Antonio I. Hernández-Cordero

Vegetation, distance to the coast, and aeolian geomorphic processes and landforms in a transgressive arid coastal dune system

The main objective of this study was to determine the nature and relative importance of environmental factors that shape the distribution of dune vegetation in the Maspalomas dune field in the Canary Islands, an arid transgressive dune system. Environmental factors were defined according to their expression related to the linear distance from the coast and to the local aeolian geomorphic process-landform context. Plant communities were characterized through an integration of field mapping, digital orthophoto interpretation and GIS analysis. The vegetation of the study area consists of 19 plant communities. In areas with active sedimentary processes, vegetation tends to be localized in slacks. In areas with more stabilized landforms, vegetation appears at both dunes and slacks. In conclusion, the main factor controlling the distribution of vegetation in the transgressive dune system of Maspalomas is the local aeolian sedimentary process-landform context. Distance to the coast is not as significant as an influence. The gradient structuring of environmental factors associated with retentive coastal dune systems and expressed as distance to the coast does not fully capture the biogeomorphic dynamism of transgressive dune fields.

Proposal for new EU habitats associated with coastal dune fields of the Macaronesian region. A case study in the Canary Islands (Spain)

The aim of this work is to identify habitats of European interest for the existing dunes in the Canaries, in order to provide data for their proper management. Dune systems considered were the following: aeolian sedimentary systems that cover both most of the island of La Graciosa and also the dune fields of Maspalomas (Gran Canaria) and Corralejo (Fuerteventura). The methodology consisted of overlapping layers of habitats and vegetation by using geographic information systems, so the correspondence between habitat and plant community are analyzed. The results indicate that dune habitats in the Canary Islands have not been well defined. The habitat “2110 embryonic shifting dunes” is associated with several situations incompatible with their biotic and abiotic characteristics. Meanwhile, habitat “2130 fixed dunes with herbaceous vegetation (grey dunes)” is linked, among others, to the phytosociological association Traganetum moquinii. However, embryonic dune formation in the Canaries is mainly done by this community, which is inconsistent with its inclusion in the grey dunes habitat. The proposed habitats of European interest associated with dunes in the Canaries are the following: Coastal shifting dunes with Traganum moquinii, dunes with Tamarix canariensis, Macaronesian aeolian sand sheets and humid dune slacks. It is also suggested the need for a comprehensive study of dune habitats existing in the Canaries and Macaronesia, covering the whole of aeolian sedimentary systems, performing a proper identification, characterization and detailed mapping of these habitats, based on both the existing vegetation and also on the associated landforms and geomorphic processes.

Procedure to automate the classification and mapping of the vegetation density in arid aeolian sedimentary systems

The temporal variation in vegetation cover in aeolian sedimentary systems, especially those in arid regions, provides an indication of environmental change. Based on this, the objective of this paper is to design a simple method for classifying the vegetation density of arid aeolian sedimentary systems through the digital processing of aerial images. The green band of a high resolution orthophoto of La Graciosa island (Canary Islands, Spain) is used as an example. The pixels identified as vegetation were vectorized to point geometry, the vegetation density was then calculated, and a digital vegetation density model (DVDM) thereby obtained. Both spatial and statistical analyses were performed to find the optimal procedure to achieve the objective. Speed, objectivity, cost, and the possibility of working with historical records are discussed, and the proposed method is compared with others based on visual analysis or digital remote sensing. The importance of this method for countries with less research funding or low GDP per capita is also discussed. The proposed procedure opens up future lines of research for comparison of results across various environmental and anthropogenic variables. In addition, vegetation density can be used as a variable in computational fluid dynamic modeling of vegetation in arid dune systems.

