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Lutte antiérosive

Thème 6. Aspects socio-économiques de la lutte antiérosive

History and economics of soil and water conservation in Jamaica (1960-2000)

Joseph Lindsay, Marcia Walker et Jan de Graaff

Résumé

Le gouvernement de Jamaïque a acquis une grande expérience en conservation des sols ces dernières décennies. L’approche développée par la Land Authority a été recommandée en 1945 pour réhabiliter des bassins versants (projet pilote de la Yallahs Valley). Les techniques les plus simples furent recommandées mais elles disparurent graduellement. En 1967, le Gouvernement a lancé le projet d’aménagement de bassin défini par les forestiers FAO : Ils ont préparé un programme national de conservation des sols et un centre de démonstration et d’entrainement (Smithfield). Leurs recommandations aboutirent à deux grands projets de développement rural intégré dans la zone ouest et centrale de l’île en 1870 et 1980. Le premier s’est consacré à la polyculture sur terrasses en gradins. Le second projet a renforcé les institutions de planning de développement des bassins versant en 1980-82. Ce projet a fourni des formations pour les gens du service et a dressé les plans pour six bassins majeurs et leur suivi (IFAD Hillside Farmers Support Project (1988-94). D’autres projets ont été développés apres les dégats causés par les cyclones (ex : Hope River Project 1988-91).
La plupart des projets avant 1987étaient orientés vers des techniques physiques basées sur des critères de land capability : pour lutter contre l’érosion sur les pentes fortes des collines, on a développé des terrasses et la reforestation. Cependant, à cause de l’absentéisme des propriétaires, les terrasses n’ont pu couvrir tout les bassins et ont été insuffisamment entretenues. Les généreux subsides de l’Etat (75 % des frais de terrassement) ont permis à certains fermiers de s’enrichir. Une analyse coutbénéfices a montré que les terrasses en gradins n’étaient pas rentables financièrement ni économiquement (de Graaff, 1996). Le projet IFAD s’est alors orienté sur la culture du cacao dans les plaines et du café en altitude. Le MYADP project a aussi tenté d’intégrer les pratiques de GCES dans les systèmes de production existants.
Entretemps, les fermiers impliqués dans la CES ont développé des techniques traditionnelles simples comme les barrières végétales et les haies vives qui s’adaptent mieux aux systèmes de culture. Cette communication donne un apercu historique des projets de conservation des sols durant les dernières décennies en Jamaique et discute des retombées économiques des mesures de CES impliquant les effets de l’érosion au champs et en aval.

The Government of Jamaica has gained considerable experience with soil conservation activities over the last decades (Edwards, 1995; Kent, 2002). In 1945 the Land Authority approach was recommended for rehabilitating watershed areas with the Yallahs Valley as pilot project. The simpler soil conservation measures were favoured, but most of them gradually disappeared. In 1967 the Government initiated a FAO Forestry and watershed management project, which prepared a national soil conservation programme and established the Smithfield training and demonstration centre. Its recommendations were followed up by two large integrated rural development projects in the western and central parts of the island in the 1970s and early 1980s. The project in the central region focused on multiple cropping systems on terraced land. Attention to the eastern part of the island was given by a second FAO Project, that was involved in institutional strengthening and watershed planning from 1980-1982. This project provided in-service training courses, made plans for six major watersheds and prepared a follow-up project, which in adapted form was implemented as the IFAD-Hillside Farmers Support Project (1988-1994). Meanwhile some other soil conservation projects and activities were implemented, in some cases following the damage caused by hurricanes (e. g. Hope River Project, from 1988-1991).
Most of the projects implemented before 1987 focused in their approach on physical land capability criteria, and because of the steep terrain the emphasis was on terracing and on reforestation. However, because of absentee land owners and disinterest, the terraces could not be executed on a micro-watershed basis and were often insufficiently maintained. And the generous subsidies (up to 75% of all terracing costs) allowed farmers to make profits by hiring local labourers (Blustain, 1982). A cost-benefit analysis showed that bench terracing was not financially nor economically viable for the great majority of farmers with their traditional and intermediate level of management (de Graaff, 1996). The IFAD project therefore decided to focus on the treecrops cocoa (at lower altitude) and coffee (at higher altitude). And farmers involved in annual cropping have gradually improved simple conservation measures, such as trash barriers, which fit better in the farming systems. This paper provides an historical overview of soil and water conservation projects and activities in the past decades in Jamaica and it discusses some financial and economic analyses of several SWC measures with their on-site and off-site effects.

