4. THE ROLE OF TREES IN LAND USE

4.2 Food and nutrition

Traditional African agriculture was designed in such a way that the various systems offered a variety of food, although mostly with a low output per unit area of land. Fallow lands, savannah grasslands and forests offered a further variety of fruits and other edible products. Children used to eat these naturally occurring fruit, nuts, etc., while they were herding cattle, but nowadays they depend almost entirely on food from the home. This variety of indigenous fruits, many of which were children's favourites, are no longer readily available to children or adults.

Figure 4.1 Trees provide many products and services

Although undoubtedly malnutrition did exist under traditional agricultural systems, the nutritional benefits that resulted from the availability of a wide variety of trees and crops have been lost in modern times.

This negative impact of "development" has to some extent been compensated for by the introduction of exotic fruits, but there is still a need to give more emphasis to the nutritional aspects in agroforestry extension.

Malnutrition

The main nutritional problems can be summarized as follows:

Low energy and protein intake

People do not eat enough food of all kinds. In many areas food shortages are seasonal, being most severe at the end of the dry season and at the beginning of the rains. With the exception of oil-rich seeds and fruit, food from trees can do relatively little to address the energy needs of rural populations on a large scale. A possible exception is the avocado which is high in fat and micronutrients and apart from being eaten as a fruit can be used as a substitute for margarine on bread.

Lack of variety in the diet

A varied diet is likely to be a well-balanced one. More important, the use of different foods, even in small quantities, improves the flavour of the staple food and thus tends to increase the overall consumption of the staple foods (Forestry and Nutrition, FAO, 1989). Dietary deficiencies and food insecurity are strongly related to the decreasing diversity of traditional diets.

Lack of vitamin A

Low levels of vitamin A can lead to partial or complete blindness, and children who lack vitamin A are more likely than healthy children to die from infectious diseases. Yellow fruit and vegetables, as well as dark green leaves, are good sources of this vitamin. Fats, protein and zinc help the body to absorb and use vitamin A, thus a diet low in these nutrients can contribute to vitamin A deficiency. Nuts and oil seeds, in addition to fruit and vegetables, help to meet this nutritional shortfall.

Low levels of riboflavin (vitamin B)

Riboflavin deficiency is another nutrient-related problem which is responsible for eye and skin disorders. Many tree foods, especially leaves, are good sources of this vitamin, and wild leafy vegetables have sometimes been found to have significantly higher riboflavin contents than cultivated varieties. This deficiency is not usually a significant health problem in Kenya.

Iron and iodine deficiency

Iron is essential for the manufacture of haemoglobin. Low levels of iron intake lead to anaemia which is a major health problem in many parts of eastern Africa. Many forest foods supply iron.

In some areas in the region soils are deficient in iodine and therefore the diet is also deficient in this mineral. Iodine deficiency can cause serious disease. The deficiency can be prevented by importation of foodstuffs grown in areas where (there is no iodine deficiency and by iodization of salt supplies.

In addition, supplies of medicine and energy are of course important for the health and general well-being of the people, and these factors are discussed in Sections 4.3 and 4.5 in this manual. The service functions that trees can have in sustaining agricultural and livestock production are discussed in Sections 4.4 and 4.8-4.10.

Edible parts of trees

Wild leaves, either fresh or dried, frequently accompany staple grain dishes. They add flavour, minerals and vitamins to the staples. Some leaves also have a high protein content. Seeds and nuts are also used in side dishes and sauces. Fruits are a seasonal food supply and are often eaten as snack food. In some cases, fruit may provide a very substantial part of the diet, e.g. coconuts. Roots and tubers provide energy, carbohydrates and minerals. They are especially valuable dry-season and famine-period foods. Some may be eaten raw as snacks, while others require complicated processing and thus are only used in times of food scarcity. Some Acacia species yield edible gum, and the sap from other trees is used in various ways. The bark of some trees can also be eaten. All these types of food provide essential elements in the human diet.

Figure 4.2 Fruit and leaves of the baobab, Adansonia digitata

The role of food from trees in the diet

Food from trees makes supplemental, seasonal and emergency contributions to household food supplies.

Supplements to the staple food add taste which enhances the appetite. Some foods increase the absorption of vitamins, e.g. gum arabic (from Acacia Senegal) increases the intensity of vitamin synthesis and may help maintain the normal intestinal flora.

Perhaps the most common use of food from trees is as snacks. Traditionally, people ate fruit between meals while herding cattle or working in the fields. Snack foods are especially important for children since they need to eat more often than adults. In addition, these wild fruit may supply micronutrients that are very important for the healthy growth of children but that may be deficient in the cereal-based diet in the home.

Trees and forests can provide crucially important food and fodder during hunger periods, and such foods may often be more important during periods when people have less time for food preparation such as during the peak agricultural seasons. This use of tree foods is especially important in arid regions where seasonal food-supply fluctuations may be acute.

Traditionally, food from trees provided a buffer during emergency periods, especially during drought, famines and wars. Trees provide food for consumption as well as products that can be gathered and sold. These foods are characteristically energy rich, but may require complicated processing. Food aid, transport of food and increased commercialization have diminished the importance of the emergency role of such foods in some areas. In addition, the decline of forest resources has led to a decline in availability of these emergency foods as well as in knowledge about them.

Figure 4.3 A variety of nutritious fruits

Agroforestry extension and research in relation to nutrition

Extension efforts aimed at maintaining a wide range of species accessible to people can go a long way in improving nutrition. Children often have long school days with little to eat, and a rich flora of trees providing a variety of snack food in the school compound could contribute much to improving their health.

Trees that provide edible parts ought to be left standing whenever possible, and there is scope for planting more of these trees, both exotic and indigenous, in homesteads, along boundaries and in places less suitable for agriculture. We should promote fruit trees of different species so that there will be some fruit to eat all the year round.

So far little or no research has been done on improving indigenous fruit trees. There would be scope for the development of larger and better-tasting varieties of many of them in the same way that the common domesticated fruits were developed. A necessary precondition for such work is that the genetic resources be preserved.

Figure 4.4 Fruit trees in the school compound can improve children's nutrition

Footnote__________

Some of the information in Section 4.2 is based on Forestry and Nutrition: A Reference Manual, FAO, 1989.