Global Change Can Make Coastal Eutrophication Control in China More Difficult

Fast socio-economic development in agriculture and urbanization resulted in increasing nutrient export by rivers, causing coastal eutrophication in China. In addition, climate change may affect hydrology, and as a result, nutrient flows from land to sea. This study aims at a better understanding of how future socio-economic and climatic changes may affect coastal eutrophication in China. We modeled river export of total dissolved nitrogen (TDN) and phosphorus (TDP) in 2050 for six scenarios combining socio-economic pathways (SSPs) and Representative Concentration Pathways (RCPs). We used the newly developed MARINA 2.0 (Model to Assess River Inputs of Nutrients to seAs) model. We found that global change can make coastal eutrophication control in China more difficult. In 2050 coastal waters may be considerably more polluted or considerably cleaner than today depending on the SSP-RCP scenarios. By 2050, river export of TDN and TDP is 52% and 56% higher than in 2012, respectively, in SSP3-RCP8.5 (assuming large challenges for sustainable socio-economic development, and severe climate change). In contrast, river export of nutrients could be 56% (TDN) and 85% (TDP) lower in 2050 than in 2012 in SSP1-RCP2.6 (assuming sustainable socio-economic development, and low climate change). Climate change alone may increase river export of nutrients considerably through hydrology: We calculate 24% higher river export of TDN and 16% higher TDP for the SSP2 scenario assuming severe climate change compared to the same scenario with low climate change (SSP2-RCP8.5 vs. SSP2-RCP2.6). Policies and relevant technologies combining improved nutrient management and climate mitigation may help to improve water quality in rivers and coastal waters of China.</p

Recent advancement in water quality indicators for eutrophication in global freshwater lakes

Eutrophication is a major global concern in lakes, caused by excessive nutrient loadings (nitrogen and phosphorus) from human activities and likely exacerbated by climate change. Present use of indicators to monitor and assess lake eutrophication is restricted to water quality constituents (e.g. total phosphorus, total nitrogen) and does not necessarily represent global environmental changes and the anthropogenic influences within the lake's drainage basin. Nutrients interact in multiple ways with climate, basin conditions (e.g. socio-economic development, point-source, diffuse source pollutants), and lake systems. It is therefore essential to account for complex feedback mechanisms and non-linear interactions that exist between nutrients and lake ecosystems in eutrophication assessments. However, the lack of a set of water quality indicators that represent a holistic understanding of lake eutrophication challenges such assessments, in addition to the limited water quality monitoring data available. In this review, we synthesize the main indicators of eutrophication for global freshwater lake basins that not only include the water quality constituents but also the sources, biogeochemical pathways and responses of nutrient emissions. We develop a new causal network (i.e. multiple links of indicators) using the DPSIR (drivers-pressure-state-impact-response) framework that highlights complex interrelationships among the indicators and provides a holistic perspective of eutrophication dynamics in freshwater lake basins. We further review the 30 key indicators of drivers and pressures using seven cross-cutting themes: (i) hydro-climatology, (ii) socio-economy, (iii) land use, (iv) lake characteristics, (v) crop farming and livestock, (vi) hydrology and water management, and (vii) fishing and aquaculture. This study indicates a need for more comprehensive indicators that represent the complex mechanisms of eutrophication in lake systems, to guide the global expansion of water quality monitoring networks, and support integrated assessments to manage eutrophication. Finally, the indicators proposed in this study can be used by managers and decision-makers to monitor water quality and set realistic targets for sustainable water quality management to achieve clean water for all, in line with Sustainable Development Goal 6

Modeling water quality in the Anthropocene : directions for the next-generation aquatic ecosystem models

