Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia;
Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.
Proc Natl Acad Sci U S A. 2018 Jul 3;115(27):E6116-E6125. doi: 10.1073/pnas.1708001115. Epub 2018 Jun 18.
Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef conditions are declining worldwide. Effective solutions to the crisis facing coral reefs depend in part on understanding the context under which different types of conservation benefits can be maximized. Our global analysis of nearly 1,800 tropical reefs reveals how the intensity of human impacts in the surrounding seascape, measured as a function of human population size and accessibility to reefs ("gravity"), diminishes the effectiveness of marine reserves at sustaining reef fish biomass and the presence of top predators, even where compliance with reserve rules is high. Critically, fish biomass in high-compliance marine reserves located where human impacts were intensive tended to be less than a quarter that of reserves where human impacts were low. Similarly, the probability of encountering top predators on reefs with high human impacts was close to zero, even in high-compliance marine reserves. However, we find that the relative difference between openly fished sites and reserves (what we refer to as conservation gains) are highest for fish biomass (excluding predators) where human impacts are moderate and for top predators where human impacts are low. Our results illustrate critical ecological trade-offs in meeting key conservation objectives: reserves placed where there are moderate-to-high human impacts can provide substantial conservation gains for fish biomass, yet they are unlikely to support key ecosystem functions like higher-order predation, which is more prevalent in reserve locations with low human impacts.
珊瑚礁为数百万热带地区的人们提供生态系统商品和服务，但全球范围内的珊瑚礁状况正在恶化。有效解决珊瑚礁面临的危机，部分取决于理解在何种背景下可以最大限度地实现不同类型的保护效益。我们对近 1800 个热带珊瑚礁的全球分析表明，周边海域人类活动的强度（以人口规模和接近珊瑚礁的程度衡量，即“重力”）如何降低海洋保护区维持珊瑚鱼生物量和顶级捕食者存在的有效性，即使保护区的规则得到高度遵守。至关重要的是，位于人类活动强度高的地区且遵守保护区规则的珊瑚礁中的鱼类生物量往往不到人类活动强度低的保护区的四分之一。同样，即使在遵守保护区规则的地区，人类活动强度高的珊瑚礁上遇到顶级捕食者的可能性也接近于零。然而，我们发现，在人类活动影响适中的地区，与开放捕捞区相比（我们称之为保护增益），鱼类生物量（不包括捕食者）的相对差异最大，而在人类活动影响较低的地区，顶级捕食者的相对差异最大。我们的研究结果说明了在实现关键保护目标方面的关键生态权衡：在人类活动中度至高度影响的地区设立保护区可以为鱼类生物量提供实质性的保护增益，但它们不太可能支持关键的生态功能，如更高层次的捕食，而这种功能在人类活动影响较低的保护区更为普遍。
