Coupling process-based and empirical models to assess management options to meet conservation goals

Abstract

Conservation lands face mounting threats of ecosystem transformation and loss of biodiversity from the invasion of fire-prone grasses. Managers must make difficult decisions to find efficient ways to expend limited resources across large and complex landscapes amidst substantial uncertainty regarding effective treatment strategies, climates, and invader-induced novel processes. Coupled empirical and process-based models can simulate the effects of management activities, quantify potential management costs and ecological impacts, while considering uncertainties associated with climate, spread rates, and wildfires lacking historical precedent. We developed a state-and-transition simulation model coupled with a fire behavior model to study impacts to native biodiversity and fire regimes in a national park invaded by a perennial grass. We evaluated resources required to meet management objectives, and efficient and effective spatial allocation of those resources. Management strategies and ecological scenarios strongly influenced the ability to minimize potential invasion impacts. Adding aerial precision spot spraying, which can target low cover levels in remote regions, may be enough to conserve the desert ecosystem from small scale transformation through invasive competition and from broad functional transformations through invasive-induced fire regime changes. Spot spraying may also be beneficial if wetter monsoonal conditions create faster invader growth rates when likelihoods of achieving management goals decreases even with unlimited resources. Given current park budgets with the addition of spot spraying, management goals may be achievable regardless of spatial prioritization. Our techniques could be applied to other situations to evaluate conservation goal feasibility and determine actions that would be most efficient in meeting those goals.