2. Environmental impacts and protective measures
2.1 Types of husbandry
2.1.1 Pasture use in general
The most noticeable consequence of grazing is the
defoliation of plants by the animals, which influences the structure of
the pasture vegetation and the variety of species which it contains. The precise
nature of this influence depends on the type of animal concerned, the stocking
rate (grazing pressure) and possibly also the time of year. Cattle and sheep
tend to eat grass, whereas camels and goats prefer leaves.
An ideal sheep or cattle pasture will thus consist
primarily of grass and herbaceous plants, while an ideal camel or goat
pasture will contain more trees and bushes.
Grazing can stimulate plant growth and encourage
the growth of creeping ecotypes of a particular plant species rather than those
which grow upright. In grass/legume pastures, grazing often favours the legume
component, because animals generally prefer grass during the early part of the
vegetation period; with competition reduced in this way, legume growth is
promoted. However, the young stages of some legumes are also popular with
animals. While light grazing and browsing on bushes and trees can stimulate
growth, removal of vegetation by livestock on a larger scale can reduce
growth or even cause plants to die off and may hinder regeneration of
fodder bushes from seeds and suckers.
The effects resulting from trampling of the vegetation by
livestock depend primarily on the type of animal concerned, the stocking rate,
the soil condition and the topography. Damage caused by trampling can
increase soil erosion; however, the roughening-up of the ground can also
create better conditions for germination and thereby promote plant
regeneration. Where the soil in humid regions is heavily waterlogged, the
vegetation cover can be destroyed as a result of trampling.
The seeds of many pasture plants are very small and can
pass through the animals' digestive tract without any impairment of their
germination capacity. Certain plants are thus dispersed with the animals' dung.
Hard-shelled seeds are also scarified and the seeds are redistributed and
sown by the animals.
Only a small proportion of the nutrients and energy
intake by livestock actually finds its way into the animal products used by man.
The remainder is excreted via dung, urine and, in the case of ruminants, methane
(a gas which plays a part in the greenhouse effect). The breakdown of organic
matter in the digestive tract of ruminants gives rise to energy and nutrient
losses similar to those resulting from microbial breakdown in the soil; as the
breakdown process in the stomach of ruminants is considerably faster, however,
the grazing animals accelerate the nutrient cycle. If the animals are
penned overnight, the excretion of dung in the pen means that the pasture is
deprived of nutrients. Although the dung collected in pens can be used in
arable farming and horticulture or for production of biogas and
can thereby contribute to improving soil fertility, the loss of nutrients
can accelerate degradation of the pasture vegetation.
In semi-arid and arid regions, the considerable
fluctuations in annual rainfall mean that vegetation growth varies greatly not
only according to the time of year but also from one year to another. The
herbaceous vegetation layer in particular will thus not exhibit consistent
growth. In drought years there may be so little vegetation growth that all the
herbage is eaten by the animals. If shrubs and trees are not to suffer
permanent damage, the amount of their vegetation consumed as fodder must not
exceed a specific proportion of the annual growth, otherwise their capacity
for survival and regeneration will be jeopardised.
Permanent damage is generally considered to have occurred
when the vegetation's capacity for regeneration has been impaired and the
surface of the ground has suffered erosion by wind or water. In view of the
differences between plant communities and the differing regeneration capacities
of the various species, it is not possible to lay down any universally valid
standards specifying how much land can be used without impairing the
productivity of the vegetation and what stocking densities are possible.
