The biodiversity loss due to human activities is occurring at an alarming rate and there is an urgent need to reverse biodiversity decline. No net loss is widely used in environmental impact assessments and serves as an important approach to advancing global biodiversity conservation goals. We systematically reviewed the concept, approach, and effectiveness of no net loss of biodiversity. The early stage of no net loss focused on wetlands, gradually shifting to biodiversity. No net loss of biodiversity is defined as compensating for biodiversity loss caused by human activities, to ensure that the overall biodiversity will not suffer from net loss. Mitigation hierarchy is a recognized systematic approach for achieving no net loss of biodiversity, with avoidance and minimization as preventive measures and restoration and offset as remedial measures. Firstly, negative impacts should be avoided as much as possible. Secondly, if impacts are unavoidable, they should be minimized. Thirdly, the affected area should be restored. Finally, all remaining impacts should be offset. Existing research focuses mostly on biodiversity offset, but it is urgent to move towards effective combinations of mitigation hierarchy to achieve no net loss. Effectiveness evaluation of no net loss of biodiversity has received increasing attention in recent years, and evaluation approaches include statistical matching and regression models. The determination criteria largely influence effectiveness evaluation and are mainly categorized into fixed and dynamic reference baselines, but counterfactual scenarios determination and biodiversity measurement remain challenging. Evidence on the effectiveness of no net loss policies remains scarce, mainly because of unreliable measurement approaches and lack of data to assess whether no net loss is achieved. Future research on no net loss of biodiversity needs to focus on the topics such as the synergistic conservation between diversity and endemism, as well as uncertainty about the achievement of goals, temporal trade-offs of mitigation hierarchy measures, and spatial ranges in achieving no net loss.

Urbanization and land development drive large-scale land cover changes, posing significant threats to biodiversity in China. To assess ecological risks and guide mitigation strategies, it is crucial to quantify the biodiversity impacts of urban land expansion. Using the countryside species-area relationship, we estimated regional species loss for plants, mammals, birds, reptiles and amphibians as a consequence of land occupation from 2020 to 2100 under three scenarios: the sustainable pathway (SSP1), the middle pathway (SSP2), and the fossil-fuelled development pathway (SSP5). We also developed new regional characterization factors (CFs) for 31 provincial-level regions (hereafter provinces) in China and six land cover types. Our findings reveal the projected provincial diversity losses ranging from 0.001% to 0.449% for plants, 0.0005% to 0.523% for mammals, 0.001% to 3.431% for birds, 0.001% to 2.365% for reptiles, and 0.001% to 3.924% for amphibians. Regions such as Beijing, Tianjin, Shanghai, and coastal provinces are expected to experience higher potential terrestrial biodiversity loss compared to other areas. The largest terrestrial biodiversity loss is attributed to the conversion of croplands to urban construction lands, followed by the conversion of moderately utilized forests. The aggregated CFs, ranging from 1.10×10^-9 to 4.50×10^-7 PDF/ha, enable the estimation of regional terrestrial biodiversity impacts from future urban land occupation. These regional CFs show significant variations in biodiversity loss across land cover types and provinces, underscoring the importance of regionalized assessments of land use impacts on biodiversity.

Ecosystem quality is to the overall state of an ecosystem within a specific spatial and temporal context, serving as an indicator to diagnose whether the ecosystem remains healthy under human activities and environmental pressures. The combined effects of climate change and a series of ecological restoration projects have led to substantial changes in the condition of ecosystems across China. However, current knowledge of the spatiotemporal evolution of China's ecosystem patterns remains limited, necessitating a systematic assessment of ecosystem quality to support ecological civilization construction and sustainable ecosystem management. Limitations in ecosystem quality assessment frameworks and biases in ecosystem service function simulations are the primary sources of uncertainty in quality evaluations. To address these issues, this study developed an ecosystem quality assessment system based on the ecosystem service evaluation process model (CEVSA-ES) and the "Structure-Function-Stability-Stress" framework, and we further analyzed the spatiotemporal patterns and driving factors of terrestrial ecosystem quality in China from 2003 to 2020. The results indicate that ecosystem quality in China generally exhibits a spatial distribution pattern of being higher in the south and east and lower in the north and west. Over the past two decades, ecosystem quality in China has significantly improved, with an average annual increase of 0.28% (p < 0.01). Significant differences were observed in the long-term trends of different components of ecosystem quality, with ecosystem services, stability, and structure showing considerable improvements (p < 0.01). However, ecological pressure resulting from human activities has continued to intensify. Relative importance analysis revealed that increased forest coverage contributed 53% to the improvement in ecosystem quality by enhancing ecosystem services and structure, while increased precipitation accounted for 33% of the improvement by boosting ecosystem services and stability. This study provides a deeper understanding of the dynamic processes underlying changes in ecosystem quality and offers valuable insights for the conservation and sustainable management of ecosystems in China.