Entrées d'index

Keywords :

Jamaica, history, economics, SWC

Texte intégral

1. Background

Jamaica, land of wood and water

1Jamaica was called ‘Land of Wood and Water’ by its early Arawak inhabitants. One wonders whether the island still merits this title. Most of the watershed areas remained in fact under natural forest until after the British occupation of the island, in 1655. The introduction of coffee after 1717, applying fire clearance and clean weeding, caused much man-made erosion and this was aggravated when ex-slaves acquired small plots of land after 1838, and population pressure increased (McGregor and Barker, 1991).

2With its 11,425 square kilometres Jamaica probably contains a greater variety of landscapes than any other island or country of comparable size. The terrain varies from towering mountains to coastal plains. Some 65% of the land is composed of hilly limestone areas used for bauxite mining and extensive cattle raising. Another 15% comprises alluvial plains, traditionally devoted to sugar and banana plantations for export. The final 20% comprises three areas, developed on cretaceous deposits, which have been used for intensive, small-scale hillside farming and have produced food crops for local consumption and some tree crops (Ramsay et al., 1982). These three areas are located in the Western region (south of Montego Bay), in the central part of the island (around Mandeville) and around the Blue Mountains in the eastern part of the island. Much of these lands are either too steep or have soil too thin to support intensive agriculture. The predominant soil types in these steep hillsides are derived from granite porphyry, from conglomerates and shales and in the lower parts from limestone. All of these soils are shallow, with rapid internal drainage, rapid runoff and high erodibility. Most have a low fertility (Vernon and Jones, 1959). Jamaica has a tropical climate, influenced by the sea-wind. Annual rainfall varies, and is highest on the northern side of Blue Mountains in Portland parish (Table 1). The capital Kingston and the watersheds around it are situated on the leeside of the Blue Mountains and have an average annual, bimodal, rainfall of less than 2,000 mm. The island is regularly ravaged by hurricanes. The hurricanes Charlie (1951), Flora (1963), Allen (1980), Gilbert (1988), Ivan (2004), Dean (2007) and Gustav (2008), were accompanied by severe flooding and caused considerable damage in both rural and urban areas.

Table 1. Mean monthly rainfall (1931-1980)

Table 1. Mean monthly rainfall (1931-1980)

Source: Metservice, Jamaica

Socio-economic situation

3More than one third of Jamaica's relatively large population of 2.8 million lives in and around the capital Kingston. The town has attracted many people from the rural areas seeking work. The agrarian structure is highly uneven: 80% of all farms have less than 2 ha and control only 16% of the land, while the very large farms constitute less than 1% of the total and control 57% of the land (Rao, 1990). The former, called mini-farmers by Wright (1979), are the main suppliers of staple food and vegetables in the country, but because of the steep terrain the production is not sufficient to meet the needs of the people. Soil erosion will also eventually destroy the basis of this important form of agriculture and livelihood system.

Figure 1. Map of Kingston watersheds (southern part of Blue Mountains)

4In a household survey, carried out in the watersheds around Kingston (Figure 1), only about a quarter of the small and medium farm households were considered to be fulltime farmers with an “advanced' level of management, keen on further developing their farm. Most other farmers, classified as having a traditional or intermediary level of management, were either much involved in off-farm activities or too old or not much interested in farm development. Some of these latter farmers keep part of their land uncultivated or under “food forest', a multi-storey mixture of trees and crops, which provides good protection against erosion and requires relatively little labour input.

