Applications of systematic approaches in freshwater conservation planning

Systematic conservation planning (SCP) is a widely accepted biodiversity-focused approach to selecting priority areas for protection. Since freshwater ecosystems are globally in urgent need of more conservation and the development of freshwater protected areas has lagged behind such need, SCP is proposed to be widely applied in freshwater conservation. As SCP originates from terrestrial realms, freshwater-specific characteristics should be considered when applied to freshwater systems. The challenges mainly include difficulty in data collection for freshwater species and uncertainty in classification of coarse-filters for representation, while also considering the maintenance of natural connectivity in fresh waters and taking longitudinal, lateral, and climate-change-caused threats into account. Only by addressing these issues may the representativeness and persistence of freshwater biodiversity be ensured in the proposed conservation network. Though challenging at times, the application of systematic approaches in freshwater conservation planning has been widely attempted throughout the last 12 years and applied in different freshwater ecosystems at different scales. In addition, the consideration of freshwater-specific issues has been becoming more and more comprehensive. This review divides the whole process of SCP into successive steps while discussing detailed applications of freshwater planning at each step. First, according to the review, each step attempts to explore many alternatives, such as using surrogates from the species level to the ecosystem level (or a combination within this range) to represent the spatial variation of freshwater biodiversity, deriving raw data from various sources to use for planning, applying different techniques to expand or integrate data, setting various target forms to ensure representativeness or persistence, considering existing protected areas in different ways in the process of planning, using priority principles in various paradigms for both representativeness and persistence, and applying several types of software to the final design of the protection network. Second, applications in each step (except “setting representative targets”) have been more or less tried in considering freshwater-specific issues. For representativeness issues, accepting various sources of information and attempting different ways of data reduction are the main approaches to solving these challenges. For persistence issues, identifying the main ecological processes and threats in freshwater systems and involving them in the process of prioritization are major concerns, and setting targets or priority principles are key steps for taking these persistence issues into account. Finally, more systematic conservation of freshwater systems and new or improved alternatives of each step are expected to enrich this field of study.