Climate-driven Environmental Change Research Articles

Assessing the impacts of economic and climate changes on land-use in mountain regions: A spatial dynamic modeling approach

Future land-use changes are predicted to be influenced by both climate-driven environmental changes and concomitant changes in local economic conditions. Assessing the impact of climate change on ecosystems, and the goods and services that they provide, therefore requires an understanding of the dynamic link between land-cover, ecosystem services and economic-driven land-use decisions. The economic land allocation model (ALUAM) simulates the competition between forest and a range of agricultural land-uses to estimate land-use conversions in a spatially explicit manner at high resolution. Using a modular framework, ALUAM was linked with the forest-landscape model LandClim, and a crop yield model, that simulate the response of forests and crops to changes in climate. An iterative data exchange between the models allows a detailed assessment of the dynamic changes in the provision of agricultural and forest based services. We apply our model to the temperature sensitive inner-alpine region of Visp, Switzerland. Our results demonstrate that land-use is influenced directly by environmental shifts and economic decisions, but are also highly dependent on the interactions between these two components. These shifts in land-use will correspondingly affect the provision of ecosystem goods such as food and timber production.

Declining oaks, increasing artistry, and cultivating rice: the environmental and social context of the emergence of farming in the Lower Yangtze Region

There is a growing body of evidence that reliance on rice cultivation emerged gradually in the Lower and Middle Yangtze river basin during the mid-Holocene amongst societies that had a heavy emphasis on the seasonal collecting and storage of acorns (Cyclobalanopsis, Lithocarpus and/or Quercus) and aquatic nuts (Trapa, Euryale). Recent archaeobotanical research, like that at Tianluoshan, provides evidence for the emergence of cultivation and the decrease in importance of gathered plant foods, and this paper situates these changes in relation to environmental, including climatically driven, changes especially in the Hangzhou Bay (Lower Yangtze) region. A growing number of pollen and other palaecological studies have become available in recent years, and here they will be reviewed to test the hypothesis that regional declines in nut-bearing trees (especially oaks, but also possibly Castanea/Castanopsis chestnuts) was one of the factors that favoured the increasing reliance on rice, which in turn drove the evolution, expansion and intensification of cultivation and the evolution of morphologically domesticated rice. Another factor, however, that also needs to be considered is the evidence for the emergence of social hierarchy and specialised craft production which may have concurrently pushed for an increasingly socially controlled and reliable staple food source in the form of rice. In this regard, it is important to note that intensification of rice use required increasing degrees of labour mobilisation, and landscape transformation, which could provide returns on labour investment to a degree that was not possible with oak groves. Current evidence indicates that both climate-driven environmental changes and social motivations correlate with the shift to domesticated rice and rice agriculture over the latter part of the Neolithic (6000–3000 BC). The earlier beginnings of rice cultivation, the first steps along this pathway, remain obscure although some earlier Holocene climatic events appear correlated.

Spatiotemporal dynamics of the Clovis–Folsom transition

Despite the importance of the Clovis–Folsom transition for understanding the history of western North America, its spatiotemporal dynamics remains unclear. Here we report a three-part study in which we investigated the transition using radiocarbon dates from Clovis and Folsom sites. In the first part of the study, we used dates from Folsom site-phases to determine when and where Folsom originated. In the second part of the study, we employed Clovis and Folsom dates in analyses designed to determine whether Folsom spread via demic diffusion or cultural diffusion. In the third part of the study we investigated the velocity of the Clovis–Folsom transition. The analyses suggest that Folsom first appeared around 12,800 calBP in the northern High Plains and spread north and south from there. They also suggest that the spread of Folsom was, at least in part, the result of population expansion. In addition, the analyses indicate that the spread of Folsom was relatively fast for a prehistoric diffusion but well below the maximum velocity that has been estimated for such events. These findings, in turn, have implications for the hypotheses that have been put forward to explain the Clovis–Folsom transition. They refute the idea that the Clovis–Folsom transition resulted from an extraterrestrial impact over northern North America at 12,900 ± 100 calBP but are consistent with the alternative proposal that the transition was a response to climate-driven environmental change.

Climate-driven environmental change in the Zhada basin, southwestern Tibetan Plateau

Climate-driven environmental change in the Zhada basin, southwestern Tibetan Plateau

Climate-driven environmental change in the Zhada basin, southwestern Tibetan Plateau

Climate-driven environmental change in the Zhada basin, southwestern Tibetan Plateau

Climate-driven environmental change in the Zhada basin, southwestern Tibetan Plateau

The Zhada basin is a large Neogene extensional sag basin in the Tethyan Himalaya of southwestern Tibet. In this paper we examine environmental changes in the Zhada basin using sequence stratigraphy, isotope stratigraphy, and lithostratigraphy. Sequence stratigraphy reveals a long-term tectonic signal in the formation and filling of the Zhada basin, as well as higher-frequency cycles, which we attribute to Milankovitch forcing. The record of Milankovitch cycles in the Zhada basin implies that global climate drove lake and wetland expansion and contraction in the southern Tibetan Plateau from the Late Miocene to the Pleistocene. Sequence stratigraphy shows that the Zhada basin evolved from an overfilled to underfilled basin, but continued evolution was truncated by an abrupt return to fluvial conditions. Isotope stratigraphy shows distinct drying cycles, particularly during times when the basin was underfilled. A long-term environmental change observed in the Zhada basin involves a decrease in abundance of arboreal pollen in favor of nonarboreal pollen. The similarity between the long-term environmental changes in the Zhada basin and those observed elsewhere on and around the Tibetan Plateau suggests that those changes are due to global or regional climate change rather than solely the result of uplift of the Tibetan Plateau.

