Biogeomorphological responses of nebkhas to historical long-term land uses in an arid coastal aeolian sedimentary system

Abstract

Coastal dunes have received growing attention in recent years because of the ecosystem services they provide and the high anthropic pressure that they have historically been subjected to and continue to endure. Such pressure especially affects arid dune fields where any changes are more noticeable due to their natural dynamics. The aim of this paper is to analyze the relationship between the degradation of an arid aeolian sedimentary system (El Médano, Tenerife, Spain) due to historical long-term land uses and its subsequent biogeomorphological evolution. The methodology combines historical sources (historical documents, aerial and common photographs and oral sources) and current ones (orthophotos, LiDAR data and field work). In order to analyze the response of the system to these uses, 8 plots were chosen in which 3 different historical land uses had resulted in the total or partial elimination of the vegetation and landforms. Biogeomorphological variables were measured on 461 nebkhas in these plots. The main results show that the historical land uses studied in this paper (aerodrome, aggregate extraction and crop cultivation) modified the entire system, with changes observed in the topography, vegetation cover and sediment availability for transport. Changes in topography and distance from shore were important factors in its recovery capacity. This research contributes to our understanding of the different aeolian sedimentary dynamics that can be detected in the same dune field (especially with nebkha landforms) and is of particular importance for making appropriate environmental management decisions to facilitate the recovery of the ecosystem.

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

“…The aeolian sedimentary system of El Médano (28 02 0 07.7 00 N; 16 32 0 35.7 00 W) is located on the southern coast of Tenerife. Three main historical land uses were identified in different areas of the aeolian sedimentary system of El Médano: an old aerodrome, and aggregate extraction and a crop cultivation area (Marrero-Rodríguez, García-Romero, Peña-Alonso, et al, 2020). The study area includes the sector of this system affected by the extraction of aggregates for construction.…”

“…The study area is part of an area that was declared a Nature Reserve of National Interest (Law 12/1987, of 19 June, on the Declaration of Natural Spaces of the Canary Islands) in 1987 before its reclassification in 1994 as a Special Nature Reserve (Law 12/1994, of 19 December, on Natural Areas of the Canary Islands). However, the associated planning instrument for the protection of the area (Gobierno de Canarias, 2004) was not definitively approved until October 2004 (Marrero-Rodríguez, García-Romero, Peña-Alonso, et al, 2020). In addition, the area has had protected status since 2000 as a result of the European Union (EU) Habitats Directive of that year.…”

“…This normalization allowed a comparison of the temporal variability of the wind speeds and to eliminate differences in wind speed variations due to changes in the sample points, thereby enabling inclusion of the complete study area and data comparisons (García-Romero et al, 2019). The input wind direction during the field experiment varied between 45 and 90 , in accordance with the prevailing ENE winds described in Marrero-Rodríguez, García-Romero, Peña-Alonso, et al (2020).…”

“…Topographic modification due to sediment extraction generated a flooded area as excavations took place below sea level. While the response of the system itself in other areas where different historical land uses were carried out (e.g., an aerodrome and crop cultivation area) has resulted in a current look and functioning closer to the ideal status described in the scientific literature, the erratic distribution pattern of nebkhas and plant species generated in the aggregate extraction area does not respond to the characteristic distribution of this type of aeolian sedimentary system (Marrero-Rodríguez, García-Romero, Peña-Alonso, et al, 2020). Moreover, the sediment budget was drastically reduced due to the extraction (Gobierno de Canarias, 2004).…”

Diversity of Volcanic Geoheritage in the Canary Islands, Spain

“…This is especially true in the Canary Islands, where the driving force of the economy is coastal tourism. For example, in 2019 the islands received more than fourteen million tourists (Table 2), which has contributed to the disappearance of many of the volcanic features and processes in the islands coastlines, e.g., the aeolian sedimentary systems [93,94]. At the same time, signs of the exhaustion of this tourism model are highlighting the need to diversify the range of tourist leisure activities on offer in the Canary Islands, and volcanic geoheritage can undoubtedly contribute to this through geotourism or volcanic tourism [2,5,[12][13][14]39,59,92].…”