Land use management recommendations for reducing the risk of downstream flooding based on a land use change analysis and the concept of ecosystem-based disaster risk reduction

Groundwater quality evolution across China

China is facing a severe groundwater quality crisis amid economic development and climate change, yet the extent and trajectory of this crisis remain largely unknown. Here we developed a machine-learning model, incorporating natural and social-economic factors, to construct annual probabilistic maps of poor groundwater quality (PGQ, i.e., Class V based on the Chinese groundwater quality standard) across China from 1980 to 2100. Alarmingly, our findings indicate a concerning escalation in PGQ area ratio, rising from 17.3% in 1980 to 30.1% in 2000, and surging to 40.8% by 2020, adversely affecting 6.8%, 17.5%, and 36.0% of the Chinese population, respectively. The predominant drivers of this degradation were identified as agricultural discharge (contributing to 10.7% growth in PGQ area ratio), followed by groundwater exploitation (5.6%), industrial discharge (5.3%), domestic discharge (1.7%), climate change (0.5%), and land use change (-0.3%). By 2050, the PGQ area ratio could range from 37.9% to 48.3% under different socio-economic and climate scenarios. Our study highlights the urgent need for effective water resources management and conservation measures to mitigate the deteriorating trend of groundwater quality and address the challenges posed by socio-economic development and climate change, thereby safeguarding water security for China and the global community.

Assessing forest fragmentation due to land use changes from 1992 to 2023: A spatio-temporal analysis using remote sensing data

The increasing pressures of urban development and agricultural expansion have significant implications for land use and land cover (LULC) dynamics, particularly in ecologically sensitive regions like the Murree and Kotli Sattian tehsils of the Rawalpindi district in Pakistan. This study's primary objective is to assess spatial variations within each LULC category over three decades (1992-2023) using cross-tabulation in ArcGIS to identify changes in LULC and investigates into forest fragmentation analysis using the Landscape Fragmentation Tool (LFTv2.0) to classify forest into several classes such as patch, edge, perforated, small core, medium core, and large core. Utilizing remote sensing data from Landsat 5 and Landsat 9 satellites, the research focuses on the temporal dynamics in various land classes including Coniferous Forest (CF), Evergreen Forest (EF), Arable Land (AR), Buildup Area (BU), Barren Land (BA), Water (WA), and Grassland (GL). The Support Vector Machine (SVM) classifier and ArcGIS software were employed for image processing and classification, ensuring accuracy in categorizing different land types. Our results indicate a notable reduction in forested areas, with Coniferous Forest (CF) decreasing from 363.9 km2, constituting 45.0 % of the area in 1992, to 291.5 km2 (36.0 %) in 2023, representing a total decrease of 72.4 km2. Similarly, Evergreen Forests have also seen a significant reduction, from 177.9 km2 (22.0 %) in 1992 to 99.8 km2 (12.3 %) in 2023, a decrease of 78.1 km2. The study investigates into forest fragmentation analysis using the Landscape Fragmentation Tool (LFTv2.0), revealing an increase in fragmentation and a decrease in large core forests from 20.3 % of the total area in 1992 to 7.2 % in 2023. Additionally, the patch forest area increased from 2.4 % in 1992 to 5.9 % in 2023, indicating significant fragmentation. Transition matrices and a Sankey diagram illustrate the transitions between different LULC classes, providing a comprehensive view of the dynamics of land-use changes and their implications for ecosystem services. These findings highlight the critical need for robust conservation strategies and effective land management practices. The study contributes to the understanding of LULC dynamics and forest fragmentation in the Himalayan region of Pakistan, offering insights essential for future land management and policymaking in the face of rapid environmental changes.

Pathways of ecosystem-based disaster risk reduction: A global review of empirical evidence

