Mapping Mediterranean temporary ponds in SW Portugal using remote sensing

Mediterranean temporary ponds on the Southwest Portuguese coast are areas of significant biodiversity and are recognized as priority habitats by the Habitat Directive (92/43/EEC). The fauna and flora species that inhabit these ponds are well adapted to the variability of the Mediterranean climate, exhibiting a high resistance to drought and the ability to survive without water for months. Among them, the Triops vicentinus species stands out for its uniqueness, considered a living fossil that has persisted since the time of the dinosaurs.

These temporary ponds are situated in shallow depressions where rainwater accumulates for seasonal periods. They face increasing threats due to anthropogenic pressures, primarily arising from intensive farming techniques, real estate development linked to tourism, and a general lack of awareness among the population regarding the significant biological and ecological value of this habitat. The area was the focus of the LIFE + project titled 'Conservation of Temporary Ponds in the Southwest Portuguese Coast of Portugal' conducted between 2013 and 2018. During this initiative, georeferenced mapping of the ponds and associated biodiversity was produced. However, the geographical evolution of these ponds has not been monitored since then.

This study aims to map the ponds and track their evolution between 2018 and the present. To map the water bodies, we use Sentinel-1 and 2 datasets along with the Sentinel application platform SNAP. The surface water extraction method relies on the Normalized Difference Water Index and a supervised classification algorithm. The applied methodology has proven to be efficient in detecting and interpreting the dynamics of water bodies. The results of this investigation enhance our understanding of the uncertainties associated with the applications of Sentinel-2 and Sentinel-1 for monitoring temporary ponds and contribute to our knowledge of the current status of this habitat.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) –

UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020),

UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and

LA/P/0068/2020(https://doi.org/10.54499/LA/P/0068/2020).