Search

Context: Banked systems that modify natural wetlands to enhance reliability of grass production for cattle are common along coastal Central Queensland. These are mostly positioned in the supratidal zone of extensive marine plains, leaving mangroves and saltmarsh with regular tidal influence intact. Perceived negative impacts on fisheries and carbon sequestration are frequently cited as reasons to remove banks and restore tidal influence, yet there is no specific evidence relating to the banked wetlands in this region. All ecosystem services provided by these systems need to be considered before decisions are made. Aims: This study aimed to evaluate the biodiversity values of marine plains with tide-exclusion banks. Methods: Five banked sites (39 000 ha) were compared to a single unbanked site of similar vegetation and tidal position with multiple counts of waterbirds (13-48/site) over several years. Key results. Banked sites collectively supported six threatened and 22 migratory species, including 17 migratory shorebirds, some with counts of international importance. All sites matched criteria used to define Ramsar wetlands. Banked sites had more waterbird species and a similar species richness of migratory shorebirds to the unbanked site. Conclusions: Given these wetlands support substantial numbers of migratory shorebirds and endangered species such as Capricorn Yellow Chat, as well as their importance to food production and improving water quality reaching reef ecosystems, any proposed 'restoration' of these areas to the previous tide-influenced state should be subject to impact assessment. Implications. Our study demonstrates that existing tide-excluded banked wetlands are beneficial for biodiversity and economic production, soundly justifying their retention. [ABSTRACT FROM AUTHOR]

The Capricorn Yellow Chat (Meliphagidae: Epthianura crocea macgregori) is a poorly known, endangered passerine of coastal north-eastern Australian wetlands. Recent research has highlighted the need for evidence based management and that recovery programmes may be hampered by a lack of sound ecological knowledge. Capricorn Yellow Chats were found at 15 sites near Rockhampton between Broad Sound and the Fitzroy River delta in the south. Overall, suitable habitat was limited with an area occupied of about 6 000 ha, confirming the need for careful management. Habitat may be typified as grass-sedge wetlands or tall supratidal saltmarshes that are temporarily flooded, with pools becoming brackish to hypersaline as they dry. Over 96% of sightings were on coastal plains formed by marine sedimentation processes, most without current tidal influence, and many less than 5 m above sea level. The remaining 4% were associated with alluvial-formed plains, but only where these bordered existing marine plain sites; suggesting a preference for marine plain habitats, possibly reflecting structural differences and foraging preferences (marine plains tend to be more open due to the presence of salt-tolerant samphire vegetation). Sea level rise was identified as a major threat to the subspecies with chat sightings at most sites averaging less than 2 m above current highest astronomical tidal influence, and sites becoming tidal or with regular storm surge influence under future modest predicted sea level rise scenarios of 0.5 m by 2100. Most sites had some form of banking to reduce tidal influence and promote freshwater pasture grasses for cattle production. The site supporting most chats had small banks that allowed floods to flow around them, maintaining connectivity with the downstream marine systems. This study contributes to baseline information essential to the evaluation of any future management interventions; thus avoiding the pitfalls hampering much of the global conservation efforts directed at threatened species. [ABSTRACT FROM AUTHOR]