Artificial aquatic habitats impoverish amphibian diversity in agricultural landscapes of central Argentina

In central Argentina, agro-ecosystems constitute the dominant landscape, representing the replacement of extensive grassland areas by crops and pastures. Agriculture has caused the loss of extensive areas of Pampean inland wetlands through drainage and the construction of artificial aquatic habitats such as ditches and ponds. This study evaluated the availability and amphibian breeding use of 194 natural and artificial open water habitats and identified those attributes that affect amphibian diversity (richness, abundance and species occurrence). Interviews with farmers revealed that all artificial ditches, drainage channels and ponds were constructed directly or indirectly to support agricultural activities, and 61.5% of them were created at the expense of natural wetlands. The results from generalized linear mixed models) indicated a significant decrease (P < 0.05) in amphibian richness (14.2-35.7%) and abundance (35.3-86.6%) in artificial habitats compared with natural habitats. Overall, vegetation cover, average depth and edge slope emerged as the most important attributes affecting amphibian diversity in artificial open water habitats. Vegetation cover had a significant (P < 0.05) positive influence on species richness and abundance, whereas average depth and edge slope had the opposite effect. Given the substantial modification of inland wetlands in central Argentina, natural aquatic habitats should be considered top priorities for conservation, and law enforcement is urgently needed to control the drainage and levelling of lagoons, ponds and low-lying areas. The appropriate design and planning of constructed wetlands, including shallow depth and slightly sloping edges, could greatly improve the ability of artificial wetlands to favour native amphibians in these altered landscapes. Artificial wetlands could offer complementary habitats to natural habitats for amphibians and aquatic wildlife if actions leading to sustainable management and territorial planning are applied.