Addressing the mismatch between restoration objectives and monitoring needs to support mangrove management
Restoration projects require an underpinning of science to maximise success at restoring ecological function. Occasionally wetland restoration objectives focus on clearing intertidal vegetation, including removal of introduced and rapidly expanding native species, such as the expansion of mangrove forests in New Zealand. Typical objectives of these restoration projects addressing mangrove expansion include restoring intertidal sites to historically sand-dominated substrates that are associated with higher societal and cultural values through recreational access, natural character (e.g., viewscape) and enhancement of shellfish resources. Historically, mangrove management occurred with minimal or no monitoring to confirm if these objectives were achieved, and with no consistent approach in terms of restoration methodology or monitoring used across the various management jurisdictions. This paper reviews the monitoring programs associated to date with restoration projects in New Zealand involving mangrove removal, with an aim to outline the key management considerations and environmental measures that should be included in future monitoring programs. Monitoring techniques that should be included in management activities that involve mangrove removals are summarised, highlighting methodologies to document changes in surface topography, sediment characteristics and various biological changes. The monitoring objectives have been categorised in three levels, relative to the complexity of the technique and the cost. We hope that this paper will be useful to any group or organisation around the globe who wish to document the extent and rate of change where mangrove vegetation has been cleared. Better documentation on successes and failures of management actions related to mangrove expansion can inform future management strategies, and prioritise cost-effective actions in locations that are likely to result in successful restoration of ecological function of estuarine habitats.