Tropical deforestation in a future international climate policy regime—lessons from the Brazilian Amazon

The possibility of adopting national targets for carbon dioxide (CO₂) emissions from tropical deforestation in a future international climate treaty has received increasing attention recently. This attention has been prompted by proposals to this end and more intensified talks on possible commitments for developing countries beyond the United Nations Framework Convention on Climate Change Kyoto Protocol. We analyze four main scientific and political challenges associated with national targets for emissions from tropical deforestation: (1) reducing the uncertainties in emission inventories, (2) preserving the environmental integrity of the treaty, (3) promoting political acceptance and participation in the regime, and (4) providing economic incentives for reduced deforestation. We draw the following conclusions. (1) Although there are large uncertainties in carbon flux from deforestation, these are in the same range as for other emissions included in the current Kyoto protocol (i.e., non-CO₂ GHGs), and they can be reduced. However, for forest degradation processes the uncertainties are larger. A large challenge lies in building competence and institutions for monitoring the full spectrum of land use changes in developing countries. (2 and 3) Setting targets for deforestation is difficult, and uncertainties in future emissions imply a risk of creating ‘tropical hot air’. However, there are proposals that may sufficiently deal with this, and these proposals may also have the advantage of making the targets more attractive, politically speaking. Moreover, we conclude that while a full carbon accounting system will likely be politically unacceptable for tropical countries, the current carbon accounting system should be broadened to include forest degradation in order to safeguard environmental integrity. (4) Doubts can be cast over the possible effect a climate regime alone will have on deforestation rates, though little thorough analysis of this issue has been made.

137Cs in the Danish Wadden Sea: contrast between tidal flats and salt marshes

The 137Cs activity of salt marsh and tidal flat sediments of the northern part of the European Wadden Sea was studied based on a comprehensive dataset of 210Pb dated cores. The 137Cs inventory of salt marsh sediments shows a major peak corresponding to the Chernobyl accident in 1986, and a minor peak located in the late 1960s interpreted as the combined effect of atmospheric testing of nuclear weapons. Emissions from the nuclear reprocessing plant Sellafield are not reflected as peaks in 137Cs activity, but may contribute to the rising 137Cs activity in the years prior to 1986. The 137Cs activity of tidal flat sediments differs from salt marsh sediment in two respects. First, the activity is much lower and, second, the major peak in the 1980s is located in the beginning instead of in the middle of the decade. The differences in 137Cs inventory between the two environments are interpreted to result from repeated cycles of deposition/resuspension and mixing on tidal flats. A simple model illustrating the consequence of mixings returns an apparent shift of major peaks in 137Cs activities backwards in time corresponding to the mixing depth divided by the deposition rate.     

Nutrient pathways and their susceptibility to past and future change in the Eurasian Arctic Ocean

Climate change is altering nutrient cycling within the Arctic Ocean, having knock-on effects to Arctic ecosystems. Primary production in the Arctic is principally nitrogen-limited, particularly in the western Pacific-dominated regions where denitrification exacerbates nitrogen loss. The nutrient status of the eastern Eurasian Arctic remains under debate. In the Barents Sea, primary production has increased by 88% since 1998. To support this rapid increase in productivity, either the standing stock of nutrients has been depleted, or the external nutrient supply has increased. Atlantic water inflow, enhanced mixing, benthic nitrogen cycling, and land–ocean interaction have the potential to alter the nutrient supply through addition, dilution or removal. Here we use new datasets from the Changing Arctic Ocean program alongside historical datasets to assess how nitrate and phosphate concentrations may be changing in response to these processes. We highlight how nutrient dynamics may continue to change, why this is important for regional and international policy-making and suggest relevant research priorities for the future.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01673-0.     

Biogeochemical consequences of a changing Arctic shelf seafloor ecosystem

Unprecedented and dramatic transformations are occurring in the Arctic in response to climate change, but academic, public, and political discourse has disproportionately focussed on the most visible and direct aspects of change, including sea ice melt, permafrost thaw, the fate of charismatic megafauna, and the expansion of fisheries. Such narratives disregard the importance of less visible and indirect processes and, in particular, miss the substantive contribution of the shelf seafloor in regulating nutrients and sequestering carbon. Here, we summarise the biogeochemical functioning of the Arctic shelf seafloor before considering how climate change and regional adjustments to human activities may alter its biogeochemical and ecological dynamics, including ecosystem function, carbon burial, or nutrient recycling. We highlight the importance of the Arctic benthic system in mitigating climatic and anthropogenic change and, with a focus on the Barents Sea, offer some observations and our perspectives on future management and policy.     

Monitoring a changing Arctic: Recent advancements in the study of sea ice microbial communities

Sea ice continues to decline across many regions of the Arctic, with remaining ice becoming increasingly younger and more dynamic. These changes alter the habitats of microbial life that live within the sea ice, which support healthy functioning of the marine ecosystem and provision of resources for human-consumption, in addition to influencing biogeochemical cycles (e.g. air–sea CO₂ exchange). With the susceptibility of sea ice ecosystems to climate change, there is a pressing need to fill knowledge gaps surrounding sea ice habitats and their microbial communities. Of fundamental importance to this goal is the development of new methodologies that permit effective study of them. Based on outcomes from the DiatomARCTIC project, this paper integrates existing knowledge with case studies to provide insight on how to best document sea ice microbial communities, which contributes to the sustainable use and protection of Arctic marine and coastal ecosystems in a time of environmental change.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01658-z.     

