Quandaries of a decade‐long restoration experiment trying to reduce invasive species: beat them, join them, give up, or start over?

Abstract

We evaluate the outcomes and consequences of a decade‐long restoration project in a Hawaiian lowland wet forest as they relate to long‐term management actions. Our initial study was designed both to promote native biodiversity and to develop knowledge that would enable land management agencies to restore invaded forests. Our premise of success followed the prevalent perception that short‐term management, such as removal of invasive species, ideally translates into long‐term and sustainable restoration. We were therefore disappointed and perhaps discouraged in our results—little recovery of native biodiversity despite ongoing and labor‐intensive management. Not only did we fail to return the invaded forest to a native‐dominated system but also our efforts lead to recruitment of new non‐native species assemblages. The sobering truth of many restoration projects in Hawaii and elsewhere is that we can never completely walk away and “consider the job finished,” or we have to accept that some ecosystems cannot be returned to an all‐native state. Essentially, costs of restoration may outweigh the accomplishment. This setback gave us an opportunity to reconsider and modify our initial approach. By starting over with a new direction using both native and non‐invasive but non‐native species, we have adopted a new philosophy of “join them.” In our revision, we changed the players in the game by following invasive species removal with outplantings of native and non‐invasive non‐native species that will functionally fill missing roles in the ecosystem. We link social interest in the new experiment to changing attitudes about naturalness.