Anthropocene最新文献

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.

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.

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.

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.

Settler colonialism and active fire exclusion greatly eliminated recurrent fire from forests and grasslands in the United States. Pyrogenic carbon (PyC), a key legacy of fire and a stable form of carbon (C) in soils, has inadvertently been lost with the cessation of biomass burning. Using a simple simulation, we estimate that fire exclusion from grasslands over the last 125 years has resulted in a loss of 963–1,028 Tg of PyC, approximately equivalent to a 12% - 22% decline in the soil PyC reservoir. This loss of PyC from grassland ecosystems and the lack of introduction of fresh PyC has likely had a significant impact on soil health in the Great Plains. To rebuild this lost stable C pool and the associated ecosystem function of PyC, we recommend combining Indigenous Knowledge and western science to restore historical fire regimes to forests and grasslands and reintroduce PyC via biochar application to agricultural fields.

Our research aimed to evaluate, how urbanization affects lake ecosystems and Cladocera in particular. For this purpose, we chose a small urban lake with a well-documented history. Lake Velnezers (located in Riga, Latvia) is currently surrounded by apartment building complexes. Construction works around this lake started in the 1950s and continued up until the 1970s. To investigate how the transition from forested to agricultural and further urbanized land affected the lake ecosystem we took a sediment core that covers the time period from before 1875–2018. We evaluated ecological changes in the lake based on chemical and Cladocera species composition in sediment records and linked these changes to the historical information about alterations in the landscape around Velnezers. Our results show lake transitioned from oligotrophic to eutrophic conditions already before urbanization. The Lake ecosystem reacted to urbanization gradually, showing small changes in the beginning. However, in the 1980s lake experienced rapid deterioration in water quality – sediment records show an increase in heavy metal pollution, anoxia, and nutrient input. These stressors resulted in Cladocera functional group structure changes and loss of Cladocera species richness and diversity. Improvements in nature protection – such as wastewater management have reduced heavy metal and nutrient input into Lake Velnezers towards the present. However, previous deterioration, i.e. loss of species diversity and phosphorous legacy effect do not allow natural lake recovery under current conditions.

In Anthropocene, unbalances of the water cycle have created a severe threat to the supply of this crucial element for current and future generations. In addition, water quality degradation has been promoted by the land-use change from natural ecosystems to urbanized and industrialized areas, favoring the nutrient input into water bodies. In the last two decades, the San Roque reservoir (SRr), situated in central Argentina, has become hypereutrophic. In this work, we proposed an integrated study strategy that included a multiproxy examination of the reservoir sedimentary record and a study of land-use changes, in order to: 1) link land-use change to primary productivity of the SRr over the last 100 years; and 2) identify the processes involved in the SRr's environmental evolution prior and after urban expansion occurred by 1980 CE. Results allow to recognize two distinctive scenarios: a) Pre-urban scenario (1898–1983 CE) reflected by a dominance of allochthonous organic matter in the sedimentary record derived from the catchment's deforestation and, b) A transition towards increasing lake internal productivity (1984–2018 CE), resulting in a eutrophic state with cyanobacteria dominance due to catchment urban densification, particularly in the peri-lacustrine area. This work constitutes a novel tool by combining a paleolimnological approach with demographic analysis to accurately track the consequences of land use change on the water body and, in addition, provide the basis for modeling future scenarios.

Flood damage has increased worldwide in recent decades with a concomitant increased risk of flood-induced pollution. From the perspective of urban political ecology, we ask whether scientists acknowledge flood-induced pollution as a problem and if so how they address it. Using a mixed-methods approach, we analyse 30 semi-structured interviews with researchers in France and Quebec. Our results show that flood pollution can be framed not only in terms of its impact on the environment and our societies, but also as a social representation that varies with the spatial context. The diversity of flood-induced pollution, whether in terms of materiality, visibility, or causation, highlights the undefined contours of flood pollution for the scientific community. We identify obstacles to the emergence of this problem in the scientific arena explained by the structuring of this arena, the vagueness of the term pollution, regulation, and individual and collective approaches to resilience. We argue that these obstacles can be overcome by considering pollution as a social construct and viewing cities in a metabolic framework.

Physical and chemical modifications within soils have been proposed as a marker of the Anthropocene, as soils can preserve modifications due to past land use for long periods of time. Soils are the primary terrestrial reservoir of C and N and are especially important for sequestration and emission of C related to land use changes. The northeast US has a well-documented sequence of deforestation and reforestation related to land use changes following European settlement, yet the impact of land use and recovery on C and N stocks and isotopes is still poorly constrained. We analyze δ¹⁵N, δ¹³C, and C/N to evaluate changes to soil C and N related to historical land use across an Anthropocene chronosequence comprised of four land use classes that vary in terms of duration of disturbance and recovery time from past agricultural activity. Reforested soils show minimal difference in δ¹⁵N and δ¹³C and display no overall statistical relationship with abandonment length, while modern agricultural soils have higher δ¹⁵N values. Differences in total C and N between land use classes are more distinct, as SOC decreases and total N increases with longer land use duration. Historic agriculture increased C and N storage, and recently abandoned land still has the potential to act as a sink to store more organic C. In total, land use imparts clear changes to SOC and N stocks that persist long after abandonment, providing a distinct marker of anthropogenic activities. However, stable C and N isotopes of soils within reforested classes show only slight differences between land use classes, indicating shorter timescales of isotopic resetting of C and N signatures following abandonment.

Following its advent as a concept, the Anthropocene has flourished as a new worldview in academic and public communities alike. Yet, the Subcommission on Quaternary Stratigraphy recently voted against formally ratifying the Anthropocene as an Epoch, pointing to the restrictive geologic framework, and highlighting the need for a globally represented and synchronous marker. In this Viewpoint, we utilize global bibliographic data, Google search data, IPCC authors, and the Global Climate Risk Index (GCRI) to examine the global diversity of the Anthropocene discourse by measuring academic interest and public engagement in the topic, while also considering the proportional influence, justice, and inclusivity of this discourse. We argue that the conceptual and geological frameworks of the Anthropocene share a complex and non-translatable relationship. Further, we urge reconsideration of geologically rigid definitions in the spirit of recognizing holistic identification of human impacts to the Earth System, while also addressing the gaps in global influence with this pressing concept. Last, we explore successful examples integrating disparate disciplinary perspectives to achieve greater understanding of the Anthropocene and discuss avenues for future directions in the areas of human-environment interactions, as well as environmental justice and equity.