Cumulative effects on habitat networks: How greedy should we be?

Connectivity conservation and restoration are key strategies to preserve biodiversity under the pressure of habitat loss and fragmentation. Numerous quantitative approaches have been developed to help conservation practitioners take the most effective and cost-efficient actions to conserve, restore or create habitat patches or corridors that preserve or enhance landscape connectivity. This problem is often solved by ranking habitat patches (or corridors) with suboptimal algorithms that do not account for the cumulative effects that may occur in the case of simultaneous or sequential losses (or enhancements) of multiple habitat patches. Accounting for these cumulative effects is one of the current challenges for connectivity conservation. Here, we quantify these cumulative effects and explore the trade-off between solution quality and computational time when optimizing the selection of conservation/restoration actions that maximize landscape connectivity under a budget constraint; connectivity is here measured by the frequently-used Equivalent Connected Area. We compare the solutions obtained with a new optimization pipeline with solutions obtained with four simpler algorithms used in most connectivity conservation studies. Comparison is performed for four case studies covering a wide range of possible applications for conservation practitioners. We show that the simpler algorithms can provide suboptimal solutions, when conservation/restoration actions have a strong impact on least-cost paths between the habitat patches, and that optimal resolution should be considered whenever possible.