Maximizing colonial waterbirds' breeding events using identified ecological thresholds and environmental flow management

Abstract

Global wetland biodiversity loss continues unabated, driven by increased demand for freshwater. A key strategy for conservation management of freshwater systems is to maintain the quantity and quality of the natural water regimes, including the frequency and timing of flows. Formalizing an ecological model depicting the key ecological components and the underlying processes of cause and effect is required for successful conservation management. Models linking hydrology with ecological responses can prove to be an invaluable tool for robust decision-making of environmental flows. Here, we explored alternative water management strategies and identified maximal strategies for successful long-term management of colonial waterbirds in the Macquarie Marshes, Australia. We modeled fluctuations in breeding abundances of 10 colonial waterbird species over the past quarter century (1986-2010). Clear relationships existed between flows and breeding, both in frequencies and total abundances, with a strong linear relationship for flows > 200 GL. Thresholds emerged for triggering breeding events in all 10 species, but these varied among species. Three species displayed a sharp threshold response between 100 GL and 250 GL. These had a breeding probability of 0.5 when flows were > 180 GL and a 0.9 probability of breeding with flows > 350 GL. The remaining species had a probability greater than 0.5 of breeding with flows > 400 GL. Using developed models, we examined the effects of five environmental flow management strategies on the variability of flows and subsequent likelihood of breeding. Management to different target volumes of environmental flows affected overall and specific breeding probabilities. The likelihood of breeding for all 10 colonial waterbirds increased from a regulated historical mean (+/-SD) of 0.36 +/- 0.09 to 0.53 +/- 0.14, an improvement of 47.5% +/- 18.7%. Management of complex ecosystems depends on good understanding of the responses of organisms to the main drivers of change. Considerable opportunity exists for implementing similar frameworks for other ecosystem attributes, following understanding of their responses to the flow regime, achieving a more complete model of the entire ecosystem.

Policy considerations for managing wetlands under a changing climate

“…Given limited resources, biotic surrogates of wetland condition have often been used, and these should be easily detectable, measurable and sensitive to ecological change. Waterbirds, among the more conspicuous of wetland animals, are a vital component of wetland function, and have been regularly used as indicators of the condition of a wetland (Kingsford and Auld 2005;Bino et al 2014b). Native freshwater fish and invertebrate communities are also directly influenced by changes in flow regimes (Death et al 2016), making them potential climate response indicators.…”

Inundation requirements for persistence and recovery of river red gums ( Eucalyptus camaldulensis ) in semi-arid Australia

“…Floods in high frequency inundated areas have decreased by 92% (Thomas et al, 2011), with an estimated 59% of the original floodplain not flooded since 1979 (Steinfeld and Kingsford, 2012). Besides waterbird abundance and breeding (Bino et al, 2014;Kingsford and Thomas, 1995), there are few long term analyses of other aquatic biota, although there is evidence that many river red gum (Eucalyptus camaldulensis) communities on the floodplain are in poor ecological health, or disappearing (Steinfeld and Kingsford, 2012). Ongoing degradation of the floodplain ecosystem has resulted in the notification by the Australian Government of a likely change in ecological character to the Ramsar Bureau (DEWHA, 2009).…”

Extreme drought pushes stream invertebrate communities over functional thresholds

“…TheYin et al (2017) approach therefore provides a logical and elegant threshold detection method, using information on the slope of a relationship to identify thresholds in the strictest sense of the term (i.e., where the rate of change in a response variable exceeds that of a predictor;King and Baker (2014),Capon et al (2015)). Furthermore, GAMs are an effective tool for detecting ecological thresholds(Ficetola & Denoël, 2009), and by identifying a specific breakpoint (or breakpoints) theYin et al (2017) approach eliminates the subjectivity in threshold interpretation inherent in methods based on simple visual inspection of slopes (cf Bino, Steinfeld, & Kingsford, 2014;Dézerald et al, 2015;White, McHugh, & McIntosh, 2016)(Ficetola & Denoël, 2009), and by identifying a specific breakpoint (or breakpoints) theYin et al (2017) approach eliminates the subjectivity in threshold interpretation inherent in methods based on simple visual inspection of slopes (cf Bino, Steinfeld, & Kingsford, 2014;Dézerald et al, 2015;White, McHugh, & McIntosh, 2016)…”