Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Potential for tidal restoration to reduce methane emissions from impounded wetlands in the Burdekin catchment (#87)

Charles Cadier 1 , Adam Canning 2 , Nathan Waltham 2 , Scott Fry 3 4 , Fernanda Adame 1
  1. School of Environment and Science, Griffith University, Nathan, QLD, Australia
  2. Center for tropical water and aquatic ecosystem research (TropWATER), James Cook University, Townsville, QLD, Australia
  3. Natural Resources Management, North Queensland Dry Tropics, Townsville, Queensland, Australia
  4. Natural Resources Management, North Queensland Dry Tropics, Townsville, Queensland, Australia

Saline coastal wetlands such as mangroves and saltmarsh have low methane emissions, with salinity playing a key role in methane regulation. Tidal restriction is a common anthropological alteration of coastal wetlands hydrological connection and may lead to the creation of artificial freshwater impounded wetlands, which are hypothesised to emit significantly more methane compared to tidally connected saline coastal wetlands. In this study, we investigated the potential for tidal restoration of impounded coastal wetlands by comparing their greenhouse gas emissions with tidally connected mangrove and saltmarsh saline wetlands in the Burdekin catchment located in Queensland, Australia. We found that despite high variation between sites, tidal restriction leads to significantly higher methane emissions compared to natural coastal wetlands. Tidally restricted wetlands were emitting 2175 mg CO2-eq.m2.d-1, two orders of magnitude higher than tidally connected wetlands which emitted 18 mg CO2-eq.m2.d-1. This research is supporting tidal restoration as a cost-effective strategy to mitigate climate change with the potential to enhance blue carbon burial rates and avoids long-term emissions of methane. We further recommend that future restoration projects should also assess the impact of tidal restoration on freshwater impounded wetlands ecosystem services such as biodiversity and water quality improvement to investigate restoration trade-offs.