Eva Schlecht

Implications of agricultural transitions and urbanization for ecosystem services

Historically, farmers and hunter-gatherers relied directly on ecosystem services, which they both exploited and enjoyed. Urban populations still rely on ecosystems, but prioritize non-ecosystem services (socioeconomic). Population growth and densification increase the scale and change the nature of both ecosystem- and non-ecosystem-service supply and demand, weakening direct feedbacks between ecosystems and societies and potentially pushing social–ecological systems into traps that can lead to collapse. The interacting and mutually reinforcing processes of technological change, population growth and urbanization contribute to over-exploitation of ecosystems through complex feedbacks that have important implications for sustainable resource use.

A critical analysis of challenges and opportunities for soil fertility restoration in Sudano-Sahelian West Africa

Since the 1970s, research throughout West Africa showed that low soil organic matter and limited availability of plant nutrients, in particular phosphorus and nitrogen, are major bottlenecks to agricultural productivity, which is further hampered by substantial topsoil losses through wind and water erosion. A few widely recognized publications pointing to massive nutrient mining of the existing crop–livestock production systems triggered numerous studies on a wide array of management strategies and policies suited to improve soil fertility. Throughout Sudano-Sahelian West Africa, the application of crop residue mulch, animal manure, rockphosphates and soluble mineral fertilizers have been shown to enhance crop yields, whereby yield increases varied with the agro-ecological setting and the rates of amendments applied. In more humid areas of Western Africa, the intercropping of cereals with herbaceous or ligneous leguminous species, the installation of fodder banks for increased livestock and manure production, and composting of organic material also proved beneficial to crop production. However, there is evidence that the low adoption of improved management strategies and the lack of long-term investments in soil fertility can be ascribed to low product prices for agricultural commodities, immediate cash needs, risk aversion and labour shortage of small-scale farmers across the region. The wealth of knowledge gathered during several decades of on-station and on-farm experimentation calls for an integration of these data into a database to serve as input variables for models geared towards ex-ante assessment of the suitability of technologies and policies at the scale of farms, communities and regions. Several modelling approaches exist that can be exploited in this sense. Yet, they have to be improved in their ability to account for agro-ecological and socio-economic differences at various geographical scales and for residual effects of management options, thereby allowing scenario analysis and guiding further fundamental and participatory research, extension and political counselling.

Livestock related nutrient budgets within village territories in western Niger

Poor cropland fertility and a rapidly rising demand for food force Sahelian farmers to cultivate more land and shorten fallow periods. This mostly leads to a gradual decline in crop yields per hectare, which can be counterbalanced by the systematic use of livestock manure on cropland. To assess the potential and limits of manuring practices, annual nutrient budgets were established for different land-use types, based on forage and crop yields and livestock and cropland management in five village territories in western Niger, which were selected along the Sahelian climatic gradient. Stocking rates per km2 of pasturing area range from 8–22 tropical livestock units (TLU, animal of 250 kg live weight). Faecal excretion during grazing directly returns 18–25% of the consumed forage dry matter, 21–29% of the ingested nitrogen and 44–56% of ingested phosphorus to the grazed land. Corralling animals on fields at night leads to a spatial concentration of nutrients, benefiting at most 9% of the arable village land. Where livestock consume only 15–20% of the total amount of forage produced, there is some scope for increasing village livestock numbers in order to increase the area manured, but eventually manuring must be complemented by additional measures such as the application of inorganic fertilizers to sustain overall productivity of the farming systems.

Opportunities and Challenges of Urban and Peri-Urban Agriculture in Niamey, Niger:

Urban and peri-urban agriculture (UPA) provide about 10% of the global food supply and have a significant potential to reduce poverty and increase food security in urban households. To characterize UPA types and intensities and to assess their resource use efficiencies, semi-structured interviews were conducted with 130 households actively involved in UPA in Niamey, Niger. The survey data indicated high use of livestock manure for vegetable gardening and to a lesser extent for the production of staple food. The UPA livestock component depended heavily on the supply of live animals and feed from the rural hinterland. The application of organic and inorganic fertilizers in combination with the indiscriminate use of nutrient-loaded wastewater for irrigation purposes led to important nutrient surpluses in UPA gardens. First calculations of partial nutrient balances indicated that gaseous emission of nitrogenous compounds as well as leaching of nitrogen, phosphorus and potassium to the groundwater might be large. Insect attack and the lack of irrigation water or high labour needs for irrigation were identified respectively as major constraints to UPA gardening activities. Despite this, gardening proved to be the most economically beneficial occupation of the three main UPA activities. Lack of workforce and lack of cash to hire labour and purchase inputs constituted major constraints to millet farmers, as against soil fertility, which, in contrast to researchers, only a few farmers viewed as a major problem.

