Landscape surrogates of forest fragmentation: synthesis of Australian Montreal Process case studies

Abstract

Habitat loss and fragmentation are key biodiversity indicators of the Montreal Protocol for monitoring progress towards ecologically sustainable forest management. Over the last 15 years, an array of landscape metrics have been developed as spatial measures of habitat loss and fragmentation. However, most metrics require rigorous empirical testing if they are to provide scientifically credible information to managers and policy makers. We present a synthesis of three Australian case studies for developing Montreal Indicator 1.1e, fragmentation of forest type, each representing different levels of landscape modification: St Mary State Forest, south-east Queensland; Tumut, southern New South Wales; and the Central Highlands, Victoria. Collectively, the studies found that no single landscape metric captured the response of the target species and fauna assemblages, or served as a reliable ecological surrogate for the conservation of a large set of species. Rather, species demonstrated a diversity of responses to habitat loss and fragmentation. Fragmentation effects were more important for the Tumut study, but not important for the Central Highlands study. Stand-scale habitat variables and area of suitable habitat were dominant explanatory variables for the St Mary study. Differences in observed response are partly explained by: (i) differences in landscape structure, particularly the proportion of preferred forest habitat remaining; (ii) differences in the ecology of target species; and (iii) the insensitivity of the landscape measures. Based on the outcomes of the three case studies, we propose principles for developing landscape surrogates for conserving biodiversity in Australia's eucalypt forest landscapes.