Vegetation of Mediterranean temporary pools: a fading jewel?

Abstract

Although Mediterranean temporary pools are of great value for conservation, they are in rapid decline under the impact of various forms of anthropogenic pressure. Their disappearance from the landscape may result in a weakening of the biological connections between pools due to increasing isolation and the impoverishment of their communities. In Western Morocco (province of Benslimane), temporary pools have undergone severe regression over the past decades. The quantification of these losses and the impact on the richness of plant communities remain, however, unstudied. Since this is of vital importance for the conservation of the biodiversity of these habitats, a study has been undertaken associating (1) an assessment of the pool losses (both in density and surface area) between 1955 and 2001 using remote sensing, (2) surveys of vegetation and water depth (in 2006) in 48 pools, and (3) an assessment of the density and surface area of pools occurring within a 3 km radius around each of the sampled pools. The results show a loss of 23% in number and 61% in surface area of pools in the province over a period of 47 years. This decline, promoted by their small size and shallowness, is probably related to socio-economic changes (intensification of agricultural practices and population growth). The richness in characteristic and rare species of the pools was related to both local (water depth) and regional features (land use, pool density and total water surface area in the surrounding landscape). The significant impact of the current density of pools and their total surface area on the conservation value of the studied pools suggests a weakening of the metacommunity dynamics between pools. Given the rapid socio-economic changes in the province and the current rate of pool disappearance (0.5% per year) we predict a continuing reduction in pool density with a high risk of the widespread loss of their unique flora in the long term.

Temporary pond ecosystem functioning shifts mediated by the exotic red swamp crayfish (Procambarus clarkii): a mesocosm study

“…Temporary ponds contribute largely to increase regional richness in diversity inventories, because they harbour species exclusively occurring in such a system (Boix et al, 2001;Waterkeyn et al, 2008;Díaz-Paniagua et al, 2010;Rhazi et al, 2012). In the case of macro-invertebrates, abundance and richness are positively correlated to macrophyte beds in ponds (Della Bella et al, 2005).…”

“…More specifically, Mediterranean temporary ponds are recognized in international treaties for their biodiversity, for example, by the European Union's Habitat Directive (Natura code 3170, 92/43/CEE, 21 May 1992) and the Ramsar Convention (Resolution VIII 33). In arid or semi-arid areas such as the Mediterranean basin, these ecosystems are vital for numerous aquatic plants, vertebrates and invertebrates (Grillas et al, 2004;Gómez-Rodríguez et al, 2009;Díaz-Paniagua et al, 2010;Céréghino et al, 2012;Rhazi et al, 2012). Biological communities and ecosystem functioning in temporary ponds are mainly controlled by abiotic factors such as natural flooding events and water mineralization (Williams, 2005), so the arrival in the pond of a large omnivorous predator such as the red swamp crayfish (Procambarus clarkii, Girard) should represent a new and severe biological stressor for the communities.…”

Artificial ponds in Central Europe do not fall behind the natural ponds in terms of macrophyte diversity

“…Based on our results, significantly lower counts of helophytes were caused by the common absence of gradual banks and shallow littoral zone in artificial waterbodies mainly in case of gravel or mud pits. Moreover, relatively shallow water and fluctuating water regime in natural ponds enhances the colonisation by helophytes in littoral zone Rhazi et al, 2012;Lukács et al, 2013). In addition to mentioned characteristics, higher variance of water reaction and higher ammonia content in case of natural ponds can play important role for presence of broader groups of macrophytes including helophytes (cf.…”

Assessing the ecological integrity of endorheic wetlands, with focus on Mediterranean temporary ponds

“…They offer (temporary) housing to both general (opportunistic) species as well as to unique (temporary pond specific) species that are adapted to living under time stress and extreme environmental conditions (Grillas et al, 2004). Unfortunately, temporary wetlands are often neglected and disappear at an alarming rate, with percentage loss during the last century ranging from 60% to 97% in different parts of the world (Brendonck and Williams, 2000;Nicolet et al, 2004;Rhazi et al, 2012). Due to their small size and shallowness, these habitats are poorly buffered and easily destructed or degraded by human activities, such as urbanization, agriculture and pollution (Rhazi et al, 2012).…”