“Everything changes and nothing stands still” (Heraclitus). Here we review three major improvements to freshwater aquatic ecosystem models — and ecological models in general — as water quality scenario analysis tools towards a sustainable future. To tackle the rapid and deeply connected dynamics characteristic of the Anthropocene, we argue for the inclusion of eco-evolutionary, novel ecosystem and social-ecological dynamics. These dynamics arise from adaptive responses in organisms and ecosystems to global environmental change and act at different integration levels and different time scales. We provide reasons and means to incorporate each improvement into aquatic ecosystem models. Throughout this study we refer to Lake Victoria as a microcosm of the evolving novel social-ecological systems of the Anthropocene. The Lake Victoria case clearly shows how interlinked eco-evolutionary, novel ecosystem and social-ecological dynamics are, and demonstrates the need for transdisciplinary research approaches towards global sustainability. Highlights • We present a research agenda to enhance water quality modeling in the Anthropocene. • We review adaptive responses in organisms and ecosystems to global environmental change. • We focus on eco-evolutionary, novel ecosystem and social-ecological dynamics. • These dynamics act at different integration levels and different time scales. • Lake Victoria is an iconic example of an evolving novel social-ecological system

River export of nutrients to the coastal waters of China: the MARINA model to assess sources, effects and solutions

Rivers export increasing amounts of nitrogen (N) and phosphorus (P) to the coastal waters of China. This causes eutrophication problems that can damage living organisms when oxygen levels drop and threaten human health through toxic algae. We know that these problems result from human activities on land such as agriculture and urbanization. However, the relative importance of these human activities for river export of nutrients to Chinese seas is not well studied. There are two important issues that need further investigation: the relative importance of upstream pollution on downstream impacts and the relative importance of typical sources of nutrients in Chinese rivers that are often ignored in existing modeling studies. My PhD thesis, therefore, aims to better understand trends in river export of nutrients to the coastal waters of China by source from sub-basins, and the associated coastal eutrophication. To this end, I developed the MARINA model: Model to Assess River Inputs of Nutrients to seAs. For this, I used the existing Global NEWS-2 model (Nutrient Export from WaterSheds) as a starting point. I formulated five sub-objectives to achieve the main objective: To analyze the original Global NEWS-2 model for river export of nutrients and the associated coastal eutrophication (Chapter 2); To develop a sub-basin scale modeling approach to account for impacts of upstream human activities on downstream water pollution, taking the Pearl River as an example (Chapter 3); To quantify the relative share of manure point sources to nutrient inputs to rivers at the sub-basin scale (Chapter 4); To quantify the relative share of sources to river export of nutrients at the sub-basin scale (Chapter 5); To explore optimistic futures to reduce river export of nutrients and coastal eutrophication in China (Chapter 6). The study area includes rivers draining roughly 40% of China. This includes the most densely populated areas, and areas with intensive economic activities. The rivers include the Yangtze (Changjiang), Yellow (Huanghe), Pearl, Huai, Hai and Liao. In the MARINA model, the drainage areas of the large Yangtze, Yellow and Pearl rivers are divided into up-, middle- and downstream sub-basins. The principle of the sub-basin approach of MARINA is that nutrients from human activities are transported by tributaries to outlets of sub-basins and then to the river mouth (coastal waters) through the main channel. The model takes into account nutrients that are partly lost or retained during transport towards the river mouth. The model quantifies river export of nutrients by source from sub-basins for 1970, 2000 and 2050. The main six findings of the MARINA results for China are: Finding 1: Dissolved N and P export by Chinese rivers increased by a factor of 2-8 between 1970 and 2000; Finding 2: The potential for coastal eutrophication was low in 1970 and high in 2000 in China; Finding 3: Most dissolved N and P in Chinese seas is from middlestream and downstream human activities; Finding 4: Manure point sources are responsible for 20-80% of dissolved N and P in Chinese rivers; Finding 5: In the future, river export of nutrients may increase in the Global Orchestration (GO) scenario of the Millennium Ecosystem Assessment. Current policy plans (CP scenario) may not sufficient to avoid this increase; Finding 6: In optimistic scenarios (OPT-1 and OPT-2), the potential for coastal eutrophication is low in 2050, mainly as a result of assumed full implementation of: (1) high recycling rates of animal manure (OPT-1 and OPT-2), and (2) high efficiencies of nutrient removal in sewage systems (OPT-2, see Figure 1). Figure 1. Illustration of future scenarios for coastal water quality in China. GO is Global Orchestration of the Millennium Ecosystem Assessment and assumes environmental actions that are either absent or ineffective in reducing water pollution. CP is based on GO, but incorporates the “Zero Growth in Synthetic Fertilizers after 2020” policy. OPT-1 and OP-2 are optimistic scenarios that assume high nutrient use efficiencies in agriculture (OPT-1, OPT-2) and sewage (OPT-2). My PhD thesis reveals novel insights for effective environmental policies in China. It shows the importance of manure point sources in water pollution by nutrients. Clearly, managing this source will likely reduce coastal eutrophication in the future. Furthermore, the implementation of advanced technologies is essential when dealing with urban pollution. My PhD thesis may also be useful for other world regions with similar environmental problems as in China. The new, sub-basin scale MARINA model is rather transparent and thus can be applied to other large, data-poor basins that may benefit from the allocation of effective management options. With this I hope to contribute to future availability of sufficiently clean water for next generations, not only in China, but also in other world regions

