Water transfers promote invasions

Positive (grey) and negative (black) interactions among three major stressors in aquatic ecosystems: climate change, biological invasions and water transfers; and their potential impacts on the conservation of native protected species. Extracted from Gallardo and Aldridge (2018).

Inter-basin Water Transfers (IBWT) provide a direct link between previously isolated catchments and may modify the habitat conditions of the receiving waters such that they become more favourable for the establishment of invasive species. The compounded deleterious effects of climate change, water transfers and biological invasions will intensify the stress upon native species, with the potential to ultimately provoke local extinctions. Here we use a planned transfer between the River Severn and the River Thames in UK as a case study to investigate these three factors simultaneously. Climate-based distribution models highlighted major areas in both catchments suitable for the establishment of invaders now and under future scenarios. Additional models based on water chemistry narrowed down the areas under highest threat, and landscape analysis mapped the potential routes of migration among alternative water uptake and discharge points. We finally discussed the risks associated to different discharge locations in the Thames River and alternative engineering options such as open canal vs underground pipelines.

Results from regional species distribution models used to calculate habitat suitability for invasive and native species. B and C: cumulative regional suitability for two invasive species and three native species in the Severn and Thames river catchments. Points of interest, located at regular 30-km intervals in each river, represent potential withdrawal and discharge river sections for an interbasin water transfer.

This publication illustrates the use of novel spatially-explicit techniques to help managers make informed decisions about the biological risks associated to engineering. Such information is especially important under new legislation (e.g. EU Invasive Species Regulation No 1143/2014) which increases the responsibility of water managers to contain and not transfer invasive species into new locations.

Gallardo, B. and Aldridge, D.C. (2018) Inter-basin water transfers and the expansion of aquatic invasive species. Water Research 143, 282-291.