Technical Note TN661
January 2015 • Elec
Practical guidelines for recognising
general signs of Overgrazing and
Undergrazing within semi-natural
Habitats
SUMMARY
• Identify clearly what the objectives are for managing the specific habitat type at
the chosen site.
• Undertake a species survey of the habitat (plants and animals), to assess overall
biological diversity and distribution, across the site.
• Put in place a short, medium and long term management plan for the site.
• Establish a grazing management plan for the site and be prepared to alter it at
any time, should any of the factors influencing habitat condition change.
• Look out for signs of overgrazing or undergrazing, as highlighted in this
Technical Note and take remedial action.
• Determine whether livestock grazing management is the only factor influencing
habitat condition or if there are additional influences, such as rabbits or deer.
Introduction
overgrazed or undergrazed. Regular site condition monitoring is
important, not only on Designated Sites but on all semi-natural
farmland habitats, to ensure that sites do not degrade, as a result
of over or undergrazing. Regular monitoring throughout the year,
allows for changes in grazing management to take place. The
purpose of this Technical Note is to provide practical guidelines
for recognising general signs of overgrazing and undergrazing
within semi-natural Habitats. Grazing plans are important. Good
grazing plans will be site specific.
Grazing is a gradual form of vegetation removal. Grazing
by livestock, is a key habitat management tool which has a
significant effect on habitat composition and the amount and
type of wildlife a habitat will attract and retain. Most farmland
habitats are either grazed all year, for part of the year or not
grazed at all during the year. On Designated Sites, habitats are
considered to be in ‘optimum or favourable condition’ if the
nature conservation objectives for that particular site are being
met. With respect to grazing levels, if the site is not in optimum
condition, the habitat is generally considered to be either
SRUC 2014. Peter Wilson Building, Nicholas Kemmer Road, Edinburgh EH9 3FH. SRUC is a charity registered in Scotland, No. SC003712
©
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Benefits of Conservation Grazing
* Increase in ‘undesirable weeds’ such as Ragwort, Docks
and Thistles
* Domination by coarse grass species
* Development of thick grass litter layer
* Reduced number of flowering plants
* High insect numbers
* Undergrazing is most noticeable on larger sites
Across Scotland and the north of England, most habitats we
value for their wildlife interest and landscape appeal, have
been created and managed by farmers over many generations.
Habitats such as wildflower rich grasslands, wetlands, heather
moorland, native woodland and coastal grasslands, depend
upon grazing to some extent. Without grazing, (and without
mans influence) dense woodland would ultimately dominate
the landscape. To maintain this rich diversity of habitat types,
grazing is essential. Over recent years, many habitat re-creation
schemes have been undertaken, such as arable reversion to
species rich wildflower grassland or sowing upland grassland
with heather seed, to create heather moorland. Almost all such
schemes require grazing by livestock to attain and later maintain
optimum habitat condition. Inappropriate grazing can lead to
over or undergrazing and ultimately deterioration in the overall
habitat condition.
Signs of overgrazing in grassland
* Uniform short sward height (under 5cm)
* Bare patches/poaching of exposed soil by livestock
trampling
* Excessive dunging by livestock (via supplementary feeding)
leading to increased fertility
* Browsing damage to adjacent field margin hedges/trees
* Lack of invertebrate species
* Lack of ground nesting birds, due to disturbance by stock
* Overgrazing is most noticeable on smaller sites
Optimum Stocking Levels
It is recognised, that factors other than grazing livestock,
affect the condition of a habitat, such as; other animals,
feeding preferences, palatability of plants, weather, soil type,
geology, altitude, aspect and fire. Availability of drinking water,
supplementary food, shelter and shade, are also key determinants
of animal movement and grazing behaviour on sites. This
Technical Note is intended to be a practical tool but the author is
aware that most land management decisions are determined by
factors such as; location, stock availability, access, cost, fence
condition and labour. Add to this, animal types and age ranges
and it becomes clear, that being prescriptive regarding annual
stocking densities and duration is unrealistic. Sward height and
structure is generally a better guide to the site condition, than
number of stock on the site. However, there are some general
principles which can be applied to various habitat types, to
assess whether they are being over or undergrazed.
Undergrazed wildflower grassland - With coarse grasses,
scrub and undesirable weeds dominating the site. Light
summer and autumn grazing with cattle (and/or sheep )
would benefit this site
Recognising overgrazed and
undergrazed habitats
Wetland and Waterside margins
For this Technical Note, an assumption has been made that the
conservation objective on all semi-natural habitats is to maintain
or enhance the diversity of plants and animals at the site.