The Loess Plateau, serving as a significant ecological barrier in the central and western regions of China, is of paramount importance for safeguarding the ecological security of the country. Elucidating the influence of human activities on the trade-offs/synergies of ecosystem services in the Loess Plateau is conducive to promoting ecological protection and high-quality development in the Yellow River Basin. This study employs methods such as the InVEST model and geographically weighted regression to examine the spatio-temporal patterns of human activities and key ecosystem services, including food production, soil retention, water yield, and carbon sequestration, in the Loess Plateau from 2000 to 2020, and explores the impact of human activities at both grid and county scales on the trade-offs/synergies of ecosystem services. The results indicate that: (1) Human activities in the study area have been continuously intensifying from 2000 to 2020, presenting a distribution feature of "higher in the southeast and lower in the northwest". (2) Food production, soil retention amount, and water yield all exhibit an increasing trend, while the change in carbon sequestration is relatively stable, generally showing a distribution pattern of "higher in the southeast and lower in the northwest". (3) Among the six ecosystem services in the plateau from 2000 to 2020, the synergistic relationships prevail at different scales. Compared with the grid scale, the proportion of synergistic relationships of ecosystem services at the county scale is higher. (4) Human activities mainly have a negative impact on the six ecosystem services, and they will cause the relationship between ecosystem services to shift from synergy to trade-off. (5) As the scale expands, the degree of human activity concentration intensifies, the dispersion degree of ecosystem service distribution increases, and the ecosystem service pairs show a trend of first dispersion and then concentration. The dispersion degree of the trade-off/synergy impact of human activities on ecosystem services also increases. In the future, targeted regional control and management policies should be implemented based on the spatial differentiation of the intensity of human activities to enhance the effectiveness of ecological protection.

The Tibetan Plateau, as the Asian Water Tower, is a crucial ecological security barrier for China. It plays a vital role in sustaining water resources for downstream and in supporting the national carbon neutrality strategy. However, the trade-offs between ecosystem carbon-gain and water-loss in this region, especially in the context of climate change and land surface changes, remain poorly understood. Focusing on the relatively well-vegetated headwater region in the eastern Tibetan Plateau (HRETP), this study employs a water-carbon coupled model, PML_V2, to investigate the spatiotemporal variations of the ecosystem water use efficiency (WUE, i.e., ratio of gross primary productivity to evapotranspiration) and the possible drivers. The PML_V2 model was calibrated using observations from nine eddy-covariance flux stations, thereby improving its accuracy in simulating gross primary productivity and evapotranspiration in the HRETP. The results suggest that the multi-year mean WUE during the growing season in HRETP is 1.26 g C kg^-1 H₂O. From 1982 to 2016, the HRETP-averaged WUE increased significantly by 11.9%, at a rate of 4.3×10^-3 g C kg^-1 H₂O a^-1 (p < 0.001), suggesting a notable rise in gross primary productivity under the same water loss condition. Based on the multi-scenario modeling of PML_V2, it is found that the leaf area index (LAI) dominated the temporal changes in the HRETP-averaged WUE with a relative contribution of 38.3%, suggesting that vegetation change was the primary driver WUE increase over the past 35 years. Atmospheric CO₂ concentration and temperature were secondary drivers, with their opposing effects nearly canceling each other out. Spatially, LAI dominated WUE changes in most parts of HRETP, which accounts for 65% of the total study area. While temperature and precipitation were the dominant factors influencing WUE in the eastern and western marginal regions of the HRETP, respectively, their overall impacts on the regional averaged WUE appeared comparatively weak due to their smaller spatial coverage. Our results provide valuable scientific insights for the water resource and ecological security barrier protection in the Asian Water Tower.

