Anthropocene最新文献

The United States (U.S.) coastal plain is subject to rising sea levels, land subsidence, more severe coastal storms, and more intense droughts. These changes lead to inputs of marine salts into freshwater-dependent coastal systems, creating saltwater intrusion. The penetration of salinity into the coastal interior is exacerbated by groundwater extraction and the high density of agricultural canals and ditches throughout much of the rural U.S. landscape. Together saltwater intrusion and sea level rise (SWISLR) create substantial changes to the social-ecological systems situated along the coastal plain. Many scholars and practitioners are engaged in studying and managing SWISLR impacts on social, economic, and ecological systems. However, most efforts are localized and disconnected, despite a widespread desire to understand this common threat. In addition to variable rates of sea level rise across the U.S. outer coastal plain, differences in geomorphic setting, water resources infrastructure and management, and climate extremes are resulting in different patterns of saltwater intrusion. Understanding both the absolute magnitude of this rapid environmental change, and the causes and consequences for its spatial and temporal variation presents an opportunity to build new mechanistic models to link directional climate change to temporally and spatially dynamic socio-environmental impacts. The diverse trajectories of change offer rich opportunities to test and refine modern theories of ecosystem state change in systems with exceptionally strong socioecological feedbacks.

Records of environmental changes at regional or continental scales in less-developed regions may aid clarification of the onset of the Anthropocene. A sediment core was collected from Bosten Lake in Xinjiang Province, northwestern China, to investigate historical variations of combustion indicators of black carbon (BC), char and soot and to reflect human influences over the past 150 years. Results show that a rapid increase in soot fluxes (over 1.5 times on average) happened after 1950, consistent with the Great Acceleration period as well as establishment of the People's Republic of China, following a rapidly developing economy. Soot flux peaked around the 1960, coincident with wasteland reclamation in Xinjiang Province, decreasing after the year 2000 owing to environmental protection requirements such as desulfurization. Average char/soot ratios before and after 1950 were 0.56 and 0.37, respectively, such low ratios suggest a predominant contribution of soot from long-range transport, while the industrialization in China since the 1950 s may have caused further reduction in the ratios. Sedimentary soot deposition flux in less-developed areas thus recorded key anthropogenic activities occurring in China and supports the onset of the Anthropocene in the mid-20th century, as proposed by the Anthropocene Working Group.

Vertical distributions of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in a sediment core from Lake Issyk-Kul are powerful tools for reconstructing historical anthropogenic activities over the past 350 years. Four periods were identified according to the variations in these environmental proxies. Period Ⅰ (1670s–1800s) corresponds to a phase of limited anthropogenic activity reflected by the lowest ΣPAH₁₆ concentrations, mainly from biomass combustion and petrogenic processes. Along with pronounced deforestation due to wildfires documented in the pollen record, a similar decrease in PAHs suggests that PAHs were most likely generated by natural sources around Lake Issyk-Kul during this period. Period Ⅱ (1800s–1930s) reflects increasing agricultural activities with fluctuations in various PAH concentrations. Anthropogenic biomass-derived PAH inputs from agricultural activities gradually replaced natural inputs to Lake Issyk-Kul, coinciding with several historical events. However, natural factors still mainly controlled changing lake levels before the 1930s. Period Ⅲ (1930s–1970s) corresponds to rapid development of agricultural activities, inferred by slight increases in ΣPAH₁₆ concentrations dominated by coal-derived PAHs and a considerable increase in ΣOCP₁₈ concentrations. Concentrated agricultural activities around Lake Issyk-Kul significantly influenced environmental changes in grain size and water level in the lake. Period Ⅳ (post-1970 s) corresponds to intensive industrial and urban activities, including a 10-year economic depression (1990s–2000s), characterized by the highest ΣPAH₁₆ concentrations mainly from petroleum combustion followed by a sharp drop after the 1990s as the dissolution of the Soviet Union. Industrialization and urbanization in study area have changed the trophic state of Lake Issyk-Kul, particularly in recent years. Climate change has also induced “lateral remobilization” of contaminants, increasing pollution levels in this mountain lake.

