Topsoil Selling - extreme anthropogenic erosion and its consequences for paddy soil quality (Mekong Delta, Vietnam)

Increasing urbanization and industrialization leads to rising demands for construction material, particularly in low-income countries. Thus, agricultural topsoil is sometimes removed and used as raw material e.g. for brick production. Topsoil selling (TSS) is practiced around the world from America, Europe, and Afrika to Asia. In the Mekong, Delta farmers sell the topsoil from their paddy fields to contractors. The temporal effects of topsoil removal on soil quality are not yet fully understood. We hypothesized that after soil removal, soil quality is significantly lower compared to the original topsoil. To test this hypothesis, we sampled paddy soil chronosequences in two different provinces, ranging between 1 and 8 years after TSS. Soil organic carbon (Corg) stocks at TSS sites were up to 20 t/ha lower than at control sites (control: 50 t/ha) in Sóc Trăng and up to 15 t/ha lower in Trà Vinh (control: 30 t/ha). The C/N ratio was nearly constant around 10. Analysis of inorganic nutrients (e.g. P, K, Na, S, Zn, Cu) showed that changes are variable in space, time and among nutrients. Annual average changes ranged from less than a kg per hectare and year for micronutrients (e.g. Cu, Zn) to several tens and hundreds of kg for macronutrients (e.g. P, S). The so far available data revealed that TSS induces mainly a dramatic loss of soil organic matter. It was ongoing up to the 8th year of the chronosequences but was not necessarily accompanied by losses in inorganic nutrients. As a result, there appears to be a chance for farmers in the Mekong Delta to overcome risks of soil quality decline after topsoil removal. Within the next months, we will receive the results from P- and S fractionation and also results from lignin analysis (lignin-derived phenols) will complement to the available data. Thus, we will gain further insights into soil evolution after topsoil selling shortly

Does sea-dyke construction affect the spatial distribution of pesticides in agricultural soils? – a case study from the Red River Delta, Vietnam

The Red River Delta is a major agricultural production area of Vietnam with year-round use of pesticides for paddy rice cultivation and other production systems. The delta is protected from flooding, storm surges and saline water intrusion by a sophisticated river and sea-dyke system. Little is known about the effects of such a dyke system on pesticide pollution in the enclosed landscape. Our aim was to address this gap by i) determining pesticide prevalence in soils and sediments within a dyked agricultural area, and by ii) assessing whether and to which degree this dyke system might affect the spatial distribution of pesticides. After sampling paddy rice fields (topsoil) and irrigation ditches (sediment) perpendicular to the dyke in Giao Thuy district, we analysed 12 of the most commonly used pesticides in this area. In soils, we detected most frequently isoprothiolane (100% detection frequency), chlorpyrifos (85%) and propiconazole (41%) while in sediments isoprothiolane (71%) and propiconazole (71%) were most frequently found. Maximum concentrations reached 42.6 μg isoprotiolane kg−1 in soil, and 35.1 μg azoxystrobin kg−1 in sediment. Our results supported the assumption that the dyke system influenced residue distribution of selected pesticides. More polar substances increasingly accumulated in fields closer to the sea-dyke (R2 = 0.92 for chlorpyrifos and 0.51 for isoprothiolane). We can thus support initiatives from local authorities to use the distance to dykes as a mean for deliniating zones of different environmental pollution; yet, the degree at which dykes influence pesticide accumulation appear to be compound specific

Editorial: Knowledge gaps from the IPCC special report on the ocean and cryosphere in a changing climate and recent advances (volumes I and II)

This is the final version. Available from Frontiers Media via the DOI in this record. Natural Environment Research CouncilSwiss Agency for Development and CooperationSwiss Agency for Development and CooperationSwiss Academy of Science

Pesticides and antibiotics in permanent rice, alternating rice-shrimp and permanent shrimp systems of the coastal Mekong Delta, Vietnam

Background: Salinity intrusion into coastal regions is an increasing threat to agricultural production of salt sensitive crops like paddy rice. In the coastal Mekong Delta, farmers respond by shifting to more salinity tolerant agricultural production systems such as alternating rice-shrimp and permanent shrimp. While shrimps are sensitive to pesticide residues used on rice, the use of antibiotics in shrimp farming can cause contamination in rice crops. These patterns of cross-contamination are not well documented empirically in the rapidly changing agricultural landscape. Objective and methods: Our objective was to understand changing pollution patterns induced by shifts in agricultural land use system. We addressed this by i) documenting pesticide and antibiotic use in three different agriculture land use systems (permanent rice, alternating rice-shrimp and permanent shrimp), and by ii) determining residues of pesticides and antibiotics in top soil layers of these three land use systems. Samples were taken in Sóc Trăng and Bến Tre province in the Mekong Delta, Vietnam. Chemical analyses comprised 12 of the most commonly used pesticides in rice paddies and six common antibiotics used in shrimp production. Results: Results showed that residues of pesticides were present in all agricultural land use systems, including shrimp aquaculture. Active ingredients were mostly fungicides with a maximum concentration of 67 μg kg−1 found for isoprothiolane in permanent rice systems, followed by alternating rice-shrimp and permanent shrimp systems. Furthermore, antibiotics were present ubiquitously, with fluoroquinolones accumulating to larger amounts than sulfonamides and diaminopyrimidines. All concentrations were below critical lethal threshold values. Conclusion: Overall, farmers were most conscious of agrochemical use in alternating rice-shrimp systems to prevent harm to shrimps, which was reflected in overall lower concentrations of agrochemicals when compared to rice systems. Thus, alternating rice-shrimp systems present a low risk option in terms of food safety, which may bring additional benefits to this so far rather low-input system in brackish water transition zone

