Utilising digital technologies to map river thermal habitat availability for key indicator freshwater species: a decision-support conservation tool for best-practice riparian woodland management
This PhD will explore the use of digital technologies (drone-based unmanned aerial vehicles (UAVs) for thermal and habitat imagery, remotely sensed satellite data, GIS) as conservation tools for investigating best-practice riparian woodland management for moderating river temperatures and improving thermal habitat availability for keystone species such as the Freshwater Pearl Mussel (FPM) and their host salmonids, and identification of high-risk populations. The project will work with Forestry and Land Scotland (FLS), NatureScot, SEPA and local fishery trusts.
Climate change and biodiversity loss are the most significant global challenges we face today. Freshwater biodiversity provides essential ecosystem services fundamental for human well-being. However, global freshwater biodiversity has declined by >80% since the 1970s. Impacts of climate change, through increased water temperature and frequency of extreme flow events (floods/droughts), are key drivers of decline.
River water temperature is a key aspect of rivers’ ecological functioning. Water temperature influences physicochemical processes and biological activity (Caisse, 2006), with rivers exhibiting patches of warm and cool water habitat, highly variable through space and time (Dugdale et al, 2019). This heterogeneity exerts considerable influence on distribution, behaviour, and abundance of aquatic species. However, river temperature regimes are changing due to climate change and there remains uncertainty over how biological communities will respond.
It is suggested temperatures in Scottish rivers could increase by an average 2.2°C by 2050, and the high degree of exposure of large tracts of Scottish rivers (forest cover in Scotland is only 17.1% means that such a warming could have serious impacts on Scotland’s fluvial ecosystems, including ecologically and economically important salmonid fish species such as Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)(Jackson et al, 2021). In 2018, ~ 70% of Scottish rivers experienced temperatures exceeding the threshold for thermal stress in juvenile Atlantic salmon (23oC). Research is therefore needed to help understand and mitigate river temperature extremes and this PhD seeks to do this.
Riparian treescape expansion is a potential solution to delivering multiple local benefits, not just environmental benefits such as providing shade and reducing river temperature, stabilising riverbanks, reducing erosion, increasing riparian biodiversity, Natural Flood Management, reducing greenhouse gas emissions, reducing pollution, and enhancing water quality, but societal benefits such as providing an attractive environment which inspires, encourages recreation, well-being and boosts physical and mental health. Riparian restoration is a key element in this PhD’s CASE partner Forestry and Land Scotland’s (FLS) land management planning. Over the next 50 years FLS plans to restore 10,000 hectares of plantation forestry to riparian woodlands.
We need, however, to improve the evidence-base, to provide practitioners with a decision support framework to help inform best-practice riparian treescape expansion. Little is known about the relative ability of different riparian forest types to moderate stream temperatures. Further research is therefore necessary. A clear need has been highlighted for more information into combinations of tree species, size and buffer spacing that are most effective in generating shade to moderate water temperature (Orr et al, 2015). This PhD will extend the knowledge base informing treescape expansion, by assessing evidence-based impacts of different riparian woodland/forest forms and types on river water temperature heterogeneity using digital technologies, remote sensing and in-stream measurements, and assess how that heterogeneity impacts key indicator species. By targeting key indicator species, riparian woodland management decisions that benefit those species, will have additional benefits, or environmental net gains, to other species due to the ecosystem services they provide. This project will focus on the critically endangered freshwater pearl mussels and their host salmonids as key indicator species (Atlantic salmon and brown trout are functional hosts for a parasitic phase of the mussel life cycle)(Skinner et al 2003).
Aims of the PhD are therefore to:
1. Assess thermal habitat availability for keystone species FPM and host salmonids at key sites with different riparian woodland management using a combination of drone-based UAVs, remotely sensed satellite data and in-stream measurements.
2. Develop a decision-support framework that determines best-practice riparian woodland management strategies for moderating river temperatures and improving thermal habitat availability for FPM and host salmonids, directly addressing UK/International Biodiversity policy and Scottish Government’s Forest Strategy..
3. Identify at-risk FPM and host salmonid populations across Scotland, categorized as high, medium, and low risk, based on remotely-sensed satellite data of riparian land use, environmental secondary data (river flow and temperature, FPM and host salmonid population status) thus prioritizing remedial actions.
This will be achieved by working with the CASE partner FLS and end users of this research, including NatureScot, SEPA, Marine Scotland and relevant fishery trusts.
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Freshwater Pearl Mussel Lifecycle,The endangered Freshwater Pearl Mussel,Riparian woodland influencing river thermal habitats (Getty stock photos),Atlantic salmon (Woodland Trust)