Review of potential management interventions to reduce peat subsidence and CO2 emissions in the Waikato

Report: TR 2021/10

Author: J Pronger (Manaaki Whenua - Landcare Research), J Wyatt (Waikato Regional Council), G Glover-Clark (University of Waikato)

The Waikato region has about 89,000 ha of peatland, of which 69,000 ha have been drained and developed mostly for pastoral agriculture. This drainage causes land subsidence and carbon dioxide (CO₂) emissions. Section 14.5 of the Waikato Regional Policy Statement (WRPS) directs Waikato Regional Council to slow the rate of peat subsidence and the loss of carbon by oxidation. However, Waikato Regional Council lacks robust data to implement the WRPS policy.   

The purpose of this technical report was to review local and international literature and identify land and drainage management options, and inform future research directions, for improving management practices to reduce peat subsidence and CO₂ emissions from drained peatlands in the Waikato. For each management practice identified (e.g. cultivation, sub-surface drainage) the review provided an overview of current research and summarised the effect on subsidence and CO₂ emissions.

The report concluded by recommending the following steps to reduce peat subsidence and CO₂ emissions in the Waikato region:

1. Develop a spatial vulnerability index to identify locations where the most severe consequences are likely to occur.
2. Test a range of potential mitigation strategies including priority water management, land management, and land use strategies as identified in the review.
3. Combine knowledge gained from experimental testing of mitigation strategies with modelling of catchment hydrology to develop a spatially appropriate management decision support tool to provide guidance for drainage and land managers to select the most appropriate mix of mitigation approaches. 
4. Update good practice guidelines and, if necessary, develop policy incentives or interventions to encourage adoption of management strategies and decision support tools.

The recommended steps will be used to inform future investigations into improving peatland management.