A total of 16 543 artificial ponds were inventoried. Ninety-one per cent of the ponds were classified as for farming use. Generally, the fraction of farm land converted to pond structures was close to that predicted from the average annual precipitation in the region. However, in several areas, this fraction was remarkably higher than the value predicted, probably due to excessive groundwater extraction. Overall, the naturalisation stage of ponds was poor. However, ponds sited on natural substrate basins had more structured-marginal vegetation, compared with ponds of artificial substrate basins. Furthermore, other factors related to pond management might seriously limit their naturalisation stage. Despite the high abundance of ponds in Andalusia, our results suggest that, in order to improve the potential for biodiversity conservation in these environments, substantial structural and management changes are required

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1. Agricultural intensification has caused dramatic biodiversity loss in many agricultural landscapes over the last century. Here, we investigated whether new types of farm ponds (made of artificial substrata) in intensive systems and natural-substratum ponds in traditional farming systems differ in their value for aquatic biodiversity conservation. 2. We analysed the main patterns of environmental variation, compared a-, b- and c-diversity of macroinvertebrates between ponds types and evaluated the role of submerged aquatic vegetation (SAV). Generalised additive models (GAM) were used to analyse the relationships of a- and b-diversity with environmental predictors, and variation partitioning to separate the effect of environmental and spatial characteristics on the variation in macroinvertebrate assemblages. Moran’s eigenvector maps (MEMs) were used to define spatial variables. 3. A principal coordinate analysis (PCoA) detected a primary environmental gradient that separated nutrient-rich ponds from those dominated by SAV; a secondary morphometric gradient distinguished natural-substratum ponds, with large surface area and structural complexity, from artificial-substratum ponds with steeper slopes. Natural-substratum ponds had almost twice the a- and c-diversity of artificial-substratum ponds, and diversity significantly increased when SAV was present, particularly in artificial-substratum ponds. Total phosphorus (TP) strongly contributed to explain the patterns in diversity, while SAV was a significant predictor of assemblage composition and diversity. GAMs revealed optima of both a-diversity at intermediate SAV covers and b-diversity at intermediate–high TP concentrations. 4. These findings have important implications for conservation planning. Adaptation of artificialsubstratum ponds by adding natural substratum and smoothing the gradient of pond margins would improve their conservation value. Development of SAV with occasional harvests and certain cautionary measures to control nutrient levels may also improve both the agronomical and environmental function of ponds

We compared morphometric and physicochemical characteristics of farm ponds and natural wetlands in Andalusia (southern Spain) to determine whether artificial waterbodies might act as alternative and/or complementary habitats for aquatic biodiversity. Farm ponds were much smaller than natural wetlands, making them unsuitable for species requiring large waterbodies. However, we observed high farm pond density in areas lacking natural wetlands, which suggests a prime role for the conservation of species with low dispersal capacities. Natural-substrateponds were abundant in traditional extensive farming systems and showed shoreline complexity as high as the most complex natural wetlands. Areas with more intensive agriculture were dominated by artificial-substrate ponds and wetlands, with low physical complexity in both. The high copper load in sediments, due to the use of copper sulphate as biocide, differentiated the artificial-substrate ponds from natural-looking ponds and all natural wetland types. Aqueous mineral levels in farm ponds were much lower than in natural wetlands. We can conclude that farm ponds might play a principal role in region-wide habitat complementarity, by providing a relatively high density of small, permanent, oligohaline waterbodies that is not matched by natural wetland. To enhance this role, measures regulating both pond construction and management are needed, particularly for artificial-substrate ponds

Abstract. The relationship between communities of submerged annual macrophytes (predominately Chara spp.) and environmental characteristics is studied in three habitats with different dominant perennial species (Arthrocnemum, Juncus, Scirpus) and areas of bare soil. The distribution of submerged annual macrophytes is significantly dependent on two independent environmental factors: a dominant gradient of flooding/salinity, and a secondary gradient of nutrients related exclusively to the combined abundance of helophytes of the genus Scirpus (S. maritimus and S. litoralis). The results suggest that these emergent helophytes (1) are able to modify water column parameters (such as concentration of nitrates, phosphates, potassium, and bicarbonates) which are important for the communities of submerged macrophytes, and (2) play a fundamental role in the generation of secondary sources of environmental variability which, superimposed on the main gradient of flooding/salinity, favours the appearance of new compositional equilibria in such communities. The existence of a process of facilitation is discussed by which the emergent helophytes induce changes in nutrient availability that would favour relatively nutrient‐demanding charophyte species (such as Chara connivens and Nitella hyalina), altering the established relationships with other coexisting charophytes (such as Chara canescens and C. galioides) that dominate in the absence of the facilitating species. Nevertheless, the increased nutrient concentration associated to the presence of helophytes would not introduce significant changes in the total biomass of submerged aquatic macrophytes.

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