Geomorphological changes in an arid transgressive coastal dune field due to natural processes and human impacts: Geomorphological changes in an arid transgressive coastal dune field

Geomorphological changes in recent decades in an arid transgressive coastal dune system (Maspalomas, Gran Canaria, Canary Islands) are analyzed. The methodology used is based on the generation of two geomorphological maps (1961 and 2003) by interpretation of digital orthophotos. The overlay of both maps in a geographic information system (GIS) enabled the spatial and surface changes of the landforms to be determined, and the processes that generated these changes. Twelve cultural and geomorphological processes were identified from highest to lowest importance, namely: anthropization by urban occupation (114ha changed), stabilization (92.5 ha), barchanization (37 ha), salinization/halophytication (15 ha), anthropization (12.4 ha), deflation (11.8 ha), dune loss/beach gain (11.3 ha), dune formation (9.6 ha), progradation (8 ha), retrogradation (7.7 ha), destabilization (2.7 ha) and flooding (0.7 ha). Geomorphological changes are associated with a combination of five main factors, three of anthropogenic origin and two natural ones. The natural factors are: (1) the arid climate, which favors changes occurring at high speed; (2) the existence of a progressive sedimentary deficit. Anthropogenic factors are: (3) construction of tourist urbanizations, infrastructures and facilities; (4) installation of equipment or infrastructure on the beaches; (5) the activities carried out by users. These human factors have altered the aeolian dynamics and reduced the area occupied by vegetation in some areas, causing changes in aeolian sedimentary processes. The geomorphological processes identified can be used as indicators of environmental change, allowing us to synthesize the changes in landforms detected, and group all combinations derived from the analysis by GIS and analyze them spatially. Thus, the environmental changes in the transgressive coastal dune systems could be interpreted more effectively. Copyright

Biogeomorphological processes in an arid transgressive dunefield as indicators of human impact by urbanization

Urban and tourist developments can have long-lasting impacts on coastal environments and fundamentally alter the evolution of coastal dune systems. This is the case of the Maspalomas dunefield (Gran Canaria, Canary Islands), hosting one of the largest tourist resorts in Spain. The resort was built on top of a sedimentary terrace at 25 m above sea level (El Inglés) in the 1960s, and has subsequently affected local winds and therefore aeolian sediment transport patterns. Buildings on the terrace deflect the winds to the south of the dunefield, where the rate of sediment transport accelerated. A shadow zone appeared to the lee side of the resort with a consequent decrease in wind speed and aeolian sediment transport and an increase in vegetation cover. In this paper, first we characterize the environmental changes around El Inglés terrace in recent decades, and describe the changes in the shadow zone through an analysis of the evolution of sedimentary volumes and vegetation characteristics (density, spatial patterns, and plants communities). A series of historical aerial photographs, recent orthophotos and digital elevation models obtained by digital photogrammetry and LiDAR, as well as fieldwork were used to characterize plant communities and spatial-temporal changes in erosive landforms. Results show changes in the pattern and migration rates of dunes located at the southern edge of the urbanization, as well as the formation of blowouts and large deflation areas, where the vegetation increases in density and number of plant communities. We discuss eco-anthropogenic factors that have produced these environmental changes.

Aeolian Sedimentary Systems of the Canary Islands

The aeolian sedimentary systems of the Canary Islands have certain natural and socio-economic characteristics that make them differentiated environments, both in the context of the dune fields of Spain and Europe. This is a consequence of their location in intraplate hot spot volcanic islands, their climatic conditions, the high pressure exerted on them by society and the lack of adequate management measures. The relationship between their elements and the continuous change to which they are exposed make them environments with high complexity and fragility. In recent decades, some research lines have been opened around these systems, based on geomorphological, biogeographic, historical, cultural, landscape and socio-ecological analysis. These new approaches have allowed to expand the knowledge about the diversity and complexity of the processes that occur in these systems, as well as to obtain information regarding their management.

