Large floodplain river restoration in New Zealand: synthesis and critical evaluation to inform restoration planning and research

New Zealand (NZ) has a diversity of large river ecosystems that provide essential ecosystem services but are impaired by multiple ecological impacts. River restoration is an active field worldwide and there is good potential for river restoration practitioners in NZ to draw on lessons from elsewhere, although there is also a need to tailor approaches to national and local contexts. Here, we provide a critical review of large floodplain river restoration to guide environmental management in NZ and inform research and management priorities. The review is structured using a driver-pressure-state-impact-response framework, with a focus on responses, i.e. large river restoration methods. Thirty-one river restoration methods aligned with 14 broad restoration goals were evaluated collaboratively and semi-quantitatively. Evaluation outcomes are presented to inform regional and national scale restoration planning. Recommendations were identified to address eight key knowledge or policy gaps: (1) understanding cumulative impacts facing large river systems, (2) prioritising restoration measures at the landscape-scale, (3) promoting lateral connectivity in large river floodplains, (4) incorporating knowledge of geomorphology into river management, (5) enhancing understanding of cultural priorities and community aspirations, (6) assessing how costs and benefits of river restoration vary among timescales, (7) understanding the feasibility of restoration methods that have received limited application in NZ and (8) improving protection of threatened native fish species.