Influence of soil properties and aging on the toxicity of copper on compost worm and barley

Influence of soil properties and aging on Cu partitioning and toxicity was assessed on 10 artificial soils constituted using a statistical design considering pH (5.5 and 7.5), organic matter (1-30% [w/w]), and clay content (5-35% [w/w]). Total Cu as well as water-, CaCl2-, and diethylene triamine pentaacetic acid (DTPA)-extracted Cu fractions were determined for each soil mixture. Ecotoxic effect was assessed by determining growth inhibition of barley (Hordeum vulgare L.) and compost worm (Eisenia fetida) mortality. Analyses were repeated after a 16-wk aging period of the soils at pH 7.5 (8 x 2-wk wetting and drying cycle). Results indicated that pH was the main factor controlling Cu partitioning, ahead of organic matter and clay content. Calcium chloride (0.5 M)-extracted Cu fractions showed the best correlation with toxic responses (r = 0.55-0.66; p < 0.05), while total and DTPA-extracted Cu concentrations could not explain differences in toxicity. Direct regressions between toxicity and soil properties (pH, organic matter, and clay content) provided better explanation of variance: r2= 0.50 (p = 0.00006) for compost worm mortality, r2= 0.77 (p < 0.00001) for barley shoot inhibition, and r2= 0.92 (p < 0.00001) for barley root inhibition. Copper toxicity was mainly influenced by pH and, to a lesser extent, by organic matter and clay content. Aging in organic soils revealed a slight reduction in ecotoxicity while an increase was observed in soils with low organic matter content. Further investigation using longer aging periods would be necessary to assess the significance of this observation.     

The influence of metal source uncertainty on cost-effective allocation of mine water pollution abatement in catchments

In mine water pollution abatement, it is commonly assumed that known mine waste sites are the major pollution sources, thus neglecting the possibility of significant contribution from other old and diffuse sources within a catchment. We investigate the influence of different types of pollution source uncertainty on cost-effective allocation of abatement measures for mine water pollution. A catchment-scale cost-minimization model is developed and applied to the catchment of the river Dalälven, Sweden, in order to exemplify important effects of such source uncertainty. Results indicate that, if the pollution distribution between point and diffuse sources is partly unknown, downstream abatement measures, such as constructed wetlands, at given compliance boundaries are often cost-effective. If downstream abatement measures are not practically feasible, the pollution source distribution between point and diffuse mine water sources is critical for cost-effective solutions to abatement measure allocation in catchments. In contrast, cost-effective solutions are relatively insensitive to uncertainty in total pollutant discharge from mine water sources.     

Potential of fly ash for neutralisation of acid mine drainage

Lignite (PK), bituminous (FI) and biomass (SE) fly ashes (FAs) were mineralogically and geochemically characterised, and their element leachability was studied with batch leaching tests. The potential for acid neutralisation (ANP) was quantified by their buffering capacity, reflecting their potential for neutralisation of acid mine drainage. Quartz was the common mineral in FAs detected by XRD with iron oxide, anhydrite, and magnesioferrite in PK, mullite and lime in FI, and calcite and anorthite in SE. All the FAs had high contents of major elements such as Fe, Si, Al and Ca. The Ca content in SE was six and eight times higher compared to PK and FI, respectively. Sulphur content in PK and SE was one magnitude higher than FI. Iron concentrations were higher in PK. The trace element concentrations varied between the FAs. SE had the highest ANP (corresponding to 275 kg CaCO₃?tonne^?1) which was 15 and 10 times higher than PK and FI, respectively. The concentrations of Ca²⁺, SO₄ ^2?, Na⁺ and Cl^? in the leachates were much higher compared to other elements from all FA samples. Iron, Cu and Hg were not detected in any of the FA leachates because of their mild to strong alkaline nature with pH ranging from 9 to 13. Potassium leached in much higher quantity from SE than from the other ashes. Arsenic, Mn and Ni leached from PK only, while Co and Pb from SE only. The concentrations of Zn were higher in the leachates from SE. The FAs used in this study have strong potential for the neutralisation of AMD due to their alkaline nature. However, on the other hand, FAs must be further investigated, with scaled-up experiments before full-scale application, because they might leach pronounced concentrations of elements of concern with decreasing pH while neutralising AMD.     

Integrated spatial health assessment of yellow perch (<Emphasis Type="Italic">Perca flavescens</Emphasis>) populations from the St. Lawrence River,Quebec, Canada) part A: physiological parameters and pathogen assessment

A multi-disciplinary approach was used to evaluate the health of yellow perch (Perca flavescens) in the St. Lawrence River (Quebec, Canada), which is experiencing a severe population decline in the downstream portion of the river. Physiological parameters, liver alterations, trace metal concentrations, parasite prevalence and abundance, stable isotope composition, and the presence/absence of the viral hemorragic septicemia virus (VHSV) were evaluated in perch collected at six sites along the river: Lake St. François, Lake St. Louis (north and south), Beauregard Island, and Lake St. Pierre (north and south). Trace metal concentrations in surface water were higher in Lake St. Louis and downstream of a major urban wastewater treatment plant discharge, indicating that this effluent was a significant source of Cu, As, Ag, Zn, and Cd. Levels of Pb in surface water exceeded thresholds for the protection of aquatic life in Lake St. Louis and were negatively correlated with body condition index in this lake. In Lake St. Pierre, Cu, Ag, and Cd bioaccumulated significantly in perch liver and lower body condition index and greater liver damage were observed compared to upstream sites. Parasite analyses indicated a higher abundance of metacercariae of the trematodes Apophallus brevis and Diplostomum spp. in Lake St. Louis, and VHSV was not detected in the liver of yellow perch for all studied sites. Overall, results suggested that the global health of yellow perch from Lake St. Pierre is lower compared to upstream studied sites, which could contribute to the documented population collapse at this site.