Livestock Production Systems Officer
Animal Production Service
FAO Animal Production and Health Division
Il est de notori�t� publique que l'exploitation ad�quate et durable des ressources en mati�re de parcours contribue pour une large part � satisfaire la demande mondiale de produits de l'�levage et � assurer ainsi la s�curit� alimentaire de l'ensemble de la population du globe, toujours plus nombreuse. Toutefois, la d�gradation des sols et le surp�turage sont rest�s des questions essentielles qui pr�tent � controverse eu �gard au d�veloppement de l'�levage, notamment en Asie et en Afrique. C'est apr�s la seconde guerre mondiale que ces sujets de pr�occupation se sont fait jour. Depuis lors, les populations de ruminants ont plus que doubl�, alors que la superficie des parcours s'est r�duite par suite des empi�tements de l'agriculture. Malgr� cela, l'effondrement attendu des syst�mes pastoraux ne s'est pas produit. Il n'y a cependant pas lieu de faire preuve d'optimisme, car certaines zones font indubitablement l'objet d'un surp�turage occasionnant une d�gradation marqu�e des sols. Les experts estiment cependant qu'il existe un taux de charge optimal des parcours. C'est dans ce contexte que cette question de haute importance a �t� soumise � un nouvel examen approfondi, qui donnera sans doute lieu � de multiples r�flexions et �changes de vues.
Est� generalmente admitido el hecho de que una utilizaci�n apropiada y sostenible de los recursos de pastizales contribuye de manera considerable a la satisfacci�n de la demanda mundial de productos pecuarios con vistas a conseguir una seguridad alimentaria adecuada para una poblaci�n humana siempre en aumento. Sin embargo, la degradaci�n de la tierra y el sobrepastoreo han seguido siendo cuestiones muy controvertidas en relaci�n con el fomento de la ganader�a, especialmente en zonas como Asia y Africa. Este tipo de preocupaci�n ya se expres� en el per�odo de la posguerra. Desde entonces, la poblaci�n de rumiantes se ha duplicado con creces, mientras que los pastizales han disminuido, debido al avance la agricultura. A pesar de esto no se ha producido el colapso que se hab�a pronosticado de los sistemas pastorales. Sin embargo, existen zonas con un sobrepastoreo manifiesto que provoca una degradaci�n grave de la tierra. Se estima que en los pastizales se puede alcanzar una densidad de pastoreo �ptima. En el presente n�mero se ha sometido esta importante cuesti�n a un nuevo examen, que sin lugar a dudas dar� origen a nuevos an�lisis y debates.
Raising livestock represents the only feasible agricultural activity for
utilizing the world's extensive natural grasslands, estimated to cover about 21 million km2
. A wide range of species - cattle, sheep, goats and camelids - are used to exploit these
resources, with the ecoclimatic zones largely determining the mix of species. Pastoral and
extensive grazing systems provide a livelihood and security for an estimated 40 million
full-time pastoralists and many more involved in seasonal transhumant systems.
Rangeland management remains one of the most controversial issues facing livestock
development, especially in sub-Saharan Africa. Africa's rangelands, the experts tell us,
are overstocked and the residents should learn, or be forced to adopt, new habits before
widespread and irreversible degradation occurs. A review of technical reports going back
to the postwar era shows that exactly the same concerns about overstocking were being
expressed then. Yet, since then, ruminant populations have doubled while the grazing area
has contracted owing to agricultural encroachment. Despite this, the predicted collapse of
the pastoral systems has not occurred and they remain the most rational land use for such
areas. This is not to say there is room for complacency. Indeed, there are many examples
of severe degradation caused, in part, by overstocking. Such examples are often the result
of irresponsible policies and interventions, such as the provision of subsidized grains
for sheep feeding which has led to irreversible range degradation in West Asia and North
Africa.