Opportunities for considering green infrastructure and ecosystems in the Sendai Framework Monitor

Ecosystem-based disaster risk reduction has gained attention to complement or replace grey infrastructure. The paper explores ways in which ecosystems and green infrastructure (GI) are critical infrastructure in the context of disaster risk reduction to report respective losses in the Sendai Framework Monitor (SFM). We argue that reporting on GI under indicators D-4 and C-5 in the SFM represent an opportunity for tracking losses, yet do not provide direct information on progress made in reducing risk. Custom targets and indicators according to countries' needs within the SFM might be a more practical opportunity to report on both losses and progress

Einfluss der Eindeichung auf Pestizidrückstände in Böden eines landwirtschaftlichen Gebietes des Red River Deltas, Vietnam

Fruchtbare Böden und eine hohe Verfügbarkeit von Wasser machen Deltaregionen zu den wichtigsten landwirtschaftlichen Produktionsflächen. Zur Sicherstellung hoher Erträge werden insbesondere in Reismonokulturen, Pestizide in einer erhöhten Menge und Häufigkeit eingesetzt. Während das Verhalten dieser Stoffe im Nassreisanbau bereits in früheren Studien beschrieben wurde, hat diese Studie zum Ziel den Einfluss von Deich-Konstruktionen auf die räumliche Verteilung der Pestizide zu untersuchen. Dazu wurden Boden- und Sedimentproben im Delta des Roten Flusses im Landkreis Giao Thuy entnommen. Dieses Gebiet ist von einem Meer- und Flussdeich mit verschiedenen Einlass- und Abflussschleusen umgeben. Dadurch findet eine Regulation der Wasserbewirtschaftung statt und das eingedeichte Gebiet wird vor Überschwemmung, Stürmen und das Eindringen von Salzwasser geschützt. In der Vergangenheit beobachteten regionale Behörden eine Abnahme der Wasserqualität vom Flussdeich hin zum Meerdeich. Dies ist vermutlich auf einen verringerten Wasseraustausch zurückzuführen, hervorgerufen durch das Deichsystem, was zu einer Akkumulation der Pestizidrückstände innerhalb des eingedeichten Gebietes führt. Um diese Hypothese zu prüfen, wurden Boden- und Sedimentproben von Reisflächen, Bewässerungsgräben und auch von Salzwasseraquakulturflächen außerhalb des eingedeichten Gebietes entnommen und anschließend auf Rückstände von 12 verschiedenen Pestiziden hin untersucht. Die Pestizide wurden wie folgt bestimmt: Extraktion mittels accelerated solvent extraction (ASE), gefolgt von einer Aufreinigung nach Laabs et al. (2007) und der Quantifizierung mittels Gaschromatographie gekoppelt an ein Massenspektrometer (GC-MS). Vorläufige Ergebnisse lassen vermuten, dass Chlorpyrifos, Propiconazole und Isoprothiolane häufig in den Proben der Reisflächen vorhanden sind. In Reisflächen nahe des Meerdeiches wurden keine erhöhten Pestizidkonzentrationen ermittelt. Die Pestizidrückstände in den Proben der Reisflächen sind eher der direkten Applikation verschuldet, wohingegen die Kanalproben keiner direkten Applikation ausgesetzt sind

Aligning the Global Delta Risk Index with SDG and SFDRR Global frameworks to assess risk to socio-ecological systems in river deltas

River deltas globally are highly exposed and vulnerable to natural hazards and are often over-exploited landforms. The Global Delta Risk Index (GDRI) was developed to assess multi-hazard risk in river deltas and support decision-making in risk reduction interventions in delta regions. Disasters have significant impacts on the progress towards the Sustainable Development Goals (SDGs). However, despite the strong interlinkage between disaster risk reduction and sustainable development, global frameworks are still developed in isolation and actions to address them are delegated to different institutions. Greater alignment between frameworks would both simplify monitoring progress towards disaster risk reduction and sustainable development and increase capacity to address data gaps in relation to indicator-based assessments for both processes. This research aims at aligning the GDRI indicators with the SDGs and the Sendai Framework for Disaster and Risk Reduction (SFDRR). While the GDRI has a modular indicator library, the most relevant indicators for this research were selected through a delta-specific impact chain designed in consultation with experts, communities and stakeholders in three delta regions: the Red River and Mekong deltas in Vietnam and the Ganges–Brahmaputra–Meghna (GBM) delta in Bangladesh and India. We analyse how effectively the 143 indicators for the GDRI match (or not) the SDG and SFDRR global frameworks. We demonstrate the interconnections of the different drivers of risk to better inform risk management and in turn support delta-level interventions towards improved sustainability and resilience of these Asian mega-deltas

Burning embers: towards more transparent and robust climate-change risk assessments

The Intergovernmental Panel on Climate Change (IPCC) reports provide policy-relevant insights about climate impacts, vulnerabilities and adaptation through a process of peer-reviewed literature assessments underpinned by expert judgement. An iconic output from these assessments is the burning embers diagram, first used in the Third Assessment Report to visualize reasons for concern, which aggregate climate-change-related impacts and risks to various systems and sectors. These burning embers use colour transitions to show changes in the assessed level of risk to humans and ecosystems as a function of global mean temperature. In this Review, we outline the history and evolution of the burning embers and associated reasons for concern framework, focusing on the methodological approaches and advances. While the assessment framework and figure design have been broadly retained over time, refinements in methodology have occurred, including the consideration of different risks, use of confidence statements, more formalized protocols and standardized metrics. Comparison across reports reveals that the risk level at a given temperature has generally increased with each assessment cycle, reflecting accumulating scientific evidence. For future assessments, an explicit, transparent and systematic process of expert elicitation is needed to enhance comparability, quality and credibility of burning embers