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  • Ellie Smith

Protecting Hertfordshire’s Ancient Woodlands

Updated: Nov 24, 2022

What is ancient woodland?

Woodlands can be described as ancient if they have been continuously wooded since at least 1600 AD. They are categorised as either Ancient Semi-Natural Woodland (ASNW) or Plantation on Ancient Woodland Sites (PAWS) (Figure 1).

Ancient woodlands are rich habitats, having developed relatively undisturbed over centuries. As a result, they have complex soil communities and support a vast array of wildlife, including many rare and protected species that can be found nowhere else. They also play an important role in capturing and storing carbon from our atmosphere. Combined with their cultural and historic value in our landscapes today, they are therefore considered to be one of our most important habitats, and irreplaceable if destroyed.

Figure 1. Types of ancient woodland.

The Ancient Woodland Inventory

The Ancient Woodland Inventory in England is a spatial dataset identifying the location and extent of these ancient woodlands across the country. It provides an essential reference tool for planners and developers, policy makers, woodland owners and managers, in turn supporting the protection of these long-established habitats.

Time for an update!

The Ancient Woodland Inventory was originally compiled between 1981 and 1992, initially on paper maps which were later digitised. Since this time, computer mapping technology and methods of identifying ancient woodlands have improved considerably, driving the need for an update to this dataset.

The Ancient Woodland Inventory update, coordinated by Natural England will:

  • Allow for the incorporation of new evidence to support ancient woodland classification.

  • Improve on the accuracy and precision of existing ancient woodland boundaries, and remove mapping errors created when the original dataset was digitised.

  • Identify omissions from the original dataset, including any ancient woodland parcels smaller than 2 hectares and wood pastures (another important ancient habitat).

Once completed, the updated Ancient Woodland Inventory will become available as Open Data on

Figure 2. Balls Wood, an ancient woodland in Hertfordshire. © Charlotte Hussey.

What we’ve done so far…

HERC, along with other Local Environmental Records Centres across the country, have already completed an initial phase, creating GIS layers for each county which highlight potential changes to the Inventory where further investigation is needed. This was achieved by comparing current woodland cover using aerial imagery with Epoch 1 maps (published in the late 1800s) and the existing Ancient Woodland Inventory layer.

Next steps and how to get involved

The next stage of this project is to refine this dataset, using a range of sources including earlier historic maps and field evidence to support decision-making. In Hertfordshire, a Landscape Historian will direct and carry out the bulk of the historical map research, and we are currently recruiting for a new Data Officer (Ancient Woodland and Habitats) to deliver the rest of this update.

This Data Officer will be responsible for overseeing the overall progress of the project, carrying out the bulk of the GIS documentation following Natural England’s guidelines, prioritising and organising field survey, coordinating volunteers and liaising with stakeholders. More information about the role, and how to apply, can be found here. Application deadline: Tuesday 13th December at 9am.

We are also looking to engage with volunteers interested in carrying out field surveys of long-established woodlands in Spring and Summer 2023, to collect evidence of ancient woodland features. If you would like to get involved, or if you have any questions, please contact us at

We would also be very interested to hear from woodland owners – if you believe your woodland may be ancient and would like to request a survey for next year (subject to availability), please get in touch!


SANSUM, P. & BANNISTER, N.R. 2018. A Handbook for updating the Ancient Woodland Inventory for England. Natural England Commissioned Reports


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