Disentangling land use and climatic roles in sediment delivery to upland British lakes

Description

Changes to agricultural land use practices and climate represent serious challenges to the future management of rural landscapes, as humans have dramatically altered the European landscape over thousands of years. In the U.K., the ‘modern’ rural landscape may seem comparatively stable relative to this long history of human impact. However, there have been important changes linked to agricultural practices during the last ca. 100 years, particularly since the 1940s, with recent improvements in land management designed to reduce impacts on land and water resources. These changes correspond to simplification in crop rotations and loss of non-crop features, such as the removal of abandonment of hedgerows. Such changes have affected both the aesthetic qualities of the countryside as well as impacting on the biophysical environment. In response, many current policy and management initiatives aim to reduce soil erosion and river pollution by fine sediment. However, few studies attempt high-resolution spatial reconstruction of historic land use change, which is essential for understanding human-environment interactions in the recent past. Furthermore, the absence of detailed spatio-temporal records of agricultural land use/land cover change at the catchment-scale presents a challenge in assessing recent developments in land use management and policies. This PhD project will adopt a newly developed integrated approach for reconstructing high-resolution time-series of past agricultural change based on environmental and social records at the catchment-scale for hydro-environmental modelling applications and decision-making in environmental planning and management.

The studentship seeks to exploit existing datasets compiled at Liverpool for a series of catchments from around the UK and develop new sites to disentangle the competing roles of land use and climate on sediment delivery to lakes. The PhD will include bespoke training in field data collection and processing, reconstruction of past landscapes using archival sources, GIS mapping, with training in lacustrine sediment characterization for geochemistry (XRF), mineral /organic content (NIRS), and particle size (laser granulometry) using the Environmental Change Laboratories at Liverpool. This studentship will benefit from a broad suite of training provided and work with a range of stakeholders. 

Project Outline

Changes to agricultural land-use practices and climate represent serious challenges to the future management of rural landscapes. Humans have dramatically altered the European landscape over thousands of years. In the U.K. and across much of northern Europe, the ‘modern’ rural landscape may seem comparatively stable relative to this long history of human impact. However, there have been important changes linked to the intensification of agricultural practices during the last ca. 100 years, particularly since the 1940s, and more recently improvements in land management designed to reduce impacts on land and water resources (Cohen, 2003), such changes have affected both the aesthetic qualities of the countryside as well as impacting on the biophysical environment. In response, many current policy and management initiatives aim to reduce soil erosion and river pollution by fine sediment (e.g. the EU Water Framework Directive 2000/60/EC). However, few studies attempt high-resolution spatial reconstruction of historic land use change, which is essential for understanding human-environment interactions in the recent past. Furthermore, the absence of detailed spatio-temporal records of agricultural land use/land cover change at the catchment-scale presents a challenge in assessing recent developments in land use management and policies (Sangster et al., in prep.).

Lakes and reservoirs act as sinks for both anthropogenic and natural processes occurring in catchments, therefore their sediments can provide valuable information on temporal changes in catchment processes. The role of land use change and climate on British upland systems over the last 150 years has resulted in notable and in places significant changes in sediment delivery to the hydrological system (Smith et al., 2018), with phases of erosion being recorded within lake systems (Schillereff et al., 2014). Changes to sediment delivery can have numerous detrimental effects on river and lake systems including flooding, disruption to habitats, and increased pollutant delivery. Consequently, an understanding of both magnitudes of sediment delivery, and drivers of variability are vital to support catchment and lake management.  Recent methodological developments permit a now much higher resolution analysis of sedimentary depositional rates within British upland lake systems (Chiverrell et al., 2019).  These developments alongside advances in archival analysis and mapping of archive-based materials in GIS (Sangster et al., 2018) provide new opportunities for exploring the competing roles of climate and land use on sedimentary processes using landscape evolution models (LEM: e.g. CAESAR Lisflood).

The studentship seeks to exploit existing datasets compiled at Liverpool for a series of catchments from around the UK and develop new sites to disentangle the competing roles of land use and climate on sediment delivery to lakes. This will be achieved through several objectives:

1. Reconstruct land use patterns through time, using existing archival sources the project will examine how land use and farming practices have modified the landscape.
2. Reanalyse and reconstruct precipitation series for areas where no/partial existing records extending back to 1860, the start of British Rainfall - systematic rainfall recording across the UK

1. Evaluate how changes in regional, national and international policies have shaped agricultural practices
2. Develop new lake profiles, characterising sedimentary characteristics and depositional processes and rates of sediment accumulation.

1. Use these new land use and precipitation data in catchment scale LEM’s to simulate change in sediment fluxes to lake basins, and validate these using the lake sediment record.

The PhD will include bespoke training in field data collection and processing, reconstruction of past landscapes using archival sources, GIS mapping, with training in lacustrine sediment characterization for geochemistry (XRF), mineral /organic content (NIRS), and particle size (laser granulometry) using the Environmental Change Laboratories at Liverpool. LEM simulations would draw on experience using CAESAR Lisflood to test the comparative importance of human and climate drivers of catchment erosion and sediment flux.change in sediment fluxes to lake basins, and validate these using the lake sediment record.