Tide-excluded banked wetlands on the marine plains of northeastern Australia provide important habitat for migratory shorebirds, other threatened bird species and the Capricorn Yellow Chat

Abstract

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.