Salt marsh restoration: nature-based solutions to climate change mitigation : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Landscape Architecture at Lincoln University

Abstract

Salt marshes are one of the most productive ecosystems on Earth and home for many birds. They also protect coastlands from erosion, storms, and floods. Salt marshes sequester and keep a considerable quantity of сarbon dioxide in their soil for a long time, thereby reducing the amount of carbon dioxide emitted and mitigating the effects of climate change. Therefore, restoration of salt marshes is considered to be a nature-based solution to climate change mitigation. However, these fragile systems are threatened by climate change and sea level rise, urbanisation, and hydrological changes. This study focuses on three salt marsh systems in the Canterbury region in Aotearoa New Zealand. These are Teddington salt marsh, Avon-Heathcote Estuary, and Brooklands Lagoon. They represent the geomorphological types of harbours, estuaries, and lagoons, respectively. The study also examines key environmental and management factors affecting the vulnerability of salt marshes and possible future changes. Analysis has shown that the Avon-Heathcote Estuary is a central ecological link between Teddington salt marsh and Brooklands Lagoon. These findings highlight the importance of planning restoration on a regional scale instead of isolated site-based projects. Using GIS-based spatial analysis combined with Forman’s landscape ecology concepts, habitat loss was modeled in accordance with four scenarios of sea level rise (+0.4 m, +0.6 m, +1.0 m and +1.5 m) for each case study site. The results showed a significant loss of salt marsh area across all case studies under a 0.4 m sea level rise scenario and an almost complete loss at 1 m, suggesting that the salt marsh may not be capable adapting to sea level rise.