Investigating the Social-ecological Trade-offs Between Removing and Preserving Mangroves in New Zealand

Dencer-Brown, Amrit
Alfaro, Andrea
Milne, Simon
Perrott, John
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Doctor of Philosophy
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Auckland University of Technology

How we perceive and interact with the natural world will govern our future in times of great environmental change. In New Zealand, the indigenous mangrove species Avicennia marina (subsp.) australasica has expanded within estuaries in the North Island at a rapid rate over the past few decades. This has led to polarity in public perceptions and attitudes towards mangrove preservation and removal. Although protected, removal of large areas of mangroves has occurred and continues to take place. This thesis investigates the social-ecological trade-offs between removing and preserving mangroves in New Zealand. The research approach employs a mixed methods Holistic Mangrove Framework, which explores gaps in the social-ecological monitoring of mangroves both nationwide and specifically at four sites of removal in the Manukau Harbour, Auckland. Chapter two’s review of the literature on mangrove social-ecology showed that prominent knowledge gaps remain in ecological monitoring of mammals, reptiles, insects and spiders, which is also true globally. In a social context, little is known about the cultural value of mangroves (manawa) to Māori or the intrinsic value of this ecosystem. Chapter three showed the creation of a novel framework to investigate the creeping environmental problem of mangrove expansion in New Zealand. This framework has the capacity to be applied to any social-ecological system for a holistic understanding of interactions between humans and nature. Chapter five’s integrated biodiversity assessments revealed that there is much heterogeneity in habitat complexity, species richness and abundance among sites. The study site adjacent to the largest mangrove removal area possesses the greatest abundance of bird species, and richness and abundance of arboreal arthropods compared to all other study sites. This highlights that a site- by-site management approach is required and generalisations about the i habitat value of mangroves for wildlife cannot be made in the New Zealand context. Chapter six’s exploration into perceptions and attitudes towards mangrove preservation and removal revealed significant disparity in attitude between community groups and conservation organisations. Sediment and nutrient retention properties of mangroves are the highest rated ecosystem services. The desire for reversion of estuaries to a pre-urban state is the greatest issue affecting mangroves. Iwi recommend monitoring of water quality and contaminants in mangrove soils. Based on the findings of this study, it is recommended to look beyond mangroves as an ecosystem which has expanded and replaced other adjacent habitats and start thinking about managing our coastal landscapes in a holistic manner. Embracing connectivity and complexity of coastal landscapes and addressing wider land-based issues of sedimentation and nutrient run-off is a necessity. It is advisable for us to work with and be part of our natural environment in order to create a more sustainable future in Aotearoa New Zealand. This is true for interactions with social-ecological systems globally. This study has added to baseline data on social and ecological information on New Zealand’s mangroves and contributes to the international body of work on this coastal ecosystem using a mixed methods approach.

Mangroves , Social-ecology , Perceptions , Attitudes
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