Loss of wetlands since 1990 in Southland, New Zealand

Reports of wetland loss in New Zealand are typically related to the historical, pre-European coverage of wetland ecosystems. It is widely accepted that large areas of wetlands were converted to other land uses prior to the 1990s before comprehensive national and regional environmental legislation was established. We sought to investigate recent (post 1990) changes in wetland extent to determine if current rates of wetland loss remain a concern for natural resources management. Remote sensing images from 1990–2012 for three regions of Southland, New Zealand, were analysed to determine whether wetlands present at 1990 exhibited ‘little or no change’, were ‘at risk’ due to recent drainage, were ‘restored’ due to revegetation, or had been ‘lost’. Of the 32 814 ha of wetlands assessed across Southland 3452 ha were no longer present in the landscape and a further 3943 ha were at risk. Most of the change in wetland extent occurred on the Southland Plains. A large proportion of the wetlands mapped as being lost or at risk were within the catchment of the Awarua Wetland, a large coastal Ramsar site. The rate of wetland loss in Southland since 1990 (0.5% of wetland area yr⁻¹) is equivalent to the global average (0.5% yr⁻¹). Taking into account wetlands that have been partially drained, the rate of decline increases to 1.0% yr⁻¹. The predominant cause of the loss of wetlands is conversion to other land use, typically to pasture used for agriculture. A review of policy mechanisms and enforcement efforts intended to protect wetlands at regional and national levels is urgently called for, as well as increased effort to promote sustainable wetland management in agricultural environments.