Evaluating the impact of watershed development and climate change on stream ecosystems: A Bayesian network modeling approach

Ecosystem-based management approaches for watershed conservation and geosustainability

When contributors' goals and legislative and political structures vary, as they often do in the case of worldwide fish populations, it becomes more challenging to implement ethical fishing tactics. Canada, the United States, and Mexico all fish from Pacific regions anchovies in the California Modern. Climate-driven numbers and geographic dynamics may pollute the waters of collaborative aquaculture and lead to overloading. This research expands upon prior works using a game theoretic model of Tran's boundary sardine fisheries in different climatic conditions to account for ecological links. More significant economic advantages accrue from cooperation fishing tactics that consider the mackerel's role as feed for other species in the natural system, as opposed to plans that merely take note of the worth of mackerel harvests to a particular fishing nation. The maximum environmental benefit is obtained at a fishery rate for sardines barely less than the sardine Fishery Management Safe Yield. Ecological-based control of fisheries can increase sustainability and profits, but only if investors and policy makers consider the ecology in business-applicable models. Understanding and adapting to the fast alterations in habitat distributions due to climate change and designing ways to achieve viable and lucrative fishery amidst altering environments will necessitate an increased emphasis on ecosystem-based governance.

Coupling hydrological, habitat and water supply indicators to improve the management of environmental flows

Highly regulated basins have traditionally required management practices to mitigate the negative environmental impacts and ensure human well-being. This paper proposes and assesses environmental and water supply deficit indicators to assist in the management of environmental flows (e-flows). For that, a water allocation model is applied, and hydrological alteration, habitat alteration and water supply indicators are quantified, normalized and integrated into a general basin management indicator. This basin management indicator is analyzed for four management approaches and seven e-flow scenarios in the Júcar River Basin (eastern Spain). Hydrological alteration indicators show a less pronounced alteration in the river sections located upstream of the basin while a higher alteration in the downstream sections. As for the habitat indicators, they experience an improvement compared to the natural regime. Based on the values of the basin management indicator, the best e-flow scenario to adopt in the Júcar River Basin is selected. The indicators proposed in this work are useful for supporting decision-making regarding the planning and management of e-flows in regulated river basins worldwide.

Nutrient reduction mitigated the expansion of cyanobacterial blooms caused by climate change in Lake Taihu according to Bayesian network models

Although nutrient reduction has been used for lake eutrophication mitigation worldwide, the use of this practice alone has been shown to be less effective in combatting cyanobacterial blooms, primarily because of climate change. In addition, quantifying the climate change contribution to cyanobacterial blooms is difficult, further complicating efforts to set nutrient reduction goals for mitigating blooms in freshwater lakes. This study employed a continuous variable Bayesian modeling framework to develop a model to predict spring cyanobacterial bloom areas and frequencies (the responses) using nutrient levels and climatic factors as predictors. Our results suggested that both spring climatic factors (e.g., increasing temperature and decreasing wind speed) and nutrients (e.g., total phosphorus) played vital roles in spring blooms in Lake Taihu, with climatic factors being the primary drivers for both bloom areas and frequencies. Climate change in spring had a 90% probability of increasing the bloom area from 35 km² to 180 km² during our study period, while nutrient reduction limited the bloom area to 170 km², which helped mitigate expansion of cyanobacterial blooms. For lake management, to ensure a 90% probability of the mean spring bloom areas remaining under 154 km² (the 75th percentile of the bloom areas in spring), the total phosphorus should be maintained below 0.073 mg·L^-1 under current climatic conditions, which is a 46.3% reduction from the current level. Our modeling approach is an effective method for deriving dynamic nutrient thresholds for lake management under different climatic scenarios and management goals.

Optimization and multi-uncertainty analysis of best management practices at the watershed scale: A reliability-level based bayesian network approach

Best management practices (BMPs) have been widely adopted to mitigate diffuse source pollutants, and the simulated processes of its pollutant reduction effectiveness suffer from manifold uncertainties, such as watershed model parameters and climate change. We presented a novel Bayesian modeling framework for BMPs planning, integrating process-based watershed modeling and Bayesian optimization algorithm to reveal the impact of multiple uncertainties. The proposed framework was applied to a BMPs planning case study in the Erhai watershed, the seventh-largest freshwater lake in China. Firstly, priority management areas (PMAs) were identified for BMPs siting using a simulation-optimization approach. Bayesian networks were subsequently embedded to reveal the multiple uncertainty sources in the optimal planning and the reliability level (RL) is introduced to represent the probability to meet the water quality target with BMPs implementation. The results suggest that E_NS of discharge and nutrients concentration simulation by LSPC are both greater than 0.5, which displays satisfactory performance. The identified PMAs account for 0.8% of the total watershed areas while contribute to more than 15% of nutrient loadings reduction. The analysis of multiple uncertainty sources reveals that precipitation is the most influential source of uncertainties in BMP effectiveness. The construction of hedgerows plays an important role in the nutrient reduction. With the improvement of the reliability levels, the cost increases sharply, indicating that the implementation of BMPs has a marginal utility. The study addressed the urgent need for effective and efficient BMPs planning by identifying PMAs and addressing multi-source uncertainties.

Assessing impacts of global climate change on water and food security in the black soil region of Northeast China using an improved SWAT-CO2 model

Future climate change may have substantial impacts on both water resources and food security in China's black soil region. The Liao River Basin (LRB; 220,000 km²) is representative of the main black soil area, making it ideal for studying climate change effects on black soil. In this study, the Soil and Water Assessment Tool (SWAT) model was first initialized for the LRB. Actual evapotranspiration (ET_a) values calculated using the Surface Energy Balance System (SEBS) model and city-level corn (Zea mays L.) yields were then used to calibrate the SWAT model. Finally, the SWAT model was modified to accept dynamic CO₂ input and output crop transpiration, soil evaporation, and canopy interception separately to explore the impacts of future climate change on ET related variables and crop water productivity (CWP) in the LRB. Simulation scenario design included 22 General Circulation Models (GCMs) and 4 Shared Socioeconomic Pathways (SSPs) scenarios from the latest Coupled Model Intercomparison Project 6 (CMIP6) for two 30-year periods of 2041-2070 and 2071-2100. The predicted results showed a significant (P < 0.05) increase in air temperatures and precipitation in the LRB. In contrast, solar radiation decreased significantly and was most reduced for the SSP3-7.0 scenario. Reference evapotranspiration (ET_o), ET_a, and soil evaporation significantly increased in future scenarios, while canopy interception and crop transpiration showed significant reductions, particularly under the 2071-2100 SSP5-8.5 scenario. Overall, corn yield elevated considerably (P < 0.05) with the largest increase for the SSP5-8.5 scenario during 2071-2100. However, the SSP3-7.0 scenario indicated a significant decline in yield. Future changes in CWP were similar to those for corn yield, with significant increases in the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios. These findings suggested future climate change may have a positive impact on corn production in the black soil region of the LRB.