Advances and challenges in ecological connectivity science

Maintaining and restoring ecological connectivity will be key in helping to prevent and reverse the loss of biodiversity. Fortunately, a growing body of research conducted over the last few decades has advanced our understanding of connectivity science, which will help inform evidence-based connectivity conservation actions. Increases in data availability and computing capacity have helped to dramatically increase our ability to model functional connectivity using more sophisticated models. Keeping track of these advances can be difficult, even for connectivity scientists and practitioners. In this article, we highlight some key advances from the past decade and outline many of the remaining challenges. We describe the efforts to increase the biological realism of connectivity models by, for example, isolating movement behaviors, population parameters, directional movements, and the effects of climate change. We also discuss considerations of when to model connectivity for focal or multiple species. Finally, we reflect on how to account for uncertainty and increase the transparency and reproducibility of connectivity research and discuss situations where decisions may require forgoing sophistication for more simple approaches.

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.

Using sentinel nodes to evaluate changing connectivity in a protected area network

It has been recognized that well-connected networks of protected areas are needed to halt the continued loss of global biodiversity. The recently signed Kunming-Montreal biodiversity agreement commits countries to protecting 30% of terrestrial lands in well-connected networks of protected areas by 2030. To meet these ambitious targets, land-use planners and conservation practitioners will require tools to identify areas important for connectivity and track future changes. In this study we present methods using circuit theoretic models with a subset of sentinel park nodes to evaluate connectivity for a protected areas network. We assigned a lower cost to natural areas within protected areas, under the assumption that animal movement within parks should be less costly given the regulation of activities. We found that by using mean pairwise effective resistance (MPER) as an indicator of overall network connectivity, we were able to detect changes in a parks network in response to simulated land-use changes. As expected, MPER increased with the addition of high-cost developments and decreased with the addition of new, low-cost protected areas. We tested our sentinel node method by evaluating connectivity for the protected area network in the province of Ontario, Canada. We also calculated a node isolation index, which highlighted differences in protected area connectivity between the north and the south of the province. Our method can help provide protected areas ecologists and planners with baseline estimates of connectivity for a given protected area network and an indicator that can be used to track changes in connectivity in the future.

Demystifying ecological connectivity for actionable spatial conservation planning

Connectivity underpins the persistence of life; it needs to inform biodiversity conservation decisions. Yet, when prioritising conservation areas and developing actions, connectivity is not being operationalised in spatial planning. The challenge is the translation of flows associated with connectivity into conservation objectives that lead to actions. Connectivity is nebulous, it can be abstract and mean different things to different people, making it difficult to include in conservation problems. Here, we show how connectivity can be included in mathematically defining conservation planning objectives. We provide a path forward for linking connectivity to high-level conservation goals, such as increasing species' persistence. We propose ways to design spatial management areas that gain biodiversity benefit from connectivity.