Jamaican economy and the agriculture sector

5The Jamaican economy's performance since 1975 has been adversely affected by a series of external shocks. Oil prices increased, while the prices of bauxite, alumina and agricultural export commodities declined. Agriculture now contributes only 5% of GDP against not less than 60% for the services sector. Half of the original population of Jamaica does live abroad and remittances account for nearly 20% of GDP and are equivalent to tourism revenues. The economy faces serious long-term problems: high but declining interest rates, increased foreign competition, exchange rate instability, a sizable trade deficit, large-scale unemployment and underemployment, and a debtto-GDP ratio of 135%. And almost 15% of the population has an income below the poverty line. Jamaica's economy also frequently suffers economic setbacks from damages caused by hurricanes, as mentioned above (CIA World fact book, 2008).

6Other obstacles faced by the Jamaican agricultural sector over past decades include: - Highly skewed land ownership, with the small farms concentrated on steep land; - Insufficient land tenure security of in hillside areas; - Despite unemployment, a continued disenchantment with agricultural work, and consequently a chronic shortage of agricultural labour;-A lack of agricultural support services to farmers (e. g. extension, credit); - Inadequate measures and organisation to conserve the limited soil resources.

2. Soil and water conservation programmes and natural resource management

7The Government of Jamaica has gained considerable experience with rural development, soil conservation and afforestation activities over the last decades (Edwards, 1995). In 1945 the Land Authority approach was recommended for rehabilitating watershed areas, with the Yallahs Valley as pilot project. The simpler soil conservation measures were favoured, but most of them gradually disappeared, although some farmers continue to use such traditional practices. An example are the annually renewed trashbarriers on vegetable fields, shown in Figure 2 and described by Kent (2002).

8The Government initiated in 1967 a first FAO forestry and watershed management project, which prepared a national soil conservation programme and established the Smithfield training and demonstration centre in the western part of the island (Figure 3).

9Because of the very steep terrain, the national soil conservation plan gave much emphasis to land capability in the planning and implementation of watershed development activities (Sheng, 1972). The recommendations based on the demonstrations were followed up in the 1970s by two large integrated rural development projects in the western and central parts of the island. Initially these projects focussed much on terracing activities. However, because of absentee land owners and disinterest, these terraces could not be executed on a micro-watershed basis and were often insufficiently maintained (Blustain, 1982). Besides, the generous subsidies (up to 75% of all terracing costs) allowed farmers to make profits by hiring local labourers. The project in the central region focused on multiple cropping systems on the terraced land. A similar approach was followed by other soil conservation projects in that part of the island, e. g. the IICA project with its Allsides pilot implementation area (Johnson, 1984).

10Attention to the (south-)eastern part of the island was given by a second FAO Project (JAM 78/006), that was involved in institutional strengthening and watershed planning from 1980-1982. The project provided in-service training courses to 20 counterparts, made detailed plans for six major watersheds (Figure 1) and prepared a follow-up watershed development project, which was for financing taken up by IFAD. This implementation project eventually started in 1988 as the IFAD-Hillside Farmers Support Project, and focussed largely on the tree crops cocoa and coffee. There was also the Hillside Agriculture Project (HAP), financed by USAID, focusing on agronomic measures. A separate soil conservation project was established in Hope River watershed, where much damage was done by hurricane Gilbert in 1988. In the Blue Mountain areas, Japanese financed projects were engaged in large scale coffee plantations, and the CIDA Trees for Tomorrow project was involved in reforestation (World Bank, 1993).

