and outside reserves to define baseline conditions. Reserves established from 2004 to 2016 were overall 75.4% less likely to have lost tree cover and 16.0% more likely to have had tree cover gain compared with controls. Patterns of loss and gain varied by protection level and governance type. Multiple-use reserves were as effective as reserves in which human activities were more restricted. Privately managed reserves contributed to tree cover growth, and public reserves helped avoid loss. This highlights reserves’ distinct contributions to conservation targets, with private reserves allowing for growth and restoration and public reserves acting as stable anchor points. Our results emphasize the importance of having a diverse array of protected areas to enhance the resilience of reserve networks. We advocate for adaptive regional measures and robust monitoring to achieve global ecological targets.