American estimates work on the basis that 50% of the vegetation can be used,
while studies from West Africa take figures of 30-50% (le Houerou 1980). Others
graduate permissible vegetation use according to rainfall and take different
levels of permissible utilisation for the bush/tree layer (25-50%) and the
grass/herbaceous layer (30-50%) (Schwartz 1989). Factors which can assist
in assessing degradation include the age structure and species composition of
the tree and shrub community, seed reserves in the soil for the herbaceous
plants and possibly also soil cover as well as depth and condition of the
The distribution of animals in an arid pasture area is
determined primarily by the availability of water. Deep wells
containing plenty of water supply a large number of animals and may thus
give rise to serious overgrazing in their immediate vicinity. The size of
the area around a well that can be used by animals for grazing depends among
other things on the dry-matter content of the fodder, the type of animal and the
animals' physiological status. Inadequately protected wells and watering places
can easily be contaminated by dung and may also constitute a health risk
for the local population if drinking water becomes contaminated. The
concentration of animals around wells can promote the spread of epizootic
diseases. Around every watering place there is a certain area which,
although it contains an accumulation of nutrients by virtue of the dung produced
by numerous animals, is almost totally devoid of vegetation as a result of
trampling. The size of this area depends on the design of the watering place
(e.g. troughs on hard ground) and the way in which access to it is controlled
(e.g. fencing-in of watering places). Use of fertiliser in arable farming
and horticulture in the vicinity of the watering place will not give rise to any
Pastureland comprises natural pastures, fallow land and
harvested fields. Forested areas, which in some cases are under the
control of forest administrations, can also be used as pastures. In many
cases, for instance in North Africa, the major proportion of the forest yield is
derived from livestock farming. Fodder production is an integral part of
agroforestry. It must be pointed out, however, that forest pastures are
often over-used. If this is to be prevented, a wide variety of
measures are necessary: reduction of tensions between forest administration
and local farmers; employment of an adequate number of appropriately motivated
personnel in order to enforce the regulations limiting pasture use; provision of
alternative fodder resources for local livestock owners; steps to prevent use of
pastures by non-local livestock owners not engaged in agriculture; reasonable
charges (where payment is made for use of forest pastures) by comparison with
the price of other fodder resources; and involvement of the local population in
pasture-use planning. Both the dry and humid tropics offer examples of
balanced pasture management which takes forest growth dynamics into
2.1.2 Pasture use with supplementary feeding
The environmental impacts of supplementary feeding depend
on the context and the type of feed. Where fodder is of poor quality but
available in large quantities, supplementary feeding of minerals can improve
utilisation of the "standing hay". Provision of supplementary feed in the form
of feed concentrate or high-quality roughage soon leads to a reduction in the
amount of fodder consumed per animal during grazing, which benefits
the pastureland. If, however, the number of animals is increased on
account of the improved fodder supply and the natural pasture continues to be
used, there is a greater risk of degradation. In some cases (e.g. in
North Africa) livestock are given so much supplementary feed that this feed
covers not only their performance requirement but also part of their maintenance
requirement. Another reason for overgrazing is the desire to improve the
quality of the animals' meat, since this will be reflected in higher meat
prices. Meat quality is influenced in particular by the fact that the animals
move around more and by the improved basic fodder supply.
2.1.3 Fodder production
Erosion-control strips can be used for fodder production.
Appropriate planting of permanent fodder crops (such as sulla in North Africa)
can serve as a form of "soft" erosion control. Fodder growing within a crop
rotation system can have positive effects on soil structure and soil fertility
(see Plant Production). The possibility that fodder crops may compete for
land with crops that can be used as food for human beings must be borne in mind.
In the case of certain fodder crops, a large quantity of
nutrients is taken from the soil together with the green matter.
If these nutrients are not replaced, or if the dung is not returned to the
field, there is a danger that the nutrient balance may be disturbed. If
mineral fertilisers and herbicides are used in fodder production, there is a
risk that surface water and groundwater may become contaminated and that
the diversity of species may be reduced at the same time.
While pasture use primarily involves ruminants, chickens, pigs
and small livestock such as rabbits and guinea pigs are generally kept in
The environmental impacts of keeping livestock in
confinement depend on the number of animals, the type of animal, the nature and
origin of the feed and whether the livestock housing is open or closed. The
environment prevailing in the animal-sheds (temperature, humidity, light,
presence of noxious gases, dust and germs) has an effect on the animals, while
livestock housing itself has an effect on its immediate environment through
odours, liquid manure and noise. Where ruminants are kept, methane
(a gas which plays a part in the greenhouse effect) is also released.
