Arresting the pernicious decline of keystone habitats in agricultural landscapes

A project undertaken at the Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, and supervised by Dr Tim Doherty

Agricultural expansion is one of the greatest threats to biodiversity. Apart from habitat loss and fragmentation, other pernicious impacts accumulate over decades, including weed invasion and loss of keystone habitat features. Their accumulation and interaction could be accelerating species loss from farming regions beyond the rate due to habitat loss alone, but there exists a major knowledge deficit in this area. The key challenge lies in detecting the subtle yet pervasive changes taking place in remnant vegetation and understanding their underlying causes and impacts on animal populations. By understanding the causes of decline of keystone habitat species in agricultural areas, practical management approaches can be developed that enable the conservation of species and habitat in concert with food production.

Our study will address these important questions using a model landscape in central New South Wales. The study area is dominated by cropping land, but also contains remnant mallee woodlands with a spinifex understorey, which is a keystone habitat for many reptile species. Weeds and native grasses dominate the understorey of much remnant mallee in the region, particularly along roadsides, and this may be to the detriment of spinifex and hence reptile populations. Our overall objective is to understand the condition and trajectory of a keystone habitat feature (spinifex, Triodia scariosa) across a large (5,000 km2) study area dominated by cropping land, but containing remnant mallee vegetation.

Figure 1. Habitat condition photos: top: healthy spinifex; middle: over-abundant native Austrostipa grass engulfing spinifex clumps; bottom: exotic weeds and dead spinifex clumps.