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Identifying Indicators of Active Dune Condition From Remotely Sensed Aerial Imagery

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Thesis(5.6 MB)

Date

2023

Authors

Ryan, Cate

Supervisor

Buckley, Hannah
Case, Bradley
Bishop, Craig

Item type

Thesis

Degree name

Doctor of Philosophy

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Volume Title

Publisher

Auckland University of Technology

Abstract

Coastal active dunes, which face global threats such as sea level rise, play a pivotal role in providing ecosystem services and supporting biodiversity. Despite this, they remain inadequately studied. This thesis investigated the question: Can the ecosystem condition of active dunes be discerned from remotely sensed imagery, specifically aerial imagery, at a national scale? The research addressed the challenge of efficiently monitoring these ecosystems by investigating the potential of remotely sensed imagery for monitoring their condition. Specifically, low-cost, high-resolution red-green-blue aerial imagery at a national scale for Aotearoa New Zealand was used as a case study. First, the potential maximum extent of active dunes was estimated using geospatial datasets and aerial imagery. Second, the vegetation cover within 135 x c. 1 ha plots of a nationally-representative set of active dunes was characterised using Object-Based Image Analysis. This resulted in a national typology of seven, dominant vegetation types, including two native sandbinder types. Third, the spatial pattern of active dune cover classes within plots on active dunes revealed distinct patterns in dunes dominated by native sandbinders, associated with geomorphic disturbance, while patterns associated with exotic and woody vegetation indicated anthropogenic influences. These results demonstrated that native sandbinder dominance can serve as an indicator of active dune condition. Thus, this study has provided a methodology to derive useful indicators of active dune condition and offers a feasible, cost-effective approach for large-scale conservation management decisions of this ecosystem and lays the groundwork for future research in coastal active dune ecosystems at a national scale.

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http://hdl.handle.net/10292/18335

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Doctoral Theses