Sliding baselines, ghosts, and reduced expectations in kelp forest communities
Sliding baselines, ghosts, and reduced expectations in kelp forest communities
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DOI：
10.1890/1051-0761(1998)008
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发表时间：
1998-05-01
影响因子：
5
通讯作者：
Riser, KL
中科院分区：
文献类型：
--
作者：
Dayton, PK;Tegner, MJ;Riser, KL
生态系统趋势的检测取决于（1）对衡量变化的基础或基准的良好描述和（2）自然变化和人为变化之间的区别。在大型海带森林中观察了25年的模式和机制表明，定义一个有意义的基准是不可能的，因为许多大型动物已经消失了数年至数十年，海带对大规模，低频率的厄尔尼诺南方涛动事件和长期的政权转移很敏感。海洋气候的变化大大减少了占主导地位的植物的平均大小和承载能力。已从群落中功能性地移除的动物包括海獭、黑鲈鱼、黄尾鱼、白色鲈鱼和鲍鱼。其他物种仍然存在，但渔业对羊头鱼、海带鲈鱼、鳐、比目鱼、岩鱼、刺龙虾和红海胆的丰度、大小频率和/或空间分布产生了巨大影响。现在连海参、螃蟹和小蜗牛都受到不受管制的捕捞。这些植物继续存在，丝毫没有受到如此多动物生物量损失的影响。此外，大多数巨型动物已经被移除，几乎没有关于自然群落的文献或历史了解。因此，我们将人为影响与系统的“自然”动态分开的能力受到严重损害。我们讨论了生态系统关注生产力和仔细监测尽可能多的人口的重要性。此外，我们表明，这个社区是不紧密结合的相互依赖性，因此，许多物种可以被删除，而不会影响到生态系统的其余部分。
The detection of trends in ecosystems depends upon (1) a good description of the foundation or benchmark against which changes are measured and (2) a distinction between natural and anthropogenic changes. Patterns and mechanisms observed over 25 years in a large kelp forest suggest that definition of a meaningful benchmark is impossible, because many of the large animals have been gone for years to decades, and kelps are sensitive to large-scale, low-frequency El Nino-Southern Oscillation events and longer term regime shifts. A shift in the oceanographic climate has significantly reduced the average size and carrying capacity of the dominant plant. The animals that have been functionally removed from the community include sea otters, black sea bass, yellowtail, white sea bass, and abalones. Other species are still present, but fisheries have had huge effects on the abundances, size-frequencies, and/or spatial distributions of sheephead, kelp bass, rays, flatfish, rock fish, spiny lobsters, and red sea urchins. Now even sea cucumbers, crabs, and small snails are subject to unregulated fishing. The plants continue to exist without a hint of the effects of the loss of so much animal biomass. Furthermore, most of the megafauna have been removed with very little documentation or historical understanding of what the natural community was like. Thus, our ability to separate anthropogenic impacts from the "natural" dynamics of the system is severely compromised. We discuss the importance of both an ecosystem focus on productivity and careful monitoring of as many populations as possible. In addition, we show that this community is not tightly integrated with mutual dependencies; hence, many species can be removed without much affecting the rest of the ecosystem.