If livestock are kept in confinement, the vegetation suffers
far less damage than if the animals are allowed to graze. However, use of
cut fodder means that the soil is deprived of nutrients on a considerable
scale; if these nutrients are not replaced, there is a danger that soil
fertility may be reduced.
The enormous quantities of liquid manure produced where a
large number of animals are kept can impair drinking-water quality and
contaminate both surface water and groundwater. Large-scale chicken farms
located near cities give rise to particularly adverse environmental
impacts on account of their need to dispose of dead birds and droppings.
Liquid and solid manure represent a major potential source of infection -
especially for children - in many developing countries, particularly if no
measures are taken to prevent contact with them. When used as
fertilisers, liquid and solid manure can have a beneficial effect
on soil fertility and soil structure, provided that they are not
applied in excess.
2.2 Farming systems
Ranches permit uniform management of comparatively large areas.
Large-scale farms of this type nevertheless do not guarantee conservationist
use of pasture resources (Harrington et al. 1984). In dry years a ranch too
requires alternative fodder resources or the number of animals must be reduced
in good time, otherwise heavy losses are likely. Supplementary feeding can lead
to over-use of pastureland and thus increases the risk of erosion.
When a large farm with "rational" stocking rates or a pasture reserve with a
controlled stocking rate is established in an area where traditional livestock
husbandry predominates, it should be borne in mind that although the reduced
stocking rate on the land concerned may be more appropriate to site conditions
than the original rate, the exclusion of animals from this land will increase
the grazing pressure in the surrounding area.
Particularly in humid regions, large-scale land clearance
to create pastures for ranches substantially reduces the diversity of species
found in the vegetation. Apart from the resulting erosion problems,
there may also be a risk of climatic changes over a wide area. The fact
that ranches generally keep only cattle gives rise to one-sided utilisation
of resources, which either permits only very low stocking rates or calls for
sizeable inputs to preserve the pastureland. There is also a danger that the
pastureland may be acidified as a result of waterlogging. Damage
caused by trampling can have an adverse effect on the soil structure,
leading to increased surface-water run-off and a greater risk of
Although ranches can improve the urban population's food supply,
their carrying capacity per unit of area is smaller than that of traditional
farming systems (e.g. Cruz de Cavalho 1974, de Ridder & Wagenaar 1986).
Environmental protection measures are difficult to
realise where ranching is concerned. Attempts to standardise the
carrying capacity of pastures are the subject of considerable
dispute on account of the complex interrelationships and numerous
variables involved, particularly in assessment of vegetation (e.g. Sandford
Some systems, such as those found in Australia, are based on
detailed long-term studies and official determination of the permissible maximum
stocking rate. As the land in Australia is generally not in private ownership,
but is instead leased out by the government on a long-term basis, specific
conditions can be imposed and the lease revoked if need be. In many countries
the necessary data are not available and monitoring institutions
are either non-existent or not equipped to perform the essential tasks.
Rules aimed at preventing erosion should be worked out together with the ranch
2.2.2 Pastoral systems
In such systems, animal husbandry is the sole or principal
economic occupation. Herding and a high degree of mobility make it possible to
utilise resources in a manner complementing arable farming or to utilise areas
that can be used for grazing only at certain times of year.
Pastoralists often keep mixed species herds, which permits
intensive use of a wide variety of fodder resources. The products derived from
the herds include milk, meat, traction power and manure.
