Stockholm Environment Institute

Abstract Forests play a critical role in the global carbon cycle, being considered an important and continuing carbon sink. However, the response of carbon sequestration in forests to global climate change remains a major uncertainty, with a particularly poor understanding of the origins and environmental responses of soil CO 2 efflux. For example, despite their large biomass, the contribution of ectomycorrhizal (EM) fungi to forest soil CO 2 efflux and responses to changes in environmental drivers has, to date, not been quantified in the field. Their activity is often simplistically included in the ‘autotrophic’ root respiration term. We set up a multiplexed continuous soil respiration measurement system in a young Lodgepole pine forest, using a mycorrhizal mesh collar design, to monitor the three main soil CO 2 efflux components: root, extraradical mycorrhizal hyphal, and soil heterotrophic respiration. Mycorrhizal hyphal respiration increased during the first month after collar insertion and thereafter remained remarkably stable. During autumn the soil CO 2 flux components could be divided into ∼60% soil heterotrophic, ∼25% EM hyphal, and ∼15% root fluxes. Thus the extraradical EM mycelium can contribute substantially more to soil CO 2 flux than do roots. While EM hyphal respiration responded strongly to reductions in soil moisture and appeared to be highly dependent on assimilate supply, it did not responded directly to changes in soil temperature. It was mainly the soil heterotrophic flux component that caused the commonly observed exponential relationship with temperature. Our results strongly suggest that accurate modelling of soil respiration, particularly in forest ecosystems, needs to explicitly consider the mycorrhizal mycelium and its dynamic response to specific environmental factors. Moreover, we propose that in forest ecosystems the mycorrhizal CO 2 flux component represents an overflow ‘CO 2 tap’ through which surplus plant carbon may be returned directly to the atmosphere, thus limiting expected carbon sequestration from trees under elevated CO 2 .

Abstract In a number of recent field studies, the positive response of soil respiration to warming has been shown to decline over time. The two main differing hypotheses proposed to explain these results are: (1) soil microbial respiration acclimates to the increased temperature, and (2) substrate availability within the soil decreases with warming so reducing the rate of soil respiration. To investigate the relative merits of these two hypotheses, soil samples (both intact cores and sieved samples) from a 3‐year grassland soil‐warming and shading experiment were incubated for 4 weeks at three different temperatures under constant laboratory conditions. We tested the hypothesis that sieving the soils would reduce differences in substrate availability between warmed and control plot samples and would therefore result in similar respiration rates if microbial activity had not acclimated to soil warming. In addition, to further test the effect of substrate availability, we compared the respiration rates of soils taken from shaded and unshaded plots. Both soil warming and shading significantly reduced respiration rates in the intact cores, especially under higher incubation temperatures. However, sieving the soil greatly reduced these differences suggesting that substrate availability, and not microbial acclimation to the higher temperatures, played the dominant role in determining the response of heterotrophic soil respiration to warming. The effect of shading appeared to be mediated by reduced plant productivity affecting substrate availability within the soil and hence microbial activity. Given the lack of evidence for thermal acclimation of microbial respiration, there remains the potential for prolonged carbon losses from soils in response to warming.

• Although arbuscular mycorrhizal (AM) fungi are a major pathway in the global carbon cycle, their basic biology and, in particular, their respiratory response to temperature remain obscure. • A pulse label of the stable isotope 13C was applied to Plantago lanceolata, either uninoculated or inoculated with the AM fungus Glomus mosseae. The extra-radical mycelium (ERM) of the fungus was allowed to grow into a separate hyphal compartment excluding roots. We determined the carbon costs of the ERM and tested for a direct temperature effect on its respiration by measuring total carbon and the 13C:12C ratio of respired CO2. With a second pulse we tested for acclimation of ERM respiration after 2 wk of soil warming. • Root colonization remained unchanged between the two pulses but warming the hyphal compartment increased ERM length. δ13C signals peaked within the first 10 h and were higher in mycorrhizal treatments. The concentration of CO2 in the gas samples fluctuated diurnally and was highest in the mycorrhizal treatments but was unaffected by temperature. Heating increased ERM respiration only after the first pulse and reduced specific ERM respiration rates after the second pulse; however, both pulses strongly depended on radiation flux. • The results indicate a fast ERM acclimation to temperature, and that light is the key factor controlling carbon allocation to the fungus.

