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close this bookCERES No. 109 (FAO Ceres, 1986, 50 p.)
close this folderCerescope
View the documentClimatologists fear prolonged drought in Sahelian zone
View the documentMosquito control aided by tiny fish with big appetite
View the documentNew cropping system reveals promise for low-input farming
View the documentFrogs' usefulness cited in campaign to ban their export from India
View the documentLoss of markets feared for Sudan's gum arabic output
View the documentNew species, techniques help to rehabilitate African fishponds
View the documentLocal language use helping to spread new farming techniques
View the documentIntegrated approach adopted by Rwanda for fishery project

Climatologists fear prolonged drought in Sahelian zone

Throughout human history, rainfall in sub-Saharan Africa has been variable from year to year and from place to place. There were recurrent droughts during the first 60 years of this century, but the rain has usually returned within one to four years. For this reason, agricultural planners have become confident, even in years of low rainfall, that "normal" rains would return within a few years.

Since 1960, however, rainfall in the Sahel has been declining. More precisely, the year-to -year variations in rainfall in any particular place have been superimposed on a continuing long-term decline. The same is true of overall rainfall in the western Sahel as reflected in the statistical indices constructed by climatologists. Through out this region rainfall has become sparser and more variable. To cite one dramatic example, rainfall in Dakar has declined from 500-800 mm in the 1950s (that typical of the mid western United States) to 130-200 mm in the 1970s (that typical of the American arid southwest). The effect of this long-term decline is exacerbated by a shorter-term drought that extends over a huge crescent-shaped area that stretches across the Sahel and doubles back down through southern and southeastern Africa, an area twice the size of the United States.

The historical precedents for this kind of prolonged Sahelian drought have made climatologists seriously concerned that the current drought will persist for another decade or so. The last period comparable to this one took place in the 1820s and 1830s. According to the rather meagre records available, rainfall declined for a period of 20 to 30 years and the level of Lake Chad fell to about where it is today. The geological record shows several similar drops in the level of the lake in the past 600 years. (The Sahel has also seen much wetter periods. The area near Timbuktu, which now has 100 mm of rainfall a year, exported wheat to other regions of West Africa in the late nineteenth century, taking advantage of then higher rainfall and river flow.)

Climatologists still do not know the extent to which the drought and its persistence are due to human activities. Any climatic phenomenon that extends over an entire continent and which has occurred intermittently in the past cannot be due to human activities alone, but must be related to the global atmospheric circulation that controls the climate of the entire earth.

Other areas of the tropics are affected by periodic droughts, but these last for one or, at most, two seasons. Many of these are known to be caused by the El Nino/Southern Oscillation (ENSO) phenomenon. A global change in the oceans and atmosphere that causes drought in India, Australia, South America, and the Pacific Islands. (See Ceres, Nov.-Dec. 1985).

The year-to-year variability caused by the ENSO phenomenon can be seen in African climatic records. Of the last 28 ENSO years, 22 have been unusually dry in southeast Africa. Since ENSO-related changes take place a few months before the rainy season, further research may make it possible to use them to give a few months' notice of some particularly bad drought years in southeast Africa, south of Zimbabwe. However, their usefulness for this purpose in the Sahel is doubtful.

In the Sahel, by contrast, some dry years are correlated with a warming of the surface of the Atlantic just north of the equator. This change may be related to the movements of the Intertropical Convergence Zone (ITCZ), the great band of equatorial clouds whose north-south migrations bring rain to the humid tropics and the Sahel.

But unlike the situation in other parts of the world, Africa has had many dry years that are not correlated with ENSO or other sea surface phenomena. And the trend line of its rainfall regime in the Sahel has gotten steadily worse for 20 years. It is the persistence of the Sahelian drought that sets it apart from droughts in other parts of the world.

While the cause of this persistence is not known, the obvious suspect is the large-scale changes in the land surface in Africa. Some of these changes are probably due to human activities, such as deforestation. But the most important changes are probably caused by the drought itself. In other words, there is probably a natural feedback mechanism that causes the drought to feed on itself.

Both human and natural changes involve major changes in surface hydrology, reflectance (albedo), and dust - all of which are major influences on climate. In particular, surface runoff increases, and percolation and soil moistture decrease, decreasing in turn the amount of water available for evapotransportation back into the atmosphere. In addition, crops and grasses evapotranspire less than trees because they have shallower roots. These changes can have a serious effect on local precipitation, since in many areas rainfall is derived from water evapotranspired locally. Another possible contribution comes from the coaling effect caused by the increase in reflectivity and dust. This draws dry air down from the upper atmosphere, reinforcing the effect of decreased soil moisture.