· Integration of grazing and arable farming
Where pasture resources are used in combination with arable
farming, the amount of land available for grazing varies greatly in the course
of the year. During the growing season only natural pasture and fallow land can
be used for grazing, while during the dry season harvested fields are also
available for this purpose. Grazing has a variety of effects on fallow land and
natural pasture. The species composition of the vegetation may change
in such a way that a larger proportion of the vegetation can be used as
fodder or for other purposes; at the same time, however, intensive grazing can
also lead to degradation. If herded animals are penned at night,
nutrients accumulate in the night paddock as a result of the droppings and urine
produced by the livestock. These nutrients can be used to preserve soil
fertility on arable land (dung), but are thereby removed from the nutrient cycle
on the land used for grazing. Leaching from the night paddock can lead to
contamination of surface water and groundwater. Use of crop residues as
fodder may accelerate the nutrient cycle and result in redistribution
of nutrients in a particular field or among fields. If crop residues are
used on a large scale the soil cover may be reduced and this can lead to
erosion. Rights to use fodder resources must be established through
agreements between pastoralists and arable farmers.
A high degree of flexibility and mobility is required on the
part of the pastoralists in order to permit ecologically appropriate and
economically sound use of arid regions. Mobility in turn calls for large
herds. In the course of their migration the pastoralists and their
families must for the most part live on the products which they can derive from
their herds. Reduced mobility generally leads to overgrazing, accompanied
by increased soil erosion, in the area around the newly created
settlements and to under-use of other areas. Under-use can also give rise
to changes in the balance of species and reduce the vegetation's productivity.
As herds and people become increasingly sedentary and
concentrated in specific areas, use of green twigs and branches to construct
livestock paddocks and as domestic fuel leads to destruction of the woody
· Grazing rights
Land and pasture use rights may comprise seasonal rights of use
in specific areas and grazing rights in areas located a long way from one
another. Apart from creating an opportunity to use land resources for grazing
as well as for arable farming, this also helps to balance risks, as rainfall
in arid regions is often highly localised. Communal grazing rights predominate
in such areas. Communal pastures are traditionally used by clearly definable
groups of livestock owners. Depending on the
group's structure and effectiveness, this makes it possible to
stipulate stocking rates and times at which the pasture is not to be
used. In regions such as East Africa, controlling access to water is an
important means of controlling stocking rates. Open access pastures - frequently
equated with common pasture - offer virtually no opportunity for such a step. In
such a context, creation of watering places outside the traditional
structures can encourage opportunistic use and thus contribute to
overgrazing. The secondary consequences of such a development will
be degradation of the vegetation, reduction of the soil's rainwater infiltration
rate and increased soil erosion.
· Changes in ownership
Changes in the herd ownership structure can likewise adversely
affect the pastoralists' resource management. When herdsmen look after cattle
owned by other people, for example, they are often allowed only to use the milk.
In order to have a secure livelihood they require large herds of their
own if they are not to become impoverished. Moreover, the owners' desire to
keep a check on their property may cause them to restrict the herdsmen's
mobility and thus also their flexibility where pasture management is concerned.
This too can result in over-use of the vegetation (disturbance of the
balance of species within the flora, disturbance of the water balance, soil
· Division of labour
In pastoral systems, the men are generally responsible for
management and marketing of the largestock, while the women frequently tend the
small ruminants and have responsibility for milk processing and marketing. The
women's role is often underestimated, as it is the men who represent the family
vis-is other people. The decentralised processing and marketing of milk
ensures a relatively reliable milk supply in rural areas, even though a woman
may process and market only a few kilograms of milk a day. When milk is
processed at household level, consideration must be given to possible
hygiene risks (e.g. danger of infection).
· External influences
Pastoral land use frequently necessitates agreements between
various population groups. External influences - and that includes government
programmes - may disturb the often fragile equilibrium. If, for example,
arable farming is expanded onto land used by pastoralists for dry-season grazing
or as reserve pasture, the loss of this pastureland can increase the
pressure on other areas and lead to overgrazing. Should the arable farmers
start to keep livestock on a larger scale, the pastoralists
may find themselves driven out into marginal areas. This
not only has consequences in terms of grazing management and livestock
productivity but can also affect the welfare of the population groups concerned.
