UK woodlands are increasingly under threat from changes in land management, climate, diseases and deer populations – and vegetation is responding differently, requiring tailored action to protect biodiversity. That is the finding of comprehensive surveys of broadleaf woodlands over the past 50 years by the UK Centre for Ecology & Hydrology (UKCEH).
First carried out in 1971 by the late Professor Bob Bunce, the survey was repeated in 2001 and most recently in 2021, the survey examines 97 broadleaf woodlands in different landscapes across Britain.
It found that over the past 50 years, canopy growth due to lack of management over time has led to widespread shading and an overall reduction in plant biodiversity, but in some forests, ash dieback has created canopy gaps. Dense forests protect ecosystems from some of the impacts of climate change, so a lot of gaps could reduce the ability of plants and trees to mitigate the effects of warmer temperatures and storms.
Climate change will bring more extreme weather events and increase trees’ sensitivity to disease, which could result in a vicious circle, where gaps are opened in forest canopies due to disease and storm events, which then reduces the ability of forest vegetation to cope with the changing climate and pest invasions.
Some plants, such as bramble, may benefit from these changes but specialist woodland species such as Lily of the valley (Convallaria majalis) and Common dog-violet (Viola riviniana) will lose out.
Complex responses
UKCEH ecologist Dr Fiona Seaton, who led an analysis of the impact of ash Dieback and deer grazing published in Proceedings of the Royal Society B, said: “Our study confirms that the woodland ecosystem responds in complex ways to changes in management, disease, deer populations and climate, and the future of our woodlands will depend upon the interactions between these threats rather than their individual effects.
“It is important therefore to consider the impacts of all these factors together, and establish clear goals within woodland management, dependent on your priorities.”
The analysis led by UKCEH showed that while ash dieback has reduced tree regeneration, it has also actually led to an increase in the diversity of the ground flora but only where there are enough deer to keep bramble levels low. This indicates there is a trade-off between maintaining ground flora diversity and woodland regeneration.
Deer grazing is, however, likely to increase the diversity of grasses as opposed to specialised woodland plants.
If the priority is diversity of ground flora then active management may be required, particularly in small woods, to both create canopy openings, and control plants such as bramble that inhibit growth of other species.
Promoting tree regeneration would require seedlings to be protected from deer. This could be achieved by deer control and/or by allowing bramble cover.
In most cases, maintaining a mosaic of both lighter and darker conditions across a forest to protect overall biodiversity and woodland regeneration is desirable.
Further information
The detailed analysis of the surveys is contained in a new open access paper in Proceedings of the Royal Society B, titled The increasing role of tree disease and decreasing influence of anthropogenic management over 50 years of woodland dynamics (DOI: 10.1098/rspb.2025.055). It involved UKCEH, Woodland Trust, University of Oxford, Forestry Commission and Natural England.
This follows the publication last year of the overall results from the survey in a report, Fifty years of change across British broadleaved woodlands.
The findings were part of the evidence base for the State of the UK’s Woods and Trees 2025 report published by the Woodland Trust on 10 June 2025. The trust says the deteriorating ecological condition within UK woodlands is resulting in a significant reduction in the quantity and variety of wildlife in these habitats.