Importance of Hedgerows as Wildlife Corridors

Ancient woodland now covers just 2.5% of the UK’s land area and we have lost 50% of our hedgerows since 1945, and they are still in decline. As a result, animals that once flourished in these habitats are also significantly diminished.

• Up to 75% of all of Britain’s rural hedgehogs have been lost in the past 20 years.
• Dormouse numbers have declined by 76%-80% between 1994 and 2018.
• There has been a 41% decline in the woodland butterfly index for the UK between 1990 and 2019.

This project aimed to collect definitive evidence for the role of hedgerows in nurturing woodland biodiversity by studying the distribution of invertebrates in woodland patches. The findings of the study are being disseminated to the scientific community and through the Agricology platform to reach as wide an audience as possible. As a result we hope that landowners will be motivated to introduce and/or maintain healthy hedgerows on their land, thus improving local biodiversity.

Project summary

The project found that hedgerows enhance the local biodiversity value of woodland patches in intensively farmed landscapes. More open agriculture was associated with lower diversity but higher total abundance, whereas greater hedgerow length was associated with higher diversity and lower abundance.

The main conclusion is that hedgerows are valuable local habitats and important components of ecological networks, but should not automatically be assumed to provide effective stand-alone corridors between woodlands.

The work also produced practical outcomes beyond the scientific analysis. Participating landowners received site-specific management advice and comparative biodiversity results. This helped translate the research into local action and created relationships that may support continued woodland improvement and future collaborative research.

The project’s wider relevance was communicated through Groundswell 2026 session involving Lisa Norton from CEH, Tim Coates and Colin Tosh. By placing the results within both scientific and farming contexts, the session helped translate the findings into messages relevant to practical land management.

Most significant discoveries and data insights

• Open agricultural land was the strongest predictor of woodland arthropod biodiversity and abundance.
• Across the observed 1 km landscape gradient, fitted arthropod biodiversity declined by approximately 19.5%, while abundance increased by approximately 31.5%.
• This showed that high abundance did not necessarily indicate a diverse or balanced community. Agriculture-dominated landscapes appeared to support large numbers of individuals from a narrower range of arthropod groups.
• After accounting for open agriculture, greater hedgerow length was associated with approximately 7.1% higher biodiversity and approximately 14% lower abundance.
• Hedgerow-rich landscapes may therefore support more even and heterogeneous communities rather than very high numbers of a few dominant taxa.
• Hedgerow length received more statistical support than hedgerow fragmentation, suggesting that the total amount of hedgerow habitat may matter more for local woodland biodiversity than mapped continuity alone.
• There was little evidence that hedgerow structure between woodland patches explained community similarity. Hedgerow measures each explained less than approximately 0.9% of the variation in community dissimilarity, and the permutation tests were non-significant.
• The results suggest that hedgerows mainly provide local habitat, shelter, resources and spillover benefits rather than producing detectable broad-scale connectivity at order-level taxonomic resolution.

What was learned for future research?

The project showed that hedgerow quantity, quality and functional connectivity should be treated as separate concepts. A hedge may physically connect two sites without generating enough successful movement to affect entire arthropod communities.

Future work should:

• identify selected arthropods to species, family or functional-group level;
• use direct movement or population-genetic methods;
• include larger, deliberately stratified samples of connected and unconnected woodlands;
• record hedge quality, management, vegetation, mature trees and gaps in the field;
• include woodland characteristics such as deadwood, tree diversity, understorey structure, wet features and patch size; and
• test targeted hedge planting or restoration through long-term monitoring.

The relationships developed with landowners are an important asset for this work. They provide a potential network of study sites, local knowledge and engaged managers who could participate in repeat monitoring, experimental management and future landscape-scale projects.

The Groundswell session also demonstrated the value of bringing researchers and farmers together when interpreting ecological evidence. Future dissemination should continue to combine scientific findings with practical experience so that research questions and management recommendations remain relevant to landowners.

Where does the research go from here?

The immediate priorities are peer-reviewed publication, permanent data archiving and wider communication of the findings.

A follow-on study should combine landscape sampling with finer taxonomic identification, direct movement studies and population-genetic analysis. This would test whether hedgerows support occasional but important movement that was not detectable through broad community comparisons.

For land management, the results indicate that increasing hedgerow habitat should benefit local arthropod diversity. However, effective woodland connectivity is more likely to require hedgerows to be combined with hedgerow trees, scrub, flower-rich margins, ponds, ditches, riparian strips, small copses and stepping-stone habitats.

Continued engagement with participating landowners would allow the scientific findings to be tested through practical management and would help maintain the long-term research relationships created by the project. The network developed through the fieldwork, individual landowner feedback and the Groundswell session provides a strong foundation for future research, demonstration and knowledge-exchange activity.

ORC’s Role

This is an ORC independently owned and managed project. ORC is the project lead, coordinator and budget holder.

Current progress highlights

BigGive The Importance of Hedgerows campaign

May 2024

Colin Tosh has been insect water trap sampling 18 woodlands across the Suffolk agricultural landscape. The data collected will be analysed using GIS to determine how landscape hedgerow density and gappiness is impacting woodland species diversity and community composition.

Sampling insects is very easy. Stick a yellow cereal bowl to the top of a wooden steak and fill it with water with a drop of detergent in to catch the flying insects. Ground dwellers are caught in pitfall traps: a disposable party cup dug level with the ground and full of the same soap water. Insects found in the water after a few days can be preserved in 70% isopropanol or 80% alcohol for later identification

Previous relevant work

Related News Posts:

Are we asking too much of our hedges?

Where there’s a Will there’s a way

Join us at the Agroforestry Tent at Groundswell

Agroforestry at Groundswell

ORC 2024 Annual Review: Another action-packed year

Will Simonson profiled in CJS Focus on Forestry and Arboriculture