There is currently great interest in increasing the total land area in ‘conservation’ by the year 2030 to stabilize biodiversity and reduce net carbon emissions to combat climate change; however, there remains a lack of clarity on what actually constitutes ‘conservation.’ Land placed into permanent protection from resource utilization falls under the category of land preservation (e.g. National Parks) where land ‘conservation’ can include resource utilization to meet human resource needs. Land ‘preservation’ is an effective means of protecting habitat, but isolation of preserved parcels can limit their effectiveness. The trade-off between land preservation and conservation requires that we consider land use strategies in a global context and as complementary of one another. Most assessments for increasing land conservation are based on vegetative and wildlife inventory, where far fewer assessments are based on soils or belowground accounting. Herein, we present a soil based perspective that could be useful in evaluating the capacity for different land management strategies to meet broader conservation goals, including 30 by 30 and provide a focus on forest management to demonstrate our approach. Our soils-based assessment of different land-use practices suggests that land management practices that cause minimal soil disturbance, generate minimal bare soil, and exhibit a dominance of native species would be effective at achieving meaningful land conservation benefits while continuing to meet human resource needs. Incentivizing conservation oriented land management practices could dramatically accelerate our ability to achieve large scale conservation objectives such as 30 by 30.

This study estimated the mass accumulation rates of sediment (MAR), carbon (CMAR), and phosphorus (PMAR) in small Finnish lakes with agricultural clayey catchments over a 25-year period (1986–2011) and compared these with the conditions before major agricultural land use. Twenty-two lakes were cored for recent and reference (pre-disturbance) sediments. The recent sediment section was selected based on the 1986 ¹³⁷Cs fallout peak (TOP), whereas the pre-disturbance section (REF) was selected immediately below the first signs of human-induced erosion. The 50-cm reference section was dated with ¹⁴C at both ends. The mass accumulation rates were estimated based on dating, weighing, and chemical analysis for both sediment sections. Furthermore, sediment-penetrating echo soundings were used to estimate the amount of sediment in the whole lake basins. These data were used to examine area-specific loading from clay-rich catchments. The average whole-basin pre-disturbance MAR, PMAR, and CMAR were 62 g m⁻² a⁻¹, 0.06 g m⁻² a⁻¹, and 4.7 g m⁻² a⁻¹, respectively. The corresponding recent rates were 11, 13, and 8-fold (693 g m⁻² a⁻¹, 0.79 g m⁻² a⁻¹, and 37 g m⁻² a⁻¹). In the recent conditions, sediments were generally more minerogenic and MAR, PMAR, and CMAR were higher in lakes with more arable fields in their catchments. Average area-specific suspended sediment load from the catchment for the region (∼39% clayey soils) was approximately 69–137 kg ha⁻¹ a⁻¹ in the undisturbed state and 767–1534 kg ha⁻¹ a⁻¹ in recent conditions based on 100–50% retention. The results demonstrate that the increases in sediment, nutrient, and organic matter accumulation due to agriculture can be several fold over undisturbed state.

Prescribed fire (Rx-fire) is a common management tool for many forested ecosystems and promotes tree and forest soil health. Although burned materials from Rx-fire areas can enter adjacent aquatic environments, very few studies have focused on the water quality impacts of increased nutrients on aquatic primary producer communities. Here, we applied paleolimnological techniques on a 170-cm sediment core collected from Ditch Pond, AL, USA, a subtropical lake system located in the Conecuh National Forest where Rx-fire has been the primary management tool for ∼90 years. Macroscopic charcoal, nutrients (C, N, P) and photosynthetic pigments were measured throughout the core which spans from the middle Holocene until modern day. Our research questions were: 1) What were the sedimentary nutrient and stoichiometric changes associated with the Rx-Fire period beginning in 1937 CE? and 2) Did these nutrient changes alter historic algae/cyanobacteria groups? Following the onset of Rx-fire, nutrients (C, N, P) increased in deposition in the lake with P showing the greatest proportional increase at over 300%, suggesting that P inputs from Rx-fire are a primary artifact of burning. Photosynthetic pigments showed that increases in nutrients from Rx-fire caused extensive increases in total primary producer abundance and cyanobacteria dominance, called pyroeutrophication. These data suggest a greater need to understand the implications of fire-associated nutrients on aquatic primary producers wherever fire (but especially Rx-fire) is occurring, as well as an increase in collaboration between forest and aquatic ecosystem managers.

