Threats to the conservation of biotic integrity in Iberian fluvial ecosystems

Abstract

Fluvial ecosystems are highly modified by human activity and the species inhabiting them are more imperiled than their aerial
\nor oceanic counterparts. In addition, freshwater biodiversity per surface unit is higher than terrestrial and marine biodiversity.
\nBut from a conservation point of view rivers and streams have received less attention than any other natural system. Impacts in
\nwater and habitat quality, flow regime and biotic interactions can be considered the main factors responsible for the lack of biotic
\nintegrity in Mediterranean rivers. Dams and impoundments alter drastically the physical habitat structure and the ecological
\nfunctioning of running waters. But at the same time also modify the flow regime. Biotic interactions are deeply altered by
\nintroduced invasive species, which are common and proliferate in reservoirs and other artificial lentic habitats. In this paper we
\nhave adapted this classification of the main human impacts on fluvial ecosystems to the Iberian situation summarising them in
\nthree groups: water pollution, damming, and introduction of invasive species. We discuss their effects on biotic integrity of
\nrunning waters through some examples from some of our previous works. Pollution is treated in two alternative ways.
\nQuantifying its importance in the drainage network of a large Mediterranean area in southern Spain, as well as analysing its
\neffect on the structure of macroinvertebrate communities and otter (Lutra lutra) distribution. Invasive species are widespread
\nin Iberian inland waters. We hereby present the spatial relationship between native fish communities and invasive centrarchids
\nthat populate the peninsula. Finally, the damming impacts are considered through the analysis of its role in the spread and establishment
\nof the invasive species. All of them are just a few examples about how alterated is the natural composition and dynamics
\nof Iberian rivers and streams, i.e. its biotic integrity. The challenge for the future lies in the efficient protection of the biodiversity
\nof Iberian freshwaters in the face of increasing pressures on the aquatic resources. But the first step in preserving our
\nrivers is the real recognition of the extent of the problem, particularly among scientists.