Schooler Nicholas K, Dugan Jenifer E, Hubbard David M, Straughan Dale
Marine Science Institute University of California, Santa Barbara Santa Barbara CA USA.
Ecol Evol. 2017 May 25;7(13):4822-4834. doi: 10.1002/ece3.3064. eCollection 2017 Jul.
Evaluating impacts to biodiversity requires ecologically informed comparisons over sufficient time spans. The vulnerability of coastal ecosystems to anthropogenic and climate change-related impacts makes them potentially valuable indicators of biodiversity change. To evaluate multidecadal change in biodiversity, we compared results from intertidal surveys of 13 sandy beaches conducted in the 1970s and 2009-11 along 500 km of coast (California, USA). Using a novel extrapolation approach to adjust species richness for sampling effort allowed us to address data gaps and has promise for application to other data-limited biodiversity comparisons. Long-term changes in species richness varied in direction and magnitude among beaches and with human impacts but showed no regional patterns. Observed long-term changes in richness differed markedly among functional groups of intertidal invertebrates. At the majority (77%) of beaches, changes in richness were most evident for wrack-associated invertebrates suggesting they have disproportionate vulnerability to impacts. Reduced diversity of this group was consistent with long-term habitat loss from erosion and sea level rise at one beach. Wrack-associated species richness declined over time at impacted beaches (beach fill and grooming), despite observed increases in overall intertidal richness. In contrast richness of these taxa increased at more than half (53%) of the beaches including two beaches recovering from decades of off-road vehicle impacts. Over more than three decades, our results suggest that local scale processes exerted a stronger influence on intertidal biodiversity on beaches than regional processes and highlight the role of human impacts for local spatial scales. Our results illustrate how comparisons of overall biodiversity may mask ecologically important changes and stress the value of evaluating biodiversity change in the context of functional groups. The long-term loss of wrack-associated species, a key component of sandy beach ecosystems, documented here represents a significant threat to the biodiversity and function of coastal ecosystems.
评估生物多样性受到的影响需要在足够长的时间跨度内进行基于生态学知识的比较。沿海生态系统易受人为和气候变化相关影响，这使其有可能成为生物多样性变化的重要指标。为了评估生物多样性的数十年变化，我们比较了20世纪70年代以及2009年至2011年期间在美国加利福尼亚州500公里海岸线上13个沙滩的潮间带调查结果。使用一种新颖的外推方法来调整物种丰富度以弥补采样工作量的差异，使我们能够解决数据缺口问题，并有望应用于其他数据有限的生物多样性比较。沙滩间物种丰富度的长期变化在方向和幅度上有所不同，且与人类影响有关，但未呈现出区域模式。潮间带无脊椎动物不同功能组的物种丰富度长期变化差异显著。在大多数（77%）沙滩上，与漂浮植物相关的无脊椎动物的丰富度变化最为明显，这表明它们对影响的脆弱性不成比例。这一组别多样性的降低与一个沙滩因侵蚀和海平面上升导致的长期栖息地丧失相一致。尽管观察到潮间带总体丰富度有所增加，但在受影响的沙滩（沙滩填埋和修整）上，与漂浮植物相关的物种丰富度随时间下降。相比之下，在超过一半（53%）的沙滩上，包括两个从数十年的越野车影响中恢复的沙滩，这些类群的丰富度增加了。在三十多年的时间里，我们的结果表明，局部尺度过程对沙滩潮间带生物多样性的影响比区域过程更强，并突出了人类影响在局部空间尺度上的作用。我们的结果说明了总体生物多样性的比较可能如何掩盖具有生态重要性的变化，并强调了在功能组背景下评估生物多样性变化的价值。此处记录的沙滩生态系统关键组成部分——与漂浮植物相关物种的长期丧失，对沿海生态系统的生物多样性和功能构成了重大威胁。