From the scientific point of view, the problem is, first, that no one knows the relative contribution of human and natural causes to the persistence of the drought. (To be sure, erosion and deforestation caused by humans seriously affect the availability of soil and water for agriculture, but this is another matter.) There is no empirical evidence that even large-scale changes in land surface (covering an area of, say, more than 500 km2) can affect climate. But they are not yet capable of modelling climate reliably at the continental level, or of modelling the details of surface hydrology or the relations between plant cover, soil, and atmosphere. Hence, scientists are unwilling to rely on their ability to predict the climatic effects of even large-scale changes in land surface in the absence of empirical data. These research techniques are now rapidly improving.

Rainfall data in Africa, both current and historical, is meagre. Local research capacity is almost non-existent. The network of operational meteorological stations is poor and deteriorating. Upper air measurements of wind and temperature, which are essential for research, are few and dwindling over the Sahel. Even routine rainfall observations are often not communicated to international networks or are subject to long delay. Historical records are difficult of access; one researcher reported that she had to visit the station in person and copy the records by hand in order to obtain satisfactory historical records. Satellite data help, but are still mostly qualitative and extend back at most ten years. Well-trained African meteorologists do exist, but they are employed mostly in routine forecasting and administrative duties.

Two conclusions can be drawn. First of all, rainfall atlases based on the historical records of the last three or four decades are clearly not applicable to the next decade or two. Specifically, agricultural and other projects now being planned for the Sahel should not use farm models based on the assumption that "normal rains will return". The causes of the drought are not understood, and there is no assurance that the rain will return soon. On the contrary, it is prudent to assume that the pattern of the last decade may persist for another decade or more.

Charles Weiss

Mosquito control aided by tiny fish with big appetite

Since 1970, mosquito abatement programmes in the state of California have reduced their use of insecticides by more than 75 per cent. Part of the credit for this is due to a hardy minnow from the rivers and lakes of the southeastern United States, the gambusia, whose prodigious appetite for mosquito larvae has earned it the more common title of "mosquitofish". Although the full-grown female is only as long as a human finger and the male is even smaller, each can eat dozens of mosquito larvae and pupae a day. The fish occupy some amazing habitats: tunnels, abandoned swimming pools, bonds, rainbarrels, stagnant rice fields, and waterways that dry out only slowly in the spring. Mosquitofish have been introduced statewide into sewage-treatment ponds, roadside ditches, and watering troughs on ranches. The city of Fresno has them in drains under the streets. Disneyland has them inits aquatic exhibits and its many storm drains.

Yet the discovery of the species' effectiveness in controlling mosquitoes is not new. The tiny grey or grey-and-black fish were first used for mosquito control in the United States in the early 1900s. Stocks were sent to Hawaii in 1905, where they were credited with reducing the populations of the encephalitis mosquito. Mosquitofish also helped conquer the yellow Fever epidemic that threatened to halt all work on the Panama Canal. They were dumped into flooded excavation pits, into plants that trap water in their leaves, and even into gutters around houses.

In the 1940s, however, the spectacular early success of DDT and other synthetic compounds made the tiny minnow seem obsolete. Its use declined. This natural form of mosquito control is only now coming back.

The fish require no special egg-laying site: they bear live young. Under favourable summer conditions a single female can produce 200 young every 21 days. Small size allows them to penetrate most sites where mosquito larvae and pupae are found. They thrive when combined with other control techniques, such as bacterial pesticides, and even chemical insecticides used to spray mosquitoes do not hurt them. They tolerate wide ranges of temperature and salinity, as well as moderate sewage pollution. "Mosquitofish can take terribly poor water," notes Graham Gall, an aquaculture specialist at the University of California. "The oxygen level can be down to practically nothing. They're a surface fish, they work on the interface with air, and are okay."

Most of California's 53 mosquito abatement programmes use some mosquitofish. Some have full-time fish biologists on staff. Mosquito control personnel have fish trucks and other special equipment for handling fish. (Mosquitofish have been dropped out of helicopters in plastic bags; the beg explodes, releasing the fish into little pools that are hard to find except from the air.) The study of the metabolism, feeding, and aquaculture of mosquitofish are leading programmes in statewide mosquito control research.

For mosquito control in rice fields, the fish reduce the number of pesticide treatments by 90 per cent and reduce both inspection time and costs per acre by around 65 per cent. Only insufficient supplies of the fish are hampering the increased use of this integrated control. Many mosquitofish die during the cool California winter, and there are not enough available in the spring when mosquito populations are small and most vulnerable. No one yet knows how to culture the fish, although researchers are attempting to mass rear it. To recover the fish, rice growers now drain their fields before drying them out in the autumn. The fish wash down through canals, where mosquito control personnel recover them. They are overwintered in warm water ponds at power plants or sewage treatment facilities.