If their mobility is restricted, pastoralists may be forced to
make intensive long-term use of marginal areas on a scale which exceeds the
natural carrying capacity.
The resultant degradation process intensifies competition
for the decreasing fodder resources. By promoting over-use of the available land
it also reduces the number of species found locally and marginalises large
sections of the pastoral population.
2.2.3 Smallholder livestock husbandry
The number of livestock owned by a smallholder can range from a
few small animals (e.g. chickens) to large herds, e.g. twenty goats or ten head
of cattle. Livestock management normally takes second place to the
interests of arable farming. Many smallholders keep more than one type of
Smallholders generally use pastures with supplementary
feeding (at least on a seasonal basis) or keep their livestock in
confinement. Large herds - such as village herds - may be mobile (cattle
placed in the charge of a herdsman by their owners).
The animals may be allowed to graze freely, or may be herded,
tethered or kept in fenced pastures. The practice of fencing off pastures
with wooden posts - which may have to be replaced at frequent intervals on
account of termite damage - can have adverse effects on the species
composition and density of the tree stand. By contrast, use of
"living fences" or hedges to subdivide pastureland has positive
effects on the tree stand but requires a considerable amount of labour.
Clearing land to create improved pastures can increase
the erosion risk and thus have an adverse influence on soil fertility.
Creation of improved pastures, particularly with legumes, can be integrated into
ley farming (seeded pasture rotation) and will improve soil structure and
fertility. Competition for use of fodder resources may arise between
livestock owners, above all between pastoralists and smallholders as well as
between the smallholders themselves, and can thus impose increased
pressure on the available land.
As in pastoral systems, management of largestock is
frequently the men's responsibility, while the women are in charge of the
smallstock. As women in many rural societies have no land ownership rights,
livestock husbandry plays an extremely important part in enabling them to
accumulate capital. The income earned from animal husbandry can be used to
finance necessary expenditure for arable farming (fertiliser, seed, hired
labour, creation of erosion-control strips), while the animals' dung can be used
to preserve soil fertility. Livestock perform a particularly important
function as a form of "risk reduction" in regions where arable yields tend to be
unreliable. If the harvest is insufficient to meet the family's subsistence
requirements, animals can be sold to permit the purchase of staple foods.
Without this means of offsetting risks it would be necessary to extend the area
under cultivation, which would have negative effects in terms of soil erosion,
soil structure, nutrient balance and diversity of species.
A changeover from pasture use to keeping livestock in
confinement can have beneficial effects on the diversity of plant species
and assist in preventing erosion. The increased concentration of liquid
manure and dung may lead to greater pollution of surface water and
groundwater. Keeping livestock in confinement requires more labour than pasture
use and it is generally women who are called upon to perform the extra work.
High-performance animals have more demanding requirements
in terms of fodder supplies and veterinary care. If chemoprophylaxis is
necessary, pathogen strains resistant to the chemotherapeutic agents used
can develop (see environmental brief Veterinary Services). Introduction of
high-performance animals frequently does not lead to a reduced number of
livestock; it does not lessen the burden on the available fodder resources
The actual and potential advantages of indigenous breeds and
species are often underestimated. With a one-sided promotion of the use and
importation of high performance animals, there is a danger of losing genetic
resources adapted to the natural environmental conditions.
Urban livestock husbandry can be regarded as a special
category of smallholder livestock husbandry. As urban livestock owners purchase
far more fodder than those in rural areas, their existence can encourage
fodder growing in the vicinity of towns. This can have positive effects
on soil structure and fertility, besides boosting the fodder growers' income.
Dairy cattle are kept in urban areas to supply the urban population with fresh
milk. While other animals are kept primarily to meet their owners' food
requirements, they can also serve as a form of "savings bank" and as a means to
accumulate capital. The dung produced by the animals can help to improve
the soil structure and nutrient balance, but may well give rise to direct and
indirect health risks if it is used or disposed of incorrectly. As in rural
areas, women make an important contribution to urban livestock husbandry,
although it can be assumed that the division of labour between the sexes is less
strict than in rural society.