It is widely believed that there is an optimum stocking rate for rangeland, a rate that
will conserve the range while maximizing profit, and that estimating this rate is
primarily a technical matter. Furthermore, it is thought that the optimum rate applies
equally to all types of livestock production from the fully commercial to the total
subsistence systems. Despite these assumptions, policy-makers, development agencies and
livestock and range specialists have persistently disagreed with African pastoralists over
what the optimum rate is. This difference of opinion has been commonly attributed to
pastoral ignorance and, hence, remedial extension campaigns and administrative regulations
have been recommended.
This issue revisits the overstocking controversy from different perspectives. The Editor
has taken the unusual step of including three papers by the same authors, Roy Behnke and
Nick Abel, for the reason that they develop a theme. They argue that many of those
involved have had a muddled idea of what constitutes overstocking, that existing stocking
rates are often appropriate to pastoral management objectives, and that these rates may be
ecologically sustainable. The first paper takes experimental data from stocking rates
trials for beef cattle to expose the potential for confusion embedded in the concept of
overgrazing. The paper postulates that there is unlikely to be a single optimum stocking
density for different husbandry practices and objectives. The second paper examines the
characteristic management objectives and resource endowments of pastoralists and herders.
African herders, unlike commercial ranchers, often choose to produce a range of different
outputs. Production objectives such as these require higher stocking rates to maximize
yields which usually equal, or exceed, per hectare output from commercial ranches with
comparable natural resources. While it may be profitable for African herders to stock
heavily, it is not necessarily environmentally sustainable in the longer term. The third
paper addresses the issue of rangeland degradation. It presents a technique for estimating
environmental costs, measured in rates of soil loss or in terms of economically
disadvantageous changes in rangeland vegetation, which result from different stocking
rates.
The article on Swaziland summarizes the approach that was taken there. Swaziland is a
traditional cattle-owning country where animals remain attached to the agricultural
homestead throughout the year and are not taken away to "cattle posts" located
in more remote grazing areas, as is customary elsewhere in southern Africa. This has
resulted in pockets of very high stocking rates, as high as 5.3 livestock units (LU) per
hectare, with a consequent loss of topsoil through soil erosion. Many communities are only
too aware of the problem but ask the question, "How many cattle can we safely
keep", i.e. the elusive "optimum stocking rate" described in the first
paper. FAO's Technical Cooperation Programme (TCP) provided assistance in addressing the
problem. A local rainfall-related carrying capacity model was developed which indicated a
preliminary recommended stocking rate for each of the identified vegetation units (VU).
Such models can only indicate "safe" stocking rates under average conditions,
while the reality is that there is considerable variation between seasons and years. What
these models can do, however, is to provide local communities with guidelines to enable
them to initiate control over their own resources - both animals and vegetation.
In most pastoral-based production systems, there are very pronounced seasonal differences
in the amount of grazing available. This is particularly so in the temperate, semi-arid
regions where limited winter feed is the major constraint for the transhumant production
systems. The transitory spring and autumn grazing areas are also subjected to very high
stocking pressures, as herds are forced to leave their winter grazing areas early and
remain on the transitory grazing areas as long as possible in the autumn. The introduction
of appropriate fodder crops can greatly improve the availability of winter feed and allow
a more efficient exploitation of the abundant summer grazing. The article on fodder
production in Xinjiang and the short communication on improved fodder in smallholder
livestock production in Pakistan's northern areas describe the successes achieved by
FAO-assisted programmes in these two areas. The Altay programme in China involves the
establishment of over 20 000 ha of irrigated alfalfa as part of a resettlement programme
for 6 100 Kazak households. In the northern areas of Pakistan the introduction of small
plots of improved, temperate fodders has proved immensely successful and, within two
years, over 2 500 farmers were participating in the scheme and demanding planting
material.
Clearly, the controversies surrounding overstocking and environmental degradation will not
go away. A fresh and challenging review of the issues should provoke further discussion
and, more important, leave technicians, officials and donors better informed when it comes
to important decision-making. Hopefully, you will find the series of papers relating to
the various aspects and issues affecting the pastoral systems both informative and
thought-provoking. We would welcome your comments.