Ecosystems provide valuable services in reducing the risks of disasters through various pathways, which are increasingly recognized as sustainable strategies for disaster management. However, there remains limited information on the underlying ecological processes of risk reduction. This paper addresses this gap by synthesizing ecological mechanisms and evaluating the 'level of evidence' and 'scale of use' through a review of 64 peer-reviewed research articles published between 2015 to 2022. These research articles covered nine types of disasters, predominantly floods (42.19 %), followed by urban heat waves (18.75 %), storm runoff (10.94 %), coastal erosion (9.38 %), tsunamis (4.69 %), and avalanches and landslides (6.25 % each). The level of evidence supporting ecological processes for disaster risk reduction is moderate, as is the 'scale of use'. Results show that there are a few studies describing the mechanism of ecosystem-mediated risk reduction and are mostly limited to the causal relationship. Empirical evidence demonstrates that forest and freshwater ecosystems buffer the risk of urban heat through processes such as transpiration, solar radiation interception, and evaporative cooling, while flood risks are mitigated by enhancing evapotranspiration, reducing water runoff time, and facilitating infiltration rates. Coastal erosion is reduced by dissipating wave energy and through beach nourishment, which facilitates ecological succession. The review underscores that hazard attenuation depends on factors such as forest type (e.g., species composition, age structure, and area), and landscape characteristics (e.g., matrix, composition and configuration). Moreover, the geographic scope of published research is largely confined to developed countries and the global north. Multidisciplinary research involving ecologists and disaster experts is imperative to address existing knowledge gaps and enhance the integration of ecosystem-based adaptation into disaster risk reduction strategies.

Ecological ditch technology and development prospect based on nature-based solutions: a review

The core of the concept of nature-based solutions (NBS) is ecological protection, which is the same direction as China's double-carbon goal and has attracted much attention in China. Ecological ditch sewage treatment technology has been widely used in controlling agricultural non-point source pollution because of its advantages of high pollutant removal efficiency and low energy consumption. Suppose the NBS concept of sustainable management, restoration, and ecological protection is integrated into the research and development and application of ecological ditch technology. In that case, it can not only improve the effective removal of pollutants, achieve the purpose of recycling water resources and nutrient elements, but also realize economic, environmental, and social benefits. This paper describes the ecosystem service functions provided by ecological ditches in detail, evaluates their economic values through literatures review, so as to raise people's awareness of natural resource conservation and realize the sustainable management of ecological ditches.

Resilient landscape pattern for reducing coastal flood susceptibility

Evaluating flood susceptibility, identifying flood-prone areas, and planning reasonable landscape patterns are important measures in promoting sustainable urban development and flood mitigation. To this end, this study evaluated the flood susceptibility using a neural network model depending on a flood inundation map created from satellite data from 2010 to 2020, and explanatory factors for flood inundation selected by Geodetector and regularized random forest. Subsequently, the landscape pattern of the coastal city was quantified based on the land cover, and key landscape pattern metrics for flood susceptibility were selected at patch and class levels using statistical approaches. Eventually, urban spatial planning strategies for flood management were proposed based on the ecological significance of key metrics. Taking Xiamen as a case study, the flood susceptibility map showed that flood-prone areas in Xiamen are mainly distributed along river banks and coastlines. Key landscape pattern metrics for flood susceptibility selected by statistical approaches showed that patch-level metrics account for more explanatory power than class-level metrics, and the classes of the landscape would affect the role of patch-level metrics. Overall, the division index of the forest, the connectance index of water, the number of core areas and the fractal dimension index of urban, and the Euclidean nearest-neighbor distance of urban and water are significantly positively related to flood susceptibility, while the core area and the proximity index of urban, the similarity index, the core area index, and the edge contrast index of the forest, and the contiguity index of forest, grass, farmland, and shrub negatively related with flood susceptibility. Based on these findings, intensive urban planning and integrative Nature-based Solutions networks should be considered as strategies for enhancing coastal flood resilience.

Characterising the spatiotemporal dynamics of drought and wet events in Australia

Global climate change has altered precipitation patterns and disrupted the characteristics of drought and rainfall events. Climate projections confirm that more frequent, intense, and extreme droughts and rainfall events will continue. However, knowledge around how drought and wet events move dynamically through space and time is limited, especially in the southern hemisphere. Australia is the driest inhabited continent, renowned as the land of droughts and flooding rains, but recent climate-driven changes to the severity of wildfires and floods have garnered global attention. Here we used S-TRACK, a novel method for spatial drought tracking, to build pathways for past drought and wet events in Australia to examine their spatiotemporal dynamics. Characteristics such as duration, severity, and intensity were obtained from these pathways, and modified Mann-Kendall tests and Sen's slope were used to detect significant trends in characteristics over time. Drought conditions in southern Australia have intensified, particularly in the southwest of Australia and Tasmania, while the north of the country is experiencing longer, more severe, and more intense wet conditions. We also found that the location of drought and wet hotspots has clearly shifted in response to precipitation changes since the 1970's. Finally, pathways for the most extreme events show peak severity is reached in the middle to late stages of pathways, and that the largest drought and wet areas of a pathway have moved further west in recent times. The findings in this study provide the necessary knowledge to improve preparedness for extreme precipitation events as they become more common and to inform predictions for agricultural output or the extent of other climate events such as wildfires and flooding.

