Mediterranean Temporary Ponds in wet and dry phase
(photos of Carla Pinto-Cruz)
Mediterranean temporary ponds are seasonal wetland habitats, subjected to extreme and unstable ecological conditions. Due to their uniqueness and scientific value, they are listed as a priority habitat for conservation in Annex I of the EU Habitats Directive. The coastal plain of southwest Portugal is a Natura 2000 (N2000) site (Costa Sudoeste) and hosts a large number of such temporary ponds, as a consequence of climatic and edaphic (soil-related) characteristics.
Temporary ponds appear in depressions along the upper layer of the soil during the first occurrences of rain in the hydrological year. Rainwater accumulates due to the existence of a soil layer inside the ponds, with lower permeability than the surrounding soils, which enables water retention. The first flooding occurrences are ephemeral since these first waters end up infiltrating and/or evaporating. These ponds are hydraulically connected to the groundwater and from the moment it reaches and surpasses the base elevation of the pond the water retention period becomes longer. Therefore, the hydroperiod of most of these ponds is higher than the one corresponding to simple accumulation of rainwater in soil depressions with low permeability. Learn more about the hydrogeology of Temporary Ponds here.
The fauna and flora species that naturally colonize temporary ponds are well adapted to these specific ecological conditions of Mediterranean habitats, such as the seasonality of available water. Hence, these species must have the ability to live underwater during months and afterwards endure extreme conditions of draught during summer.
The spatial and temporal dynamics determine the composition and zonation of living creatures in ponds. In the beginning of spring it is possible to find fluctuating water plants with leaves and flowers on the water surface. Simultaneously amphibious plants begin their vegetal development underwater and bloom only when water begins to dry. As a result, pond biodiversity persists until the arrival of the dry season (beginning of summer). In terms of fauna, temporary ponds are used as feeding and reproduction sites by several birds, amphibians and invertebrates species, which is crucial for the existence of various uncommon species with great conservation value.
Learn more about the biodiversity of Temporary Ponds:
The Mediterranean Temporary Ponds are one of the most notable and unique freshwater habitats in Europe, they are considered a priority habitat (3170*). In spite of having a crucial role in connectivity with other freshwater habitats, the life diversity in a temporary pond is very high and generally greater than one found in other aquatic environments, such as permanent pools, streams or rivers. Many hosted species are considered to be rare and endangered, both in Europe and throughout the world.
However, over the last two-decades, modern industrialised agriculture and tourism have caused a steep decline in the condition of this habitat in the N2000 site. Traditionally seen as non-productive areas, MTPs are nowadays subjected to strong anthropogenic pressures, such as deep soil turning, accelerated drainage, flattening of the surface topography or transformation into permanent reservoirs for irrigation. Therefore, urgent action is needed in order to halt this downward trend and assure their long-term protection