Issue 54:4’s Editor’s Choice post is written by Shelley Arnott. The article chosen is Critical catchments for freshwater biodiversity conservation in Europe: identification, prioritisation and gap-analysis by Savrina F. Carrizo and colleagues.

Aquatic ecosystems around the world are threatened with environmental changes resulting in critical loss of biodiversity; 81% of freshwater populations monitored for the Living Planet Index have declined in abundance between 1970 and 2012. Nations are faced with the difficult problem of prioritizing conservation of habitats in order to protect endangered species and ensure the maintenance of biodiversity. This is especially challenging in freshwater systems because their protection requires consideration of habitats (i.e., catchments) beyond the borders of the lakes, streams or wetlands.  Despite the critical importance of freshwater biodiversity for ecosystem services, including drinking water, food, recreation and flood regulation, most conservation efforts to date have focused on terrestrial and marine habitats.

A strategy that has been used for conservation planning and the protection of biodiversity is to identify Key Biodiversity Areas (KBAs), which are sites that meet globally standardized criteria related to the vulnerability and irreplaceability of local species.  A site meets the vulnerability criterion if it contains a single individual of a species that is critically endangered or endangered, or if it contains 30 individuals of a vulnerable species, based on the IUCN Red List. A site meets the irreplaceability criterion if it contains a species with a restricted range or clumped distributions, which could include seasonal or source populations.  Identifying KBAs is a useful way of earmarking critical areas that could be set aside for protection to meet Aichi Biodiversity Targets (such as Aichi Target 11, which calls for an increase in protected areas in areas that are of importance to biodiversity).  To date, very few KBAs have been identified for freshwater habitats despite human reliance on freshwater biodiversity and associated services.

Carrizo and associates have developed a tool which allows for the identification of freshwater sites that would qualify as KBAs (called critical catchments) and the prioritization of a subset that would offer protection to aquatic species that are threatened, have restricted ranges, or are unique. Data on 1296 species of fish, molluscs, odonates, and aquatic plants were used in the analyses.  In addition to protecting catchments associated with threatened aquatic species, keeping costs low and making use of existing protected areas were important goals of the prioritization exercise. Catchment area was used as a proxy for cost and the maximum allowable cost was set to 17% of the total area, the Aichi target for protected areas to be set aside by 2020. Critical catchments and prioritized critical catchments obtained from several contrasting scenarios were then compared with existing protected areas using European Union’s Natura 2000, and the World Database of Protected Areas.  Irreplaceable critical catchments, defined as catchments that were prioritized in each of 1000 model runs, were also compared against Natura 2000 protected areas to identify gaps and highlight future areas for protection.

The results revealed that critical catchments covered 45% of Europe, mostly in the southern regions.  The prioritization exercise allowed the identification of 17% of the area that was most important for the conservation of threatened species – mostly in southern and eastern Europe. An alarming result was that the current areas set aside for protection in Europe are not adequate to protect freshwater biodiversity. However, results from these analyses can be used to guide the expansion of Natura 2000 and protect areas that are critical for threatened freshwater biodiversity. In addition, areas identified can be considered for protection by local conservation groups, possible sites for remediation and habitat improvement, and monitoring efforts. Conservation planning is an iterative process and the analyses by Carrizo and colleagues provide an excellent starting place for strategic efforts to protect freshwater biodiversity.

The full article, Critical catchments for freshwater biodiversity conservation in Europe: identification, prioritisation and gap-analysis is available in the Journal of Applied Ecology.