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Abstract

The 2023 Canadian forest fires have been extreme in scale and intensity with more than seven times the average annual area burned compared to the previous four decades1. Here, we quantify the carbon emissions from these fires from May to September 2023 on the basis of inverse modelling of satellite carbon monoxide observations. We find that the magnitude of the carbon emissions is 647 TgC (570–727 TgC), comparable to the annual fossil fuel emissions of large nations, with only India, China and the USA releasing more carbon per year2. We find that widespread hot–dry weather was a principal driver of fire spread, with 2023 being the warmest and driest year since at least 19803. Although temperatures were extreme relative to the historical record, climate projections indicate that these temperatures are likely to be typical during the 2050s, even under a moderate climate mitigation scenario (shared socioeconomic pathway, SSP 2–4.5)4. Such conditions are likely to drive increased fire activity and suppress carbon uptake by Canadian forests, adding to concerns about the long-term durability of these forests as a carbon sink5,6,7,8.

Summary

Background

Inadequate micronutrient intakes and related deficiencies are a major challenge to global public health. Analyses over the past 10 years have assessed global micronutrient deficiencies and inadequate nutrient supplies, but there have been no global estimates of inadequate micronutrient intakes. We aimed to estimate the global prevalence of inadequate micronutrient intakes for 15 essential micronutrients and to identify dietary nutrient gaps in specific demographic groups and countries.

Methods

In this modelling analysis, we adopted a novel approach to estimating micronutrient intake, which accounts for the shape of a population's nutrient intake distribution and is based on dietary intake data from 31 countries. Using a globally harmonised set of age-specific and sex-specific nutrient requirements, we then applied these distributions to publicly available data from the Global Dietary Database on modelled median intakes of 15 micronutrients for 34 age–sex groups from 185 countries, to estimate the prevalence of inadequate nutrient intakes for 99·3% of the global population.

Findings

On the basis of estimates of nutrient intake from food (excluding fortification and supplementation), more than 5 billion people do not consume enough iodine (68% of the global population), vitamin E (67%), and calcium (66%). More than 4 billion people do not consume enough iron (65%), riboflavin (55%), folate (54%), and vitamin C (53%). Within the same country and age groups, estimated inadequate intakes were higher for women than for men for iodine, vitamin B12, iron, and selenium and higher for men than for women for magnesium, vitamin B6, zinc, vitamin C, vitamin A, thiamin, and niacin.

Abstract

Global climate change disrupts key ecological processes and biotic interactions. The recent increase in heatwave frequency and severity prompts the evaluation of physiological processes that ensure the maintenance of vital ecosystem services such as pollination. We used experimental heatwaves to determine how high temperatures affect the bumblebees’ ability to detect floral scents. Heatwaves induced strong reductions in antennal responses to floral scents in both tested bumblebee species (Bombus terrestris and Bombus pascuorum). These reductions were generally stronger in workers than in males. Bumblebees showed no consistent pattern of recovery 24 h after heat events. Our results suggest that the projected increased frequency and severity of heatwaves may jeopardize bumblebee-mediated pollination services by disrupting the chemical communication between plants and pollinators. The reduced chemosensitivity can decrease the bumblebees’ abilities to locate food sources and lead to declines in colonies and populations.