Elsewhere in the United States mosquitofish have proved singularly successful as well, and they could have worldwide possibilities. They are not, however, without their potential problems. Mosquitofish are so effective that they can consume most of the plankton in an area, and scientists worry that this might harm other fish species. There are no quantitative data to confirm any adverse effects in field practice - indeed, the mosquitofish are preyed upon by larger fish and in some waterways they seem to have improved the numbers of food- and sport-fish species - but it is still possible that problems may arise in the future, especially in areas where the fish do not die off over the winter. Most biologists are opposed to introducing the mosquitofish to new habitats.

Instead, countries worldwide should investigate their own indigenous fish and identify those that consume mosquito larvae. (This is done by observing the faeces under the microscope; the species that eat mosquito larvae are identified by the undigested outskeletons, which are easily seen.)

The World Health Organization has already begun this process for some areas. Mosquito-eating fish that have been identified include guppies, blackfish, the desert pupfish, goldfish, and even "annual fish" whose eggs resist desiccation when a pond dries out.

Therefore, the most important message of California's success is that fish in general can be valuable in mosquito control. In the future, this natural form of pest management is likely to be used the world over, employing dozens of local species and involving many fish biologists in suppressing mosquitoes and preventing diseases.

Noel Vietmeyer

New cropping system reveals promise for low-input farming

For centuries, African farmers have relied on shifting cultivation and bush fallow systems to regenerate soil fertility. Although these provide only a subsistence living, they are ecologically stable and therefore suited to the tropical environment. They are, however, wasteful, especially where urbanization and the introduction of large-scale mechanised farming make the practice of idling land for several years unrealistic.

Many programmes for improving tropical agriculture have tried to remove components of the bush fallow system, but the replacements, usually based on temperate-climate farming methods, have often had a destabilizing effect on tropical environments. Thus the search for a stable and suitable alternative to shifting cultivation has engaged the attention of researchers for many years. Now, after a series of studies and experiments at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, scientists have come up with a method called "alley cropping" which holds promise for making tropical soils more productive

Alley cropping is a low-input soil management technology that can sustain crop production where farmers cannot afford expensive inputs and where increasing pressure on land does not favour traditional shifting cultivation. While introducing important and more reliable improvements, it retains the basic features of bush fallow and can easily be adopted by resource-poor farmers. As a biological low-input production system, alley cropping represents a useful production technique in developing countries where shortage of foreign exchange prohibits the importation or use of larger quantities of inputs such as fertilizers and herbicides.

Alley cropping consists essentially of planting food crops between rows of leguminous trees or shrubs whose leaves are periodically slashed to supply nutrients to the soil. A major advantage of alley cropping over the traditional shifting cultivation and bush fallow is that the cropping and fallow phases can take place concurrently on the same land, thus allowing the farmer to crop for an extended period without returning the land to bush fallow.

Alley cropping is another arm of the no-tillage or zero-tillage package being emphasised by IITA scientists as part of a worldwide campaign to find an alternative to the conventional system of land preparation in the tropics. Scientists discourage use of heavy equipment for land clearing and preparation because tropical soils are prone to rapid degradation as a result of high humidity and temperature. With alley cropping, conventional ploughing and harrowing are not required. As long as there is adequate mulch from prunings, tillage makes little difference in crop yields. Besides, like bush fallow, alley cropping helps to suppress obnoxious weeds, a big advantage especially in small-scale farming, in which weeding constitutes more than 30 per cent of the labour in crop production.

Perhaps the greatest gain in alley cropping is the supply of nutrients to food crops by the leguminous trees and shrubs. According to three IITA scientists, Drs B.T. Kang, a soil scientist; G.F. Wilson, an agronomist, and T. L. Lawson, an agroclimatologist, coauthors of a publication called "Alley Cropping", trees and shrubs in alley farming provide green manure or mulch for companion food crops. Eight years of continuous experimenting in Nigeria have shown that a wellmanaged row of leucaena used in the alley system produced between 15 and 20 tons of fresh prunings (5 to 6.5 tons dry matter) per hectare with five prunings per year. These prunings, excluding stakes, yielded over 160 kg N. 15 kg P. 150 kg K, 40 kg Ca, and 15 kg Mg per hectare per year. A similar study carried out in Hawaii showed that nitrogen fixation was as high as 500 to 600 kg N per hectare per year. The study also showed nitrogen yield of 127 kg per hectare from four-month-old leucaena plants grown in the Cauca Valley of Colombia. This is a reaffirmation of the high nitrogen fixation ability of leucaena. The recycling of nutrients to the surface soil is a major benefit of alley cropping. Where nitrogen fixing leguminous trees or shrubs are used, some of the nitrogen fixed is eventually released to the companion crops through decomposition of prunings of leaves and twigs. Reports show that yields of open pollinated maize, when alley cropped with leucaena continuously for six years without additional chemical fertilizer on a sandy entisol near Ibadan, was never less than two tons per hectare.