Human influence on ecological systems

11As a result of the high rainfall intensities, steep slopes and erodible soils, natural rates of soil erosion are quite high in Jamaican watershed areas (Barker and McGregor, 1988). But human-induced soil erosion is more important, since hillside farmers are mostly involved in small scale cultivation of erodible staple crops, as yam and other root crops, and vegetables (e. g. shallots, cabbage, carrots). Of the 33 watersheds, 19 are badly eroded (World Bank, 1993). On the basis of land use mapping and the USLE formula, the second FAO project estimated the overall soil erosion rate for the Kingston watershed areas at about 100 t/ha/year (FAO, 1982). More than half of this erosion was assumed to be derived from the 10% of the area under annual crops, part of which was rented land. Other land use consisted of perennial crops, ‘food forest', mixed plantings, grassland, fallow or ‘ruinate' and governmental forest land. More recent small scale erosion research in the upper watershed areas suggested that the erosion rates were over-estimated. This research found (sheet) erosion rates for farm land and natural forest of 16 and 1 t/ha/yr respectively (McDonald et al., 1993). And on the basis of suspended sediment data in the Hope River over 1988-1990 a mean annual sediment yield of 13.7 t/ha was calculated. A sediment delivery ratio of 0.5 would then give an erosion rate of about 30 t/ha in this small and steep watershed. However, since soils are derived from shales and other materials with high soil formation rates, farmers do not mind much about erosion (Lindsay and Douglas, 1993). However, soil conservation is also needed for down-stream interests, in particular in the areas upstream the water supply reservoirs.

The water supply situation

12Since 1930 the Jamaican Government has had difficulties coping with the water demand of Kingston, in particular after years of severe droughts. Soil erosion has led to sedimentation in the Hermitage reservoir, and surface and ground water contamination have reduced water supplies over the years. In 1980 domestic water for Kingston was supplied by surface water and by 18 deep wells, supplying 104,000 and 68,000 m3 per day respectively. Surface water was obtained from the Hermitage-and Monareservoirs (with storage capacities of 1.8 and 2.7 million m3) and from three rivers outside the area. Watershed management is needed to induce a more continuous flow of surface water, without reducing the supply to the wells.

13Some investments have already been made, such as the 30 km pipeline (including a tunnel) between the Yallahs river and the Mona reservoir (Porter, 1990). In 1989 the Water Resources Development Masterplan analyzed the water supply and demand situation up to the year 2015. It drew up water balances for ten areas regrouping the island's 26 watersheds. It foresaw water scarcity in 2015 and the likely need for a costly pipeline through the Blue Mountains.

3. Soil and water conservation activities and their financial viability

Soil and water conservation activities on trial basis

14The second FAO project prepared detailed soil and water conservation plans for six watersheds surrounding Kingston (Figure 1). Since 80% of the area constituted private land operated by mini-farmers, the emphasis was on small farm development. To test the technical feasibility, economic viability and social acceptability of the various soil conservation measures (developed at Smithfield) the FAO project established two pilot zones of about 40 ha in 1980, where two different approaches for implementation were followed. The attempt to implement a conservation plan for a whole sub-watershed in Rosemount (Wagwater watershed) failed for various reasons: several landowners were living in town and the active farmers were old and in fact also living outside the small sub-watershed, and as a result of that there was also little collaboration between the farmers. The concentrated individual approach in Mount Charles (Upper Yallahs) was more promising. Tree crop planting (coffee, cocoa and citrus) with eyebrow terraces (cuvettes en demi-lune) was the most successful activity.

The target farm households

15Experiences of projects in other areas and socio-economic survey data showed that the mini-or hillside farmers were facing many constraints, and that it was important to differentiate between farm households. From the ten farm types distinguished in the Kingston watershed areas (based on a sample survey of 360 households), only two farm types constituted full-time, progressive farmers, interested enough to participate in terracing their land for annual cropping and/or engage in tree crop plantations (de Graaff, 1996). These (advanced) farmers were using considerable amounts of fertilisers allowing them to grow two or even three annual crops (often vegetables) a year, and some of them also used simple irrigation methods. The financial analysis indicated that for such farmers these activities were viable on moderately sloping land (Table 2). Three other farm types represented farmers with an intermediate level of management with low off-farm earnings and some land of their own. These farmers used only small amounts of fertilisers and were growing usually one, sometimes two, annual crop(s) a year, often rootcrops or peas. The financial analysis indicated that for such farmers terracing would not be a viable option, but that tree crops would be an attractive investment.

