Forecasting land management and extreme weather effects on earthworm populations, soil function and ecosystem services

Soils form the basic substrate for terrestrial life. They benefit the human population by supporting the production of food, fuel and fiber and regulating the climate, disease and water resources by facilitating essential services such as soil formation and nutrient cycling. Crucial for an exponentially growing human population are the foundations that soils provide for agriculture.

The activities of ecosystem engineers are important to the soil functions that underpin the provision of ecosystem services. Earthworms act as ecosystem engineers in soils both directly through digestion and burrowing activities and indirectly by encouraging other beneficial soil organisms. Management practices which optimise soil environmental conditions (e.g. soil organic carbon (SOM) and soil moisture) also stimulate earthworm biomass production. In turn the effects of earthworm activity on soil aggregate stability, nutrient cycling and soil carbon dynamics improve crop yields.

Although changes in land management may increase the abundance of soil organisms, these effects depend on specific combinations of management practices and environmental factors. This makes the results of experimental field studies hard to extrapolate for different scenarios, such as in extreme weather. Thus, tools are needed to better forecast how management practices affect the provision of ecosystem services through their effects on important ecosystem engineers.

Existing population models of how populations will respond to anthropogenic environmental change ignore the underlying mechanisms. Many focus only on the level of populations or individuals, rather than representing the processes which link both levels of biological organisation. Mechanistic models are needed that capture key biological, physiological and ecological mechanisms underpinning system functioning. Such models will have much better predictive power.

In this proposal I show how I will develop and validate mechanistic models of earthworms which deliver important soil functions in a range of habitats. Once the models have demonstrated that they realistically capture earthworm population dynamics in the field, they will be applied to numerous agricultural scenarios, with different combinations of soil and weather conditions, crop management practices (e.g. tillage) and extreme weather (flood and drought) events. Model results will indicate the ecological consequences of the different agricultural systems by forecasting earthworm populations in these different scenarios.

Relatively little is known about how earthworms respond to flood and drought. This proposal will identify the underpinning mechanisms by refining the mechanistic models to match new data under these extreme weather conditions. I will relate the role of earthworms as ecosystem engineers to soil functions and ecosystem services such as crop production and yield, by reviewing the relevant scientific literature. This knowledge will be used to provide new methods for quantifying the value of earthworms as ecosystem engineers which will allow better cost-benefit analysis of contrasting land management systems and promote the use of earthworms as a natural resource to land managers.

The ecological tools developed during this proposal have a breadth of practical applications in sustainable soil management throughout Europe. The results of this project will also provide a better understanding about how biological populations and soil functions respond to combinations of land management practices and extreme weather events. New methods for quantifying the value of earthworms as ecosystem engineers in soils will further facilitate better cost-benefit analysis of land management systems.

These project outcomes will directly benefit land managers, from individual farmers to environmental consultancies such as ADAS, as the modelling tools can be used at the individual field scale and account for farm specific weather, soil and management conditions. Ecological risk assessors, such as Syngenta and Bayer CropScience, and regulatory bodies who make decisions about the risks that new chemicals pose to the wider environment (e.g. Chemicals Regulation Directorate (CRD) and European Food Safety Authority (EFSA)) will have an accessible tool which will be fully validated against independent data. Using this tool for ecological risk assessment will allow more accurate judgements (e.g. chemical effects in flood and drought as well as standard weather conditions) to be made on the soil system for the refinement of guidance materials. The models' forecasting abilities will also be of direct relevance to policy makers, such as Defra, as the effects of land management on soil functions can be quantified. The models can also be used to explore implementation of EU soil protection strategies in different locations. Statutory agencies involved in water and soil conservation (e.g. Environment Agency) will also benefit from having tools to communicate the central idea of sustainable land management to a range of stakeholders, from the general public through the simple models that I will design for young children, to farmers.

The immediate benefits of this research to the stakeholders outlined above will be realised within 10 years. A key vehicle for this impact is the training of myself, along with other Soil Security programme fellows, as early career scientists in agricultural sustainability which have much longer term impact. Larger societal benefits to the general public, to be realised in the long term through resulting collaborative research from this and similar proposals, include potential insights into the links between soil and food security, and how these can be optimised by management practices under uncertain future weather conditions (flood and drought). Within the context of the NERC Soil Security programme, the potential long term impact is a new consensus on how to approach sustainable agricultural intensification and new inter-disciplinary research agendas to progress these concepts.