Putz Francis E, Romero Claudia, Sist Plinio, Schwartz Gustavo, Thompson Ian, Roopsind Anand, Medjibe Vincent, Ellis Peter
Department of Biology, University of Florida, Gainesville, FL 32641, USA.
Cirad-ES, Forêts et Sociétés and Université Montpellier, Campus International de Baillarguet, TA C-105/D 34398 Montpellier Cedex 5, France.
PNAS Nexus. 2022 Jul 1;1(3):pgac102. doi: 10.1093/pnasnexus/pgac102. eCollection 2022 Jul.
What is meant by sustainability depends on what is sustained and at what level. Sustainable forest management, for example, requires maintenance of a variety of values not the least of which is sustained timber yields (STYs). For the 1 Bha of the world's forests subjected to selective or partial logging, failure to maintain yields can be hidden by regulatory requirements and questionable auditing practices such as increasing the number of commercial species with each harvest, reducing the minimum size at which trees can be harvested and accepting logs of lower quality. For assertions of STY to be credible, clarity is needed about all these issues, as well as about the associated ecological and economic tradeoffs. Lack of clarity about sustainability heightens risks of unsubstantiated claims and unseen losses. STY is possible but often requires cutting cycles that are longer and logging intensities that are lower than prescribed by law, as well as effective use of low-impact logging practices and application of silvicultural treatments to promote timber stock recovery. These departures from business-as-usual practices will lower profit margins but generally benefit biodiversity and ecosystem services.
可持续性的含义取决于所维持的内容以及维持的水平。例如，可持续森林管理要求维护多种价值，其中最重要的就是维持木材产量（STY）。对于世界上10亿公顷遭受选择性或部分砍伐的森林而言，监管要求以及诸如每次采伐增加商业树种数量、降低可采伐树木的最小尺寸和接受较低质量原木等有问题的审计做法，可能会掩盖产量无法维持的情况。要使STY的断言可信，就需要明确所有这些问题，以及相关的生态和经济权衡。对可持续性缺乏明确认识会增加无根据声称和隐性损失的风险。实现STY是可能的，但通常需要比法律规定更长的砍伐周期和更低的采伐强度，以及有效采用低影响采伐做法和应用造林措施来促进木材蓄积量的恢复。这些与常规做法的背离将降低利润率，但总体上有利于生物多样性和生态系统服务。