Assessing the geomorphological vulnerability of arid beach-dune systems

In this study, an arid dune vulnerability index (ADVI) is developed using a system of indicators to evaluate the geomorphological vulnerability of beach-dune systems of arid regions. The indicators are comprised of three analytical dimensions (susceptibility, exposure and resilience) and their corresponding sub-indices and variables and were assessed for eleven sites located in four aeolian sedimentary systems of the Canary archipelago (Spain). The selected sites have varying geomorphological characteristics, vegetation types, marine and wind conditions and human pressure degrees, and have seen different trends in their geomorphological evolution since 1960. The eleven sites were separated into three groups according to their different conservation status and different management needs, and the results of the ADVI dimensions and variables were compared and analyzed for these three groups. In general, the results obtained in the analyzed sites reveal that susceptibility and exposure dimensions are related to low-moderate values, while resilience was high. Only one site presented a state of critical vulnerability, due to the loss of its capacity to maintain its geomorphological function in recent decades. Given the lack of knowledge about geomorphological vulnerability processes in foredunes of arid regions, ADVI is the first approximation to geomorphological diagnostic in these environments and can be useful for managers.

Vegetation species mapping in a coastal-dune ecosystem using high resolution satellite imagery

Vegetation mapping is a priority when managing natural protected areas. In this context, very high resolution satellite remote sensing data can be fundamental in providing accurate vegetation cartography at species level. In this work, a complete processing methodology has been developed and validated in a complex vulnerable coastal-dune ecosystem. Specifically, the analysis has been carried out using WorldView-2 imagery, which offers spatial and spectral resolutions. A thorough assessment of 5 atmospheric correction models has been performed using real reflectance measures from a field radiometry campaign. To select the classification methodology, different strategies have been evaluated, including additional spectral (23 vegetation indices) and spatial (4 texture parameters) information to the multispectral bands. Likewise, the application of linear unmixing techniques has been tested and abundance maps of each plant species have been generated using the library of spectral signatures recorded during the campaign. After the analysis conducted, a new methodology has been proposed based on the use of the 6S atmospheric model and the Support Vector Machine classification algorithm applied to a combination of different spectral and spatial input data. Specifically, an overall accuracy of 88,03% was achieved combining the corrected multispectral bands plus a vegetation index (MSAVI2) and texture information (variance of the first principal component). Furthermore, the methodology has been validated by photointerpretation and 3 plant species achieve significant accuracy: Tamarix canariensis (94,9%), Juncus acutus (85,7%) and Launaea arborescens (62,4%). Finally, the classified procedure comparing maps for different seasons has also shown robustness to changes in the phenological state of the vegetation.

Insights of long-term geomorphological evolution of coastal landscapes in hot-spot oceanic islands: Long-term geomorphological evolution of coastal landscapes

The Canary Islands form a volcanic archipelago in which a west–east (W–E) chain of progressively older and less active islands can be observed. In the Canary Islands, unlike most hot-spot archipelagos, certain geodynamic peculiarities have promoted longer periods of island survival, exceeding 20 Myr. This factor makes these islands a suitable context for this work, which aims to analyze extensively the coastal geomorphic structure on islands with different development states. For this, three islands in different volcanic phases were selected: La Palma (1.8 Myr), Gran Canaria (14.5 Myr) and Fuerteventura (22.6 Myr). An ad hoc landform-based hierarchical taxonomy was designed to analyze the coastal geomorphic structure of the three islands. Based on a multi-sourced analysis in geographic information system (GIS) and field recognition, a comprehensive cartographic database was collected using the coastline data-storing (CDS) method as a feature abundance proxy. Three different aspects of the geomorphological structure were compared and related between the islands: (i) composition, (ii) abundance and (iii) diversity. Through their comparison, we attempt to explore geomorphological aspects of coastal evolution over geological spatiotemporal scales. Composition was explored analyzing the distribution of the feature’s longshore frequencies (p). Abundance, by metrics of local abundance (N∩) and whole density (NU). Diversity, through four indices: normalized richness (S) and Margalef index (M) to estimate richness; Simpson index (D) and Shannon index (H’) to estimate evenness. We identified a systematic transformation in the dominant landform composition and a systematic trend in increasing geomorphological abundance and diversity from younger to older islands. The results show a long-term structural pattern defined by the increase in coastal geomorphic complexity (abundance and diversity) over geological time, as the coasts evolve from predominantly rocky-erosive to increasingly clastic-depositional environments. This longterm geomorphological pattern may be a general aspect of hot-spot island archipelagos, which can bring a new perspective to the knowledge of their coastal evolution.