Habitat-based biodiversity assessment for ecosystem accounting in the Murray-Darling Basin

Farm revegetation has substantial potential to improve biodiversity outcomes

Agricultural expansion and intensification has caused habitat loss, contributing to the current biodiversity crisis. Reliable, efficient and consistent information at the farm-scale is critical to understand the magnitude of recent changes in biodiversity and to inform future management actions aimed at reversing historical declines. We apply a habitat-based biodiversity assessment approach to examine the potential for grazing farms across Australia to improve outcomes for biodiversity by revegetating 10 % of the farm area. Fourteen case-study farms distributed across Australia with diverse attributes were assessed, including an analysis of likely benefits for biodiversity 30 years after commencing a hypothetical revegetation scenario, within the context of estimates of recent historical changes. From 2004 to 2020, the three biodiversity indicators considered decreased for the majority of farms. The scenario for revegetating 10 % of the farm area was estimated to substantially increase the biodiversity indicators, with half of the farms estimated to achieve recovery for all 3 indicators to greater than 2004 levels by 2050. Smaller farms with lower average ecosystem condition in 2020 were estimated to achieve the greatest gains in biodiversity from the revegetation scenario, relative to their indicator values in 2020. Farm revegetation actions have substantial potential to improve outcomes for biodiversity, though such gains may be difficult and time consuming to achieve, emphasising the importance of avoiding further habitat loss through removal or degradation of native vegetation.

Measuring habitat quality for waterbirds: A review

Quantifying habitat quality is dependent on measuring a site's relative contribution to population growth rate. This is challenging for studies of waterbirds, whose high mobility can decouple demographic rates from local habitat conditions and make sustained monitoring of individuals near-impossible. To overcome these challenges, biologists have used many direct and indirect proxies of waterbird habitat quality. However, consensus on what methods are most appropriate for a given scenario is lacking. We undertook a structured literature review of the methods used to quantify waterbird habitat quality, and provide a synthesis of the context-dependent strengths and limitations of those methods. Our search of the Web of Science and Scopus databases returned a sample of 666 studies, upon which our review was based. The reviewed studies assessed habitat quality by either measuring habitat attributes (e.g., food abundance, water quality, vegetation structure), or measuring attributes of the waterbirds themselves (e.g., demographic parameters, body condition, behavior, distribution). Measuring habitat attributes, although they are only indirectly related to demographic rates, has the advantage of being unaffected by waterbird behavioral stochasticity. Conversely, waterbird-derived measures (e.g., body condition, peck rates) may be more directly related to demographic rates than habitat variables, but may be subject to greater stochastic variation (e.g., behavioral change due to presence of conspecifics). Therefore, caution is needed to ensure that the measured variable does influence waterbird demographic rates. This assumption was usually based on ecological theory rather than empirical evidence. Our review highlighted that there is no single best, universally applicable method to quantify waterbird habitat quality. Individual project specifics (e.g., time frame, spatial scale, funding) will influence the choice of variables measured. Where possible, practitioners should measure variables most directly related to demographic rates. Generally, measuring multiple variables yields a better chance of accurately capturing the relationship between habitat characteristics and demographic rates.