Our recent publication, 50 for the Future, lists 50 things that we believe should happen in Scotland over the next 50 years to benefit both people and wildlife. In this week's 50 for the Future article, co-authors Dr David Oliver from the University of Stirling and Professor Louise Heathwaite from Lancaster University describe the various types and sources of diffuse pollution and discuss what needs to be done to manage it effectively.

Number 16: End nitrogen and other diffuse pollution from all sources in the lowlands to secure clean water and healthy soils in the long term

The way we manage our land can leave a mark on the water that drains from our catchments in the form of diffuse pollutants. Sources of diffuse pollution can be both urban and rural and vary in their impact on water quality through time and across landscapes. Nutrients such as phosphorus (P) and nitrogen (N) can be transferred from agricultural land to water along with soils and sediments, and associated contaminants such as pathogens derived from livestock manure. Urban runoff can carry organics, metals, nutrients and microbial pollutants too. Clearly then, diffuse pollution is a multi-faceted environmental challenge.

Eliminating diffuse pollution from all lowland sources is an admirable goal, but putting a stop to it, and all transfers of pollutants from land to water, is no easy task. Tackling diffuse pollution from lowland areas is fraught with challenges, but at the same time improvements are steadily being made against a back-drop of uncertainty surrounding the impact of climate change and the complexity of land management activities and infrastructures such as tracks, drains, hard standings, and field boundaries, all of which modify the flow of water on land.

However, it is unrealistic to assume that we can manage complex landscapes to such an extent that no substances will leak or escape from catchment systems. Instead, our ambition should be to guard against poor land management decisions, which often accelerate diffuse pollution, and to manage expectations of all those with an interest in environmental protection by being open and honest about what is really achievable. Ending diffuse pollution in all forms is unrealistic, however managing it within safe limits for good environmental quality and for the benefit of wider society is not.

The Scottish landscape provides multiple benefits to society which we all enjoy. We use it to grow food, for recreation and to help support energy generation. Recognising the need to balance the varied demands that we place on our landscape is as an essential ingredient for more sustainable land and water management. Therefore ending, or rather reducing, diffuse pollution is not just about matching crop nutrient requirements to fertiliser applications, or promoting measures which block diffuse pollutants during their journey from source to stream. Instead, reducing diffuse pollution is an integral part of what should be a wider integrated assessment of how we can deliver multiple ecosystem benefits to society from changes in landscape management. Scotland’s Land Use Strategy and the Scottish Biodiversity Strategy play a role in understanding such issues and helping to shape solutions across complex needs.

Of course, during extreme events such as heavy rainfall and floods, there will undoubtedly be an increased risk of pollutants entering the aquatic environment. It should also be noted that losses of material from landscapes to water do occur naturally, and that the concern relates to the degree to which agricultural activities enhance these losses beyond the buffering capacity of the receiving waters. Some elements like P can persist in the landscape for perhaps 50 years or more, some natural processes release N and P into the environment, and for N we have atmospheric delivery to consider.

Additionally, it is recognised that microbial pollutants, such as E. coli derived from livestock faeces, can exist in the environment as a naturalised population that has adapted to survive outside of the gut environment. Therefore, the legacy impacts of diffuse pollutants in catchment systems means that even if it were feasible to end all inputs of P, N, E. coli etc. to land systems, they would continue to leak into the environment for many years from catchment storage. The reality, however, is that those inputs go hand-in-hand with livestock farming and food production. A blanket elimination of diffuse pollution is not possible, but communicating these challenges can help manage wider societal expectations and help us to understand why improvements in water quality often lag behind land management changes.

Future efforts to reduce diffuse pollution therefore requires integrated thinking, connecting ideas across different disciplines, and promoting dialogue not only between scientists, policy-makers and regulators, but with local communities too. This has of course long been recognised, but converting theory into practice is challenging.

Scotland’s ongoing approach to mitigating diffuse pollution is attempting to capture these needs, and the Diffuse Pollution Management Advisory Group (DPMAG) represents a partnership that has fostered stakeholder engagement, involving the fishery boards, forestry commission, NFU Scotland, Scottish land estates, Scottish Water, SEPA and many others. It has provided a co-ordinated, inclusive approach to reducing diffuse pollution that has, in turn, led to national awareness raising campaigns coupled with more targeted action in priority catchments across Scotland. Mechanisms such as DPMAG are essential in order to support effective delivery of water quality improvements, and are complemented in Scotland with other initiatives such as the Scottish Water Sustainable Land Management project and the Scottish Government Hydronation agenda, including the establishment of Scotland’s Centre of Expertise for Water.

A number of catchment-based initiatives in Scotland have therefore been championing the value of managing our catchments as natural assets in order to deliver better recreational and ecological water quality, improve cost-effective treatment of drinking water, and highlight the important connections that exist across food-water-&-energy provision. What we believe are now priorities for the future include better integration of expert and local knowledge of catchment functioning, with a mutual respect for different types of expertise, and greater acceptance that we do not live in a risk-free world with regard to environmental pollution.

Efforts to reconnect catchment dwellers with the hydroscapes within which they live, work and play would offer many advantages in terms of promoting a new generation of hydro-citizens, with a heightened appreciation of the delicate balance between land and water interactions. So whilst we cannot end diffuse pollution in a rapidly changing world, we can continue to work together to protect our soil and water environments given that new risks (and opportunities) will continue to unfold in the face of climate change. 

Let us know your thoughts by emailing thefuture@scottishwildlifetrust.org.uk or Tweet @ScotWildlife using #50fortheFuture.

 Dr David Oliver is a Senior Lecturer in Catchment Science at the University of Stirling.

 Louise Heathwaite is a Professor of Land and Water Science in Lancaster Environment Centre, Lancaster University.