Ecological changes in the highest temporary pond of western Crete (Greece): past, present and future

This study explores the past, present and future ecological changes in the highest Mediterranean temporary pond (Omalos pond) in western Crete, Greece. Data from downcore pollen analysis (including pollen and spores from both aquatic vegetation, and terrestrial herbaceous, arboreal and shrub vegetation), modern vegetation monitoring and existing climate scenarios have been combined to provide a picture of the ecological changes in the pond over the last 13,600 years. Downcore pollen analysis throughout the last 13,600 years indicated the presence of species typical of Mediterranean Temporary Pond (MTP) habitats and suggested relatively drier conditions towards the present. The low number of non-native, cultivated species (such as herbaceous Trifolium and Plantago species) observed over this period suggested relatively low impact from crop agriculture, despite the increasing grazing pressure in the area. In the absence of independent proxies, we cannot reliably distinguish between natural and human-induced changes. The presence of aquatic Isoetes in the palaeo-record indicates the existence of an ephemeral pond in the area as early as the beginning of the Holocene suggesting resilience of the ecosystem over time. However, the degraded state of pollen in depths over 55 cm (i.e. 3600 year BP) increases the uncertainty of the interpretation. Currently, the pond holds 76 plant species belonging to 25 families. Therophytes and chamaephytes were the most frequent, suggesting a typical ephemeral habitat life form spectrum. Species richness was found to increase during spring surveys whereas the highest turnover was observed between summer surveys of consecutive years. Cluster analysis demonstrated a distinct zonation in four vegetation belts from the periphery to the centre of the pond which is typical of these environments. Modelling, based on two IPPC scenarios (A2 and B2), predicted relatively low climate change impacts on the pond’s hydroperiod for the next 100 years (i.e. a decrease of 16 and 24 days, respectively). This reduction in the hydroperiod of the pond will have an effect on the physiognomy and spatial extent of vegetation, particularly for the transitional belts between the core and its outer area, while it will exert more pressure on the pond as a water resource for sheep in the region. However, cumulative effects and complex interactions of climate-driven environmental changes and other anthropogenic disturbances might act synergistically to accelerate impacts in the future.

Natural and human-induced environmental change in southern Albania for the last 300 years — Constraints from the Lake Butrint sedimentary record

A sediment core from Lake Butrint in southwestern Albania contains an annually-layered sequence covering the last ∼ 300 years. It provides thus an exceptionally well-dated time series to study past climate-driven environmental changes, as well as anthropogenic perturbations along the coast of the Ionian Sea. The varves are composed of organic-rich carbonate couplets and detritus-dominated clay layers. The first are deposited during spring-to-fall, and reflect the chemistry of the lake, which, in turn, is sensitive to 1) the relative importance of marine versus freshwater inputs, 2) relative evaporation rates, and 3) the productivity cycle within the lake. The detrital laminae are deposited during winter, reflecting precipitation and runoff conditions during the wet season. A 2–3‰ stable carbon isotope ratio shift in both bulk organics and authigenic carbonates was attributed to increasing eutrophication towards the end of the 20th century, and validated by historical and instrumental data. An increase in the δ 18O of authigenic carbonates by more than 8‰ indicates the progressive salinization of the lake, which can primarily be attributed to man-made perturbations that reduced the freshwater input to the lake and/or enhanced the exchange with seawater from the nearby Ionian Sea. A recent increase in the relative evaporation versus precipitation rates may have additionally contributed to the observed 18O enrichment in the Lake Butrint carbonates. The interdecadal cyclicity in the thickness of the detrital laminae seems to be at least partially controlled by NAO and/or ENSO-like phenomena that modulate precipitation patterns in the eastern Mediterranean. Thus, this study demonstrates the potential of combining microstratigraphic and stable isotopic tools to disentangle anthropogenic and natural environmental changes in Lake Butrint, validated by historical records.

Late Quaternary Bison diminution on the Great Plains of North America: evaluating the role of human hunting versus climate change

Body size changes of Bison and mortality age structure data document the effects of climate-driven environmental change and human hunting pressure on large mammals in North America. Morphometric and mortality data are drawn from 58 archaeological and 9 paleontological localities dating between 37,000 and 250 calBP. Proxy information on body size is based on measurements recorded on 901 adult calcanei (os calcis) and 1026 humeri. In addition, published mortality profiles from 24 archaeological faunal assemblages spanning the last 14,000 years were used to approximate the age structure of bison populations. These results suggest that dramatic diminution in bison body size occurred in several short bursts, rather than a continuous gradual decline. These periods of rapid size reduction correlate with times of ecological reorganization, when aridity-driven changes in grasslands decreased forage quality and availability. Mortality age data indicate that the decrease in body size occurred in a context where there was no evidence for a progressively severe juvenile bias in bison populations. Overall, it appears that the changes in body size were a reaction to environmental conditions rather than the result of human predation pressure.

