Plastic litter is encountered in aquatic ecosystems across the globe, including polar environments and the deep sea. To mitigate the adverse societal and ecological impacts of this waste, there has been debate on whether ‘biodegradable' materials should be granted exemptions from plastic bag bans and levies. However, great care must be exercised when attempting to define this term, due to the broad and complex range of physical and chemical conditions encountered within natural ecosystems. Here, we review existing international industry standards and regional test methods for evaluating the biodegradability of plastics within aquatic environments (wastewater, unmanaged freshwater and marine habitats). We argue that current standards and test methods are insufficient in their ability to realistically predict the biodegradability of carrier bags in these environments, due to several shortcomings in experimental procedures and a paucity of information in the scientific literature. Moreover, existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for the potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products or small (microscopic) plastic particles that can arise via fragmentation. Successfully addressing these knowledge gaps is a key requirement for developing new biodegradability standard(s) for lightweight carrier bags.

Summary• Wetlands were the largest source of atmospheric methane (CH 4 ) during the Last Glacial Maximum (LGM), but the sensitivity of this source to exceptionally low atmospheric CO 2 concentration ([CO 2 ]) at the time has not been examined experimentally. We tested the hypothesis that LGM atmospheric [CO 2 ] reduced CH 4 emissions as a consequence of decreased photosynthate allocation to the rhizosphere.• We exposed minerotrophic fen and ombrotrophic bog peatland mesocosms to simulated LGM (c. 200 ppm) or ambient (c. 400 ppm) [CO 2 ] over 21 months (n = 8 per treatment) and measured gaseous CH 4 flux, pore water dissolved CH 4 and volatile fatty acid (VFA; an indicator of plant carbon supply to the rhizosphere) concentrations.• Cumulative CH 4 flux from fen mesocosms was suppressed by 29% (P < 0.05) and rhizosphere pore water [CH 4 ] by c. 50% (P < 0.01) in the LGM [CO 2 ], variables that remained unaffected in bog mesocosms. VFA analysis indicated that changes in plant root exudates were not the driving mechanism behind these results.• Our data suggest that the LGM [CO 2 ] suppression of wetland CH 4 emissions is contingent on trophic status. The heterogeneous response may be attributable to differences in species assemblage that influence the dominant CH 4 production pathway, rhizosphere supplemented photosynthesis and CH 4 oxidation.

In nutrient limited soils, minerals constitute a major reservoir of bio-essential elements. Consequently, the release of nutritive elements during weathering is crucial. Bacteria have been shown to enhance weathering rates; however, there has been limited work that has focused on the bacterial weathering of bedrock or parent rock, which are the major sources of minerals, in nutrient limiting soils. In this study, both a culture-independent and culture-dependent approach was used to study the bacterial community at the interface between basaltic bedrock and nutrient limiting soil in Cadiar Idris region of Snowdonia National Park, United Kingdom. High throughput sequencing method, Ion Torrent, was used to characterise the bacterial community, which generated over 250,000 sequences. Taxonomical assignment demonstrated that approximately 50% (125,000 sequences) of the community consisted of the orders Actinomycetales, Burkholderiales, Clostridales, Bacillales, Rhizobiales and Acidobacterium, with unclassified sequences representing 44% ± 1.46% (110,000 ± 3650). Bacteria belonging to the genera Serratia, Pseudomonas, Bacillus, Paenibacillus, Chromobacterium, Janthinobacterium, Burkholderia and Arthrobacter, were isolated from the sample site. All of the isolates were able to grow in a minimal growth medium, which contained glucose, ammonium chloride with basalt as the sole source of bio-essential elements. Seventy percent of the isolates significantly enhanced basalt dissolution (p < 0.05). The rate of dissolution correlated to the production of oxalic acid and acidification of the growth medium. The findings of this work suggest that at the interface between bedrock and soil heterotrophic members of the bacterial community can enhance weathering, an essential part of biogeochemical cy-* Corresponding author. K. Olsson-Francis et al.

Forest degradation is recognized as a major environmental threat on a global scale. The recent rise in natural and anthropogenic destruction of forested ecosystems highlights the need for developing new, rapid, and accurate remote sensing monitoring systems, which capture forested land transformations. In spite of the great technological advances made in airborne and spaceborne sensors over the past decades, current Earth observation (EO) change detection methods still need to overcome numerous limitations. Optical sensors have been commonly used for detecting land use and land cover changes (LULCC), however, the requirement of certain technical and environmental conditions (e.g., sunlight, not cloud-coverage) restrict their use. More recently, synthetic aperture radar (SAR)-based change detection approaches have been used to overcome these technical limitations, but they commonly rely on static detection approaches (e.g., pre and post disturbance scenario comparison) that are slow to monitor change. In this context, this paper presents a novel approach for mapping forest structural changes in a continuous and near-real-time manner using dense Sentinel-1 image time-series. Our cumulative sum–spatial mean corrected (CUSU-SMC) algorithm approach is based on cumulative sum statistical analysis, which allows the continuous monitoring of radar signal variations, derived from forest structural change. Taking advantage of the high data availability offered by the Sentinel-1 (S-1) C-band constellation, we used an S-1 ground range detected (GRD) dual (VV, VH) polarization timeseries, formed by a total of 84 images, to monitor clear-cutting operations carried out in a Scottish forest during 2019. The analysis showed a user’s accuracy of 82% for the (conservative) detection approach. The use of a post-processing neighbor filter increased the detection performance to a user’s accuracy of 86% with an overall accuracy of 77% for areas of a minimum extent of 0.4 ha. To further validate the detection performance of the method, the CUSU-SMC change detector was tested against commonly-used pairwise change detection approaches for the same period. These results emphasize the capabilities of dense SAR time-series for environmental monitoring and provide a useful tool for optimizing national forest inventories.

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