The same system of alley cropping on an alfisol alternating maize intercropped with cowpea produced even more encouraging results. There, with leucaena prunings serving as mulch and without additional use of fertilizer, the maize yield was not less than four tons per hectare. Very promising results were obtained from alley cropping of cassava with gliricidia and also from alley cropping of rice and yams with leucaena. To further expand and select suitable tree and shrub species for alley cropping, field testing is being conducted around Ibadan and the high-density rainfall area of Port Harcourt.

A peasant farmer who has practised alley cropping for two years at Ijaiye village near Ibadan said he received the "gospel" with mixed feelings when it was introduced to him. After one year of trying the package, he added, he began to see the benefits, especially in the area of mulching and weed control. Many farmers in the area are now buying the idea through him.

In the savannah region of Benue State, noted for yam production, a major problem is the supply of stakes needed for this crop. Vegetation there is mainly grass and scattered stunted shrubs. To reduce the farmers' problems, IITA scientists introduced alley cropping in some locations about five years ago. Farmers planted fast-growing Leucaena leucocephala using the stems for yam stakes and the leaves as fodder for their ruminants during the dry season.

Taya Babaleye

Frogs' usefulness cited in campaign to ban their export from India

A conflict between ecological and economic interests has arisen over the humble Indian frog. For many months now, ecologists of the Federal Republic of Germany have been telling their countrymen that leaving bullfrogs in their native fields augurs well for the ecology of the Asian countries exporting frogs' legs. The West German National Environmental Foundation, based in Frankfurt, is trying to persuade food shops and restaurants to drop frogs' legs from their menus. German ecologists have also been carrying their campaign across the Atlantic, to the United States, which imported 3 212 tons of frogs' legs in 1983, about six times the average annual imports into the Federal Republic of Germany.

It takes at least 20 to 25 frogs to produce a kilo of frogs' legs, which fetches up to $85 on the US market. For India, which exports more than 3 000 tons of frogs' legs annually to the United States and Western Europe, this implies the killing of 9 000 tons of frogs a year. Indians traditionally worshipped frogs as harbingers of prosperity and plentiful rain, and killing them used to be considered a crime. But in the face of widespread poverty and unemployment, such traditions are rapidly fading. Frog trapping has emerged as a lucrative occupation. Favoured hunting grounds for Indian frogs are the areas surrounding Calcutta, Hyderabad, and Cochin, where unemployment is high and jobless youth need little encouragement to catch frogs which yield high returns.

Western Europe and the United States are the largest outlets for Indian frogs' legs, though, of late, Canada, Saudi Arabia, the United Arab Emirates, and Japan are growing markets.

But while the economy may benefit from the export of frogs' legs, the deficit side of these transactions will include insect damage to agricultural crops, more money being spent on pesticides, pollution of the environment by non-specific pesticides, and, more important, spread of malaria. This is the view of Dr G. M. Oza, a member of the commission of ecology of the International Union for Conservation of Nature and Natural Resources (IUCN). By feeding on a host of insects that continuously threaten agricultural crops, frogs play a prominent role in maintaining the ecological cycle and the food supply pattern. An adult frog devours its own weight in insects every day. It has been estimated that over a period of 90 days, 9 000 tons of frogs would swallow about 810 000 tons of food, including insects. Thus the killing of so many frogs will con tribute to an increase in the insect population, which in turn will lead to a steady decline in crops.

Field studies conducted by the Indian Council of Agricultural Research (ICAR) have established that crop losses in India are more pronounced during the period between May and 7 August - the peak breeding season of frogs. As a consequence of these findings, the Government of India has banned frog trapping during these months. To restrict the slaughter of wild frogs, captive breeding is being encouraged.

But it is not only the extent of the slaughter that is disturbing to the conservationists, it is the method of killing. And this is what gives their cause its emotional appeal. The trappers' normal practice is to kill frogs on capture and sever their hind legs and despatch them to the processing plant. At times, however, legs are removed in more violent fashion - the frog is chopped in two across the torso while still alive. Sometimes they are also skinned and the hides used to make small leather goods.

Further ammunition for the save-the-frog argument comes from Australian researcher Michael Tyler, an eminent authority on frogs and frog behaviour. He has discovered that certain abnormalities in frogs can be traced to specific water pollutants, often as far back as tadpole stage. But what Tyler adds to the conservationists' cause is this: frogs can serve as a highly sensitive early warning system.

