drainage

Drainage is a recognised cause of wetland loss worldwide, and New Zealand is no exception. In the last 200 years drainage has reduced the natural extent of wetlands in New Zealand by c. 90%. Avoiding further loss is a national priority. Despite recent reform to restrict new drains within 100 m of existing wetlands in New Zealand, little is known about the extent and effect of existing drains in and near wetlands.

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.