Coastal wetland responses to a century of climate change in northern Sahara, Morocco

Abstract

Coastal wetlands are highly sensitive to changes occurring at the coastline. It is critically important to determine regionspecific projections for these areas due to their specificities and vulnerabilities to climate change. This work aimed to value the impacts of recent climate changes at West Africa Sahara coastland, southern Morocco, at Khnifiss Lagoon. We have applied a combined approach using remote sensing techniques and environmental reconstructions based on highresolution analysis of sediment cores, covering the current warm period. Remote sensing highlighted changes to the lagoon inlet, accompanied by a greater meandering character of the tidal channels. As a response, the sediment cores have recorded a predominant vegetation substitution due to changes in the tidal limit, and an increase in organic carbon accumulation was observed. For the current climatology, during positive phases of the North Atlantic Oscillation, winds reaching the coast strengthen in an east-to-west direction. In the Khnifiss Lagoon, whose inlet is dominated by the ebb tide, the intensity and direction of the winds on the coast at surface level modifies its connection to the ocean by increasing sediment transport toward the interior of the lagoon. Locally biological responses to wind intensification, and possibly sea-level rise, exemplify the lagoon sensitivity to large-scale processes. Coastal vegetated wetlands are considered to be highly dynamic environments. However, we expect a loss of the upper tidal vegetation due to boundary conditions limiting the accommodation space in this arid environment in a possible future scenario of continuously inland tidal line displacement.

Impacts of the African Humid Period termination may have been delayed in the Atlantic Sahara

“…The first phase, corresponding to the period before 3428 ± 29 cal yrs BP (221 -227 cm), shows a continuous increase of COT (µ = 0.97%), C/N, and silt, followed by a decrease in salinity (Fig. 3), as indicated by the Sr/Ca ratio 45 . In a previous study, the isotope and elemental signatures of vegetation within Khnifiss Park were reported (Nogueira et al, 2022).…”

“…Previous research in the Khnifiss Lagoon suggests that, in the last century, the coast was directly affected by NAO oscillations and sea level changes 45 . A combined approach with remote sensing data and geochemical analysis reveals the sensitivity of the Khnifiss Lagoon to large-scale climatic processes, such as NAO.…”

“…A combined approach with remote sensing data and geochemical analysis reveals the sensitivity of the Khnifiss Lagoon to large-scale climatic processes, such as NAO. During its positive phase, a strong east-towest wind leads to a widening of the inlet, which, in turn, affects the hydrodynamics and biogeochemical cycles of the lagoon 45 . Previous studies indicate that the expansion of the Khnifiss Lagoon and surrounding areas is governed by the inlet's dynamic, the sea level of Morocco, and changes in the hydrological condition 45,47 .…”

“…During its positive phase, a strong east-towest wind leads to a widening of the inlet, which, in turn, affects the hydrodynamics and biogeochemical cycles of the lagoon 45 . Previous studies indicate that the expansion of the Khnifiss Lagoon and surrounding areas is governed by the inlet's dynamic, the sea level of Morocco, and changes in the hydrological condition 45,47 . Therefore, our record has the potential to improve further our knowledge of the climatic mechanisms and dynamics influencing NW Africa environments during the last ~3.5 kyrs BP.…”

Effects of spatial variability in vegetation phenology, climate, landcover, biodiversity, topography, and soil property on soil respiration across a coastal ecosystem

“…Open source remote sensing and GIS products offer a feasible solution for studying coastal terrestrial-aquatic ecosystems, providing a comprehensive and synoptic view of dynamic TAI characteristics [ 45 ], for example, coastal wetland type identification [ [46] , [47] , [48] ], flooding area monitoring [ [49] , [50] , [51] ], geomorphology investigation [ [52] , [53] , [54] ], sediment concentration [ [55] , [56] , [57] ], coastal tree mortality [ [58] , [59] , [60] ], and coastal urbanization [ [61] , [62] , [63] ]. Remote sensing techniques have also been applied to estimate carbon fluxes and analyze the response of local environments to carbon fluxes in coastal ecosystems [ [64] , [65] , [66] , [67] , [68] , [69] ]. Overall, these open-source datasets offer considerable benefits for managing the sustainability and health of coastal regions that balance environmental, economic, and human needs.…”