Climate change impacts, adaptation and vulnerability studies tend to confine their attention to impacts and responses within the same geographical region. However, this approach ignores cross-border climate change impacts that occur remotely from the location of their initial impact and that may severely disrupt societies and livelihoods. We propose a conceptual framework and accompanying nomenclature for describing and analysing such cross-border impacts. The conceptual framework distinguishes an initial impact that is caused by a climate trigger within a specific region. Downstream consequences of that impact propagate through an impact transmission system while adaptation responses to deal with the impact propagate through a response transmission system. A key to understanding cross-border impacts and responses is a recognition of different types of climate triggers, categories of cross-border impacts, the scales and dynamics of impact transmission, the targets and dynamics of responses and the socio-economic and environmental context that also encompasses factors and processes unrelated to climate change. These insights can then provide a basis for identifying relevant causal relationships. We apply the framework to the floods that affected industrial production in Thailand in 2011, and to projected Arctic sea ice decline, and demonstrate that the framework can usefully capture the complex system dynamics of cross-border climate impacts. It also provides a useful mechanism to identify and understand adaptation strategies and their potential consequences in the wider context of resilience planning. The cross-border dimensions of climate impacts could become increasingly important as climate changes intensify. We conclude that our framework will allow for these to be properly accounted for, help to identify new areas of empirical and model-based research and thereby support climate risk management.

Abstract. Quantifying soil organic carbon stocks (SOC) and their dynamics accurately is crucial for better predictions of climate change feedbacks within the atmosphere-vegetation-soil system. However, the components, environmental responses and controls of the soil CO2 efflux (Rs) are still unclear and limited by field data availability. The objectives of this study were (1) to quantify the contribution of the various Rs components, specifically its mycorrhizal component, (2) to determine their temporal variability, and (3) to establish their environmental responses and dependence on gross primary productivity (GPP). In a temperate deciduous oak forest in south east England hourly soil and ecosystem CO2 fluxes over four years were measured using automated soil chambers and eddy covariance techniques. Mesh-bag and steel collar soil chamber treatments prevented root or both root and mycorrhizal hyphal in-growth, respectively, to allow separation of heterotrophic (Rh) and autotrophic (Ra) soil CO2 fluxes and the Ra components, roots (Rr) and mycorrhizal hyphae (Rm). Annual cumulative Rs values were very similar between years (740 ± 43 g C m−2 yr−1) with an average flux of 2.0 ± 0.3 μmol CO2 m−2 s−1, but Rs components varied. On average, annual Rr, Rm and Rh fluxes contributed 38, 18 and 44%, respectively, showing a large Ra contribution (56%) with a considerable Rm component varying seasonally. Soil temperature largely explained the daily variation of Rs (R2 = 0.81), mostly because of strong responses by Rh (R2 = 0.65) and less so for Rr (R2 = 0.41) and Rm (R2 = 0.18). Time series analysis revealed strong daily periodicities for Rs and Rr, whilst Rm was dominated by seasonal (~150 days), and Rh by annual periodicities. Wavelet coherence analysis revealed that Rr and Rm were related to short-term (daily) GPP changes, but for Rm there was a strong relationship with GPP over much longer (weekly to monthly) periods and notably during periods of low Rr. The need to include individual Rs components in C flux models is discussed, in particular, the need to represent the linkage between GPP and Ra components, in addition to temperature responses for each component. The potential consequences of these findings for understanding the limitations for long-term forest C sequestration are highlighted, as GPP via root-derived C including Rm seems to function as a C "overflow tap", with implications on the turnover of SOC.