Land clearance, mining wastes, pesticides, and weed control measures have been found to exert an adverse effect on the healthy growth of frog species. According to Tyler, natural abnormalities in the frog usually vary between 0.5 and 12 per cent. Any percentage beyond this is a certain indication of aquatic contamination. "One day it may be possible to suggest the nature of pollutants in an area just from the examination of abnormal frogs," Tyler says. "But what we lack is sufficient data to exploit this unique environmental monitoring system."

Radhakrishna Rao

Loss of markets feared for Sudan's gum arabic output

For 2 000 years harvesting of gum arabic has been an essential part of subsistence agriculture in the Sudan. In good years the country's Acacia Senegal trees have provided 80 per cent of the world's requirements for gum arabic, which is used in textiles, plastics, and paint and serves as an emulsifying and adhesive agent in confectionery and drugs. It has provided cash income for farmers in lean years, and, more important, grown in rotation with other crops, it has helped to bind the soil and provide cover against the encroaching desert.

But, as in the case of other crops, years of drought in the region have taken their toll on the Acacia Senegal plantations. Gum output has fallen substantially, particularly in Kordofan province in the west of the country, which accounts for half of total national output. By the beginning of the present decade Kordofan's production of gum arabic had declined by one third from the long-time annual average of about 24 000 tons. Once the Sudan's second most valuable export commodity (after cotton), gum arabic has now slipped to fourth place. Even so, in 1983 it still earned $58 million, or more than 10 per cent of the Sudan's export revenues.

In addition to the immediate damage to the region's economy, however, the Sudan's gum arabic industry is faced with a more disturbing longer-term threat: the possibility that important export markets, weaned from gum arabic in periods of short supply, may turn to readily available synthetic substitutes. Since global demand for gum arabic is small (only about 50 000 tons a year}, the Sudan's share of the world market was assured until recently. However, synthetic substitutes made from starch and petrochemicals are making steady inroads into markets for natural gum arabic. To counter the possibility that the Sudan's customers might change more quickly to synthetics if supplies became restricted, the government-run Gum Arabic Company {GAC) drew upon its strategic reserve of 20 000 tons to help offset the immediate effects of the drought.

The Government has also recognized the environmental importance of Acacia Senegal and has initiated conservation measures. Within the 65 000 km2 area in Kordofan known as the gum belt, a major programme for restocking gum arabic plantations is under way. The Sudanese Government has been working since 1981 in collaboration with FAO, UNDP, and UNEP, the United Nations Sudano-Sahelian Office (UNSO) on a project aimed at Planting 27 000 feddans of new gum trees. The Dutch Government has contributed $1.5 million to the scheme, which has more recently been extended another four years and expanded to include assistance from the World Food Programme. The present aim is to extend the gum belt further with two plantations, one of 11 350 hectares and the other of 34 660 hectares.

The Government's interest has been complemented by increased involvement in actual production by GAC, in theory a joint venture between state and private producers.

The cultivation of and trade in gum arabic was traditionally conducted by private merchants until 1969, when the Sudanese Government set up the GAC to market the commodity. GAC's role was first confined to Port Sudan, where it bought, cleaned, and exported gum transported to the quayside by producers. However, over the years the GAC became more involved in production, evolving research and extension programmes and supplying farmers with seeds and credit. As drought worsened in 1984, the company provided farmers with water tanks and money for digging wells. Now GAC wants to improve screening, sorting, and packaging facilities at Port Sudan in order to raise standards of Sudanese gum arabic on the world market. According to the International Trade Centre, higher standards could lead to price increases of 10 to 15 per cent in ordinary grades and 15 to 30 per cent in top grades. The ITC also noted gum arabic users' need for standardized and consistent raw material supplies as their production processes become increasingly automated.

Andrew Lycett

New species, techniques help to rehabilitate African fishponds

Five kilometres of dirt road, then a path between two maizefields rising steeply before it suddenly divides - even if one knows of their existence, the two fishponds operated by a womens' group at Mwilitsa in the Lake Victoria region of Kenya would not be easy to find. Yet, in that region alone, there are at present about 4 200 such ponds. They are operated by individual farmers or by groups like the one at Mwilitsa - Teresa, Myriam, Anna, Leonida, and 35 others - to raise fish for the family table or to sell to neighbours or in the market. Since average meat consumption in this impoverished region is only about 10 kilos per person per year, the potential of these small ponds, each about 10 by 20 metres in area and a little more than half a metre deep, for improving family diets is considerable. With good management, a pond can produce from 20 to 50 kilos of fish a year.