Origination and extinction patterns of mammals in three central Western Mediterranean islands from the Late Miocene to Quaternary

An overview of the population histories of three insular realms (Gargano palaeo-archipelago, Sardinia–Maritime Tuscany palaeo-bioprovince and the Sicilian insular complex) during the Late Miocene and Quaternary are here presented. The complexity of biodiversity changes in the islands is analysed to propose an interpretation of origination and extinction patterns. The study highlighted several important aspects of insular faunas. Evolutionary radiations were found to contribute significantly only to the Gargano faunal diversity, likely because the area was an archipelago at the time. Another interesting result is that large and small mammals do not disperse and become extinct all at the same time on each island. In fact, because of their distinct body sizes, large and small mammals have different dispersal ability and therefore different chances to cross-filtering barriers. But distinct body sizes means also different influence on diversity, resistance to environmental changes and likelihood of extinction. Another important point is that large mammalian carnivores at the top of the trophic net are quite more fragile and susceptible to become extinct than other predators. The study finally shows the clear influence that the intense Middle and Late Pleistocene climate-driven environmental changes had on island communities. The reconstruction of the faunal histories of Sardinia and Sicily shows that without exchanges with the mainland the island system represents a rather stable refuge area not too affected by the changes in the “physical” parameters of the environment. In contrast, if the island is frequently connected with the continent, insular faunal assemblages tend to behave as their mainland counterparts.

Late Quaternary climate-driven environmental change in the Larsemann Hills, East Antarctica, multi-proxy evidence from a lake sediment core

Little is known about the response of terrestrial East Antarctica to climate changes during the last glacial–interglacial cycle. Here we present a continuous sediment record from a lake in the Larsemann Hills, situated on a peninsula believed to have been ice-free for at least 40,000 yr. A mutli-proxy data set including geochronology, diatoms, pigments and carbonate stable isotopes indicates warmer and wetter conditions than present in the early part of the record. We interpret this as Marine Isotope Stage 5e after application of a chronological age-depth model and similar ice core evidence. Dry and cold conditions are inferred during the last glacial, with lake-level minima, floristic changes towards a shallow water algal community, and a greater biological receipt of ultraviolet radiation. During the Last Glacial Maximum and Termination I the lake was perennially ice-covered, with minimal snowmelt in the catchment. After ca. 10,500 cal yr B.P., the lake became seasonally moated or ice-free during summer. Despite a low accumulation rate, the sediments document some Holocene environmental changes including neoglacial cooling after ca. 2450 cal yr B.P., and a gradual increase in aridity and salinity to the present.

Monte Carlo simulation of the effects of human intrusion on groundwater contaminant transport

Regulations for the long-term disposal of high-level radioactive wastes command that the performance of the disposal facility be assessed for very long periods of time and quite extensive spatial scales. By nature, then, the analysis of the performance of a disposal facility relies on the application of predictive models. However, these models are inherently affected by uncertainties which concern the future states of the disposal system, the assumptions on the relevant physicochemical processes and the numerical values of the parameters. In particular, the future states of the system are typically determined by climate-driven environmental changes, seismic and volcanic activities, and also by human actions. In this paper we perform a Monte Carlo simulation of the effects of human drilling on the transport of contaminant in groundwater. The framework provided by the Monte Carlo simulation is such as to allow incorporation of aspects of both stochastic and dynamic nature which are typical of these problems. The simulated time and location of drilling are described as aleatory variables. The stochastic occurrence of human drilling affects the dynamic process of contaminant transport in groundwater which is modelled, in our case, by means of the Kolmogorov–Dmitriev approach of branching stochastic processes recently proposed by the authors. A Monte Carlo estimate of the distribution of the time at which the contaminant level exceeds a prescribed safety threshold is obtained.

The treatment of climate-driven environmental change and associated uncertainty in post-closure assessments

Abstract The post-closure performance of radioactive waste repositories is influenced by a range of processes such as groundwater flow and fracture movement which are in turn affected by conditions in the surface environment. For deep repositories the period for which an assessment must be performed is in the order of 106 years. The geological record of the last 106 years shows that surface environmental conditions have varied considerably over such time-scales and it is thus pertinent to examine the influence of such changes on the potential performance of a repository in detail. A model of surface environmental change, known as TIME4, has been developed on behalf of the UK Department of the Environment for use with the probabilistic risk assessment code VANDAL. This paper describes the extent of surface environmental change, discusses possible driving mechanisms for such changes and summarises the processes which have been incorporated within the TIME4 model. The underlying cause of change in surface environment sub-systems is inferred to be climate change but considerable uncertainty remains over the mechanisms of such change. Methods for treating these uncertainties are described.