Measures of habitat extent are required indicators of the condition of biological diversity (a constituent descriptor of environmental status) for MSFD. Marine habitat mapping studies measure aspects of habitat extent. However, as a rapidly evolving scientific field, the methodologies and interpretive processes used to determine extent are often variable and certainty either not stated or unknown. Operational use of habitat extent as a condition criterion requires repeatable methodologies with a high certainty. This requires:
1) the most appropriate habitat mapping method is applied within specific habitats,
2) the sources of precision, accuracy and assumptive error associated with methodological and interpretive techniques are known,
3) methods to minimise error and improve repeatability,
4) quantitative understanding of sensitivity and the measureable detection of change; and
5) that measures of extent are based on cost-effective methodologies.
There are now several established methods for habitat mapping, such as aerial photography, satellite imagery, traditional field survey methods, single/multi-beam sonars and videographic/photographic transects. Each mapping approach has a variety of potential collection platforms and methodological variations depending on the purpose and habitat conditions during data collection. This invariably leads to significant variability in the measurement of common parameters between studies. The objective of this project is to identify measurement error and increase scientific rigour within habitat mapping methodologies for the calculation of habitat extent. The first phase of the project will review current habitat mapping methodologies and evaluate them according to quantitative criteria. Each mapping technique/methodological variation will then be scored according to their suitability for measuring habitat extent for at least 26 habitat types.
To better understand the sources of error associated with differing methods and habitats, a generic mapping methodology framework will be presented. Within each stage of the mapping process, all of the possible factors that influence measurement error will be identified and quantified. This will span the entire work-flow for all mapping methods from (i)-hardware specification, (ii)-data collection, (iii)-processing routines, (iv)-interpretation requirements, (v)-interpolation steps, (vi)-storage and spatial presentation of derived products, and finally (vii)-the error in overall presentation of data at unified measures of habitat extent. From this, recommendations will be provided for the reduction of error within these methodologies.
Once this information has been established, it will be possible to establish the cumulative and emerging level of overall measurement error (precision/accuracy) associated with each combination of mapping technique, methodological variation and habitat setting. These calculations provide a measure of certainty for any given measurement of habitat extent. Combination of two or more measures of overall certainly allows the estimation of the sensitivity of a comparison, i.e. what size of change is detectable for a certain level of confidence.
Although advances in mapping hardware have greatly increased the rate of seabed mapping, it is still insufficient to allow complete coverage of many broad-scale habitats. The counter balancing needs of holistic condition assessments against and cost effective monitoring requires that surrogates and indicators are the only practical alternative. This project will also provide workable surrogate methods for measuring the change in habitat extent.