Carbon and corms: Assessing the threats to Gurrumuru floodplain, northern Australia

Northern Australian coastal floodplains are threatened by saltwater intrusion (SWI) and introduced pig (Sus scrofa) and water buffalo (Bubalus bubalis). In response, emerging carbon and biodiversity offset markets have been suggested to finance ungulate culling. However, few studies have quantified the potential carbon storage and biodiversity benefits of removing ungulates, especially when SWI occurs. Through collaboration with the Yolngu Yirralka Rangers and Gurrumuru Homeland wänga watangu (Traditional Owners), this project assessed the interacting effects of SWI and feral ungulates on: (1) Aboveground carbon (AGC) stocks in a supratidal Melaleuca forest, and (2) culturally important bush food räkay (Eleocharis dulcis), between ungulate exclusion and non-exclusion plots. Field research revealed SWI was the greatest threat to AGC, whilst ungulate exclusion significantly increased understorey biomass. After five years of ungulate exclusion, räkay corm abundance increased on average by 2.4 times. These results suggest that potential market solutions for removing ungulates should account for projected future impacts of SWI on AGC, and greater benefit could occur if biodiversity and cultural values were considered. Furthermore, as most northern coastal floodplains are on Indigenous owned and managed lands, it is imperative that potential solutions are inclusive of local priorities to maximise program engagement, outcomes and sustainability.