"That may seem like a ridiculously small amount compared with the 75 000 tons of fish brought out of Lake Victoria each year," admits Frans Vallet, leader of the FAO/ UNDP project for the development of fish farming in the Lake Victoria region. "Of that total, however, only 20 000 tons are sold on the markets of the region and the supply is much below the demand. Moreover, threadfish constitutes 60 per cent of the catch and the local population doesn't eat it because they prefer tilapia." The Belgian Fund for Survival, in addition to the Kenyan Government, is contributing to the project.

In 1983 the Lake Basin Development Authority (LBDA), with the support of FAO's Technical Cooperation Programme, trained 20 extension workers and seven coordinators, who are presently working with farmers and groups in the region. Their first task, undertaken with the financial support of the World Bank, was a stocktaking of existing ponds, which made them realize that almost all of these were either badly managed or simply abandoned. "The pond should be dug on a spot where the soil is an impervious clay, the gradient very slight, and where water will be available year round," said Vallet. "When an extension worker goes to see a farmer for the first time he shows him the works that are needed to restore a pond. Generally, he also suggests that the pond should be completely emptied. The farmer can then resume his production with first quality young fish (100 fry are worth 15 shillings), that we raise in the project fish hatchery at Kibos, near Kisumu."

A regular culling of the fish or a complete emptying of the pond is essential. "Often," says Vallet, "farmers believe that fish continue to grow indefinitely. In fact, it takes about six months and sometimes a little more if it is at a higher altitude or the water is cold, until they reach their maximum length and weight. A pond-reared fish will never weigh more than 500 grams. However, tilapia reproduce very rapidly and overpopulation prevents fish from growing normally."

Each morning and evening at Mwilitsa, teams of two women come to feed their fish with food scraps, ogali leaves, manioc, and cow manure, which, deposited at the bottom of the pond, fertilizes the soil and assures the production of fungus and grass on which the fish feed. "It takes more time for the fish to gain weight with this type of feeding," Vallet explains. "The conversion rate is 10 to 1, while with commercial rations it takes only three kilos to produce a kilo of fish. Use of prepared feeds also permits more densely stocked ponds, since density of population is partly limited by the amount of feed that can be placed there. On the other hand, the cost of commercial feeds is often a negative factor for the farmer. It all depends, finally, on his main objectives."

Since the beginning of the project in July 1984, some 500 ponds have been restored to an operating state and another 500 have been constructed. However, this is still too slow in the view of some 2 100 farmers who have asked help from extension workers to take their turn in this new productive activity. Between October 1984 and June 1985 the new hatchery at Kibos was able to supply more than 43 000 selected tilapia and tilapia Nilotica to the fish farmers. Six other hatcheries are to be built before the end of the project in order to meet the needs of the extension service. Another programme of technical assistance to schools is being provided by a United Nations volunteer who arrived in early 1985 and is working in the Kisii region in collaboration with extension workers and Department of Fishery personnel.

With the expectation of achieving an annual regional output of 200 tons of fish from 4 000 ponds, this project bears the imprint of similar programmes that have been successfully established in several African countries. "Fish farming was introduced to the continent at the beginning of the 1940s," says Michel Vincke of FAO's Department of Fisheries, "but in most cases they were abandoned at the time of independence. Our main objective was to rehabilitate this activity and to introduce new fish species."

An FAO regional project covering Gabon, the Congo, and the Central African Republic has, since the end of the 1960s, provided training for groups of officials and intermediate technicians who have in turn worked to reestablish fish farming in the rural milieu. When the project was begun the Bangui region of the Central African Republic could claim only 11 ponds. Today there are not fewer than 11 000 across the country belonging either to smallholders or to organized groups. Similar developments are under way in Zambia, the Ivory Coast, the Congo, and Kenya. "The basic technique remains the same," says Vincke. "That is to contact the peasants directly, to develop the concept of production without the assistance of the government, including the production of the young fish, which farmers can do perfectly well themselves."

Dani Blain

Local language use helping to spread new farming techniques

One obvious but often overlooked reason for the difficulties encountered in upgrading agricultural practices in the developing world is the fact that an overwhelming majority of peasant farmers do not understand any of the European languages in which much of the international exchange in agricultural research is conducted. To a lesser degree, the same handicap faces many extension workers charged with disseminating improved technology. And even where some familiarity with European languages exists, there is often resistance to its use, based on post-colonial perceptions of independence and sovereignty. In the mid-1970s, when the UN Economic and Social Commission for Asia and the Pacific (ESCAP) surveyed more than 400 government agencies, research centres, academic institutions and non governmental groups in the region concerning languages to be used in education and extension programmes, the great majority indicated a preference for local languages. The proportion of respondents favouring local languages exceeding 75 per cent in seven of 13 countries and fell below 50 per cent in only two. A more recent survey by the International Rice Research Institute (IRRI) showed that educational material published only in English failed to reach millions of farmers, extension specialists, scientists, and educators in the developing world.