16Of the other five farm types, with low levels of farm management (often still some form of shifting cultivation), two were having quite high off-farm earnings, one was mainly engaged in livestock and two others had only rented land on steep slopes. These farm types were also characterised by old age and low interest in farming.

Financial analysis of soil and water conservation activities

17In the framework of the watershed planning activities of the FAO Project, a detailed cost-benefit analysis was undertaken for the major conservation and production activities, tested in the pilot-implementation areas (de Graaff and Sheng, 1994). These included: hillside ditches and bench terraces with annual crops, tree crops (coffee, cocoa and citrus) with individual basins, and forestry. The forest species were Leucaena leucocephala, Pinus caribbae and Blue Mahoe (Hibiscus elatus).

18In the analysis special attention was paid to differences in costs and benefits of the activities, when applied on land with different slopes and soil depths (de Graaff and Sheng, 1994). A distinction was also made between public and private land and between the three levels of management of private land users discussed above: advanced, intermediate and traditional. For all interventions an economic lifetime of 20 years was considered and the downstream benefits of the conservation measures were not yet included. Table 3 shows the results of the financial analysis of watershed activities on private land, by means of their internal rate of return on the investment.

19The ‘without' case was defined as a continuation of annual cropping on the slopes, with a declining production due to on-site erosion. Erosion increases with slope. Therefore each activity shows a peak at a particular slope, in which situation the efficiency (cost/benefit relationship) is highest. For farmers with a relative advanced level of management the optimal land use is to cultivate annual crops and establish hillside ditches on land with a slope below 19%, to grow annual crops on bench terraces on land from 19 – 33%, to grow coffee (or cocoa) on land from 33 – 58%, and to plant Leucaena on land from 58 – 63%. Steeper land should not be planted at all. Such recommendations correspond with the recommendations made in the land capability classification (Sheng, 1972). For farmers with an intermediate level of management the benefits of bench terracing only exceed the costs at slopes less than 19%, when hillside ditches provide sufficient erosion control and are more cost effective. These farmers could apply hillside ditches with annual cropping on slopes less than 27%, plant tree crops on slopes between 27 – 53%, and plant Leucaena on slopes from 53 – 63%. For traditional farmers with low labour availability and low interest in farming, only low input farming activities (e. g. food forest) would be financially attractive.

Table 2 Financial analysis of soil and water conservation activities by slope degree and for two levels of farm and crop management on private land (in terms of internal rates of return:%)

Table 2 Financial analysis of soil and water conservation activities by slope degree and for two levels of farm and crop management on private land (in terms of internal rates of return:%)

Source: de Graaff, 1996. Note: cut-off rate for annual and perennial crops is 12% and for forest plantations 6.5%

20For public land the analysis is different. Government land is acquired for protection purposes and is always steep. Annual cropping is not considered on such land and squatters are prevented from doing so. The ‘without' case is defined as a situation of gradual deforestation and unproductive natural vegetation, of importance for erosion control. Therefore the efficiency of interventions is declining by slope. The Government was interested in investing in tree crops (coffee and citrus) and forest plantations. For the latter a credit line was available from the Commonwealth Development Corporation (CDC) at an interest rate of 6.5%. The analysis showed that it would be attractive for the Government to plant tree crops on slopes from 33-53%. In the higher zones with steep slopes Blue Mountain coffee can be planted. This fetches premium prices on the world market. For reforestation Pinus could be considered on very steep slopes. The firewood species Leucaena could be an option on lesser slopes (de Graaff, 1996). The analysis showed why fierce discussions were held about the choice between coffee and pine plantations on public land. Intercropping of coffee in pine plantations was tried, but not successful.

Kingston watershed development plan

21Following this financial analysis for the respective watershed development activities, the FAO project prepared a US $ 13 million (1982 prices) follow-up implementation project with various watershed development activities, focusing on a target group of about 1,200 full-time and interested farm households.

