Edible perennial plants native to hot deserts - the solution to the invading sand desert
Written: June 1989
Most researchers would agree that the sand desert is spreading and that large tracts of land formerly used to cultivate crops have now become barren, denuded of vegetation with no protection against winds that blow the top soil away.
The aim of this paper is to show how the fight against the sand desert can be won using drought tolerant edible perennial plants as the weapon.
Plants which formerly stabilised the environment and provided food, shade and other resources are now fast disappearing in the Sahara and its fringes mainly because of the following factors:
a) Cultivation of annual crops.
Land is cleared in order to grow millet, wheat, sorghum, etc.. Almost all other plants are considered to be a nuisance, in the way of the annuals and are therefore cut down or uprooted. But these naturally occurring plants have important uses, many provide human food. One reason for the lack of appreciation for these plants is that their food is considered to be inferior. Plants have a definite status, over 90% of man's food is derived from only 20 species, but there are thousands which provide human food.
There are two types of annuals cultivated. One type is the 'wet' annual which requires irrigation such as rice, tomatoes and lettuce, which are mostly grown for export. These plants use a lot of water which is a scarce resource in the Sahara and its fringes. Irrigated schemes need a lot of inputs, mostly expensive and imported from the West. Machinery easily breaks down and the soil can become saline or even waterlogged so that this type of agriculture can soon prove to be loss-making and create dependence on Western economic aid and technology.
The other type is the 'dry' annual, which includes millet and sorghum etc.. These are mostly cultivated for domestic use. They grow for two to four months and after the straw has been cut, the land is completely exposed to wind erosion, except where annuals are intercropped with perennials. In poor rain years, the land is exposed for 8-9 months per year, and in drought years the land is bare, with nothing to block the movement of wind and sand.
b) Overgrazing by domestic animals.
Goats, sheep and cattle do not discriminate in their eating habits but eat almost all vegetation. Goats in particular will eat any green shoots, killing newly germinated perennial plants, preventing their establishment. (That schemes were initiated in order to increase the number of small livestock after the droughts of the 1970's and 1980's when there was so much less for the animals to eat, seems a bit contradictory).
c) Excess collection of firewood.
The pressure for firewood is now so great that some people are willing to travel over 100km. to find firewood to sell in towns and cities. Whole trees have to be felled in order to make it economic to collect and transport. A tree that has perhaps taken 30 years to grow can be chopped down in 30 minutes.
These processes leave the land bare with nothing to prevent the wind eroding the fertile top soil, and the sand can move freely to threaten new areas.
The solution is for local farmers to cultivate drought tolerant edible perennial plants, which they can use for food and that stabilise the sand at the same time. Eden sees its part in this by testing drought tolerant food plants and then via prototype farms introduce the most promising of these plants to farmers who will be given access to start-off quantities of seeds that they themselves can reproduce, when they are motivated to do so. This is a modular solution which is economically realistic for such a large area which means that it can start on a small scale in different areas, and the modules can join together when developed and become an active front against the desert.
a) The research programme.
Research being done by Eden is at a very early stage, and this is a really long term work. The species that interest Eden must be able to grow where the rainfall is _225mm. Therefore it is very important to screen, where possible, plant candidates through available botanical and agricultural literature, and later, on Environmental Survey Trips in the desert. This process allows any plant to be a candidate but at the same time gives a rigorous method of rejecting candidates which do not fit our criteria. Plant candidates are then screened through our 'Dry Farming Candidate Preparation Test' to find out the best way of establishing the perennials by direct sowing and using rainfall as the sole source of water. It becomes important to find out the optimal sowing date, sowing depth and seed treatment before thoroughly testing the species through the 'Dry Farming Values'.
The 'Dry Farming Values' is a tool to enable the researcher to find out the plant's tolerance to drought, heat, frost, wind, suffocation by sand or dust, soils poor in nutrients, very alkaline or saline soils etc.. Their growth and harvest over a period of years, ability to improve the soil, and duration of growth will be monitored. The plant's ability to provide food nutrients such as carbohydrates, protein, vitamins and minerals will be tested, and they will be analysed for any toxins. There are 50 values,each with it's own score and weighting so that each plant species can gain it's own composite score. The quality of the research can be evaluated at any stage of the research to show the accuracy of the research. Species that are found to be useful for 'Dry Farming' are then ready to be distributed to Government institutions, Universities in the region and by 'Dry Farming' agriculturalists in villages. The 'Dry Farming' agriculturalists who will be coming from North West Africa will grow demonstration farms after a period of training in the cultivation of 'Dry Farming' plants. They are to act only as a resource of information and seeds, and the people in the villages are themselves to decide how to make use of this.
'Dry Farming' plant candidates will need to be tested in different localities in order to find the most suitable species for areas with differing rainfall quantities, seasonal variations in rainfall and temperature, different soils etc..
b) Some examples of 'Dry Farming' potential candidates.
Christ's Thorn. (Ziziphus spina-christae) Native area: N.,NW. Africa - SW. Asia. In Niger: Zinder, Agadez and area around N'guimi. Approximate rainfall range: 100-600mm. Temperature tolerance: >44 degrees C. (mean monthly maximum). Food provision: Raw fruit and raw seeds. (Probably rich in carbohydrates,vitamins and minerals). Type of plant: Tree, erect, thorny, up to 12m. Fruits are appreciated in Niger,and are sold in Zinder market.
Tagart bush. (Maerua crassifolia) Native area: All Sahara, including Mauritania, Morocco, Algeria and Chad. In Niger: Aïr Mountains, West Termit, Zinder and Aderbissinat. Approximate rainfall range: <100-700mm. Temperature tolerance: >42 degrees C. (mean monthly maximum). Food provision: Fruit, cooked leaves. (Probably rich in protein, vitamins and iron). Type of plant: Shrub, small tree, 2-5m. Leaves are used in 'sauce' by villagers in Niger.
Desert panic grass. (Panicum turgidum) Native area: Morocco, Algeria, Tunisia, Mauritania to Somalia. In Niger: Agadez, Termit and Aïr Mountains. Approximate rainfall range: 25-400mm. Temperature tolerance: >44 degrees C. (mean monthly maximum). Food provision: Grain, made into flour/meal or boiled. Type of plant: Herb >1.2m. The grain looks like millet and could be made into locally acceptable dishes. This species is also useful for binding sand.
These plants are among over 130 'Dry Farming' potential candidates known to Eden that grow where rainfall is _225mm. and are supposed to provide human food.
These and other edible drought tolerant perennials have many advantages including:
The desert is spreading, engulfing large areas of land that were once fertile. There are already many perennial species growing in hot deserts such as the Sahara and it's fringes which could be used to stop and reverse the advancing desert as they are native to the desert. A thorough research of these plants can lead to their cultivation and food provision for the people of the hot deserts and their adjacent areas.
Copyright © Eden Foundation