With accelerated warming, mountain glaciers in most parts of the world have been in a state of continuous retreat in recent decades. Assessing glacier change and analyzing its influencing factors are essential for developing climate change mitigation and adaptation measures for a given region. This study provides a spatially explicit assessment and quantification of glacier changes in the early 21st century on the Tibetan Plateau (TP) at individual glacier and basin scales. We established a one-to-one correspondence between the Second Chinese Glacier Inventory (CGI-2, collected from 2004 to 2011) and a dataset of glacier inventory in Western China during 2017–2018 (CGI-2018). The majority of TP’s glaciers decreased in size with a mean area retreat rate during the investigated period of 4.1%/decade. In addition, a mean change of the median elevation of the glaciers of 6.7 m/decade was detected. Approximately 2.5% of the total number of glaciers mapped in CGI-2 disappeared, while 681 of them divided to 1758 glaciers as they retreated. The observed variations follow local trends and have different regional characteristics. Generally, the glaciers with the lowest retreat rates are found in the Karakorum and Kunlun Mountains, while those with high retreat rates are concentrated along the Gangdis and Tangula ranges. The observed changes in glaciers are mainly attributed to a significant increase in temperature. Other factors including glacier size, debris cover, orientation and mean elevation also contribute to the heterogeneity of glacier variability. This study provides for the first time a detailed spatially explicit analysis of the glacial changes on the TP in the early 21st century, substantially improving the understanding of glacier response patterns and supporting more sustainable utilization of regional water resources in the TP in the context of climate warming in the 21st century.

The conceptual framework for nature-based solutions (NbS) is well developed, however realizing the potential of NbS at scale and in widespread professional practice in infrastructure systems depends on overcoming operational challenges rooted in the historical policies and engineering practices of the action agencies capable of implementation. In this article, we explore levee setbacks as a NbS for improving the sustainability of leveed river corridors within the context of the United States (US) and its primary action agency of flood risk management, the Army Corps of Engineers (USACE). By identifying the social and environmental consequences of historical levee management and linking these consequences with historical policies and engineering practices, we highlight knowledge gaps, challenges and opportunities for progress with NbS. We also briefly discuss USACE’s decision-making processes for infrastructure investments and the valuation of ecosystem services as it pertains to operationalizing setbacks in practice. We then develop a case study of a recent setback on the Missouri River to showcase how USACE overcame implementation challenges. Lessons from past levee corridor management in the US, and USACE’s current corrective actions, may help foster understanding of how to overcome operational challenges in the implementation of setbacks in other social and political contexts.

Worldwide, trajectories of deterioration of large rivers’ natural structure and functioning have been described and related to anthropogenic pressures acting at different spatio-temporal scales. However, the variety of methodologies, time-scale resolutions and the lack of standard indicators frequently hinder the comparison of outcomes among rivers in different geographic and climatic regions. Covering between 204 and 36 years, this study applied the same multi-temporal analysis of riverine trajectories (i.e., anthropization, changeless, progression, and regression) in five large river segments within temperate (Rhine River, France and Germany), Mediterranean (Ebro and Tagus Rivers, Spain), and semi-arid climates (Aras and the Zayandeh-rud Rivers, Iran). This transferable GIS-based method includes the assessment of historical balances within natural dynamics (Natural Trajectory Index, NTI), the degree of anthropization (Anthropization Ratio, AR), and the degree of stability (Stability Ratio, SR) in the studied river-floodplain systems.

Results show similarities among the European case studies (i.e., Rhine, Ebro and Tagus rivers) in response to hydromorphological impacts, with percentage increases in human-induced changes (i.e., anthropization), and habitat development (i.e., progression). Apart from the Zayandeh-rud River, that presents a marked tendency toward progression, processes of habitat rejuvenation (i.e., regression) have almost disappeared in all case studies, and riverine forms remain unchanged. The differences found between the European and the Asian case studies are considered related to the aims and methods of engineering choices for historical river management, with a long history of river reprofiling and impounding in European rivers, while Iranian regulation is relatively recent, and involves extensive inter-basin water transfers.