Abstract for presentation at Biodiversity Extinction Crisis Conference - A Pacific Response

Bush Heritage Australia have developed an efficient and effective group of variables to monitor terrestrial biodiversity. This “minimum set” is the physical ecosystem drivers, vegetation structure, remotely sensed primary productivity, site history, soil surface stability and consumer (bird) population and community energetic variables. This presentation covers relationships between the more integrated variables i.e. bird population and community variables as they relate to variation in stand variables and seasonal conditions.
Compositional gradients for insectivorous birds exhibited maximum variation along gradients of productivity and foliage nutrient concentration. A trend was found for coexisting insectivorous and nectarivorous bird species to have equal biomass within each site.
Community energy consumption was a linear function of total densities for small insectivores and nectarivores. Consequently there are clear constraints on the densities and body sizes of each individual bird within those communities and within subsets (guilds), which imply these measurements were derived from trophically and metabolically integrated communities. In a subsequent drought year, there were very few significant relationships, largely through reductions in populations of small insectivores.
In vegetative stands not subject to drought but subject to more chronic stress induced by previous clearing or overgrazing and soil erosion, once again the physiologically less buffered small insectivores exhibit a reduction in species richness compared with stands of equivalent stature or productivity.
In common with farm outputs, factors that increase the productivity and nutrient concentrations of foliage, lead to increased bird carrying capacity and species and guild richness. This indicates that an energetic/metabolic approach to monitoring biodiversity will likely put biodiversity monitoring on an equivalent footing to the well quantified prediction of outputs from natural resource management. In common with natural resource managers, biodiversity managers need to separate the effects of variation in climatic ecosystem drivers from the effects of management regimes.