Data from: Do space-for-time assessments underestimate the impacts of logging on tropical biodiversity? An Amazonian case study using dung beetles

Human alteration of the global environment is leading to a pervasive loss of biodiversity. Most studies evaluating human impacts on biodiversity occur after the disturbance has taken place using spatially distinct sites to determine the undisturbed reference condition. This approach is known as a space-for-time (SFT) substitution. However, SFT substitution could be underestimating biodiversity loss if spatial controls fail to provide adequate inferences about pre-disturbance conditions. We compare the SFT substitution with a before–after control–impact (BACI) approach by assessing dung beetles before and after a logging exploration in the Brazilian Amazon. We sampled 34 logging management units, of which 29 were selectively logged with different intensities after our first collection. We used dung beetle species richness, species composition and biomass as our biodiversity response metrics and the gradient of selective logging intensity as our explanatory metric. Only the BACI approach consistently demonstrated the negative impacts of logging intensification on all dung beetle community metrics. Moreover, the BACI approach explained significantly more of the variance in all the relationships and it doubled the estimates of species loss along the gradient of logging intensity when compared to SFT. Synthesis and applications. Our results suggest that space-for-time (SFT) substitution may greatly underestimate the consequences on local species diversity and community turnover. These results have important implications for researchers investigating human impacts on biodiversity. Incentivizing before–after control–impact (BACI) approaches will require longer-term funding to gather the data and stronger links between researchers and landowners. However, BACI approaches are accompanied by many logistical constraints, making the continued use of SFT studies inevitable in many cases. We highlight that non-significant results and weak effects should be viewed with caution.

人类对全球环境的改造正导致生物多样性的普遍丧失。
绝大多数评估人类活动对生物多样性影响的研究，均在干扰发生后开展，通过选取空间上相互独立的样地确定未受干扰的参照状态，该方法被称为空间代时间（space-for-time, SFT）替代法。
然而，若空间对照样地无法对干扰前的环境条件做出合理推断，空间代时间替代法可能会低估生物多样性丧失的程度。
本研究通过在巴西亚马逊地区评估伐木勘探前后的蜣螂群落，对比了空间代时间替代法与对照样地前后影响（before–after control–impact, BACI）法的差异。
我们共采样34个伐木管理单元，其中29个在首次采样后接受了不同强度的选择性伐木作业。
本研究以蜣螂的物种丰富度、物种组成和生物量作为生物多样性响应指标，以选择性伐木强度梯度作为核心解释变量。
仅对照样地前后影响法能够一致地揭示伐木强度提升对所有蜣螂群落指标的负面影响。
此外，相较于空间代时间替代法，对照样地前后影响法能够解释所有关联中显著更多的变异量，且在伐木强度梯度下，其估算的物种丧失量提升了一倍。
研究综合与实践启示：
我们的研究结果表明，空间代时间替代法可能会极大低估人类活动对本地物种多样性及群落周转的影响。这一结论对探究人类活动对生物多样性影响的研究者而言具有重要指导意义。
推广应用对照样地前后影响法，需要获取长期研究资金以开展数据采集，并加强研究者与土地所有者之间的协作联系。
但对照样地前后影响法存在诸多后勤保障限制，这使得在多数场景下仍不得不继续开展基于空间代时间替代法的研究。
我们强调，对于非显著性结果与弱效应应保持审慎态度。