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the German Federal Republic, next also to Great Britain, the U.S.A., The Netherlands, Switzerland, Austria, Denmark, Norway, Sweden, Canada, and gradually even more countries. In 1957--1960 the export amounted to 1 213 horses, in 1961--1965 it was 1 353 horses, in 1966--1970 already 3 799, where- as in the years 1971--1973 the average annual export was approximately 1 000 horses. The Icelandic farmer has learned during the last decade that it is pos- sible to sell to Icelandic town<lwellers riding-horses and horse-riding tours, horse grazing and tending in the same way as milk, butter or mutton, and in the same way they have learned that it is more profitable to export riding- horses than mut ton or butter. The Icelandic economy has gained a new impetus in this way. Furthermore, such horse production can be carried out in the available landscape, needing no large-scale standardisation of this landscape and causing no excess pollution.

RECREATIONAL FARMS

Whel~ farmers offer recreational facilities on their own land, there even is a stimulus for them to maintain a varied landscape, because recreants prefer a small-scale landscape with scenic diversity to a wide open area with agrarian monocultures,

Recreational farming may be an additional source of income for a farmer, but occasionally also the only one. Mr. Bjarnason wrote to me about a Danish farmer, who founded a horse-lovers' club, converted his byre into a stable, opened a small riders' tavern and clubhouse for members in part of his hay- barn, and thus sells fodder for the horses in the old byre and refreshments to the riders. He makes a good living out of fif ty customers, who are regular guests and bring their friends with them. The example of this farmer has al- ready been followed by others.

A.A.M.

HORSE-RIDING AND LANDSCAPE MANAGEMENT

The number of people who ride horses for recreation is increasing in several developed countries. In The Netherlands their number is now almost 100 000. This numerical growth is a stimulus for research on various aspects of recrea- tional horse-riding. A working group established by various governmental bodies and private organisations did such a study for the province of Drenthe, in The Netherlands. A few results are of enough interest to be reported at this place.

The horse-riders prefer a quiet area rich in scenic variation. Most of them are satisfied with making rides, the desire for areas for crossing is small. Most riders are careful with the scenery in which they ride, but occasional riders may catise damage. Both man~ge-keepers and riders are in majority in favour

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of the introduction of a riding-passport which could be used to restrict excesses.

The study revealed a growing feeling of hostility between horse-riders and other people using the same area for recreation. Horse-riders need relatively more space and cause walkers and cyclists to give way. There is a limit to the number of times people are prepared to do so without experiencing this as a disturbance of their own recreation. This conflict in space demands results in a growing need for separate riding tracks. These should allow rides of 5--40 km. Among the horse-riders 73% would like a network of such special riding tracks.

Riding tracks for one horse should be at least 1.75 m wide and for two horses 3.00 m. When there is a railing at one or at both sides (e.g. trees, shrubs), the track should be 0.5--1 m wider. The tracks should be of simple construc- tion, smooth but not metalled, free of low tree branches (below 3 m). In open areas some kind of windshelter along the riding tracks is appreciated.

A desire for baiting places was expressed by 64% of the sampled horse- riders. They required places which offer attractive surroundings for the rider, a sheltered place for fastening the horse, and the presence of drinking water. The baiting places may be beautiful spots somewhere in the landscape, farms offering simple facilities to passing riders, or inns.

Route maps of riding tracks were appreciated by 73% of the riders ques- tioned and route descriptions by 68%. No need for these was expressed by 23 and 27%; respectively, whereas the remainder expressed no opinion.

In view of the increasing demand for space for horse-riding, care should be taken that this will not become a threat to areas with a natural vegetation, .which until now have been the preferred landscapes for horse-riding. Space for this kind of outdoor recreation should also be sought elsewhere. It is the feeling of the present writer that horse-riding could also be made attractive in small-scale areas in which a large part of the land is used for agricultural purposes. In such areas agriculture is often much less profitable than in large, open areas, because modern techniques and heavy equipment could less easily be used. Instead of reshaping such areas into more monotonous landscapes with larger parcels of land and monocultures, farmers may be stimulated by government authorities and professional organisations to strengthen the diversity of the landscape by maintaining trees, bushes and ditches, and plan- ning an attractive alternation of pasture land with cows and arable fields with different crops. Offering services in the sphere of outdoor recreation might then become a source of income which supplements limited agricultural revenues. The above figures indicate that, including a border of shrubs, a net- work of riding tracks in an agricultural area would require only a few percent of the land whereas the revenues for the collaborating farmers who provided this space could well be made to increase by more than a few percent. I refer back to the experience in Iceland and Denmark, reported earlier in this section of the journal, which suggests that the trade in recreation horses and the housing and care of them and their riders may well be more attractive to

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farmers than several of them may have thought. Fur ther study along these lines would be worthwhile.

A.A.M.

REFERENCE

Van Oostrum, H.J., 1973. Ruitersport in Drenthe. Cultuurtech. Tijdschr., 13(1): 28--41.

LEAD UPTAKE BY PLANTS AND ITS SIGNIFICANCE FOR ANIMALS

Although there are many gaps in our knowledge of the chemistry of lead in soils and the mechanisms of uptake and transport in plants, it may be con- cluded that there are four barriers restricting the movement of lead from soil to man at the end of the food chain. The first of these is in the soil, where only a small propor t ion of the total lead is available to plant roots. The second is in the roots from which only a small propor t ion of the absorbed lead is t ransportated to the shoots. The third is in the alimentary tract of the rumi- nant animal, f rom which only a very small propor t ion of the amounts ingested are absorbed. Finally, the fourth barrier results from the partioning of lead in the tissues of the ruminant animal where it accumulates in the bones, and does not therefore contr ibute significantly to man's dietary intake. This is the con- clusion of a research done on the lead uptake by plants and its significance for animals by Drs. L.H.P. Jones and R.C. Clement, published in the book "Lead in the Environment" .

A.H.D.

REFERENCE

Hepple, P. (Editor), 1973. Lead in the Environment. Applied Science Publ., Barking, Essex, on behalf of the Institute of Petroleum, London, 82 pp.

NEEDED: A COLLECTION SYSTEM FOR BIOCIDE SURPLUSES

In the course of the years legislation with regard to biocides has changed in The Netherlands. In 1962 a special Pesticides Act was promulgated and since thel~ it has already been t ightened a number of times. Since 1970 DDT and other persistent chlorinated hydrocarbon pesticides are almost completely banned.

When the use of certain biocides was forbidden, many farmers still had