By Laura A Edwards: September 2008
Supervisors: Dr Nick Voulvoulis and Dr Martin Head
Collaborators: The Environment Agency - Dr Tatiana Boucard
Soil is one of Earth’s most precious assets; it allows people, plants and animals to live on its surface. Together with air and water, it is a fundamental and irreplaceable natural resource, and essential for life.
In the European Union (EU), there is a renewed interest in the development of cross-sector, holistic environmental protection legislation to not only prevent the destruction of soils, but to protect them from poor land-use management and ensure they are used sustainably.
This has taken the form of a developing European Thematic Strategy for Soil Protection, which will be incorporating the forthcoming EU Soil Framework Directive. This drive for improved, integrated soils protection legislation has led to an increased activity in soil quality surveying and monitoring, and the identification and definition of key threats to soils requiring intervention.
The main aim of this project was to define a proven, relevant and effective methodology for in-situ soil quality assessment, with the intention that it is utilised in the OPAL soil and earthworm survey. The following objectives were set in order to achieve this aim:
- Conduct a critical review of soil quality indicators currently in use in the soil science community, including the methods of their implementation, the value of data collected, and their limitations
- Refine a list of potential soil quality indicators to be incorporated in the national survey, and investigate methods of in-situ assessment
- Define a field methodology and pilot test in a field location, with soil samples collected from varying geological settings
- Refine field methodology from the lessons learned from pilot trials.
To achieve objective 1 - academic literature and reports from governmental sources and non-governmental organisations (NGOs) were consulted.
To achieve objective 2 - methods of in-situ assessment of these indicators were evaluated.
The results of this analysis were refined and assessed in a performance assessment against their feasibility, relevance to policy and environmental objectives, relevance to earthworm distributions, value to other indicators in the suite, and their educational value. Output of Multi Criteria Analysis (MCA) was then used to define the suite of core soil quality indicators to be incorporated into the in-situ methodology, and the criteria for assessment and interpretation of each of these indicators were defined.
To achieve objective 3 - the results of the analysis were put to test in field conditions, in the form of a public trial that took place at Hounslow Heath, West London, on 2nd June 2008.
To achieve objective 4 - the lessons learned from the public and individual trials of the proposed soil quality assessment methodology were used to refine and improve the tool, resulting in a finished product.
The Environment Agency defined a list of requirements for the selection of policy-orientated soil quality indicators:
- Specific: responsive to human-induced changes to the environment
- Measurable: robust methods with defined precision (tolerance); simple and cost-effective to measure
- Achievable: signal distinguishable from noise; applicable to monitoring
- Result-orientated: provides diagnostic or predictive information with consequential policy actions (action levels with tolerance)
- Time-based: provide reliable information over a pre-determined timescale
The criterion to be considered in the refinement of a suite of soil quality indicators for the production of this assessment tool is defined as follows:
- Feasible: can be practically measured or observed in-situ with little soil science understanding
- Meaningful: provide tangible information on soil quality or soil status
- Proven: information inferred from a result must be well-documented. Process is replicable by multiple users and locations
- Policy-relevant: indicators should provide information relevant to the development and enforcement of current and future soils protection policy
- Educational and engaging: facilitate the increase in public awareness of soil science and the consequential public engagement in effective soil management
- Cost-effective: information must be obtainable at reasonable cost, and, if possible, without the need for field equipment
- Relevant to earthworm distribution: earthworm populations will be included in the OPAL soil and earthworm survey. Therefore, known indicators relevant to the abundance and distributions of earthworm populations must be included.
To this end the content of the field guide followed an iterative development process of design, testing and improvement so that the combination of data for each of the parameters could be optimised, particularly with relevance to these above criteria.
Results and discussion
When interpreting the results from a soil quality assessment, it is important to consider the output in context. For example, where possible, current or intended land-use should be incorporated; such that reasonable soil management goals can be derived against which soil quality can be assessed.
It is also important to consider seasonal fluctuations, anthropogenic disturbance and immediate land use and land-use setting when interpreting the results from the national survey. Additionally, when soil quality indicators are being applied to macro-scale analyses, such as a monitoring network, accurate consideration must be given to the design of the appropriate sampling strategy.
It must also be remembered that managing the physical and chemical quality of soil and the environment is only one pillar of effective ecological conservation. Spatial heterogeneity, habitat fragmentation and connectivity are also very important to the ecological systems that soil supports.
In this report a methodology for the in-situ assessment of soil quality relevant to the function of earthworm biodiversity was proposed, which eventually led to the creation of the field guide used in the OPAL soil and earthworm survey. The final version of this was developed with the help of the Field Studies Council.
Download the full project summary (PDF, 1.9MB)