What regulatory ecosystem services do hedges deliver?
Agri-environment theme: A review of the evidence base to inform agrienvironment scheme policy development
What are the issues?
The biodiversity, landscape and cultural benefits of hedges are well known, but hedges benefit us and our
environment in other ways too. They can help to keep the water of our rivers clean, reduce the risk of flooding,
and prevent soil loss from fields. Yet the evidence base for the extent to which hedges provide such
regulatory services is poor, largely reliant on the small amount of research that has been carried out abroad in
countries like France. Water quality will be a priority within the successor scheme to Environmental
Stewardship and Catchment Sensitive Farming, so it is important to understand what the available evidence
tells us about the best ways and places to deliver hedge-related management options in order to deliver these
services. We also need to be aware of current action which is not supported by good research.
What are the aims of the project?

To undertake a rigorous review of evidence
for hedges delivering the following nine
ecosystem services:
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Water quality improvement
Flood risk reduction
Soil loss reduction
Crop water availability
Crop pest reduction
Crop pollination improvement
Shelter provision (crops and livestock)
Climate change mitigation
Urban air quality improvement
To analyse and synthesise the evidence
relevant to hedge conservation, creation and
management, with particular relevance to the
on-going development, targeting and delivery
of NELMS. To also interpret the evidence in
the context of CAP greening and crosscompliance.

To present available information on the
quantity of service provision as well as its
quality.

To identify evidence gaps and priority areas
for future research.

To produce a leaflet summarising optimal
hedge management for the services, again
focussing on the first three.
Figure 1: Hedges can help reduce flood risk by impeding storm water run-off on
slopes, and may help flood plains retain and store water. Photo: Judy Webb.
Which policy areas will the research
inform?
In an agri-environment context, the research
informs the extent to which the conservation,
management and creation of hedges can help
deliver scheme objectives, through purifying
water, reducing flood risk, preventing soil loss
from fields, supporting pollinators and assisting
with carbon storage and reduction in greenhouse
gas emissions. Available evidence is used to
suggest appropriate management action to
enhance delivery of these services and effective
targeting of resources.
In an agricultural production context, the research
identifies the potential roles of hedges in reducing
pesticide use, increasing crop yields and
improving the welfare of livestock.
In an urban context, the research informs the use
of trees and hedges in towns and cities to improve
air quality through the removal of particulates and
other pollutants.
LM0106: Regulatory services delivered by hedges: the evidence base.
What regulatory ecosystem services do hedges deliver?
What are the results from the project and
how will they be used?
Evidence assessment. Greatest reliance was
placed on evidence from temperate regions with
climatic conditions and hedge types similar to the
British Isles. Peer-reviewed papers were given
greatest weight, followed by published reports and
expert opinion. Less weight was attached to
anecdotal information. Relevant evidence from buffer
strips, beetle banks, windbreaks and shelterbelts was
considered.
Water quality: Strong evidence exists that individual
hedges can be very effective at preventing nutrients
and other pollutants reaching water bodies if they
follow slope contours. Weaker evidence suggests
hedges with earth banks and those that are at least
2m (preferably 5m) wide, including herbaceous basal
and marginal vegetation, are particularly effective.
Little evidence exists at how effective hedge
networks can be at a catchment scale: it is probable
that hedges have high potential here, but further
research is required to confirm it. Hedges are likely to
be particularly effective at preventing diffuse pollution
where the land above is compacted or cultivated.
Planting and restoring hedges along contours, filling
in gaps including gateways as necessary, together
with the management of field drainage systems, are
the key management requirements.
diversity of pollinators, and export them into crops.
Hedges provide breeding sites, food when crops are
not in flower, shelter, protection and flight lines.
However little or no information exists on impacts on
crop yields. Another major research gap is the
importance of insects other than bees and hoverflies
for pollination. There is an indication that hedges can
influence the pollination of crops over a distance of at
least 750 m, but this is also requires further research.
Key management actions are to promote structurally
diverse hedges (with banks, emergent trees, ditches
and herbaceous margins as well as shrubs), to
encourage plentiful flowers on both shrubs and herbs
from spring to autumn, and to plant more hedges.
Climate change mitigation: Strong evidence shows
that hedges can store and accumulate significant
amounts of carbon both above and below ground.
Tree lines store most. Hedges in a Brittany landscape
were estimated to contain 13% of the carbon stored in
that landscape. To have any significant impact, carbon
needs to be locked up within hedges and soil over the
long-term. Alternatively, hedges can be cost-effectively
cropped for woodfuel, substituting for fossil fuel use.
Planting new hedges and allowing hedge trees to grow
are the key actions.
For information on Crop pest reduction, Crop water
availability, Shelter and Urban air quality
improvement, please see report.
Flood risk reduction: Strong evidence exists that
individual hedges can reduce the volume and rate of
water moving down slope and so potentially help to
reduce the risk of flooding. Hedges act as physical
barriers, especially if they contain earth banks, and
typical British hedge shrubs and trees can greatly
increase water penetration into the ground. Some
evidence exists to show that hedge networks can
reduce peak flows of nearby water courses following
heavy rainfall by up to 50%, but more research is
required at the catchment scale.
Soil loss reduction: Strong evidence exists that
hedges can significantly reduce soil loss from fields
through intercepting water-borne sediment. They do
this through acting as a physical barrier and
increasing water infiltration. As soil builds up above
them, so hedges become increasingly effective.
Strong evidence also exists, largely from other
countries, that hedges can be effective at reducing
wind erosion, in flat areas with light soils. The
effectiveness of hedges at capturing both wind and
water borne soil particles varies greatly with local
soils, topography, agricultural practices and climate.
The key management requirements are the same as
for water quality and flood risk reduction.
Crop pollination improvement: Strong evidence
exists that hedges enhance population size and
Figure 2: Hedges can stop storm water eroding soil from farmland and
reduce the risk of flooding further down the catchment. Photo: Rob Wolton
Where can I find further information about
this and related research?
Wolton, R.J., Pollard, K.A., Goodwin, A. & Norton, L.
2014. Regulatory services delivered by hedges: the
evidence base. Report of Defra project LM0106.
For further information please contact Emily Ledder
(emily.ledder@naturalengland.org.uk) or alternatively
Defra’s Sustainable Land and Soils Unit.
Defra Science – did you know?
At any one time Defra manages over 1000 research projects covering a wide range of topics. For more information on
current research see http://randd.defra.gov.uk.
LM0106: Regulatory services delivered by hedges: the evidence base.