The future of the Black Sea : More pollution in over half of the rivers

The population in the Black Sea region is expected to decline in the future. However, a better understanding of how river pollution is affected by declining trends in population and increasing trends in economic developments and urbanization is needed. This study aims to quantify future trends in point-source emissions of nutrients, microplastics, Cryptosporidium, and triclosan to 107 rivers draining into the Black Sea. We apply a multi-pollutant model for 2010, 2050, and 2100. In the future, over half of the rivers will be more polluted than in 2010. The population in 74 sub-basins may drop by over 25% in our economic scenario with poor wastewater treatment. Over two-thirds of the people will live in cities and the economy may grow 9-fold in the region. Advanced wastewater treatment could minimize trade-offs between economy and pollution: our Sustainability scenario projects a 68–98% decline in point-source pollution by 2100. Making this future reality will require coordinated international efforts

More river pollution from untreated urban waste due to the Russian-Ukrainian war: a perspective view

Since 24 February 2022, the Russian-Ukrainian war has impacted Ukrainian water resources including river pollution. In this perspective paper, our proposition is that the Russian-Ukrainian war causes likely more river pollution with untreated urban waste compared to the pre-war period. In order to check this assumption, we synthesize the current knowledge with a focus on the Dnipro Basin, containing 80% of the national water resources. Our synthesis reveals three main arguments. First, water-related infrastructures that were damaged as a result of the Russian-Ukrainian war are the important causes of pollutant release to water systems. These infrastructure damages are estimated, on average, for rural (30% of irrigation systems) and urban (35–40% of treatment plants and sewage connections) areas or both (40–90% of bridges and dams). Second, water pollution sources tend to change towards direct inputs of untreated urban waste with multiple pollutants compared to the pre-war period. Third, our illustrative example for nutrients, a painkiller, an antibacterial agent, and microplastics from urban waste showed an increase of 2–34% in their loadings into the Dnipro River due to damaged sewage pipes and wastewater treatment plants in 2022. In addition, 20–62% of those pollutants are from untreated urban waste (point sources). We propose a framework for future steps including visualizing (V) and integrating (I) the impacts into tools for quantification as well as translating (T) those quantified insights into actionable strategies and assessing (A) their feasibilities for pollution reduction. The Russian-Ukrainian war damaged 30–90% of water infrastructures in the Dnipro BasinRiver pollution sources tend to change towards untreated urban waste compared to the pre-war periodRiver pollution is estimated to increase by 2–34% in the Dnipro Basin due to damaged sewage and treatmentUntreated urban waste is responsible for 20–62% of pollutants in rivers of the Dnipro BasinThe VITA framework is proposed for actionable pollution reduction strategies The Russian-Ukrainian war damaged 30–90% of water infrastructures in the Dnipro Basin River pollution sources tend to change towards untreated urban waste compared to the pre-war period River pollution is estimated to increase by 2–34% in the Dnipro Basin due to damaged sewage and treatment Untreated urban waste is responsible for 20–62% of pollutants in rivers of the Dnipro Basin The VITA framework is proposed for actionable pollution reduction strategies</p