Cattle are generally the best livestock to use for grazing wet
grassland, fens and rush dominated sites. However, where
open water occurs, such as around ponds and along stream
sides, cattle can cause considerable damage through poaching.
Sheep or a mixture of sheep and light cattle grazing, may be
more appropriate. Cutting with the removal of biomass, may be
the only option on highly sensitive sites. Setting conservation
objectives for the site is important and setting stocking levels to
encourage the spread of wetland plants may be tolerably higher
than those set to encourage ground nesting birds such as Snipe.
Wildflower Grassland
With reference to grazing and species diversity on calcareous,
neutral and acid grasslands, (and in grazed pastures excluding
hay meadows): If the dominant grass species are palatable, then
grazing will increase biodiversity, but if the dominant species
are unpalatable, then grazing will reduce biodiversity. Generally,
light year round grazing, which creates a range in sward heights
between 5cm and 20cm, is ideal for most flowers, butterflies
and beetles. The sward should be tallest in the summer to
encourage flowering and seed setting.
Signs of undergrazing in wetland
*
*
*
*
Signs of undergrazing in grassland
* Scrub (Hawthorn, Gorse) and woody tree growth on site
* Tall and even sward height (over 20cm)
Rush/Reed encroachment at expense of grass
Growth of shrubs, particularly Willow, on the site
Habitat (wet grassland) becoming drier
Domination of stream sides by single plant species ie Reed
canary grass
Signs of overgrazing in wetland
* Reduction in overall plant species composition
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Signs of undergrazing in moorland
* Closely grazed patches of Rush
* Lack of wetland invertebrates such as Dragonflies
* Reduction in number of ground nesting birds such as
Lapwing or Snipe
* Site becoming wetter or excessive poaching
*
*
*
*
Extensive areas of tall leggy heather
100% ungrazed flower heads/new shoots on heather plants
Regeneration of trees (Rowan, Birch) through heather
Areas of tall acid grassland with thick thatch on ground layer
Signs of overgrazing in moorland
* Closely cropped grass (and moss) dominated lower hill
slopes
* Small patches/mosaics of highly fragmented heather and
grass
* Areas of low growing heather plants, ‘Carpet heather’
* Areas of pin cushion, ‘Topiary’ heather and single branches,
‘Drumstick’ heather
* More than 60% heather flowers/new shoots grazed annually
* Noticeable signs of grazing of unpalatable grasses such as
Mat grass and Purple Moor grass, particularly in Spring.
* Bracken encroachment
Undergrazed wet grassland- If the ground is not too wet, then
light summer and autumn grazing with cattle, would benefit
this site
Overgrazed Heather Moorland- Management recommendation
for this site; Stock reduction, away wintering, active shepherding
and bracken control
Upland and Heather Moorland
This habitat type comprises a mosaic of dwarf shrub heath
(Heather, Blaeberry), acid grassland (Mat grass, Purple moor
grass) and peat bogs. This habitat more than any other, is heavily
influenced by weather (particularly rainfall) and grazing levels.
In the absence of burning, sheep are crucial in maintaining the
balance between heather and grass composition on a moor.
Grass is preferred by sheep but they will eat heather in the winter.
Overgrazing of heather moorland is most likely to occur in winter.
Light summer grazing with cattle (and sheep) can significantly
enhance the condition of a moor. Stocking densities have
traditionally been well studied for upland habitats. Assuming
that native woodland regeneration is not a desired moorland
management objective, then the stocking levels in Table 1, can
be used as a guide-
Native Woodland and Wood Pasture
Table 1 - Management prescriptions for enhancing
moorland grazed by sheep. (1) – (3) gives order of stages
for each condition
Old stands of native woodland and recently planted woodland
sites add significant landscape and biodiversity value to an area.
Many woodlands are a mixture of several habitats (especially
if they are open to grazing as is the case with wood pasture)
and have elements of grassland, wetland and in the uplands,
moorland habitats. The wildlife associated with such woodlands
can be very diverse. Management plans for individual woods
may vary but most plans should include measures that enhance
the woodland environment for wildlife. In grazed woodlands,
this will involve such measures as: maintaining or creating tree
species diversity, retaining or creating age structure, keeping
rides/glades free from trees, retaining dead/fallen trees,
maintaining/creating several layers within the wood, ie field layer,
shrub layer and canopy. Other than livestock, grazing animals
such as deer, rabbits and voles can have a significant impact on
tree regeneration and distribution within a wood. In mature and
semi-mature woodland and wood pasture situations, complete
exclusion of livestock (through fencing) may well damage
existing conservation interest. Low or intermittent stocking
is the preferred management practice, leading to a mosaic of
grazed and ungrazed woodland or wood pasture.
