Agriculture is subdivided into cultivation of the land to produce crops to feed man or his livestock, or that part of animal husbandry which relies on animal production by grazing. The pastoral element ranges from the low lying water meadows, through the leys laid down as part of rotational cultivation and the fescue-agrostis fields of marginal stock farms, to the hill farms reaching to the top of mountains where nutritionally inferior grasses, sedges, rushes and heather provide the keep. In these hill areas it may take over ten acres to provide for one ewe with her single lamb. Hill grazings like these cannot fatten and "finish" cattle for the butcher but they do provide a suitable habitat for the hardy breeds of suckler cows which provide a single calf each year to be sold to low ground farmers.
Apart from lambing time, day to day supervision or storm feeding of stock, it is only at the "handlings" that the shepherd has close continuous contact with his flock. The animals are "gathered" for such handlings as shearing, dipping, dosing, drawing lambs, and paring feet. The management of suckler cow herds is similar, normally stock is allowed to get on with grazing in order to feed themselves and grow with as little disturbance and stress as possible. In grazing situations cultivation of the land may involve mole-draining, ploughing and reseeding of pasture, but usually physical interference with the soil is minimal and often non-existant. On marginal grassland and on the areas of better hill grazing the spreading of lime on acidic soils, and occasionally distributing fertilisers especially phosphates on the more leached soils is also carried out but on the poorer hills such procedures would not be cost effective in raising the stocking rates of cattle or sheep.
Experienced pasturolists are very aware that much of the work associated with keeping grazing animals is referred to as "estate work", that is work building and maintaining fences, walls, hedges, gates, ditches, drains, roads, etc. On sites where conservation grazing is practised the management would tend to be similar to that practised on hill farms viz.
The ecology of a habitat depends upon a complex relationship of extremely delicately balanced systems. The only purpose in using an animal to graze or browse is the destruction of certain vegetation in order that the growth of other vegetation or animal life is promoted.
A very old example of this is found in the olive groves in Greece. Each peasant owns about 80 olive trees, they tether their donkey to a different olive tree each day so ensuring the grass and weeds are eaten out from around every tree on an 80 day cycle. This not only controlled the weeds and organically fertilised around the trees but it also controlled the helminth parasites of the donkey by providing the animal with clean grazing daily. In contrast to this clean grazing on a small area we frequently have the opposite on open hill ground where on relatively poor grazing there are "green gairs", these are areas of wet or dry flushes, rich in nutrients, where the sweeter grasses grow, livestock in grazing these gairs pass helminth eggs and infective larvae in their faeces, causing these areas to be highly contaminated focii of infestation for the grazing stock.
It is important to consider the risks a habitat poses to a grazing animal in relation to the endoparasites which may be present. The presence of liver fluke (Fasciola hepatica) in wet or damp sites may have been the very reason that the area was not grazed historically since the sequelae of infestation in sheep and cattle can be disastrous. Ponies or pigs are less susceptible to fluke so may be the grazers of choice in such a habitat.
The choice of the grazing species must be made in relation to the site and the objectives sought, e.g. cattle to remove longer grasses, pigs to root out bracken. The season of growth must also be taken into account for both herbage and grazer. In the control ragwort, the rosettes growing in early spring are sought out and eaten by sheep, later in the year the plant is too coarse or unpalatable to be ingested. Ponies will dig up nettle roots and eat them over the winter period. It may also be desired that seed production and shedding be completed before the herbage is disturbed.
The age and state of development of the grazer is also significant. Where autumn sown rye is grown young cattle are put to graze on the crop late February to March, this provides excellent feeding at a lean time of year while at the same time the plants are pruned down which stimulates them to spread or "tiller". The reason young cattle are used is that at 1 to 2 years of age the incisor teeth are sufficiently sharp and occlude with the dental pad in such a way as to cut the rye, old cows using the tongue as well in prehension would uproot the plants. Up until the late 19th century on hill farms in the Scottish Borders about 5% of the castrated male lambs were kept each year, these were the "Bell Weathers" which were retained well into adulthood and provided not only very valuable fleeces each year but roamed the hills in bachelor groups eating out the coarse grasses and trampling bracken. Managers of conservation sites must have clear objectives before any kind of grazing animal is introduced to the area. They must consider not only what species of grazer to use but the ages of the animals and during which time of the year they will be present on the site. The available species, ages, and seasons present a variety of discretionary mixes which may be utilised.
The choice of species in conservation grazing raises the question of what is native or exotic, generally indigenous species are regarded as being more suitable. In post glacial Europe the domestic sheep is an import from central Asia, this species has been with Man over such a period of time that it has had a very large influence on the present environment, to such an extent that it would be fruitless to attempt going back to an ecology of the past.
Not only does life evolve and change but so does the ecology and landscape, to progress we must develop and look forwards.There is a scheme presently afoot to aquire land and plant it with trees creating a forest as it would have appeared 5,000 years ago. This may in time provide an inaccurate museum of the past, but are we not better in using our resources to work towards providing a forest as we would wish it 5,000 years in the future.