22An IFAD mission visited Jamaica in 1983 and made several changes in the project design. The project was to focus mainly on coffee and cocoa plantations, and on small scale rural enterprises. This ‘ Hillside Farmers Support Project'(HFSP) was appraised in 1987 and started in 1988 for a first period of six years, focusing on the Kingston watershed areas and thereafter on a much wider area. Not much attention was paid to soil conservation in critical areas, but a specific watershed management project was undertaken in the Hope River Watershed. This UNEP project implemented various physical erosion control measures on both public and private lands and undertook a public awareness campaign.

(IFAD) Hillside Farmers Support Project (1988-1998)

23This project was aimed at providing credit for coffee and cocoa planting and rehabilitation and starting up small-scale enterprises, in order to enhance income and employment and to reduce soil erosion. Project coordination was in the hands of the Agricultural Credit Bank (ACB), which channelled funds through six People Cooperative Banks (PCB's) in the rural areas. Technical extension support was provided by the Coffee Industry Development Corporation (CIDCO) and the Cocoa Industry Board (CcIB). The small-scale rural enterprise credit programme was promoted through the National Development Foundation of Jamaica (NDFJ). This small-scale industry development component assisted until 1994 only 45 small enterprises, mostly dealing with grocery retail and other services. The target group for coffee and cocoa development were hillside farmers, who live in the project area and own or operate 1 to 5 ha. IFAD estimated that 35% of farm families would participate in the programme. Until 1993 tree crop development was slower than planned, except for Blue Mountain coffee. Only 14% of farm households were engaged in the project (Table 3): about 400 ha of trees were planted and 60 ha rehabilitated in the original project area.

24There were both external and project related reasons for this. Firstly, prices of coffee and cocoa were very low over the period concerned. Secondly as result of high inflation, all credit interest rates were adjusted to commercial levels after 1990, increasing up to 24%.

25Thirdly rumours spread about tree crop diseases (e. g. coffee leaf rust), and fourthly farmers complained about the inadequacy of the delivery of inputs. For this reason the ACB took control of the field operations in 1994.

Table 3. Number of participants planned and realized under IFAD Hillside Farmers Support Project, in original project area only

Table 3. Number of participants planned and realized under IFAD Hillside Farmers Support Project, in original project area only

Source: IFAD, 1988; ACB, 1994

26Having switched the focus to tree crop development, no significant activities or resources for soil conservation were included in the project. In order to fulfil the erosion control objective 160 ha of hillside ditches were established. The project further benefited from soil conservation education efforts of previous projects and to some extent from technical advice provided to farmers by project development officers, which promoted the use of simple soil conservation measures, with individual basins for tree crops and contour planting being the most common (Kent, 2002). While it is not possible to measure the HFSP's (or other coffee development projects) effects on soil erosion, the Mid term review mission suggested to assign a more definitive position on this matter to the project's extension service (IFAD, 1994). A very valuable soil conservation study was produced by the Caribbean Agricultural Research and Development Institute (CARDI; Lindsay and Douglas, 1993), but it has not been put into use, despite its high potential value.

Other watershed development activities in Kingston watersheds (1987-1993)

27In the period 1988-1991 the UNDP/UNEP funded Hope River project was aimed at increasing ground cover and reducing erosion and sedimentation. On public land different forms of checkdams, retaining walls and landslide rehabilitation techniques were demonstrated, while on private land various conservation activities were demonstrated, whereby farmers contributed 50% of the costs. The project started in early 1988, but because of the damage caused by hurricane Gilbert, it only became effective in 1989. The project made extensive use of local (waste) materials, such as so-called ‘ Gilbert logs and poles'and discarded rubber tyres.

