Exploring Temporal Trends of Plant Invasion in Mediterranean Coastal Dunes

Alien plants represent a significant threat to species diversity and composition in natural habitats. Nevertheless, little is known about the dynamic of the invasion process and how its effects on native species change over time. In this study, we explored vegetation changes that occurred in invaded coastal dune habitats over the last 10–15 years (2005–2020), particularly addressing impacts on alien and diagnostic species. To monitor temporal trends, we used data resulting from a revisitation study. After detecting overall changes in alien species occurrence and cover over time, 127 total plots were grouped into plots experiencing colonization, loss, or persistence of alien species. For these three categories, we compared historical and resurveyed plots to quantify changes in native species composition (using the Jaccard dissimilarity index) and to measure variations in diagnostic species cover. The number of alien species doubled over time (from 6 to 12) and two species, Yucca gloriosa and Agave americana, strongly increased their cover (+5.3% and +11.4%, respectively). Furthermore, plots newly invaded appeared to record the greatest changes in both native and diagnostic species. Our results suggest the need for regular monitoring actions to better understand invasion processes over time and to implement effective management strategies in invaded coastal dune habitats.

A New Application of the Disturbance Index for Fire Severity in Coastal Dunes

Fires are a disturbance that can lead to short term dune destabilisation and have been suggested to be an initiation mechanism of a transgressive dune phase when paired with changing climatic conditions. Fire severity is one potential factor that could explain subsequent coastal dune destabilisations, but contemporary evidence of destabilisation following fire is lacking. In addition, the suitability of conventional satellite Earth Observation methods to detect the impacts of fire and the relative fire severity in coastal dune environments is in question. Widely applied satellite-derived burn indices (Normalised Burn Index and Normalised Difference Vegetation Index) have been suggested to underestimate the effects of fire in heterogenous landscapes or areas with sparse vegetation cover. This work assesses burn severity from high resolution aerial and Sentinel 2 satellite imagery following the 2019/2020 Black Summer fires on Kangaroo Island in South Australia, to assess the efficacy of commonly used satellite indices, and validate a new method for assessing fire severity in coastal dune systems. The results presented here show that the widely applied burn indices derived from NBR differentially assess vegetation loss and fire severity when compared in discrete soil groups across a landscape that experienced a very high severity fire. A new application of the Tasselled Cap Transformation (TCT) and Disturbance Index (DI) is presented. The differenced Disturbance Index (dDI) improves the estimation of burn severity, relative vegetation loss, and minimises the effects of differing soil conditions in the highly heterogenous landscape of Kangaroo Island. Results suggest that this new application of TCT is better suited to diverse environments like Mediterranean and semi-arid coastal regions than existing indices and can be used to better assess the effects of fire and potential remobilisation of coastal dune systems.

High Ground, Low Ground: Explorations in Topography and Neighbourliness in Coastal Dune Settlement

<p>The desire to live close to the ocean often brings about settlement that sprawls along the beachfront, parallel to the coastline. This settlement structure is problematic as it diminishes the importance of community while exposing beachfront housing to coastal hazards. The coastal dune settlements of Waikanae and Paraparaumu, where this research has been undertaken, exhibits this problematic settlement structure. Using these sites as a case study, the research seeks to re-examine the New Zealand coastal land settlement formation. It explores what could happen if the current coastal settlement pattern re-organised as a more social structure? The research is investigating an approach to settlement through re-examining the idea of neighbourhood by looking at its whole relation to the coastal dune topography, ecology, and wider landscape relations. However, not only does this research look at the social potentials of coastal settlement but how disaster planning can become a device to achieve this outcome. Essentially, it aligns itself with the attitude that flooding and coastal hazards should not just be looked at as an engineering problem but an opportunity to alter the way in which we settle coastlines in a way that builds community.</p>

High Ground, Low Ground: Explorations in Topography and Neighbourliness in Coastal Dune Settlement

<p>The desire to live close to the ocean often brings about settlement that sprawls along the beachfront, parallel to the coastline. This settlement structure is problematic as it diminishes the importance of community while exposing beachfront housing to coastal hazards. The coastal dune settlements of Waikanae and Paraparaumu, where this research has been undertaken, exhibits this problematic settlement structure. Using these sites as a case study, the research seeks to re-examine the New Zealand coastal land settlement formation. It explores what could happen if the current coastal settlement pattern re-organised as a more social structure? The research is investigating an approach to settlement through re-examining the idea of neighbourhood by looking at its whole relation to the coastal dune topography, ecology, and wider landscape relations. However, not only does this research look at the social potentials of coastal settlement but how disaster planning can become a device to achieve this outcome. Essentially, it aligns itself with the attitude that flooding and coastal hazards should not just be looked at as an engineering problem but an opportunity to alter the way in which we settle coastlines in a way that builds community.</p>

GIS-Based Aesthetic Appraisal of Short-Range Viewsheds of Coastal Dune and Forest Landscapes

This paper demonstrates the possibilities of a Geographical Information System (GIS) for investigating and explicating the spatial variation of the short-range viewshed aesthetic appeal in a World Heritage coastal dune and forest area. The study pursues the following objectives: (1) develop and trial a GIS-based algorithm for computing the Aesthetic Appeal Index for a Short-Range Viewshed (ǣ); (2) deliver an output map showing the spatial variation of the computed ǣ values in the target territory and distribution of the zones with high scenic quality and potential aesthetic ecosystem services (PAES); and (3) assess management alternatives in zones with high PAES and high conservation value. This study combines two key innovative aspects. First, it integrates an objective digital map of habitats with subjective scenic preferences of coastal forest and dune landscapes based on psychophysical and cognitive perceptions of scenic beauty. Second, it applies a GIS-based algorithm to translate subjective scenic preferences to an output map of ǣ. The study’s main conclusion is that the combined aesthetic appraisal of the immediate and foreground viewshed of coastal forests and dunes, by applying a specially created GIS algorithm, allows an assessment of the scenic quality of this landscape reliably in statistical terms.