Alarming extinction rates have led to the degradation of ecosystems around the world through the extirpation of key ecological functions. Rewilding has emerged as an approach aiming in restoring these extirpated functions through the introduction of locally-extinct or analogous species. While most efforts focus on the long-term survival of introduced species, little focus is done on aiming to optimize functional restoration spatially across the ecosystems, which is essential for the ecological success of such ambitious projects. We use the island of Guam as ongoing example of a potential rewilding project, which has seen all its native seed dispersers functionally or completely extirpated by the invasive brown treesnake (Boiga irregularis). The absence of seed dispersers is linked to reductions in species diversity and changes in native forest structure, as well as slowed regeneration of degraded forest. Stakeholders aim in rewilding the island with the Såli (Micronesian starling, Aplonis opaca), an effective seed disperser with a remnant population still on the island. We use this case study to present the “Spatial planning of rewilding efforts” (SPORE) framework, with the goal of maximizing both establishment rates of service providers and functional restoration of rewilding projects. Our framework combines ecological models, spatial data, economics, and participatory approaches to identify effective management scenarios for restoring ecological function.
Results/Conclusions
We applied the SPORE framework to the Guam case study. First, we identified the regions across the island where functional restoration would be the most effective and the areas that provide suitable habitat for Såli. By coupling these two maps with an optimization algorithm, we selected and ranked areas where rewilding would maximize the benefits of functional restoration. Since snakes are a threat to Såli populations, they must be controlled. We estimated the costs of control within these priority areas by considering the economic parameters behind each snake control method (e.g. fencing, toxicants, traps). Finally, we gathered input from local on their ecological system through participatory approaches in order to guide future research and management. Through this example, we illustrate how SPORE can assist decision-makers in maximizing the benefits and success rates of future rewilding projects by considering the spatial distribution of functional restoration. This framework is designed to be easily transferable to any other system envisioning rewilding as a management strategy.