Beyond adding up inputs and outputs: process assessment and upscaling in modelling nutrient flows

Departing from the historical background of scientific interest in soil fertility and sustainable agricultural production in sub-Saharan Africa, a review is conducted of nutrient budget studies carried out in semi-arid West Africa at scales ranging from individual fields to the sub-continent. For both, nitrogen and phosphorus, the comparison discloses largely diverging balances calculated for similar agro-ecosystems. In a first step, the modes of calculation of the nutrient budgets are examined. It is demonstrated that the calculations used in the different studies differ by the variables and biophysical processes taken into account, and by the choice of spatial scales as well as related time scales. One important discrepancy between approaches is whether and to which extent nutrient flows are internalized when upscaling. The extent to which the impact of individual and communal management, especially of pastoral and forestry resources, on nutrient flows is accounted for is a second cause of divergence. Moreover, it was observed that nutrient budgets tend to be increasingly negative as the spatial scale of the study increases from farm to sub-continent. This unexpected trend is traced back to the lack of internalization of nutrient flows when upscaling. The complexity of the scale patterns of nutrient flows and that of the interactions and the tradeoffs in the effects of management calls for the use of models to calculate nutrient budgets. Therefore, in a second step, examples of a static model, a multiple-goal linear programming model and a decision rules model were reviewed, all of which include the calculation of nutrient flows and balances and which were applied to West-African farming systems. The models are analyzed for their way of dealing with the critical issues of spatial and temporal scales and the impact of resource management on nutrient flows, taking into account that they have different objectives and were designed for different spatio-temporal scales. To conclude, suggestions were made for strengthening the use of models as tools enabling ex-ante testing of alternative agricultural technologies and policies that could improve soil nutrient balances in semi-arid sub-Saharan Africa.

Climate change and variability: perception and adaptation strategies of pastoralists and agro-pastoralists across different zones of Burkina Faso

Due to the dependence of its economy on rainfed agriculture and livestock husbandry, Burkina Faso, like other Sahelian countries, is particularly vulnerable to climate change. Adaptation is needed to counteract anticipated drawbacks of climate change on crop and livestock productivity; therefore, we examined climate change perceptions of pastoralists and agro-pastoralists and analysed their adaptation strategies. To this end, focus group discussions were held in six villages distributed across three agro-ecological zones. In three of these sites, 162 farmers were also individually interviewed. Perceptions of farmers were compared to actual trends of different climatic parameters extracted from official long-term meteorological records (1988–2008). Results showed that farmers in Burkina Faso were partly aware of climate change, particularly of changes in temperature and rainfall patterns, but their perception did not match well with the recorded annual rainfall data in the southern Sahelian and Sudanian zones. The most important adaptation strategies mentioned by agro-pastoralists were crop diversification, combination of cropping and livestock operations, use of water harvesting technologies and anti-erosive measures such as half-moons or stone dikes. Strategies of pastoralists included seasonal, annual and permanent migration and taking up of cereal cropping. Logistic regression analysis indicated that agro-ecological zone, cultivated surface, ruminant herd size, household size and education were the most important variables affecting farmers’ choice of adaptation strategies. These factors should be taken into account in the development and implementation of any programme of adaptation to climate change in Burkina Faso.

A comparison between urban livestock production strategies in Burkina Faso, Mali and Nigeria in West Africa

We undertook a comparative analysis of (peri-)urban livestock production strategies across three West African cities. Using a semi-structured questionnaire, livestock-keeping households (HH) were interviewed in Kano/Nigeria (84 HH), Bobo Dioulasso/Burkina Faso (63 HH) and Sikasso/Mali (63 HH). Questions covered livestock species kept, herd sizes and structure, feeds used, manure management, livestock marketing and production constraints. Sheep and goats dominated (p < 0.001) in Kano (76 and 75 % of HH) compared to Bobo Dioulasso (48 and 40 %) and Sikasso (28 and 40 %), while cattle and poultry were more frequent (p < 0.001) in Bobo Dioulasso (82 and 69 % of HH) and Sikasso (65 and 79 %) than in Kano (29 and 20 %). Across cities, ruminant feeding relied on grazing and homestead supplementation with fresh grasses, crop residues, cereal brans and cottonseed cake; cereal grains and brans were major ingredients of poultry feeds. Cattle and sheep fetched highest prices in Kano, unit prices for goats and chicken were highest in Sikasso. Across cities there was little association of gardens and livestock, whereas field cropping and livestock were integrated. There was no relation between the education of the HH head and the adoption of improved management practices (p > 0.05), but the proportion of HH heads with a long-term experience in UPA activities was higher in Kano and in Bobo Dioulasso than in Sikasso (p < 0.001). We therefore postulate that the high illiteracy rate among (peri-)urban livestock keepers in West Africa does not threaten the acceptance of improved technologies and innovations supporting the sustainability of their livestock production.

Cross-Location Analysis of the Impact of Household Socioeconomic Status on Participation in Urban and Peri-Urban Agriculture in West Africa.

This study explores the relation between household socioeconomic status (SES) and participation in urban and periurban agriculture (UPA) in three West African cities. We used a structured questionnaire to survey 700 randomly selected households: 250 in Kano, Nigeria, 250 in Bobo Dioulasso, Burkina Faso, and 200 in Sikasso, Mali. Multiple correspondence analysis was applied on household asset variables to create an index of assets which was used as a proxy for household SES. The results showed no significant differences in households’ rate of participation in UPA across socioeconomic groups. Participation in UPA was rather significantly (P < 0.001) and positively related to household size. Interestingly, the analysis revealed that field crop cultivation and gardening were more common among households in the low and medium SES groups while those in the high SES group were more likely to keep livestock.