Abstract Climate change and air pollution can interact to amplify risks to human health and crop production. This has significant implications for our ability to reach the Sustainable Development Goals (e.g. SDGs 2, 3, 13, 15) and for the design of effective mitigation and adaptation policies and risk management. To be able to achieve the SDG targets, closer integration of climate change and air pollution both in terms of impact assessment for human health and agricultural productivity and respective policy development is needed. Currently, studies estimating the impacts of climate and air pollutants on human health and crops mostly treat these stressors separately, and the methods used by the health and agricultural science communities differ. Better insights into the methods applied in the different communities can help to improve existing and develop new methods to advance our knowledge about the combined impacts of climate change and air pollution on human health and crops. This topical review provides an overview of current methodologies applied in the two fields of human health and agricultural crop impact studies, ranging from empirical regression-based and experimental methods to more complex process-based models. The latter are reasonably well developed for estimating impacts on agricultural crops, but not for health impacts. We review available literature addressing the combined effects of climate and air pollution on human health or agricultural productivity to provide insights regarding state-of-the-art knowledge and currently available methods in the two fields. Challenges to assess the combined effect of climate and air pollution on human health and crops, and opportunities for both fields to learn from each other, are discussed.

Information on environmental noise challenges was gathered for 139 countries, identified by the World Bank as of low income (31), lower middle income (52), and upper middle income (56). Data on noise levels were found in urban agglomerations of two low-income, 13 lower middle-income, and 20 upper middle-income countries. Environmental noise pollution continues to grow in all studied cities due to increase in motor vehicle fleets, airport operations and industries. The main driving forces are population growth, urbanization, motorization and to a large extent technological development. In this paper the major noise sources in two low-income countries, 13 lower middle-income countries and 13 upper middle-income countries (excluding Member States of and countries on the road to the European Union) are identified and observed environmental noise levels reviewed. The paper also compiles the adverse health effects of extensive noise exposures in urban agglomerations that have already been observed in some of these countries. The key laws and by-laws and other regulations on noise pollution in these countries and the level of their enforcement are discussed.

This review has highlighted the important developments relating to noise issues performed by international organizations and the activities in some developed and developing countries to improve environmental noise management.
 The World Health Organization is in the process of finalizing the WHO Environmental Noise Guidelines for the European Region as an update of the WHO Community Noise Guidelines of 1999/2000.
 The International Civil Aviation Organization, in Chapter 14, has lowered the current chapter 4 standards for subsonic jet aircraft and propeller driven aeroplanes.
 In 2014-2016 the European Parliament and the Council and the European Commission have achieved significant progress in amending laws and regulations and creating new legislation. Efforts referred to regulating the EU type-approval of all new buses and trucks with regard to their sound level and the introduction of noise-related operating restrictions at airports, in accordance with ICAO’s Balanced Approach. The EC amended the END and arranged for the evaluation of the END based on the criteria of relevance, coherence, effectiveness and impacts, efficiency, and EU added value. Two new regulations addressed the issues of technical specification for interoperability of high-speed trains related to sound emission levels and the implementation of provisions establishing noise-differentiated track access charges.
 The European Environment Agency published the ‘Noise in Europe’ report describing the impacts of noise exposure in terms of cases of premature death, hospital admissions, cases of hypertension and annoyance. In addition, the European Environment Agency developed a good practice guide on quiet areas, refined the methodology for a quietness suitability index, and published its report on “Quiet areas in Europe”.
 In the United Kingdom, the Civil Aviation Authority reported new and updated evidence on attitudes to aviation noise around airports in England, and the Airports commission published recommendations for development in the aviation sector around London. The Department of Transport formulated a draft Airports National Policy Statement on expansion options for South East England airports.
 Switzerland published its Environment Report 2015 and estimated the annual external costs of road traffic, railway and aircraft noise which are quite substantial.
 Developing countries become increasingly aware that noise levels have gone up abnormally high and can cause acute and chronic health impacts on the human population. In consequence, Costa Rica has lowered the permissible sound pressure levels, and India, Iraq and Mexico have set new daytime and night-time noise standards. Tanzania has approved permissible sound pressure limits, which were prepared by the National Environment Management Council almost a decade ago. The Egyptian Environmental Affairs Agency developed a national plan to combat noise, which is currently implemented on a collaborative effort of 11 ministries, a rare phenomenon in developing countries. Kenya is currently committed to develop a strategy for environmental noise management.

