A composite threat indicator approach to monitor vegetation condition in the Wet Tropics, Queensland, Australia

Abstract

Many indicators and indices have been previously developed to report biodiversity condition at a regional scale. However, none have specifically focused on vegetation condition as a surrogate for biodiversity, and also incorporated threats at multiple scales. Using five indicators (forest cover fragmentation, urbanisation, weeds, feral animals and road density) identified from the scientific literature and selected in collaboration with natural resource management (NRM) stakeholders to reflect the state of vegetation condition in the World Heritage-listed Wet Tropics Bioregion of Queensland, Australia, we constructed a simple composite threat index which allowed the spatial display of information at the regional and subregional scale. Using this approach we identified that the overall vegetation condition of the Wet Tropics in the period 2003–2007 was ‘good’, but at a finer scale five of the bioregions nine subregions had ‘moderate’ condition, and only four had ‘good’ condition. The primary threat contributing to the ‘moderate’ condition was vegetation fragmentation due to clearing for agriculture, housing and related transport infrastructure. The composite threat index approach provided managers with a report card for the Wet Tropics landscape which allows rapid assessment of vegetation condition and contributory threats, and thus prioritization for the allocation of limited resources to threatening processes at the subregional scale.