The primary time period of aerial imagery capture from which the saltmarsh extent is derived, is 2006-2015. However, some very small areas were collected before this time. In the attribute table, the ‘YEAR’ field indicates the timing of the photo capture for each feature.
The original baseline publication of this data included data from 2006-09, but large areas have been remapped since, and the downloadable version you can access now is from 2009-2015.
Also, we are in fact due to publish a further updated version, which will include some areas mapped from imagery as recent as 2018. Alongside this, we intend to publish a new product showing Saltmarsh Change, which compares the baseline (06-09) against the most recent extent. So this will show areas of recent accretion and erosion etc. Approximately 80% of the national extent has been remapped, (20% has been remapped before 2016, 60% remapped since 2016, 20% not remapped at all). I expect this data to be published some time over the summer.