28Meanwhile the USAID supported Hillside Agricultural Project (HAP), mainly operating in adjacent areas, chose and campaigned for agronomic soil conservation measures;

29More or less irrespective of the above projects, the following major changes have occurred in the watershed areas in the period 1982 - 1993:

  • The highest part of the Yallahs watershed became part of the Blue Mountain National Park;

  • A Japanese supported project planted some 1,150 ha Blue Mountain coffee, of which part (about 400 ha) is located in the Hope River and Upper Yallahs watersheds;

  • Another 400 ha ruinate land was reforested;

5. Effects of watershed development activities in Kingston Watershed area

30Total costs of the IFAD project amounted to US $ 14.2 million (1987 prices), 41% of which for investment in coffee and cocoa and 10% for small scale enterprise development. Foreign exchange costs were estimated at US $ 5.5 million for the IFAD project in 1987. Unfortunately world market prices for coffee and cocoa were depressed from 1986-1994, but they rose again in 1994. The main product, Blue Mountain coffee, is sold to Japan and receives a 50% premium price. Both tree crops and Pinus plantations suffered from hurricane Gilbert, which reduced export earnings.

Changes in land use

31To assess the eventual impact of watershed development activities on soil erosion, downstream sedimentation and the water supply one should first assess the land use changes. In 1982 aerial photo interpretation was undertaken for all six Kingston watersheds, but in 1993 aerial photos were only available for Hope River and Upper Yallahs watersheds. Photo interpretation was difficult because of the slight differences between degraded natural forest, fallow land and food forest, the heavily shaded cocoa and the tiny isolated plots of annual crops (Riksen and Versteeg, 1994). Table 4 shows that an increase in coffee area went at the expense of natural and degraded forest. The deforestation rate was in fact about 2% per year. The newly planted cocoa has been considered under food forest. Table 4 also shows that the pressure on the land is not that high, with annual crops and coffee in 1993 only covering 15% of the area.

Table 4 Estimated land use changes in two watersheds (1982-1993; in ha)

Table 4 Estimated land use changes in two watersheds (1982-1993; in ha)

Sources: FAO, 1982; Hope River Project, 1990; IFAD, 1994. Riksen and Versteeg, 1994

Changes in soil erosion

32The coffee plantations had few positive effects on erosion, since they on balance replaced forest and ruinate land. And in their soil conservation study for the IFAD project, Lindsay and Douglas (1993) found that 42% of farmers did not apply any soil conservation measure and that others often applied simple contour barriers. It is therefore unlikely that soil conservation measures have had much impact on soil erosion in the watersheds (except in Hope River).

Changes in river discharge

33The gradual deforestation and increased plantings of annual and perennial crops shown above would normally lead to an increased total discharge and possibly to a lower well distributed stream flow throughout the year. However, Table 5 shows that the annual mean daily discharge of the rivers has clearly decreased in two of the three watersheds. This may well relate to the long term gradual decrease of annual rainfall as discussed by Eyre (1987), but it is remarkable that it affected Hope River watershed much less. There the discharge distribution over the year deteriorated. The Qmin/Qmax (month with lowest and highest mean daily discharge) ratio became less favourable in Hope River and Rio Pedro watersheds. However, because of large fluctuations in the annual and monthly discharge it is not possible to draw firm conclusions from this. In all three watersheds water holding capacity and base flow are low, since conglomerates and shales do not allow much groundwater storage within the catchments.

Table 5 Main rivers and changes in annual and (wet and dry) seasonal mean daily discharge in two periods (m3/s)

Table 5 Main rivers and changes in annual and (wet and dry) seasonal mean daily discharge in two periods (m3/s)

1) For Yallahs period 1980-85; since 1985 water was detracted by pipeline. Sources: FAO, 1982; Underground Water Authority; pers. comm.

Effects on reservoirs and water supply

34Of the two reservoirs, the Hermitage reservoir is the most affected by sedimentation. The watershed of 1,300 ha upstream the reservoir is for 80% owned by the National Water Commission, but it has been encroached upon by squatters. In less than 40 years the reservoir capacity declined by half, and after dredging the reservoir lost again much of its capacity after the Gilbert hurricane in 1988. Despite this, the average yearly supply of water to Kingston increased by about 54% between 1977 and 1992, but this was largely due to the pipeline from Upper Yallahs.