Smallholder animal husbandry also includes beekeeping. Apart
from producing honey, bees can substantially increase fruit yields by
pollinating the blossoms and help to preserve the diversity of species
within the flora. Modern intensive beekeeping involves chemical control of
pests (mites etc.); such measures can create health risks for humans if the
chemical agents are incorrectly used and if residues find their way into the
honey. Importing of higher-performance strains of bee can eradicate
indigenous species. Production of honey and beeswax, which is predominantly a
male domain, can be a highly profitable source of income in rural areas.
Environmental protection measures in the field of pastoral
and smallholder livestock husbandry may involve steps to change framework
conditions or direct intervention. Examples of measures aimed at changing
framework conditions include discontinuation of subsidies for feed grains -
in North Africa such subsidies contributed to widespread overgrazing - and
changes in land law (land reform). Where direct intervention in pastoral
and smallholder production systems is envisaged, it is essential that the groups
affected be involved in the measures right from the planning stage. The
measures planned may relate to a wide variety of different areas, e.g.
water resources management, erosion control, fodder growing or - where
smallholders are involved - promotion of confinement. Simply demanding a
reduction in the number of animals - as was frequently done in the past -
reflects an inadequate understanding of the way in which pastoral and
smallholder production systems function.
2.2.4 Large enterprises with intensive animal production
Large-unit animal production generally does not depend on the
availability of land to provide forage, as fodder is imported from other parts
of the country or from abroad. For the purpose of supplying the urban
population, large-scale livestock production focuses on pigs and poultry.
Large farms consume far more fossil energy per
product unit than traditional farms. If growth stimulants such as antibiotics
or hormones are added to the fodder, there is a danger that residues may
be found in foods of animal origin and that resistant pathogens may
The high water consumption of large farms is also likely
to lead to excessive utilisation of scarce water resources.
In confinement housing, the prevailing in-house-micro-climate
(temperature, humidity, noxious gases such as ammonia, hydrogen sulphide and
methane, dust and germ content of the air) can have adverse effects both on the
animals and on the farm workers (health risks). The mere size of the farms means
that the danger of surface water and groundwater being contaminated by
liquid manure and farm effluent is far greater than in the case of
smallholdings. The problems attached to the disposal of dung and animal
carcasses are also likely to be greater, as is the related hygiene risk. Use of
disinfectants can endanger water, soil and possibly also health.
Where cattle are involved, sizeable quantities of methane
- a gas which plays a part in the greenhouse effect - are produced in the
animals' stomachs and released.
If large farm enterprises are in competition with
smallholdings, they can have an adverse effect on the smallholders' income. This
may force smallholders operating under marginal conditions to engage in arable
farming instead of livestock husbandry. Apart from giving rise to undesirable
consequences with regard to the balance of species and soil fertility, such a
step also increases the danger of erosion in the region concerned. Some
large farms, such as commercial cattle-feed lots or large dairy farms
(agricultural combinates), may also compete directly with smallholdings for
agricultural land (e.g. in irrigated areas) and thereby force the smallholders
into marginal areas. However, this risk is greater in the case of plantations
and other crop-growing farms than in the case of livestock farms.
Environmental protection measures on large farms with
intensive livestock management focus primarily on technical aspects: housing
design, whole farm layout, ventilation, distance from settlements, precautions
during storage and disposal of liquid manure and dung, hygiene measures such as
disinfection, ban on use of growth stimulants, fencing-in of livestock housing
etc. Technical standards in Central Europe are well documented (e.g. the German
DIN standard 18910 on controlled environment in livestock housing,
specifications laid down by the Association of German Engineers [VDI], maximum
workplace concentration values (MAK), construction specifications issued by the
German committee on technology and construction in agriculture