The role of barrier zones in controlling invasive species: A microcosm experiment

Around the world, invasive species have altered ecosystems, entailing both social and economic consequences. Further, preventing and controlling their spread requires high costs. One common approach to control invasive species is through barrier zones. A barrier zone is a region surrounding an initial invasion where management of the invasive species is conducted, including direct harvesting. Although barrier zones have been examined theoretically and implemented in the field, they have received limited experimental testing, which can provide replication. Here, combined with a mathematical model, we use microcosms of the invasive species, the confused flour beetle (Tribolium confusum), to assess the effectiveness of barrier zones and harvesting. We varied both harvesting levels and barrier size and found that barrier zones can be effective tools in both reducing the overall population size and controlling the spatial spread of an invasive species. In our system, increasing barrier size was generally more effective than increasing harvest rate; however, this depends on the relative costs of invasive species damage versus control strategies. Low-effort strategies produced the greatest variability in management outcomes. Together, these results highlight the promise of barrier zones and the importance of considering both desired outcomes and the costs in invasive species management.