Glaciers provide indispensable resources and services for ecological environment, human well-being and social and economic development in arid areas. Quantitative evaluation of ecological service value of glaciers is an important basis for rational utilization and protection of glacier resources and regional sustainable development. Based on Landsat remote sensing image data, meteorological data, and relevant socio-economic data, this study constructed a glacier service value assessment system to quantitatively evaluate the glacier service value of the Chinese Altai Mountains from 2000 to 2020. Utilizing the climate models from the Sixth Coupled Model Intercomparison Project (CMIP6), it explored the changes in glacier service value under three future climate scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5) from 2020 to 2100.The main conclusions were as follows: (1) In 2020, the glacier service value of the Chinese Altai Mountains was 3.623 billion yuan, with climate regulation being the most significant service of the glaciers in the area, followed by runoff regulation and freshwater supply, accounting for 88.06%, 8.70%, and 2.44% of the total service value, respectively. (2) From 2000 to 2020, the glacier service value of the Chinese Altai Mountains showed a decreasing trend, with a total decrease of 4.195 billion yuan, and a service value change rate of -53.66%. The glacier service value in each basin and county was also in a state of reduction. (3) Under the three scenarios of SSP1-2.6, SSP2-4.5, and SSP5-8.5, the glacier service value shows a downward trend after 2030. By 2100, the glacier service values under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios will decrease to 1.199 billion, 1.007 billion, and 652 million yuan, respectively, with cumulative glacial service value losses of 2.423 billion, 2.616 billion, and 2.971 billion yuan, respectively. The study reveals the impact of climate change on the glacier service value, providing important reference for the protection and sustainable development of glaciers in the Chinese Altai Mountains.

The Tarim River Basin, a typical arid-zone river system, has yet to have the influence of its dissolved organic matter (DOM) sources and composition on carbon cycling emissions fully elucidated. We aimed to investigate the spatial and temporal heterogeneity of dissolved organic matter (DOM) and carbon (CO₂ and CH₄) emissions in the river system of the Tarim River Basin. Through the analysis of 101 sampling sites across seven major water systems in the Tarim River Basin during 2023 and 2024, this study employed the headspace equilibrium method to determine the concentrations (cCO₂, cCH₄) and fluxes (FCO₂, FCH₄) of CO₂ and CH₄ in surface water. DOM sources and composition were characterized using spectral absorption, three-dimensional fluorescence, and parallel factor analysis (PARAFAC). The results revealed that DOM in the eastern Kaidu-Kongque River exhibited high aromaticity (mean a₂₅₄: (16.2±12.6) m^-1) and strong humification characteristics (mean HIX: 2.1±0.7), closely associated with urban sewage and agricultural non-point source inputs. In contrast, glacier-fed rivers in the western region showed lower humification levels but relatively high nutrient concentrations. The results of correlation, partial least squares and random forest analyses showed that DOM-related parameters explained cCO₂ (R²=0.42, p<0.001) and cCH₄ (p<0.001) variations to some extent. Comparison with global-scale rivers revealed that FCO₂ in the Tarim River Basin ((203.5±215.7) mmol m^-2 d^-1) was higher than that in other arid zone rivers (20.8-44.6 mmol m^-2 d^-1) but lower than that in non-arid zone rivers (186.0-565.3 mmol m^-2 d^-1), whereas FCH₄ ((1.7±10.2) mmol m^-2 d^-1) was roughly comparable to that of temperate rivers (0.8-1.7 mmol m^-2 d^-1), highlighting the special carbon emission characteristics of arid zone rivers under the superposition of high summer temperatures and human activities. This study clarified the carbon emission patterns of rivers in the Tarim River Basin and their potential driving mechanisms, which filled the gap in the study of river carbon emissions in the arid zone, and provided data support for the regional water-carbon interactions, as well as scientific support for ecological conservation and carbon management in the basin.