Current Heather Prescription- Ewes per hectare plus any
condition
off-wintering (O-W)1 in ordered stages
Good
(1) 0.75 – 1.5 and zero O-W
(2) 1.5 – 2.0 and 50% O-W
Poor
(1) 0.5 – 0.75 (for years 1 – 5) and
100% O-W
(2) 1.5 – 2.0 (for >5 years) and 50% O-W
Suppressed
(1) Summer graze (for years 1 – 5) and
100% O-W on grass
(2) 0.5 – 0.75 (for years 6 – 10) and
50 – 100% O-W
(3) 1.5 – 2.0 (for years 11 – 15) and
50% O-W
Note: 1 Off-wintered sheep are put on in-bye land or are
housed. Source: Adapted from Sutherland and Hill (2005)
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Signs of undergrazing in woodland
* Dense stands of single species trees such as young Birch,
Ash or Sycamore
* Impenetrable shrub layer
* Lack of diverse ground flora
* No open spaces/glades
* No open woodland rides
Signs of overgrazing in woodland
*
*
*
*
*
*
*
*
Absence of any sign of tree regeneration
Lack of young trees
Uniform age structure
Uniform tree size
Increased Bracken cover
Domination of field layer by small number of plants
Ring barking of mature trees and browsing of branches
Browse line on trees
Well managed coastal grasslands - Here, sheep are excluded
each summer which could lead to undergrazing but the dry thin
soils reduce grass vigour, allowing flowers to grow.
Grazing Management Variables
Different types of grazing animals differ in their grazing behaviour
and plant selectivity. Grazing patterns vary with age and breed,
which leads to differences in grassland species composition
and sward structure. For example, there are marked differences
between cattle and sheep grazing patterns. Cattle wrap their
tongues around herbage and pull it out. This action aerates
the soil. Their heavy bodies and pointed cleaves, break up the
soil and the root systems of invasive plants like Bracken and
Matt grass. Cattle are less selective grazers, eating rushes
and sedges along with heather, grasses and flowering plants.
They seldom eliminate any plant species. Sheep by contrast,
are highly selective grazers and will seek out the more palatable
flowers and grasses. They graze the ‘more favourable’ plants at
ground level, which in time leads to their elimination from the
sward. Poorer quality grasses are left to dominate. Horses, Red
deer and goats have their own specific grazing patterns too. It is
unrealistic to be specific regarding optimum stocking densities.
However, guideline annual average stocking rates for a range
of semi-natural habitats are listed in Table 2. Table 3, refers to
livestock unit values for a range of farm animals.
Undergrazed wood pasture - This former pasture is now
ungrazed and the woodland edge is expanding. Light grazing
could be reintroduced.
Coastal Habitats
Included here are: rocky shores, sea cliffs, dunes and saltmarshes.
Species diversity can be very high in such habitats but grazing
management can be problematic due to accessibility. For most
of these habitats, there is little active management which can be
undertaken except for grazing.
Signs of undergrazing in coastal grassland
* Scrub (Hawthorn, Gorse) and woody tree growth on sea
braes (except on cliffs, beyond the reach of browsers)
* Tall and even sward height (over 15cm)
* Increase in ‘undesirable weeds’ such as Ragwort, Docks
and Thistles
* Domination by coarse grass species
* Reduced number of flowering plants such as Thrift
Signs of overgrazing in coastal grassland
*
*
*
*
Uniform short sward height (under 2cm)
Bare patches of exposed soil/rock by livestock trampling
Lack of invertebrate species such as Butterflies
Lack of ground nesting birds due to disturbance by stock
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Monitoring
Table 2- Guideline annual average stocking rates for a
range of semi-natural habitats
Setting grazing management objectives and working to a medium
and long term management plan is important, if undergrazing
or overgrazing is to be avoided. Habitat management for
conservation, is as much an art, as a science and managing for
one species can have a detrimental affect upon another. Regular
monitoring (species composition, sward structure, ground and
animal condition) combined with flexibility to adapt, will ensure
the best general grazing management to benefit the overall
habitat and most of the species found at any given site.