An early initiative to help bridge this gap was undertaken by FAO in the early 1970s when it began publishing its Better Farming Series in non-European languages. Although still modestly budgetted at about $150 000 per year, the programme has succeeded in publishing and distributing practical farming and rural homemaking guides in Arabic, Hindi, Indonesian, Lao, Swahili, and Thai.

A new effort in this field has been launched by IRRI with its manual, "A Farmer's Primer on Growing Rice", recently made available in 22 languages worldwide. Editions in at least 14 other languages are in press.

The effectiveness of this manual and other publications in local languages as against English is now being studied in Leyte, Philippines, through a cooperative research project of Araneta University, the Philippines Bureau of Plant Industry, the FAO Integrated Pest Control Programme, and IRRI. "A Farmer's Primer on Growing Rice" was conceived and compiled by Dr Benito S. Vergara, an IRRI plant physiologist. When teaching IRRI courses on rice science to students and trainees from Third World countries, Vergara sensed the need for a simple, readable book for extension agents or progressive farmers that would explain clearly the "how" and "why" of good rice-growing practices. Although leaflets available then listed steps for successful rice cultivation, Vergara believed that farmers and rice production specialists should understand better the reasons why such practices as seed incubation or proper depth transplanting were recommended. The Science Education Centre of the University of the Philippines at Diliman used an early draft to teach principles of agricultural science to elementary students. IRRI trainees who studied early drafts of the primer in Vergara's courses returned home and realised its usefulness. But it was not then available in their local languages. Even before IRRI published the primer in English in 1979, requests were made for permission to translate it into Thai and Bahasa Indonesia. The author knew then that his primer was reaching the people for whom it was intended, those involved in rice growing.

Since IRRI does not have the staff, expertise, or equipment to translate and publish its educational materials extensively in non-English languages, it cooperates with other agricultural agencies and private publishers in developing countries in joint efforts to publish their materials in local languages. According to IRRI statistics, by late 1983, more than 600 000 copies of non-English editions of IRRI books had been or were being printed in 32 languages.

Another effort to hurdle the language barrier is being made by the Developing Countries Farm Radio Network. Based in Toronto, Canada, it supplies about 500 affiliates in Africa, Latin America, the Caribbean, Asia, and the Pacific with tapes and scripts that provide the raw material for farm radio broadcasts in more than 100 languages. The broadcasts reach an estimated 100 million listeners. Project Director George S. Atkins, a former farm radio commentator for the Canadian Broadcasting Corporation who also produced that service's renowned "National Farm Radio Forum", sends out a quarterly package of radio tapes covering a wide range of practical subjects.

The first such package was distributed in English in 1979 to 34 charter members in 26 developing countries. The first participants were all farm broadcasters. Now the network also includes agricultural extension workers, health workers, writers, missionaries, teachers, librarians, and others. Currently the tapes and scripts, which are distributed in English, French, and Spanish, have been translated into 113 languages and dialects.

Information polls sent out with each package request evaluations from participants. The evaluations and suggestions are used as a guide in determining the form and content of information prepared for future packages. Participants are also encouraged to contribute material for use in future broadcasts. Atkins lists the following criteria for his selection of material to be used: 1) it must be aimed at increasing food supplies and improving the quality of life of the small farmer and his or her family; 2) it must be simple and practical; 3) its idea must be communicable by radio or word of mouth; 4) it must have been developed, tested, and proved in the developing world; 5) it must be useable or adaptable for use in other developing countries; 6) it must cost little or no money, requiring only resources ordinarily available to the farmer; 7) it must require little or no help from extension workers.

With a staff of six, the network operates on a budget of about $1.5 million per year underwritten by three sponsors: the Canadian farm equipment firm, Massey Ferguson, the University of Guelph, which provides office space and administrative and technical support, and the Canadian International Development Agency (CIDA).

"One of the secrets of the network's success," says Atkins, "is our threeway approach to communicating with the local broadcaster, teacher, or missionary, whose knowledge of English, French, or Spanish may be somewhat limited. In the regular feedback we receive, they tell us that by following the script, by listening to a recording of the script, and by referring to illustrations with the script, they are able to fully understand the information and then pass it along to the rural people they serve in the local language and cultural mode."