Abstract

Anthropogenic contaminants can place significant stress on vegetation, especially when they are taken up into plants. Plastic pollution, including nanoplastics (NPs), could be detrimental to tree functioning, by causing, for example, oxidative stress or reducing photosynthesis. While a number of studies have explored the capacity of plants to take up NPs, few have simultaneously assessed the functional damage due to particulate matter uptake. To quantify NPs uptake by tree roots and to determine whether this resulted in subsequent physiological damage, we exposed the roots of two tree species with different water use strategies in hydroponic cultures to two concentrations (10 mg L−1 and 30 mg L−1) of model metal-doped polystyrene NPs. This approach allowed us to accurately quantify low concentrations of NPs in tissues using standard approaches for metal analysis. The two contrasting tree species included Norway spruce (Picea abies [L.] Karst), a water conservative tree, and wild service tree (Sorbus torminalis [L.] Crantz), an early successional tree with a rather water spending strategy. At both exposure concentrations and at each of the experimental time points (two and four weeks), NPs were highly associated and/or concentrated inside the tree roots. In both species, maximum concentrations were observed after 2 weeks in the roots of the high concentration (HC) treatment (spruce: 2512 ± 304 μg NPs per g DW (dry weight), wild service tree: 1190 ± 823 μg NPs per g DW). In the aboveground organs (stems and leaves or needles), concentrations were one to two orders of magnitude lower than in the roots. Despite relatively similar NPs concentrations in the tree aboveground organs across treatments, there were different temporal impacts on tree physiology of the given species. Photosynthetic efficiency was reduced faster (after 2 weeks of NPs exposure) and more intensively (by 28% in the HC treatment) in wild service trees compared to Norway spruce (ca. 10% reduction only after 4 weeks). Our study shows that both, evergreen coniferous as well as deciduous broadleaf tree species are negatively affected in their photosynthesis by NPs uptake and transport to aboveground organs. Given the likelihood of trees facing multiple, concurrent stressors from anthropogenic pollution and climate change, including the impact of NPs, it is crucial to consider the cumulative effects on vegetation in future.

Editor’s summary

Assessment of the status of fisheries stocks is a key component of their management. Although there has been much debate around how to do fishery assessments, there has been a general belief that estimates are roughly accurate. Edgar et al. used publicly available data on 230 of the best-known fisheries species to test whether stock biomass estimates made in the year of the estimate were as accurate as specifically calculated hindcast models (see the Perspective by Froese and Pauly). They found that, especially in overfished species, historical estimates were higher than later estimates, indicating the presence of excessively positive assessments of stock status. —Sacha Vignieri

Abstract

Effective fisheries management requires accurate estimates of stock biomass and trends; yet, assumptions in stock assessment models generate high levels of uncertainty and error. For 230 fisheries worldwide, we contrasted stock biomass estimates at the time of assessment with updated hindcast estimates modeled for the same year in later assessments to evaluate systematic over- or underestimation. For stocks that were overfished, low value, or located in regions with rising temperatures, historical biomass estimates were generally overstated compared with updated assessments. Moreover, rising trends reported for overfished stocks were often inaccurate. With consideration of bias identified retrospectively, 85% more stocks than currently recognized have likely collapsed below 10% of maximum historical biomass. The high uncertainty and bias in modeled stock estimates warrants much greater precaution by managers.

Marine fish populations or “stocks” are subject to fishing pressure along the world’s coastlines by local fishers and further offshore by industrial fleets, whose huge capacity is capable of decimating the fish that they target. Fishing operations are therefore typically constrained by catch limits derived from stock assessments—i.e., reports on the condition of a fish stock and its estimated future abundance. Theoretically, catch limits should ensure sustainability by not exceeding the productive ability of fish populations and by allowing depleted stocks to rebuild. In reality, the fraction of overfished stocks continues to increase, and reported global catches stagnate despite increasing fishing effort, implying that fish abundance is declining (1). On page 860 of this issue, Edgar et al. (2) report a likely explanation for the apparent inability of standard stock assessment models to provide sound catch limits. Their findings underscore the importance of accurate stock estimates for sustainable fisheries management.

Abstract

Extreme weather events lead to significant adverse societal costs. Extreme Event Attribution (EEA), a methodology that examines how anthropogenic greenhouse gas emissions had changed the occurrence of specific extreme weather events, allows us to quantify the climate change-induced component of these costs. We collect data from all available EEA studies, combine these with data on the socio-economic costs of these events and extrapolate for missing data to arrive at an estimate of the global costs of extreme weather attributable to climate change in the last twenty years. We find that US 143 billion per year of the costs of extreme events is attributable to climatic change. The majority (63%), of this is due to human loss of life. Our results suggest that the frequently cited estimates of the economic costs of climate change arrived at by using Integrated Assessment Models may be substantially underestimated.