Holly Claire Woo shares her team’s experience investigating the impact of urbanisation on ancient woodlands in the UK.
Imagine yourself in an ancient woodland: with a dappled canopy of broadleaf trees, some showing signs of historic coppicing, and a carpet of English bluebells, studded with Wood Anemones, Greater Stitchwort, Early Purple orchids, Herb Paris and other rare and specialist woodland species. You are in a rare and precious place as many of these centuries-old biodiverse woodlands were felled to make way for agricultural land and conifer plantations throughout the 20th century leaving just 364,200 ha of ancient woodland in England today (Reid et al, 2021). During this same period, the process of urbanisation saw towns and cities expand to house the growing population.
Current legislation states that planned urban developments should be refused if they result in the loss or deterioration of this irreplaceable habitat. However, development can be permitted as near as 15 metres from a woodland boundary, surrounding the woodland with housing and infrastructure.
During my PhD I have been looking into the impacts that urban development is having on these habitats, particularly in terms of the changing flora.
Using historic records to understand floristic change
- Greater London, where historical urban development occurred over several centuries and over 100 ancient woodlands were surrounded by urban development before the 1930s;
- Warwickshire, where the cities of Coventry and Solihull grew rapidly in the mid-20th century with post-war housing being built near and around several ancient woodland sites;
- NE Buckinghamshire, which includes the city of Milton Keynes that was designed as a “new town” and developed from the 1980s onwards, surrounding three large patches of ancient woodland.
Having spent time surveying the ground flora in woods in Milton Keynes, visiting rural ancient woodlands in Warwickshire with my local flora group, and working to curate botanical specimens in provincial and national museums, I’ve seen how important it can be to document where and when species occur and what this can tell us about the changing environment.
For this investigation, we collated around 19,000 records of flowering plant species from 43 sites, sourcing data from environmental records centres including Buckinghamshire and Milton Keynes Environmental Records Centre (BMERC), Warwickshire Biological Records Centre (WBRC) and Greenspace Information for Greater London CIC (GiGL), as well as the National Biodiversity Network (NBN) and independent survey reports. The records dated from 1835 to 2024, and we were able to check for differences in floral composition between rural and urban ancient woodland in the three regions. We also looked at differences in community composition before and after 1990 (the approximate date of development near the ancient woodlands in the most recently urbanised region: Milton Keynes in NE Buckinghamshire).
We found that urban ancient woodlands were home to a growing number of alien plant species, that were likely to have been introduced from urban parks and gardens.
We also discovered that woods that had been surrounded by urban development for longer showed more floristic change. Compared to Milton Keynes, where three ancient woodlands were surrounded by urban development in the 1980s-2000s, ancient woodlands like Highgate Wood in central London showed more dramatic floristic change, indicating that impacts of urbanisation occur over long time scales.
However, the urban ancient woodlands were still just as rich in ancient woodland indicator species as similar rural woods nearby, showing that they are still important places for nature conservation.
Managing change in urban ancient woodlands
The spread of alien species into semi-natural habitats is a widespread conservation concern, and our findings suggest that careful long-term monitoring is needed to detect and possibly remove potentially invasive species. We also need to think about how we manage people visiting urban ancient woodlands and advise local authorities and residents with gardens nearby on how to prevent the spread of alien plants.
These treasured irreplaceable habitats are dynamic ecosystems that have seen changes in woodland management, surrounding landuse and climate over the centuries. In the face of new threats from urbanisation, we’ve shown the value of long-term biological recording to document floristic change and give us a better understanding of how to manage ancient woodlands in the future.
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