In the context of Arab cities, this study explores the intricate interplay between cultural, historical, and environmental elements that shape their unique soundscapes. The paper aims to shed light on this underrepresented field of study by employing a three-fold research approach: systematic review, a comprehensive literature review, and the formulation of a future research agenda. The first part of the investigation focuses on research productivity in the Arab world regarding soundscape studies. An analysis of publication trends reveals that soundscape research in Arab cities is still an emerging area of interest. Critical gaps in the existing body of literature are identified, highlighting the importance of addressing these gaps within the broader context of global soundscape research. The second part of the study delves into the distinctive features that inform the soundscapes of Arab cities. These features are categorized into three overarching groups: (i) cultural and religious life, (ii) daily life, and (iii) heritage and history, by exploring these factors, the study aims to elucidate the multifaceted nature of Arab urban soundscapes. From the resonating calls to prayer and the vibrant ambiance of traditional cafes to the bustling markets and architectural characteristics, each factor contributes to the auditory tapestry that defines Arab cities. The paper concludes with a forward-looking research agenda, proposing sixteen key questions organized into descriptive and comparative categories. These questions emphasize the need for a more profound understanding of sound perception, sources, and the impact of urban morphology on the soundscape. Additionally, they highlight the need for interdisciplinary research, involving fields such as urban planning, architecture, psychology, sociology, and cultural studies to unravel the complexity of Arab urban soundscapes.

This report provides a continuation of the review of environmental noise policies and economics in 2014-2016, presented at ICBEN 2017 and published in a previous issue of the South Florida Journal of Health. The report addresses the international progress on noise mitigation policies and strategies, best practices, and guidelines for environmental noise management. It focuses on developments in evidence and policy by international bodies and in selected countries. There is a considerable amount of new relevant documents on these topics in international organizations and in some countries since the last ICBEN Congress in 2017. Much of this progress was made in the European Union, the Russian Federation, the United Kingdom, and Switzerland. Developing countries in Latin America, especially Chile, Costa Rica, Mexico, Paraguay, and Perú are increasingly committed to improve environmental noise policies. Also, China has continued to approach sustainable development goals with respect to noise challenges. Kazakhstan has started to address the noise problem by developing a code to mitigate noise-related impacts.

Ozone pollution and climate change are extremely likely to threaten future crop production in important agricultural regions around the World with the Mediterranean, South and East Asia and mid-West US being particularly at risk with implications for food security. Modelling methods used to assess risk of ozone pollution have developed in recent years away from empirical approaches based on dose-response relationships towards more process-based models. The DO3SE-Crop model has developed from an ozone deposition and effects model (having used flux-response relationships to assess damage) to a crop model capable of assessing the effect of ozone on photosynthesis and carbon allocation. Working within the AgMIP-ozone activity, DO3SE-Crop has been calibrated and evaluated against experimental ozone fumigation datasets for wheat cultivars from Spain (Mediterranean Europe), China and India and is able to assess the influence of climate variables on crop growth and yield as well as the effect of ozone on instantaneous photosynthesis and senescence. We find that the ozone effect on senescence is the primary determinant for yield loss in wheat. We are further developing the model to assess ozone effects on nutritional quality since we know that ozone is an important limiter of translocation of nitrogen to the grains. The establishment of DO3SE-Crop will allow assessments of the future impacts resulting form the combined effects of ozone and climate change on supply and nutritional aspects of food security. Importantly, this can include an assessment of the yield improvements between current and near- to mid-term future conditions for a range of adaptation options proposed for wheat in response to climate change including management of irrigation, growing season and development of new varieties from crop breeding with targeted physiological traits such as enhanced gas exchange and improved water use efficiency.