Guideline
annual
average
stocking rate
LU/ha/year
Grassland
Grassland
Improved grassland (eg Lolium)
1.00
Unimproved lowland grassland
0.30 – 0.40
Unimproved upland grassland (eg Nardus)
0.15 – 0.25
Grants, Rules and Regulations
Moorland
Young heather (< 20 cm)
0.20
Intermediate heather (20 – 40 cm)
0.05
Old heather (> 40 cm)
0.02
Blanket Bog
0.06
Grazing management grants may be available from the
Scottish Government through the Scottish Rural Development
Programme (SRDP).
Under Sections 10 and 11 of the Deer (Scotland) Act 1996 the Deer
Commission for Scotland can issue an authorisation for the control
of deer on hill land to prevent serious overgrazing, where DCS is
satisfied that overgrazing is being caused by deer. Initially DCS can
make a request in writing to the person(s) with the shooting rights
on the land concerned. If that person is unable or unwilling to kill
the deer, DCS can then authorise any competent person to do so.
Woodland
High fertility (eg Lowland broadleaves)
0.15
Moderate fertility (eg Birchwood)
0.07
Low fertility (eg Native pinewood)
0.03
Mob-stocking to enhance regeneration*
0.25 – 0.50
Overburning should be avoided by following the Muirburn Code.
Wetland
Rush pasture
0.40
Lowland raised bog
0.05
Swamp and fen
0.03
It is important to consult SNH where any land affected by
overgrazing forms part of an SSSI, SPA or SAC. Changes in
stocking density in such areas may require SNH agreement
and may affect payments due under management agreements.
Support may be available for certain grazing regimes which are
of conservation benefit.
Coastal
Coastal sand dunes
0.10 – 0.30
Coastal heath
0.15 – 0.30
Saltmarsh
0.25 – 0.50
Goose management schemes exist in a number of areas which
are heavily used by geese. You should note that certain goose
species are specially protected and must not be shot. All
shooting is illegal out of season except under a licence granted
by SGRPID.
* for short periods only, Source – Paul Chapman SAC Technical note on Conservation Grazing,
March 2007. (Information gleaned from various sources
including unpublished)
Table 3- Livestock unit values for a range of livestock
Livestock Type
Livestock Units (LU)
Ewe
0.12
Ewe and lamb
0.15
Beef cattle 6 – 12 months
0.4
Beef cattle 12 – 24 months
0.6
Beef cattle > 24 months
0.8
Suckler cow and calf
1.0
Horse > 24 months
1.0
Ponies > 24 months
0.8
Red deer
0.25
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Conclusion
References
Practical guidelines for recognising general signs of overgrazing
and undergrazing within semi-natural habitats have been
described. Conservation grazing management decisions,
which avoid under or overgrazing a site, involve knowing
what plant species are present and how livestock selectively
graze these species. A flexible grazing management plan is
essential therefore, if the conservation interest of the site is to
be maintained. A good grazing management plan will be site
specific and set clear objectives which will include regular
monitoring. Sharing of experiences and knowledge with other
land managers, should be encouraged.
Backshall, J et al (2001)
The Upland Management Handbook
English Nature
Chapman, P (2007)
Conservation Grazing of Semi-natural Habitats
SAC Technical note
Hill, D et al (2005)
Handbook of Biodiversity Methods- Survey, Evaluation and
Monitoring
RPS Group plc and SNH
Further Information
Scottish Government (2005, updated 2007)
Cross Compliance Notes for Guidance
Further information on grazing management can be obtained
from the following organisations web sites:
Sutherland, W.J & Hill, D.A. (2005)
Managing Habitats for Conservation
ICI and Cambridge University Press
* Scottish Agricultural College (SAC)
* Scottish Natural Heritage (SNH)
* Grazing Animals Project (GAP)
* Institute of Ecology and Environmental Management (IEEM)
* Scottish Government (SRDP)
Scottish Government 2015
www.ruralpayments.org/publicsite/futures/topics/inspections/
all-inspections/cross-compliance/detailed-guidance/goodagricultural-and-environmental-conditions/
Author
Dr. Derek Robeson
This technical note was written
as part of a Biodiversity
and Conservation Advisory
Activity, funded by the Scottish
Government – January 2010
Updated by Gillian McKnight
January 2015
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