Nebkha or not? -Climate control on foredune mode

Hesp, Patrick A.; Hernández‐Calvento, Luis; Gallego‐Fernández, Juan B.; Silva, Graziela Miot da; Hernández‐Cordero, Antonio I.; Ruz, Marie‐Hélène; García‐Romero, Leví

doi:10.1016/j.jaridenv.2021.104444

Cited by 30 publications

(18 citation statements)

References 37 publications

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“…In addition, although not shown in the projection data, the hummocky appearance of the sand flats (Figure 6D) and to the east show developing Ammophila-anchored nebkha dunes. These will likely join to form a new established foredune, considering the high rainfall and favourable climate on Sable Island (Hesp et al 2021), unless shoreline retreat erodes them before this process is completed. This will result in the landward linear dune becoming a relict foredune.…”

Section: Changes In Shoreline Positionmentioning

confidence: 99%

Multi-decadal coastal evolution of a North Atlantic shelf-edge vegetated sand island — Sable Island, Canada

et al. 2022

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Impacts from a changing climate, in particular sea-level rise, will be most acutely felt on small oceanic islands. A common configuration of mid-latitude islands is the sandy barrier island. Sable Island, Nova Scotia, Canada is a vegetated sand island near the shelf edge, 160 km from the nearest point of land, that is morphologically similar to a barrier island. This study uses 60 years of airphoto records to analyse changes in coastline position through digitized shore and vegetation (foredune proxy) lines. Rates of coastal movement are analysed to model the future (2039) coastal configuration. The analyses suggest that the majority of the coastline on Sable Island is in retreat, with net retreat on the south side of the island only partially offset by modest net advance on the north side. The different morphologies of the beach-dune systems of South and North Beach, driven by incident wind and waves, yield these different coastline responses. Projected loss of 10 ha by 2039 of the climax heath vegetative community to shoreline retreat suggests a trend toward island instability due to coastline migration. Island-wide dataset trends show support for two different but complementary hypotheses about whole-island evolution: either the island is mobile via bank migration driving southern coastline changes and experiencing sediment transport toward the east, or the island is generally immobile and losing subaerial sediments (and thus shrinking) likely due to ongoing (and accelerating) sea-level rise.

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Section: Changes In Shoreline Positionmentioning

confidence: 99%

Multi-decadal coastal evolution of a North Atlantic shelf-edge vegetated sand island — Sable Island, Canada

et al. 2022

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“…With respect to SP10, although it is located in the second row, wind speeds were similar to those in the first row, reaching speeds that exceeded 80% of the input wind speed. In this southern zone of the beach‐foredune environment, the foredune more closely resembles the mounded morphology typical of arid coastal dune systems (Hernández‐Cordero et al, 2019; Hesp et al, 2021; Viera‐Pérez, 2015), instead of the nearly continuous sand ridge of the foredune in the north. While the foredune in the northern area blocks the wind and reduces its speed when entering the system, the naturally fragmented foredune in the southern area allows the wind to enter between the vegetated mounds, transporting sediment to the rear areas of the foredune and forming nebkhas and shadow dunes that enable the foredune to develop in height and width (García‐Romero et al, 2021; Hernández‐Calvento, 2006; Hernández‐Cordero et al, 2012; Viera‐Pérez, 2015).…”

Section: Resultsmentioning

confidence: 56%

Foredune responses to the impact of aggregate extraction in an arid aeolian sedimentary system

Sanromualdo-Collado

Marrero-Rodríguez

García‐Romero

et al. 2022

Earth Surf Processes Landf

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Coastal dunes have long suffered the effects of human interventions that have altered the landscape and operation of these ecosystems. Aggregate extractions have been shown to modify the biogeomorphological processes in aeolian sedimentary systems. The impacts associated to aggregate extraction include the reduction of available sediment and changes to the topography and vegetation patterns, thereby altering the sedimentary dynamics and limiting the recovery capacity of the dunefield. The aim of this article is to analyse the environmental effects produced by historical aggregate extraction in the foredune area of an arid aeolian sedimentary system (El Médano, Tenerife, Spain) through a study of the airflow dynamics and spatial distribution of vegetation, sediment and topographic changes. The methodology was designed with two temporal scales: (i) a long‐term approach which compares historical sources and current ones; (ii) a short‐term approach through experimental data collection to characterize the present functioning. For the latter, a field study was carried out in June 2021, collecting wind speed and direction data at a height of 0.50 m, sediment data (sand sheet thickness, grain size and sorting), and vegetation data (cover and species richness) at 40 sample points. The main results show that when the anthropic stress ceased the foredune did not follow a natural environmental pattern, and that the way it functions at the present time is determined by the changes induced by the aggregate extraction. Changes include alterations to the topography, the creation of a lagoon, and the generation of an aeolian deflation area and flow acceleration zones with the associated sand transport. This research contributes to an understanding of the environmental consequences of aggregate extractions on the foredunes of arid aeolian sedimentary systems and can enable the relevant authorities to make better‐informed decisions that help the management of these ecosystems.

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“…is their exceptional ability to stabilize dunes, the very characteristic that led to A. arenaria's widespread introduction around the world. In the 1930s, before A. arenaria had gained a strong foothold in northern California, foredunes, if present, were either semi-stable continuous ridges or a series of nebkha [112]. Some nebkha later coalesced into a foredune ridge vegetated by a combination of Elymus mollis and native, mound-building species [5,6,76].…”

Section: Dune Morphodynamicsmentioning

confidence: 99%

Ammophila Invasion Ecology and Dune Restoration on the West Coast of North America

Pickart

2021

Diversity

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The invasive ecosystem engineer Ammophila arenaria, native to Europe, was first introduced to California (USA) in 1896. More than a century later, it has come to dominate coastal foredune vegetation on the west coast of North America to the near exclusion of native species. A. arenaria builds a narrow, steep, peaked, and densely vegetated foredune, in contrast to the broad, more sparsely vegetated foredunes built by the native Elymus mollis. As such, it has modified dune processes by fixing the foredune and disrupting exchange of sediment between the beach, foredune, and dunefield. In the 1930s the congener A. breviligulata, native to the east coast and Great Lakes USA, was first introduced to Oregon, and has been displacing A. arenaria in southern Washington. Ammophila spp. have drastically reduced biodiversity, outcompeting native plant species, and displacing both invertebrate and vertebrate species. Restoration of west coast dunes through the removal of Ammophila began in the 1990s. Methods usually consist of one or a combination of manual digging, burning/herbicides, or excavation with heavy equipment. There are benefits and disadvantages to each method. Manual removal has proven most effective at restoring foredune form and process but is expensive. Excavation and herbicides may result in the loss of foredune morphology. Managers must articulate goals carefully before selecting restoration methods.

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Nebkha or not? -Climate control on foredune mode

Cited by 30 publications

References 37 publications

Multi-decadal coastal evolution of a North Atlantic shelf-edge vegetated sand island — Sable Island, Canada

Multi-decadal coastal evolution of a North Atlantic shelf-edge vegetated sand island — Sable Island, Canada

Foredune responses to the impact of aggregate extraction in an arid aeolian sedimentary system

Ammophila Invasion Ecology and Dune Restoration on the West Coast of North America

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