Supplementation of Zebu cattle grazing Sahelian pasture. I. Diet selection and intake

From 1990 to 1992, diet selection and nutrient intake of Zebu cattle grazing Sahelian pasture were studied in Central Mali. Forty-five intact males and 12 oesophageally fistulated animals were separated into three groups of 15 intact and 4 fistulated animals. The control group (C) grazed natural pasture only, while the moderately supplemented group (M additionally received 0.8-1.5 kg OM/day of crop by-products during the dry season (November-June) and the first month of the rainy season. The third group (H) was highly supplemented with 1.2-2.7 kg OM/day in the dry season and 0.8-1.2 kg OM /day in the rainy season. Oesophageal extrusa was collected during 5 consecutive days at intervals of 4-5 weeks. Samples were analysed for contents of organic matter (OM), crude protein (CP) and neutral detergent fibre (NDF). Digestible organic matter (DOM) and metabolizable energy content (ME) were calculated from in vitro gas release. Intake of organic matter (IOM) of the fistulated animals was determined from faecal organic matter excretion (FOM) and extrusa DOM content. Intake of CP (ICP) and ME (IME) were calculated from IOM and the respective nutrient contents of extrusa samples. Extrusa CP, DOM and ME contents did not differ significantly between the three groups either in the dry or in the rainy season. The CP content was c. 230 and c. 197 g/kg OM during the rainy season, and declined to values ≤ 70 and ≤ 95 g CP/kg OM at the end of the dry season of 1990 and 1991, respectively. Average DOM and ME contents were c. 668 g DOM and c. 9.9 MJ ME/kg OM during rainy seasons. At the end of the dry seasons, these values decreased to < 550 g DOM and < 8.0 MJ ME/kg OM. Per kg of metabolic body mass, IOM of group C was c. 89 g/day during the carly dry season. It was accompanied by a daily 1CP of 8-10 g and by an IME of 691-765 kJ/day. Due to a higher nutrient content in the selected diet, energy intake was slightly increased and protein intake was significantly higher during the rainy than during the dry season, although IOM was only 77-81 g/day. At the end of the dry season, unsupplemented animals ingested < 70 g IOM/day and the concomitant CP and ME intake were < 6 g CP/day and < 51)0 kJ ME/day, respectively. Feed intake from pasture was stimulated by a moderate supplementation, but reduced by a high supplementation. The results indicate that on slightly degraded Sahelian rangeland, the nutrient intake of cattle is in the first place limited by biomass availability and only secondly by the quality of the vegetation.

Resource use efficiency in urban and peri-urban sheep, goat and cattle enterprises.

Urban livestock husbandry receives growing attention given the increasing urban demand for livestock products. At the same time, little is known about the resource use efficiency in urban livestock enterprises and eventual negative externalities. In livestock production, feeds are an important resource whose nutrients are transformed into products (meat and milk) to generate financial return to the producer. The lack of knowledge on nutrient supply through feed might lead to oversupply with severe environmental impacts. In Niamey, a typical West African city and capital of the Republic of Niger, urban livestock production is constrained by feed scarcity, especially during the dry season. Here, the issue of resource use efficiency was studied in 13 representative and differently managed sheep/goat and cattle enterprises characterized by high and low feed inputs, respectively, during a period of 28 months. Nitrogen (N), phosphorus (P) and potassium (K) inflows into each farm through livestock feeds and outflows through manure were determined using a semi-structured questionnaire; interviews were accompanied by regular weighing of feed supplied and dung produced. Live weight gain (LWG) and efficiency of conversion of total feed dry matter offered (kg TDMO/kg LWG) were computed along with nutrient balances (NBs) per metabolic body mass (kg0.75). NBs (per kg0.75/day) in the high-input (HI) sheep/goat enterprises were +1762.4 mg N, +127.2 mg P and +1363.5 mg K and were significantly greater (P < 0.05) than those in low-input (LI) units (+69.1 mg N, -98.3 mg P and +16.5 mg K). In HI cattle enterprises, daily balances averaged +454.1 mg N, +40.1 mg P and +341.8 mg K compared to +34.4 mg N, -9.0 mg P and +68.3 mg K (P > 0.05) in LI cattle systems. All systems were characterized by poor conversion efficiencies of offered feed, which ranged from 13.5 to 46.1 kg TDMO/kg LWG in cattle and from 15.7 to 43.4 kg TDMO/kg LWG in sheep/goats. LWG in HI sheep/goats was 53 g/day in the rainy season, 86 g/day in the hot dry season and 104 g/day in the cool dry season, while HI cattle lost 79 g/day in the hot dry season and gained 121 g/day and 92 g/day in the cool dry and rainy seasons, respectively. The data indicate that there is nutrient wasting and scope for improvement of feeding strategies in Niameys livestock enterprises, which might also decrease nutrient losses to the urban environment.