6. Discussion and conclusions

35In the period 1960-2000 various soil conservation and watershed development projects were executed in Jamaica. Demonstration and pilot implementation activities were followed by attempts towards large scale implementation. Because of the very steep terrain and erodible soils the initial focus was on physical conservation measures, such as bench terraces. These top-down approaches failed, since not enough attention was given to the circumstances under which most small farmers operate (e. g. off-farm work, old age, not much extension support). A financial cost-benefit analysis showed that these conservation measures would only be efficient for a limited number of full-time farmers with advanced level of management. It also showed that tree planting would be financially attractive for a larger number of farmers. The subsequent projects focussed indeed more on agro-forestry and planting of coffee and cocoa. Coffee planting was successful, thanks to the high prices of Blue Mountain coffee. But even these projects fell short of expectations and did eventually not contribute much to erosion control and to reducing sedimentation in water supply reservoirs. An attempt to stimulate off-farm activities in the watershed by the HFS project was also not successful. Many of the small farmers in the watersheds are older farmers, who see hillside farming as a way of life, also after a career elsewhere (Woodsong, 1994). They are content with their traditional farming methods and simple conservation measures and do not care about the gradually increasing downstream effects, which are anyhow usually overshadowed by the severe damage caused by the more and more frequent hurricanes. And simple annually renewed measures as trash-barriers have the advantages that the trash also contributes to soil fertility. It is clear that in the past 50 years insufficient attention has been paid to farmer’s perceptions of soil erosion and to their simple traditional practices. But, as stated by Reij et al. (1996) that technology adoption is a product of multiple influences, some farmers in the Yallahs valley have indicated that they have adapted their more or less indigenous technologies also under influence of policies and extension work as from the time of the Yallahs Valley Authority (Kent, 2002).

Bibliographie

References

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Figure 2 : Trashbarriers in the Upper Yallahs

Figure 3 : Bench terraces at Smithfield Demonstration Centre

Image 10000000000001C2000002BA535F630C.jpg

Figure 4. Coffee plantation on steep slope

Table des illustrations

Titre Table 1. Mean monthly rainfall (1931-1980)
Légende Source: Metservice, Jamaica
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-1.jpg
Fichier image/, 92k
Légende Figure 1. Map of Kingston watersheds (southern part of Blue Mountains)
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-2.jpg
Fichier image/, 228k
Titre Table 2 Financial analysis of soil and water conservation activities by slope degree and for two levels of farm and crop management on private land (in terms of internal rates of return:%)
Légende Source: de Graaff, 1996. Note: cut-off rate for annual and perennial crops is 12% and for forest plantations 6.5%
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-3.jpg
Fichier image/, 164k
Titre Table 3. Number of participants planned and realized under IFAD Hillside Farmers Support Project, in original project area only
Légende Source: IFAD, 1988; ACB, 1994
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-4.jpg
Fichier image/, 80k
Titre Table 4 Estimated land use changes in two watersheds (1982-1993; in ha)
Légende Sources: FAO, 1982; Hope River Project, 1990; IFAD, 1994. Riksen and Versteeg, 1994
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-5.jpg
Fichier image/, 152k
Titre Table 5 Main rivers and changes in annual and (wet and dry) seasonal mean daily discharge in two periods (m3/s)
Légende 1) For Yallahs period 1980-85; since 1985 water was detracted by pipeline. Sources: FAO, 1982; Underground Water Authority; pers. comm.
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-6.jpg
Fichier image/, 124k
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-7.jpg
Fichier image/, 224k
URL http://books.openedition.org/irdeditions/docannexe/image/14219/img-8.jpg
Fichier image/, 356k

Auteurs

jlindsay05@gmail.com, univ. of the WestIndies, Mona, Jamaica

marciewalks@gmail.com; Jamaica

jan.degraaff@wur.nl; Wageningen University, the Netherlands

© IRD Éditions, 2012

Conditions d’utilisation : http://www.openedition.org/6540