Neglecting biodiversity baselines in longitudinal river connectivity restoration impacts priority setting.

River habitats are fragmented by barriers which impede the movement and dispersal of aquatic organisms. Restoring habitat connectivity is a primary objective of nature conservation plans with multiple efforts to strategically restore connectivity at local, regional, and global scales. However, current approaches to prioritize connectivity restoration do not typically consider how barriers spatially fragment species' populations. Additionally, we lack knowledge on biodiversity baselines to predict which species would find suitable habitat after restoring connectivity. In this paper, we asked how neglecting these biodiversity baselines in river barrier removals impacts priority setting for conservation planning. We applied a novel modelling approach combining predictions of species distributions with network connectivity models to prioritize conservation actions in rivers of the Rhine-Aare system in Switzerland. Our results show that the high number and density of barriers has reduced structural and functional connectivity across representative catchments within the system. We show that fragmentation decreases habitat suitability for species and that using expected distributions as biodiversity baselines significantly affects priority settings for connectivity restorations compared to species-agnostic metrics based on river length. This indicates that priorities for barrier removals are ranked higher within the expected distributions of species to maximize functional connectivity while barriers in unsuitable regions are given lower importance scores. Our work highlights that the joint consideration of existing barriers and species past and current distributions are critical for restoration plans to ensure the recovery and persistence of riverine fish diversity.

Considering Fish as Recipients of Ecosystem Services Provides a Framework to Formally Link Baseline, Development, and Post-operational Monitoring Programs and Improve Aquatic Impact Assessments for Large Scale Developments.

In most countries, major development projects must satisfy an Environmental Impact Assessment (EIA) process that considers positive and negative aspects to determine if it meets environmental standards and appropriately mitigates or offsets negative impacts on the values being considered. The benefits of before-after-control-impact monitoring designs have been widely known for more than 30 years, but most development assessments fail to effectively link pre- and post-development monitoring in a meaningful way. Fish are a common component of EIA evaluation for both socioeconomic and scientific reasons. The Ecosystem Services (ES) concept was developed to describe the ecosystem attributes that benefit humans, and it offers the opportunity to develop a framework for EIA that is centred around the needs of and benefits from fish. Focusing an environmental monitoring framework on the critical needs of fish could serve to better align risk, development, and monitoring assessment processes. We define the ES that fish provide in the context of two common ES frameworks. To allow for linkages between environmental assessment and the ES concept, we describe critical ecosystem functions from a fish perspective to highlight potential monitoring targets that relate to fish abundance, diversity, health, and habitat. Finally, we suggest how this framing of a monitoring process can be used to better align aquatic monitoring programs across pre-development, development, and post-operational monitoring programs.