Floodplain environmental change during the Younger Dryas and Holocene in Northwest Europe: Insights from the lower Kennet Valley, south central England

Many lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial-interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in the context of the river Kennet, a tributary of the Thames, since c. 13,000 cal BP. Some similarities with other rivers are present, suggesting that regional climatic shifts are important controls. The Kennet differs from the regional pattern in a number of ways. The rate of response to sudden climatic change, particularly at the start of the Holocene and also mid-Holocene forest clearance, appears very high. This may reflect abrupt shifts between two catchment scale hydrological states arising from contemporary climates, land use change and geology. Stadial hydrology is dominated by nival regimes, with limited winter infiltration and high spring and summer runoff. Under an interglacial climate, infiltration is more significant. The probable absence of permafrost in the catchment means that a lag between the two states due to its gradual decay is unlikely. Palaeoecology, supported by radiocarbon dates, suggests that, at the very start of the Holocene, a dramatic episode of fine sediment deposition across most of the valley floor occurred, lasting 500-1000 years. A phase of peat accumulation followed as mineral sediment supply declined. A further shift led to tufa deposition, initially in small pools, then across the whole floodplain area, with the river flowing through channels cut in tufa and experiencing repeated avulsion. Major floods, leaving large gravel bars that still form positive relief features on the floodplain, followed mid-Holocene floodplain stability. Prehistoric deforestation is likely to be the cause of this flooding, inducing a major environmental shift with significantly increased surface runoff. Since the Bronze Age, predominantly fine sediments were deposited along the valley with apparently stable channels and vertical floodplain accretion associated with soil erosion and less catastrophic flooding. The Kennet demonstrates that, while a general pattern of river behaviour over time, within a region, may be identifiable, individual rivers are likely to diverge from this. Consequently, it is essential to understand catchment controls, particularly the relative significance of surface and subsurface hydrology. (c) 2005 Elsevier B.V. All rights reserved.

The effect of environmental change on human migration

The influence of the environment and environmental change is largely unrepresented in standard theories of migration, whilst recent debates on climate change and migration focus almost entirely on displacement and perceive migration to be a problem. Drawing on an increasing evidence base that has assessed elements of the influence of the environment on migration, this paper presents a new framework for understanding the effect of environmental change on migration. The framework identifies five families of drivers which affect migration decisions: economic, political, social, demographic and environmental drivers. The environment drives migration through mechanisms characterised as the availability and reliability of ecosystem services and exposure to hazard. Individual migration decisions and flows are affected by these drivers operating in combination, and the effect of the environment is therefore highly dependent on economic, political, social and demographic context. Environmental change has the potential to affect directly the hazardousness of place. Environmental change also affects migration indirectly, in particular through economic drivers, by changing livelihoods for example, and political drivers, through affecting conflicts over resources, for example. The proposed framework, applicable to both international and internal migration, emphasises the role of human agency in migration decisions, in particular the linked role of family and household characteristics on the one hand, and barriers and facilitators to movement on the other in translating drivers into actions. The framework can be used to guide new research, assist with the evaluation of policy options, and provide a context for the development of scenarios representing a range of plausible migration futures.

Migration and global environmental change

Introduction to a special issue on migration and global environmental change

Mesolithic to Neolithic and medieval coastal environmental change: intertidal survey at Woolaston, Gloucestershire

At Woolaston on the western shores of the middle Severn Estuary c. 7 km upstream of Chepstow intertidal Holocene sediment exposures have been surveyed and the stratigraphic sequence established by coring and limited excavation. There are two main peats each with a submerged forest. An existing dendrochronological sequence for the Upper Submerged Forest has been extended and the preliminary results of pollen analysis from the peat sequence are summarised. A few flint flakes were found but were not stratified in the mid-Holocene sequence. There is evidence for late Mesolithic / early Neolithic burning episodes which may relate to human activity. Evidence is reported for Medieval activity and the extensive modification of drainage in this period is suggested.

Migration, environmental change, and the ‘challenges of governance’

This paper provides a framework for the theme issue by exploring links between environmental change and human migration. We review evidence that demonstrates that millions of people have moved or are likely to move towards and not away from environmental risk and hazard by moving from rural areas to rapidly growing urban areas. Moreover, some people may choose not to move or be unable to move. Environmental change may further erode household resources in such a way that migration becomes less and not more likely, even in the context of quite significant environmental change posing serious threats to the sustainability of livelihoods. This creates the possibility that populations will be trapped in areas that expose them to serious risk. We argue that the links between environmental change, migration, and governance are of significant importance, and directly influence the modes and efficacy of migration governance at different levels.

Scale sensitivity of drivers of environmental change across Europe

The development of effective environmental management plans and policies requires a sound understanding of the driving forces involved in shaping and altering the structure and function of ecosystems. However, driving forces, especially anthropogenic ones, are defined and operate at multiple administrative levels, which do not always match ecological scales. This paper presents an innovative methodology of analysing drivers of change by developing a typology of scale sensitivity of drivers that classifies and describes the way they operate across multiple administrative levels. Scale sensitivity varies considerably among drivers, which can be classified into five broad categories depending on the response of ‘evenness’ and ‘intensity change’ when moving across administrative levels. Indirect drivers tend to show low scale sensitivity, whereas direct drivers show high scale sensitivity, as they operate in a non-linear way across the administrative scale. Thus policies addressing direct drivers of change, in particular, need to take scale into consideration during their formulation. Moreover, such policies must have a strong spatial focus, which can be achieved either by encouraging local–regional policy making or by introducing high flexibility in (inter)national policies to accommodate increased differentiation at lower administrative levels. High quality data is available for several drivers, however, the availability of consistent data at all levels for non-anthropogenic drivers is a major constraint to mapping and assessing their scale sensitivity. This lack of data may hinder effective policy making for environmental management, since it restricts the ability to fully account for scale sensitivity of natural drivers in policy design.

Scale sensitivity of drivers of environmental change across Europe

The development of effective environmental management plans and policies requires a sound understanding of the driving forces involved in shaping and altering the structure and function of ecosystems. However, driving forces, especially anthropogenic ones, are defined and operate at multiple administrative levels, which do not always match ecological scales. This paper presents an innovative methodology of analysing drivers of change by developing a typology of scale sensitivity of drivers that classifies and describes the way they operate across multiple administrative levels. Scale sensitivity varies considerably among drivers, which can be classified into five broad categories depending on the response of ‘evenness’ and ‘intensity change’ when moving across administrative levels. Indirect drivers tend to show low scale sensitivity, whereas direct drivers show high scale sensitivity, as they operate in a non-linear way across the administrative scale. Thus policies addressing direct drivers of change, in particular, need to take scale into consideration during their formulation. Moreover, such policies must have a strong spatial focus, which can be achieved either by encouraging local–regional policy making or by introducing high flexibility in (inter)national policies to accommodate increased differentiation at lower administrative levels. High quality data is available for several drivers, however, the availability of consistent data at all levels for non-anthropogenic drivers is a major constraint to mapping and assessing their scale sensitivity. This lack of data may hinder effective policy making for environmental management, since it restricts the ability to fully account for scale sensitivity of natural drivers in policy design.