In a recent study by Lohrer, Tai et al. “Evidence of rebound effect in New Zealand MPAs: Unintended consequences of spatial management measures“. Ocean & Coastal Management, Volume 239, 2023. Researchers have uncovered evidence of a phenomenon known as the “rebound effect,” shedding light on unintended consequences of spatial management measures in Marine Protected Areas (MPAs) in New Zealand. While MPAs are traditionally believed to enhance fish size and biomass within their borders, this investigation focused on the impact of these protected zones on fishing fleet (human) behavior and fish catches outside MPA boundaries.
Analysis and Discussion
The study examined five offshore MPAs, including a Marine Reserve, two Benthic Protected Areas, a Closed Seamount Area, and a Marine Mammal Sanctuary. Using Regression Discontinuity in Time (RDiT) models, the researchers analyzed changes in total catch and Catch per Unit Effort (CPUE) of bottom trawlers before and after MPA designation.
Contrary to expectations, the findings revealed that total catch tended to increase outside the MPAs after their implementation, despite reductions in the fishable area. The researchers argue that this increase was not driven by spillover effects from larger populations within MPA boundaries but rather by changes in the behavior of commercial fishers.
The study challenges the common belief that MPAs inherently lead to positive outcomes for fisheries. The so-called Jevons Paradox, where the rebound effect surpasses the expected benefits of conservation measures, was observed. Despite the reduction in the permitted fishable area within 50 km of MPA boundaries (ranging from 1% to 41%), total catch increased significantly across all study areas, ranging from 35% to 640%.
The research suggests that fishers altered their behavior in response to MPA implementation, potentially seeking areas with better fishing opportunities. The study highlights the importance of considering human behavior in fisheries management, emphasizing that a limited understanding of the social, cultural, and technological drivers of fishing can lead to unforeseen consequences.
While the study provides valuable insights into the complex dynamics surrounding MPAs, it also calls for a reevaluation of the expected benefits of these conservation measures. Policymakers are urged to explicitly define the underlying aims of MPAs, whether it be the reduction in total fish catch, provision of refuge or spillover, or mitigation of damage to seafloor biodiversity. The researchers emphasize the need for a comprehensive understanding of the links between changes in fisher behavior, economic factors, species abundances, and overall ecosystem effects to design effective MPA policies.
Conclusion
The study suggests that while MPAs play a crucial role in marine conservation, the unintended consequences observed underscore the necessity of refining policies and ensuring a holistic understanding of the intricate interactions within marine ecosystems. Moreover, accounting for the behavioural responses of commercial fishers is an important consideration when designing effective MPAs.
Source: Elsevier
