Wetland conservation and sustainable use under global change: a tropical Australian case study using magpie geese

Abstract

Imminent shifts in environmental parameters due to climatic change might have profound ramifications for wetlands listed under the Ramsar convention. Although the exact mechanisms by which global change will affect these systems are not known, models that simulate component drivers, particularly at a broad spatial scale, can nevertheless allow for more informed conservation decision making. Such general inference is particularly needed for wetlands across the tropics, where less knowledge and fewer resources are available to mitigate the impacts on important conservation sites. Here we develop a case study of wetland loss to sea level rise across tropical north Australia (including Ramsar‐listed sites), and link these to a metapopulation model for a keystone endemic waterbird, the magpie goose Anseranas semipalmata. We projected published models on sea level rise through to the year 2400, and found a non‐linear trajectory of inundation up to 20 m above present levels. Digital elevation models were used to simulate sea level rise and the spatially differentiated loss of wetland habitat used by geese. Range retraction was linked to decline in ecological carrying capacity, and we coupled wetland‐specific habitat loss projections to a spatially explicit demographic metapopulation model. Additionally, we included alternate harvest strategies based on present‐day estimates of indigenous and non‐indigenous offtake of geese, and examined the synergy between wetland loss and hunting on extinction risk. Our results suggest that Australia's once‐abundant and widespread magpie goose will be reduced to a fragmented population of just a few thousand individuals within the next 200–300 yr. Harvest could continue for some time, up to a “tipping point” at around 5% loss of current wetland habitat, after which the decline of geese is rapid. Given the inexorable nature of sea level rise, short‐ to medium‐term conservation of waterbirds across Ramsar wetlands must prepare for adaptive wetland management, such as through buffer‐placement, and ongoing monitoring of harvest.

Mechanisms driving change: altered species interactions and ecosystem function through global warming

“…Finally, melting of ice and snow are predicted to raise sea levels, thereby shifting tropical estuarine communities dependent on brackish water to more saline‐tolerant mangroves (Mulrennan & Woodroffe 1998). This in turn, will affect food plant availability for herbivores like magpie geese Anseranas semipalmata and even Aboriginal human communities dependent on those herbivores for food (Traill et al. 2010).…”

Managing for change: wetland transitions under sea-level rise and outcomes for threatened species

“…com), the Sea Level Affects Marshes Model allows the simulation of processes driving coastal wetland transitions and shoreline modification under SLR (Park et al, 1993;Craft et al, 2009). assessment of SLR, moving beyond qualitative assessment (Eliot et al, 1999) or 'bathtub' inundation models (Traill et al, 2010). Broad figure shows SEQ for context, indicating elevation, main urban areas (white) and major river systems (grey).…”

How interactions between animal movement and landscape processes modify local range dynamics and extinction risk

“…Our results for floodplain turtle populations are likely to underestimate extinction risk, because we did not account for future sea-level rise, which is likely to result in severe regional habitat loss [20], further threatening the persistence of C. rugosa. Table 1.…”