Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331;
Instituto de Biologia, Universidade Federal da Bahia, Salvador, 40170-115 Bahia, Brazil.
Proc Natl Acad Sci U S A. 2019 Feb 19;116(8):3322-3327. doi: 10.1073/pnas.1813072116. Epub 2019 Feb 4.
The Northwest Forest Plan (NWFP) initiated one of the most sweeping changes to forest management in the world, affecting 10 million hectares of federal land. The NWFP is a science-based plan incorporating monitoring and adaptive management and provides a unique opportunity to evaluate the influence of policy. We used >25 years of region-wide bird surveys, forest data, and land-ownership maps to test this policy's effect on biodiversity. Clearcutting decreased rapidly, and we expected populations of older-forest-associated birds to stabilize on federal land, but to continue declining on private industrial lands where clearcutting continued. In contrast, we expected declines in early-seral-associated species on federal land because of reduced anthropogenic disturbance since the NWFP. Bayesian hierarchical models revealed that bird species' population trends tracked changes in forest composition. However, against our expectations, declines of birds associated with older forests accelerated. These declines are partly explained by losses of older forests due to fire on federal land and continued clearcutting elsewhere. Indeed, the NWFP anticipated that reversing declines of older forests would take time. Overall, the early-seral ecosystem area was stable, but declined in two ecoregions-the Coast Range and Cascades-along with early-seral bird populations. Although the NWFP halted clearcutting on federal land, this has so far been insufficient to reverse declines in older-forest-associated bird populations. These findings underscore the importance of continuing to prioritize older forests under the NWFP and ensuring that the recently proposed creation of early-seral ecosystems does not impede the conservation and development of older-forest structure.
《西北森林计划》（NWFP）启动了全球范围内最广泛的森林管理变革之一，影响了 1000 万公顷的联邦土地。该计划是一个基于科学的计划，纳入了监测和适应性管理，并为评估政策的影响提供了一个独特的机会。我们利用 25 多年来的全区域鸟类调查、森林数据和土地所有权地图来检验该政策对生物多样性的影响。皆伐迅速减少，我们预计在联邦土地上与老林相关的鸟类种群会稳定下来，但在继续进行皆伐的私人工业土地上会继续减少。相比之下，我们预计联邦土地上的早生种相关物种会减少，因为 NWFP 之后人为干扰减少。贝叶斯层次模型显示，鸟类种群的趋势与森林组成的变化相吻合。然而，与我们的预期相反，与老林相关的鸟类数量的减少加速了。这些下降部分是由于联邦土地上的火灾导致老林的损失，以及其他地方的持续皆伐。事实上，NWFP 预计，扭转老林的衰退需要时间。总体而言，早生种生态系统区域保持稳定，但在沿海山脉和喀斯喀特山脉两个生态区以及早生种鸟类种群中有所减少。尽管 NWFP 已经停止了联邦土地上的皆伐，但到目前为止，这还不足以扭转与老林相关的鸟类种群的减少。这些发现强调了在 NWFP 下继续优先考虑老林的重要性，并确保最近提出的创建早生种生态系统不会阻碍老林结构的保护和发展。