Nick Kesi with Ceres staff

Integrated approach adopted by Rwanda for fishery project

For countries like Rwanda, suffering serious consequences from prolonged drought and poor harvests, it is as important to overcome present difficulties as it is to create a solid basis for food production. The opportunities for increasing agricultural production are restricted by the lack of arable land, a consequence of the country's mountainous nature and extremely high population density. This has reached an average of 180 persons per square kilometre, and reaches 390 per square kilometre on the arable land considered alone. This situation appears all the more serious when one considers the rapid growth of population - 3.7 per cent annually. The present level of agricultural production-when harvests are normal - barely covers the minimum food requirements of the population. The average dietary energy availability is around 2 300 calories per day, and animal protein is severely lacking.

Only the intensification of agricultural production and the development of all natural resources can save the country from the dangers of future famine, which could assume proportions comparable to the suffering experienced by some of the Sahelian countries. Among Rwanda's natural resources that have not yet been developed satisfactorily are the fisheries of numerous lakes and rivers. So far, these waters have been exploited in the traditional manner, and techniques that would increase their biological resources have not been introduced.

One exception is the fishery development on Lake Kivu on the border between Rwanda and Zaire. Since the beginning of 1983 some systematic studies have been pursued thanks to an FAO/UNDP project financed jointly with the Netherlands, and fish are being caught with methods completely different from the traditional ones. The project not only embraces the problems of capture technology but also includes biological studies, the processing and marketing of fish, and an evaluation of the economic impact of the development. The project director, Wilhelm Scheffers, is convinced of the value of this integrated approach, considering that fish production is intended to contribute to better nutrition for Rwanda's people.

Lake Kivu, the largest body of water in Rwanda, with a surface, including that part belonging to Zaire, estimated at 2 500 km2, belongs to the region's system of great lakes, including Lakes Tanganyika, Idi Amin-Edward, and Mobutu-Albert. However, it was isolated from the other lakes by the volcanic eruptions of the Virunga massif, which dominates the region. The present link with Lake Tanganyika, some 600 metres lower than Lake Kivu, is the gorge of the Ruzizi River, which is geologically fairly young - about 10 000 years old. Surrounded by mountain peaks at an altitude of 1 450 metres, the 100-km-long Lake Kivu is the highest body of water in the region. Its isolation and its location in a volcanic environment creates a special situation for the development of its biological resources. The lake reaches depths of 485 metres, but from 70 metres below the surface down there is a dead zone deprived of oxygen.

The initial research on Lake Kivu's waters was undertaken before the second world war. Subsequent studies have demonstrated the biological poverty of the lake. Only 21 species of fish have been identified, and their numbers are low, as is their economic utility. However, scientists who studied the lake as early as 1954 confirmed the richness of its plankton resources and the absence of plankton-eating pelagic species. They thus envisaged the artificial stocking of the lake with fish from Lake Tanganyika, which was successfully undertaken in 1959-60. For this purpose the species chosen were Stolothrissa tanganica-Ndagala and the Limnothrissa miodon-Lumpu. Both species resemble sardines in nature and size. Later surveys made in the 1970s established that the fish had adapted but that only the Lumpu were reproducing. This is probably explainable by the great hardiness of this species and especially by the fact that it tends to inhabit shallower water than does the Ndagala species and can take advantage of the upper strata of water which are rich in oxygen.

The establishment of these fish in quantities sufficient for exploitation has attracted the interest of the Rwanda Government in fishing and later resulted, in 1979, in the launching of the FAO/UNDP project which continues today.

The fishery began by employing local methods which soon proved to be inadequate. In 1981, the potential capture of the Lumpu species was estimated at 14 900 tons for the entire lake. Under ideal conditions the catch could reach as high as 35 000 tons. By comparison, productivity of local fish has been estimated at 600 to 800 tons for all of the lake.

Twenty-two pirogues have been buil-catamarans equipped with nets and lamps to attract the fish. The catch is growing systematically. At the beginning, in 1979, only one ton of Lumpu was fished; in 1983, 91 tons were fished and in 1984, 190 tons. In addition to the project's catch, there is that of some private beats on the lake as well as those of the fishery cooperative.

In parallel with this project, a small fishing port has been erected at Gisenyi - a beautiful lakeside village that was the launching point for excursions to the summit of the volcanoes. On this site have now been built a small sales pavilion, a fish-processing plant, a solar drying unit, and a fishery equipment depot.

On returning each night from the fish, each six-man crew brings in an average of about 50 kg of fish. The boats' arrival is awaited by customers who buy fresh fish for either retail or wholesale purposes. What is not sold is dried or processed and the dried waste products are made into fish meal. A small part is frozen. As a result the consumption of fresh fish in the region has increased; dried fish are exported to the interior of Rwanda. Many people have found work and have learned a new trade.

Marcin Makowiecki