Anthropocene最新文献

The current paper is a space-time analysis of agricultural land transitions in the Romanian Plain, which has been significantly impacted during the past century by the fundamental structural and functional transformations. Five maps, derived from historical cartographic materials and the recent CORINE Land Cover databases, were spatially analysed using a transition matrix procedure. The aim was to identify and measure the magnitude of the main land use/cover change flows related to agricultural lands. Furthermore, several underlying factors of the spatial and functional transformations have been discussed so as to understand the evolution of the historical agricultural lands over time. The results show that the most significant changes occurred between 1912 and 1970, when 38 % of the Romanian Plain’s surface underwent transformations, with notable regional differences. The analysis of the change flows in relation to the underlying factors was instrumental in explaining the land processes, an approach that can be used to understand future landscape transformations.

Lake ecosystems in northeastern (NE) China are sensitive to global environmental change, and are currently under threats of eutrophication and hypolimnetic anoxia. However, the lack of long-term records of lake production and anoxia in this region makes it difficult to discriminate the impacts of recent anthropogenic activity on lake ecosystems from natural ecosystem variability. This study investigates varved sediments from remote maar Lake Xiaolongwan, NE China and reconstructs high-resolution changes in lake primary production, anoxia, nutrient cycling and catchment processes over the past 1500 years using hyperspectral imaging inferred sedimentary total chlorophyll-a and bacteriopheophytin-a (Bphe-a), combined with sedimentary iron and phosphorus fractions data. Results show that, prior to discernible human impacts in this area from ∼600 CE to 1900 CE, lake primary production was higher during warm periods and reduced during cold periods. Bphe-a records show that hypolimnetic anoxia persisted regardless of temperature variability. Cluster analysis suggests that lake algal communities and biogeochemical conditions in the twentieth-century warm period are unprecedented and significantly different from any other time over the past 1500 years. This phenomenon mostly results from global warming and stronger local catchment disturbance in the early 1900s, combined with atmospheric pollution after the 1950s. Human-driven climate warming has caused stronger seasonal mixing (due to shortened ice-cover duration) and overall better oxygenation in the lake. This study demonstrates clear anthropogenic impacts to lake ecosytems in a relatively pristine region in NE China. We anticipate that our findings will have implications for understanding the status of aquatic ecosystems in NE China under future interacting stressors of anthropogenic climate warming and pollution.

Sediment accumulation in reservoirs is frequently a problem, impelling dam managers to implement strategies such as drawdown flushing to limit siltation. Drawdown and other sediment removal methods may induce riverbed clogging downstream of dams, especially in river sections where water is diverted, thereby reducing transport capacity. In this study, we investigate the effects of drawdown flushing downstream of the Plan d’Arem run-of-the-river dam (Upper Garonne, Spain – France border) using an adaptive inter-site comparison strategy to consider a range of spatial and temporal conditions, which allow us to separate the effects of dam storage and flushing from other potential factors. Drawdown flushing has been undertaken three times during the study period over a short span of time (2 months). We couple bed material sampling, which provides direct information on bed composition, with airborne infrared thermal imaging to better interpret whether fine sediment interstitial storage within the bed is associated with clogging. We also measure bed surface grain size and bed mobility in order to investigate their potential role in controlling fine sediment dynamics. We identify surface grain size and water diversion as the main factors controlling fine sediment spatial distribution, with coarse-grained bed-surfaces and by-passing promoting fine sediment enrichment. As a result, sites located upstream and within the by-passed reached of the Plan d’Arem dam show higher fine sediment interstitial storage than sites downstream from the by-passed reach. Results from thermal imagery demonstrate such interstitial storage does not induce clogging effect. The reaches with the most important sediment storage host a high number of cool-water patches, indicating water exchanges with the hyporheic zone. Post-flushing bed composition indicates systematic export of fine sediments from the bed matrix at all sites after the first operation, afterwards fine levels remain low after the second and the third flushing. The low impact of dam flushing in term of clogging is interpreted by the fact that the interstitial material is very sandy.

The spread of invasive alien species is identified as one of the most important threats to freshwater ecosystems as they can modify their trophic structure, biomass and flows. The lower Saône River is one of the most biologically productive waterways in France. It has been in strong interaction with a wide range of human activities such as fisheries for at least three millennia. To implement an ecosystem based approach, an Ecopath static trophic model was used for the first time in this river to quantify the role of three invasive or expanding species over two contrasted periods (1988–1993 and 1994–2005). The parameters used in the model integrate on the one hand catch data from fishers (professional, amateur fishing gear users, and anglers), and on the other hand the available literature data on species biomass, diet and the expert assessments of scientists and managers. Species such as the filtering Asian clam Corbicula fluminea may explain the triggering of the ecosystem shift towards a functioning where summer phytoplankton blooms are rarer. In the high trophic levels, the great cormorant Phalacrocorax carbo appears to have low trophic impact while the development of a large population of European catfish Silurus glanis has a strong effect, maintaining important trophic flows in the ecosystem in substitution for the decrease in angling landings.

