The Micronesia Challenge: Assessing the Relative Contribution of Stressors on Coral Reefs to Facilitate Science-to-Management Feedback

Fishing and pollution are chronic stressors that can prolong recovery of coral reefs and contribute to ecosystem decline. While this premise is generally accepted, management interventions are complicated because the contributions from individual stressors are difficult to distinguish. The present study examined the extent to which fishing pressure and pollution predicted progress towards the Micronesia Challenge, an international conservation strategy initiated by the political leaders of 6 nations to conserve at least 30% of marine resources by 2020. The analyses were rooted in a defined measure of coral-reef-ecosystem condition, comprised of biological metrics that described functional processes on coral reefs. We report that only 42% of the major reef habitats exceeded the ecosystem-condition threshold established by the Micronesia Challenge. Fishing pressure acting alone on outer reefs, or in combination with pollution in some lagoons, best predicted both the decline and variance in ecosystem condition. High variances among ecosystem-condition scores reflected the large gaps between the best and worst reefs, and suggested that the current scores were unlikely to remain stable through time because of low redundancy. Accounting for the presence of marine protected area (MPA) networks in statistical models did little to improve the models’ predictive capabilities, suggesting limited efficacy of MPAs when grouped together across the region. Yet, localized benefits of MPAs existed and are expected to increase over time. Sensitivity analyses suggested that (i) grazing by large herbivores, (ii) high functional diversity of herbivores, and (iii) high predator biomass were most sensitive to fishing pressure, and were required for high ecosystem-condition scores. Linking comprehensive fisheries management policies with these sensitive metrics, and targeting the management of pollution, will strengthen the Micronesia Challenge and preserve ecosystem services that coral reefs provide to societies in the face of climate change.

捕捞活动与污染均为长期胁迫因子，会延缓珊瑚礁的恢复进程并加剧生态系统衰退。尽管这一认知已得到普遍认可，但相关管理干预却面临诸多困境，因难以区分单一胁迫因子的具体贡献。本研究探讨了捕捞压力与污染对密克罗尼西亚挑战（Micronesia Challenge）推进进程的影响程度。密克罗尼西亚挑战是一项由6个国家政治领导人发起的国际保护战略，旨在至2020年前保护至少30%的海洋资源。本分析基于一套标准化的珊瑚礁生态系统健康评估体系展开，该体系由描述珊瑚礁功能过程的生物学指标构成。研究结果显示，仅42%的主要珊瑚礁生境达到了密克罗尼西亚挑战设定的生态系统健康阈值。仅作用于外礁的捕捞压力，或是部分泻湖中与污染共同存在的捕捞压力，最能解释生态系统健康状况的衰退程度与变异特征。生态系统健康评分的高离散度，反映出优质与劣质珊瑚礁之间存在巨大差距，同时也表明当前评分难以长期维持稳定，原因在于生态系统冗余度较低。在统计模型中纳入海洋保护区（marine protected area, MPA）网络的存在性，并未显著提升模型的预测能力，这表明在区域层面整体统筹的海洋保护区举措效能有限。但海洋保护区仍存在局部收益，且该收益有望随时间推移逐步提升。敏感性分析结果显示：①大型草食动物的啃食作用、②草食动物的高功能多样性，以及③顶级捕食者的高生物量，对捕捞压力最为敏感，而这些要素也是获得高生态系统健康评分的必要条件。将全面的渔业管理政策与这些敏感指标相结合，并针对性开展污染治理，将有助于推进密克罗尼西亚挑战的实施，并在气候变化背景下保护珊瑚礁为人类社会提供的生态系统服务。