Conserving migratory species while safeguarding ecosystem services

Many migratory shorebird species are undergoing severe population declines due to habitat loss. Selecting sites for protection along migratory shorebird flyways requires accounting for connectivity between sites and representing all migratory cycle stages within a protected area network. Site protection decisions often additionally account for the economic value of habitat-related ecosystem services, as shorebird habitats often provide services such as fisheries and recreational opportunities. In this study, we develop a new approach which combines graph theory, decision science, and stochastic dynamic optimization, to investigate whether habitat protection strategies aimed at safeguarding ecosystem services can also deliver efficient protection for migratory shorebirds. We use graph theory to empirically model migration routes for two shorebird species, the Curlew Sandpiper (Calidris ferruginea) and Eastern Curlew (Numenius madagascariensis), linking their migratory networks with data on habitat-related ecosystem services within the East Asian - Australasian Flyway (EAAF). Using dynamic optimization, we calculate the optimal habitat protection strategy for both ecosystem services and shorebird conservation objectives for both species. We further investigate if, and how, these two strategies can converge to achieve both objectives, and whether there is a trade-off between strategies. Our results show that the biodiversity outcome from strategies maximizing ecosystem services provided by shorebird habitat could align closely with a species-focused conservation plan. More specifically, the optimal ecosystem services oriented strategy maintains a similar level of shorebird populations as the optimal conservation strategy, while protecting an additional 45% (Curlew Sandpiper) and 42% (Eastern Curlew) of ecosystem services throughout the network. Conservation budget also matters, as small budgets would lead to inefficient protection for biodiversity. Our research shows that conservation planning can simultaneously achieve conservation and ecosystem services objectives for migratory species. By accounting for the value of ecosystem services within shorebird habitats, we provide quantitative evidence of a win-win scenario in which both shorebird conservation and ecosystem service provision can be achieved. Our model could be applied to other migratory species to improve spatially explicit planning for both biodiversity and ecosystem service targets.