Floodplain lake ecosystems are hydrologically dynamic and biologically important. Their ecosystem functioning is complex due to the concurrent influence of multiple anthropogenic stressors. Paleolimnological studies focused on a single biotic proxy might lead to biased results, as multiple trophic levels may show different responses to the same driver. In this study, multiple proxies including chlorophyll and carotenoid pigments (indicators of phytoplankton) and chironomids (indicators of invertebrates) were analyzed in a ²¹⁰Pb dated sediment core from Luhu Lake (Yangtze floodplain, China). Using these indicators, we investigated how different trophic levels respond to external driving forces (i.e., hydrological alteration represented by K/Al ratios and nutrient influxes indicated by TP) in floodplain lakes. Sedimentary pigments showed that algal production increased in Luhu Lake after the 2000s. The chironomid community shifted from a fauna dominated by Microchironomus tener-type to an assemblage characterized by macrophyte-dwelling taxa (e.g., Tanytarsus, Paratanytarsus, Paratanytarsus penicillatus-type) after the 1970s. Finally, nutrient-tolerant taxa (e.g., Microchironomus tabarui-type) increased in abundance after the 1990s. Redundancy analysis and hierarchical partitioning analysis showed that the increases in algal production were mainly correlated with anthropogenic nutrient influxes, followed by hydrological alteration. In contrast, the transition in the chironomid communities were mainly associated with hydrological alteration, followed by food sources. Our study revealed asynchronous responses of phototrophs and benthic invertebrates to hydrological alteration, highlighting the necessity of analyzing multiple trophic levels to obtain a sophisticate understanding of long-term ecosystem evolution in lotic floodplain lakes which are influenced by multiple stressors. These findings will provide valuable information for the sustainable development, as well as the conservation and restoration of floodplain lakes.

As Arctic sea ice has rapidly declined, the navigational potential of the Arctic routes has greatly increased. Based on sea ice output from the First Institute Of Oceanography-Earth System Model version 2.1 (FIO-ESM v2.1) and the Arctic Transport Accessibility Model, this study investigates the future navigability of the Arctic routes for open-water ships (OW) without icebreaking capabilities and ships with different icebreaking capabilities, namely Polar Class 7 (PC7), Polar Class 6 (PC6), and Polar Class 3 (PC3). The results show that the simulations of FIO-ESM v2.1 adequately reproduce the changes in the navigability of the four types of ships in Arctic shipping routes over the past 40 years. The navigable area for the four ship types is projected to continue to expand in the future. Under the high emission scenario (Shared Socioeconomic Pathways 5–8.5, SSP585), the four ship types are projected to achieve full Arctic navigability in summer (September) by the end of the 21st century, and PC6 and PC3 ships are projected to achieve full Arctic navigability in winter (March). Under the high emission scenario, year-round navigability in the Northwest Passage is projected for PC3 and PC6 ships, and in the Northeast Passage is projected for all four types of ships. The impact of emission scenario on the navigability of the Arctic shipping routes varies with different ship types: the largest impact is for OW ships, followed by PC6 and PC7 ships, and the smallest impact is for PC3 ships. The impact of scenario is also larger in winter than in summer.

Our study contributes to the ongoing dialogue on the impact of climate and habitat changes on migratory bird species, particularly focusing on how these effects vary based on species’ habitat preferences. We used citizen science data for 22 African-Eurasian migratory bird species and categorized them into five groups based on habitat preferences, following the classification methodology of Atkinson et al. (2014). Using ensemble species distribution modeling (SDM), we projected changes in potentially suitable habitats across Africa from 2040 to 2100 under contrasting climate and land use scenarios. Our results indicate a differential impact of climate and land use changes on habitat suitability, with species preferring habitats with shrubs and trees being the most vulnerable. Conversely, other group species, such as open country-grassland and farmland birds could experience a significant increase in suitable habitat. We anticipate a profound change in habitat suitability, with the western part of South Africa becoming unsuitable for most species, while an increase in suitable habitat is expected in the Sahel. Bioclimatic rather than land use variables emerged as the primary drivers of these changes. The extent of change in habitat suitability will be strongly influenced by the Shared Socio-economic Pathways followed by human societies.