Province of British Columbia
MINISTRY OF FORESTS
In British Columbia, all areas that are harvested on Crown land must be
reforested and tended to a free-growing state. A reforested area is
considered to be free growing when the seedlings are free from competing
vegetation and can continue to grow uninhibited.
Competing vegetation, such as salmonberry, thistles, ferns, pinegrass,
and some undesirable tree species, divert limited supplies of light,
water, and nutrients away from commercially valuable tree seedlings. This
can result in poor growth or even seedling mortality in many cases.
To combat competing vegetation and enhance the success of our
reforestation efforts, the Forest Service operates an extensive vegetation
management program throughout the province.
A variety of options are available for controlling competing
- biological methods -- living organisms, such as sheep, are
used to control competing vegetation;
- chemical methods -- herbicides are used to control unwanted
- controlled burning methods -- fire is used to clear sites of
- manual or physical methods -- hand-held cutting tools are
used to remove vegetation; and,
- mechanical methods -- heavy equipment is used to clear sites
of woody debris and vegetation.
Foresters consider all vegetation management options before determining
which method, or combination of methods, is best suited for a particular
site. Some of the factors that are considered include:
- the ability of the option to meet the required silviculture
- the impact on people;
- the impact on the environment (e.g., water supplies, soils, fish and
wildlife and their habitats); and,
- the total cost of the treatment to bring the area to a free-growing
|Sheep grazing can be used to prepare a harvested site for
reforestation, or as a means of controlling competing vegetation
after new seedlings have already been established.
The use of sheep for vegetation management in British Columbia
began, on a trial basis, in the Cariboo region in the mid 1980s.
This was followed by other trials in the Clearwater forest district,
the Bulkley forest district, and on Vancouver Island. In addition,
sheep have been used to control vegetation in the Saanich Seed
Orchard, near Victoria, for over a decade.
Currently, trials have expanded to include almost every forest
region in the province, and sheep are now being used to graze
thousands of hectares. These trials are providing valuable
information on the advantages and disadvantages of sheep grazing as
a vegetation management tool.
versus ungrazed forest site
|The effectiveness of sheep in controlling competing vegetation
can be influenced by many factors. Some of the important factors to
Choosing a site
The site location must first be suitable for sheep grazing. The
grazing area should have:
- a good supply of suitable forage;
- slight to moderate slopes;
- minimal woody debris or other obstacles; and,
- a low threat of predators.
Good road access is also important so that the sheep can be
easily transported to and from the site. An adequate water supply is
essential, and can be either hauled or pumped to a watering site to
avoid contamination of local water sources.
Selecting the right sheep
A thorough knowledge of sheep, their habits, forage preferences,
and herding instincts is essential to the success of a grazing
grazing, sheep are kept in holding pens
|Sheep from a single flock are preferable, since sheep from
different flocks will not initially stay together. Prior to moving
the flock to the site, the sheep should be inspected, vaccinated,
and treated for disease or parasites. |
|Timing a sheep grazing operation
Proper timing is crucial to a successful grazing project. The
target vegetation must be palatable and in sufficient quantity to
satisfy the sheep.
If forage is not adequate in quantity or quality, hungry sheep
may develop a taste for tree seedlings or poisonous plants. To
ensure that sufficient forage is available, sites may be seeded with
grasses, clover, or legumes. Seeding not only increases the sheep's
preferred food supply, but also reduces the establishment of
undesirable plant species.
The nutritional value of forage decreases with drought and frost,
or when the plants go to seed. During these periods, the sheep are
removed from the site to prevent them from grazing on
|While sheep grazing can be an effective method of managing
vegetation in some areas, there are certain environmental factors
which must be carefully considered before choosing this option. Some
of these are:
Introducing domestic livestock into forested areas may have an
impact on wildlife. This can occur for several reasons:
- sheep grazing may displace wildlife species that depend on
vegetation as a food source;
- conflicts can occur when sheep are located in areas with large
numbers of predators such as grizzly bears, wolves, or coyotes;
- disease and parasites may be transmitted to local wildlife
populations through contact with sheep.
Water supplies may be contaminated if sheep are allowed direct
access to streams or other water bodies. Streamside grazing and
locating holding pens too close to water sources can also lead to
grazing can lead to predator/prey conflicts
Wet conditions and crowding too many sheep into one area, over an
extended period of time, can cause soil compaction, followed by
surface crusting and soil erosion. Grazing on very dry soil can also
increase the erosion hazard by removing soil cover and loosening
Transfer of undesirable plant species to forest sites
Sheep grazing has the potential to spread undesirable vegetation
or noxious weeds, such as thistle and knapweed.
Shearing the sheep prior to transporting them to the grazing site
can reduce the possibility of dispersing undesirable seeds which
become attached to the sheep's coats. Holding the sheep in a
designated area after their arrival at the treatment site, until all
seeds have passed through their systems, will also help reduce the
possibility of dispersing undesirable plant species.
|Upon arrival at a site, the sheep should be congregated in a
pre-designated area, either a corral or fenced-in area, where they
are fed and given water before being released for grazing.
This is done because hungry sheep often do not discriminate
between the target vegetation and tree seedlings. In order to allow
the desired dietary preferences to form, and to minimize seedling
damage, the first site to be grazed is often one with established
crop trees of at least two years of age.
Movement of the sheep should be carefully regulated to achieve
uniform grazing and minimal crop tree damage. Controlling flock
movement is also a good way of avoiding or reducing predator
problems. Sheep can be controlled by using trained shepherds,
herding dogs, and portable fencing. Constant supervision is required
to keep the flock together and moving effectively over the site.
Target vegetation is suppressed by both grazing and trampling.
When the vegetation is reduced to the desired level, the sheep are
moved to another area. Sites are generally grazed once per season,
although two passes may be necessary in some cases. Additional
grazing treatments may be needed in subsequent years to ensure that
the crop trees reach the free-growing stage.
of the flock is required for effective grazing
|Good planning and careful on-site management will
result in a sheep grazing operation that is efficient and compatible
with forest regeneration. On-site management operations should
- night corrals to avoid excessive trampling of the site, and to
protect the flock from predators;
- changing bedding-down locations every day to prevent seedling
- adequate water supplies and salt licks located in appropriate
- on-site veterinary inspections to ensure the general
well-being of the sheep;
- removal of unhealthy or injured sheep from the site to
minimize risk of disease or predator attack; and,
- measures to protect the sheep and reduce the risk of
predators, such as portable fencing and guard dogs. Additional
protective measures include checking sites for signs of predators
prior to releasing the sheep, burning or removing carcasses from
the site, and disposing of other refuse properly.
As with all methods of vegetation management, sheep grazing has
characteristics which make it suitable for use in some areas of
British Columbia, but not in others.
When considering sheep grazing as a management option, the
following questions should be asked:
- Can sheep grazing meet the desired silviculture objectives for
- Is the site accessible and suitable for sheep grazing?
- Can impacts on the environment be kept to a minimum?
- Is the potential for predator / prey conflicts low?
- Is the overall treatment cost-effective?
In areas where the above conditions are met, sheep grazing can be
a viable vegetation management option.
For more information on Forest Vegetation Management or a
copy of the brochure contact the nearest BCFS regional or district
office or write to:
Forest Practices Branch
Ministry of Forests
PO Box 9513 Stn