Thresholds for adding degraded tropical forest to the conservation estate.

Logged and disturbed forests are often viewed as degraded and depauperate environments compared with primary forest. However, they are dynamic ecosystems1 that provide refugia for large amounts of biodiversity2,3, so we cannot afford to underestimate their conservation value4. Here we present empirically defined thresholds for categorizing the conservation value of logged forests, using one of the most comprehensive assessments of taxon responses to habitat degradation in any tropical forest environment. We analysed the impact of logging intensity on the individual occurrence patterns of 1,681 taxa belonging to 86 taxonomic orders and 126 functional groups in Sabah, Malaysia. Our results demonstrate the existence of two conservation-relevant thresholds. First, lightly logged forests (<29% biomass removal) retain high conservation value and a largely intact functional composition, and are therefore likely to recover their pre-logging values if allowed to undergo natural regeneration. Second, the most extreme impacts occur in heavily degraded forests with more than two-thirds (>68%) of their biomass removed, and these are likely to require more expensive measures to recover their biodiversity value. Overall, our data confirm that primary forests are irreplaceable5, but they also reinforce the message that logged forests retain considerable conservation value that should not be overlooked.

From tree to plot: investigating stem CO2 efflux and its drivers along a logging gradient in Sabah, Malaysian Borneo.

Stem respiration constitutes a substantial proportion of autotrophic respiration in forested ecosystems, but its drivers across different spatial scales and land-use gradients remain poorly understood. This study quantifies and examines the impact of logging disturbance on stem CO2 efflux (EA) in Malaysian Borneo. EA was quantified at tree- and stand-level in nine 1-ha plots over a logging gradient from heavily logged to old-growth using the static chamber method. Tree-level results showed higher EA per unit stem area in logged vs old-growth plots (37.0 ± 1.1 vs 26.92 ± 1.14 g C m-2 month-1). However, at stand-level, there was no difference in EA between logged and old-growth plots (6.7 ± 1.1 vs 6.0 ± 0.7 Mg C ha-1 yr-1) due to greater stem surface area in old-growth plots. Allocation to growth respiration and carbon use efficiency was significantly higher in logged plots. Variation in EA at both tree- and stand-level was driven by tree size, growth and differences in investment strategies between the forest types. These results reflect different resource allocation strategies and priorities, with a priority for growth in response to increased light availability in logged plots, while old-growth plots prioritise maintenance and cell structure.

An audacious approach to conservation.

New digital and sensor technology provides a huge opportunity to revolutionise conservation, but we lack a plan for deploying the technologies effectively. I argue that environmental research should be concentrated at a small number of 'super-sites' and that the concentrated knowledge from super-sites should be used to develop holistic ecosystem models. These, in turn, should be morphed into digital twin ecosystems by live connecting them with automated environmental monitoring programmes. Data-driven simulations can then help select pathways to achieve locally determined conservation goals, and digital twins could revise and adapt those decisions in real-time. This technology-heavy vision for 'smart conservation' provides a map toward a future defined by more flexible, more responsive, and more efficient management of natural environments.

Tropical beetles more sensitive to impacts are less likely to be known to science.

Insects are posited to be declining globally. This is particularly pertinent in tropical forests, which exhibit both the highest levels of biodiversity and the highest rates of biodiversity loss. However, for the hyper-diverse tropical insects there are scant data available to evidence declines. Understanding tropical insect diversity and its response to environmental change has therefore become a challenge, but it is estimated that 80% of tropical insect species remain undescribed1. Insect biodiversity predictions are based mostly on well-studied taxa and extrapolated to other groups, but no one knows whether resilience to environmental change varies between undescribed and described species. Here, we collected staphylinid beetles from unlogged and logged tropical forests in Borneo and investigated their responses to environmental change. Out of 252 morphospecies collected, 76% were undescribed. Undescribed species showed higher community turnover, reduced abundance and decreased probability of occurrence in logged forests. Thus the unknown components of tropical insect biodiversity are likely more impacted by human-induced environmental change. If these patterns are widespread, how accurate will assessments of insect declines in the tropics be?