An integrated approach of logistic-MCE-CA-Markov to predict the land use structure and their micro-spatial characteristics analysis in Wuhan metropolitan area, Central China

As human interference with the natural environment accelerates, land use has undergone great changes. However, to realize rational land development in the rural-urban ecotone, the micro-spatial (MS) unit is the best scale for the management and planning of sustainable land use. Taking Wuhan metropolitan area as research area, the integrated logistic-multi-criteria evaluation (MCE)-cellular automata (CA)-Markov model was used to simulate land use pattern for 2025. In addition, the 1 km×1 km, 2 km×2 km, 3 km×3 km, and 4 km×4 km and typical sample belt were built to reveal the spatial microcosmic expression of land use structure. The results showed that the kappa coefficient and figure of merit (FoM) were 88.01% and 26.86%, respectively, indicating the integration model has high prediction accuracy. In 2005-2025, the diversification of land use in the Wuhan metropolitan area will be generally above the medium level, and the types of land combinations will be relatively abundant. As human activities increase, the land use degree will show increases continuously, it will expand outward from Wuhan, and there is a positive correlation between cultivated land-rural residential land and urban land-cultivated land. The spatial distribution of land use structure presents regional scale characteristics, and different regions have micro-spatial scale dependence. The selection of MS scales based on local conditions can be a good way to reflect land use internal structure and provide a better reference for the compilation of regional land use optimization.

Exploring the Ecological Climate Effects Based on Five Land Use Types: A Case Study of the Huang-Huai-Hai River Basin in China

As one of the main driving forces for the change in surface energy balance, land use and cover change affects the ecological climate through different levels of biogeochemical and physical processes. However, many studies on the surface energy balance are conducted from the perspective of biogeochemistry, ignoring biogeochemical processes. By using core methods such as the surface energy balance algorithm and Mann-Kendall trend test, we analyzed the surface energy balance mechanism and ecological climate effects of five land use types in the Huang-Huai-Hai Basin in China. The results showed that: (1) the net radiation and latent heat flux in the five land use types increased significantly, and their highest values were located in cropland areas and urban expansion areas, respectively. (2) The influence of net radiation on surface energy absorption was greater than latent heat flux. This relationship was more obvious in land use types that were greatly influenced by human activities. (3) The net surface energy intake in the Huang-Huai-Hai River Basin showed a decreasing trend and decreased with the increase in human influence intensity, indicating that human activities weakened the positive trend in net surface energy intake and increased the warming effect. This study reveals the difference in energy budgets of different land use types under the influence of human activities. It is helpful for understanding how to formulate sustainable land management strategies, and it also provides a theoretical basis for judging the climate change trends and urban heat island effects in the Huang-Huai-Hai River Basin from a biogeophysical perspective.

Restoration recommendations for mitigating habitat fragmentation of a river corridor

Flow discharge and anthropogenic activities influence the composition and configuration of habitat patches in river ecosystems. Understanding the response of habitat landscapes and the corresponding fish habitat quality is crucial for river management. We investigated the reaction of fish habitat suitability and variant flow discharge performance in examining aquatic habitat patch fragmentation. The hydraulic simulation and fish habitat calculation were used to determine the flow characteristics, habitat conditions, and river landscapes. FRAGSTATS was applied to explore the composition and configuration of habitat patches. Cluster analysis and logistic regression were employed to compute the spatiotemporal variabilities of riverscape indices and establish the relationship between riverscape attributes and fish habitat quality. The results indicate that the changes in specific habitat features are associated with the riverscape indices of total edge (TE), mean nearest-neighbor distance (MNN), interspersion and juxtaposition index (IJI), mean patch size (MPS), and area-weighted mean patch fractal dimension (AWMPFD). The flow discharge is the key to determining habitat fragmentation in rivers, with natural barriers occurring at low flow. In contrast, weirs are anthropogenic obstacles that have significant adverse effects on the downstream corridor. A priority restoration activity to conserve river habitat is to create refuge pools during dry seasons by modifying channel morphology. The positive correlation between habitat suitability and MPS and the negative relationship between habitat suitability and AWMPFD highlight the patch size and shape complexity that are critical indices for pool creation. The prediction of the landscape attributes of the outcomes under different scenarios could support the decision-making in river management. The innovative integrated method presented in this study provides a solid foundation and supports the implementation of nature-based solutions for sustainable river management.