We review the consequences for biodiversity and ecosystem services from the industrial-scale extraction of logging residues (tops, branches and stumps from harvested trees and small-diameter trees from thinnings) in managed forests. Logging residue extraction can replace fossil fuels, and thus contribute to climate change mitigation. The additional biomass and nutrients removed, and soils and other structures disturbed, have several potential environmental impacts. To evaluate potential impacts on ecosystem services and biodiversity we reviewed 279 scientific papers that compared logging residue extraction with non-extraction, the majority of which were conducted in Northern Europe and North America. The weight of available evidence indicates that logging residue extraction can have significant negative effects on biodiversity, especially for species naturally adapted to sun-exposed conditions and the large amounts of dead wood that are created by large-scaled forest disturbances. Slash extraction may also pose risks for future biomass production itself, due to the associated loss of nutrients. For water quality, reindeer herding, mammalian game species, berries, and natural heritage the results were complicated by primarily negative but some positive effects, while for recreation and pest control positive effects were more consistent. Further, there are initial negative effects on carbon storage, but these effects are transient and carbon stocks are mostly restored over decadal time perspectives. We summarize ways of decreasing some of the negative effects of logging residue extraction on specific ecosystem services, by changing the categories of residue extracted, and site or forest type targeted for extraction. However, we found that suggested pathways for minimizing adverse outcomes were often in conflict among the ecosystem services assessed. Compensatory measures for logging residue extraction may also be used (e.g. ash recycling, liming, fertilization), though these may also be associated with adverse environmental impacts.

Harvesting of wood for bioenergy purpose will probably increase in importance in the future, in order to replace fossil fuel. However, the environmental impact of increased harvesting might be considerable, e.g. on soil and water chemistry, biodiversity and long-term productivity, and in this study we investigate thresholds for sustainable harvesting volumes. The study is based on scientific reviews of the impact of harvesting of logging residues (slash and stumps) on forest production, biodiversity, acidification, eutrophication and toxic substances. We define sustainability by using environmental objectives decided by the Swedish parliament (which are based on the Aichi targets), and relate the harvesting impact to these objectives within different harvesting scenarios, by using expert judgment. We demonstrate that an increase in harvesting of logging residues by 2.5 times might be sustainable. However, we also identify a number of risks and the sustainability depends on a number of requirements that should be fulfilled, such as ash-recycling. It was found that factors related to biodiversity conservation (defined in the goals ‘Sustainable Forests’ and ‘A Rich Diversity of Plant and Animal Life’) were limiting factors both for slash- and stump harvesting, and that risk of acidification (defined in the goal ‘Natural Acidification Only’) also limit slash harvesting. We also include harvesting of brushwood and energy wood from conservation cutting in the discussion, since these assortments might be important in the future