By definition SLM practices reduce soil and land degradation whether it is caused by physical (winds, runoffs, soil sealing, etc.) or chemical (nutrient leaching, loss of organic matter, etc.) factors. If sustainably managed, the soil will ensure the provisioning of land ecosystem services.1
In agroforestry systems, trees reduce wind speed and as a result young crops are protected against sand blast or being covered by sand. Farmers who 20 years ago had to plant three or four times before the crop could be established, now usually plant only once, which lengthens the growing season for the crops.
Fertility is increased through natural nitrogen fixation, organic matter recycling and carbon sequestration. Depending on its age, a good stand of Faidherbia albida fixes 80 to 90 kg of nitrogen per hectare. In Zambia, maize grown close to F. albida, a nitrogen fixing species, reached an average yield of 4.1 t/ha; the same maize grown few metres away from the trees produced an average yield of only 1.3 t/ha.2 Leaf litter adds organic matter to the soil and attracts soil fauna, which improves the structure of the soil and makes nutrients more easily available to plant roots. The young agroforestry parklands of southern Niger sequester 4–5 tonnes of carbon per hectare. When this parkland matures it will sequester much more carbon.3 The old F. albida parklands of the peanut basin in Senegal sequester up to 30 tonnes of carbon per hectare.
These chemical and physical soil improvements have significant effects on food production. A study comparing 286 projects of sustainable development in poor countries shows an average increase of crop harvest of 79 per cent.4 In Africa, yield increases of up to 128 per cent were achieved.5 In Niger, these practices have led to an estimated additional production of about 500,000 tonnes of cereals per year, which is enough to feed 2.5 million people. Because they have been underinvested over years, dryland areas are showing a high potential of yield increases that make them particularly responsive to SLM practices.
SLM practices are based on natural cycles of water, nutrients, minerals and organic matter, by managing various plant species in a complementary manner. The combination of trees in farming systems with principles of conservation farming, the so-called “evergreen agriculture”,6 helps maintain the best possible land use cover, reduces rainfall runoff, induces more water to infiltrate, limits exposure to the sun and evaporation, and increases the capacity of soil to store moisture. This is the virtuous circle of sustainable land and water resources management.7
Water-harvesting techniques that force rainfall and runoff to infiltrate the soil potentially contribute to recharging local groundwater tables and could have major effects on water levels in wells. For instance, in the villages of Rissiam and Ranawa, in the northern part of the Central Plateau of Burkina Faso, all wells used to dry up as soon as the rainy season stopped. Since the introduction of water-harvesting techniques in these villages in the early 1980s all water points in these villages have water during the entire year. Despite the fact that the population of Ranawa has more than doubled since 1985, more water is available for crops, people and livestock.
Many drylands populations have developed water-harvesting techniques that continue to be used. They are called meskats in Tunisia, khadins in Rajastan (India) and khuskaba systems in Baluchistan (Pakistan). The growing unpredictability of rainfall in many drylands increases the importance of modern and traditional water-harvesting techniques. To that end, farmers’ innovation plays a key role. By adding organic matter (manure, compost, tree litter, ash) to water harvesting pits, the combination of water management and soil fertility improving techniques allowed farmers to cultivate crops where before nothing could be grown. This technique has been used in Burkina Faso to rehabilitate tens of thousands of hectares of strongly degraded land.8
By reducing soil erosion, SLM practices can also, at a wider scale, prevent the sedimentation of dams, and thus ensure long-term downstream water provision. The sedimentation of dams measured in North Africa in 2002 could reach 80 per cent of the dam initial water storage capacity.9 The global cost of such a phenomenon has been estimated at about USD 18.5 billion.10
Economic potential for rural areas
The success achieved by these techniques may have surprising consequences and could led to the emergence of a land market. Farmers, but also local traders and women, began buying and selling strongly degraded land in order to rehabilitate these lands with the improved planting pits. A survey in 1998 in Niger showed that 40 per cent of the farmers interviewed had bought plots of degraded land.11
In the middle of the 1990s gullies on the China’s loess plateau were leased in local public auctions to the highest bidders, who subsequently were supposed to make these gullies productive again. Those who won the auctions quickly began to level part of the gullies to conserve the soil, and to plant trees. As gullies always harvest runoff the growing conditions are favourable, and by the end of the 1990s farm forests were emerging in gullies.
Definitive migration for income diversification becomes less relevant as rural areas could generate employment and incomes. However, temporary migration, such as nomadism or circular migration, can still be important as reduces the pressure on land at certain period of time.
Lack of investment in agriculture over the years (poor infrastructures (roads, warehouses, etc), weak credit systems and inadequate research and development support) has prevented farmers from accessing conventional ways to improve their yields. Because SLM practices are based on agroecology principles, complementary benefits of species (trees and crops) and systems (farming and livestock keeping), they limit the use of mineral fertilizers, of irrigation or mechanization, reducing the dependency on energy and expensive inputs. As an example, developing irrigation systems can cost about USD 10,000 per hectare. Developing water-harvesting systems can cost as little as USD 200–1,000 per hectare and all these costs concern investment of human labour.
Agrosystems under SLM are diversified and provide various outputs. In addition to edible fruits and leaves that can be marketed locally, farmers can supplement their incomes from the sale of firewood and poles. During the famine years of 2005 and 2010, there was little drought-related infant mortality in villages with on-farm re-greening. Life was harsh, but in drought years the rural poor literally survive on trees.
Furthermore, as SLM practices create jobs within the agrosystem (more labour required) and outside the agrosystem (tools makers, middle-men, retailers, etc), they have a potential for economic development of the whole rural area, and to limit rural–urban migration.
It is recognized that a 10 per cent increase in farm yields leads to a 7 per cent decrease in poverty in Africa and a 5 per cent decrease in Asia.12 When considered with the figures presented in paragraph 47, this represents a great potential for drylands and countries affected by land degradation, because agriculture still contributes at least 10 per cent to the gross domestic product of 54 per cent of UNCCD country Parties.
National policymakers should know that investments in SLM are economically rational. In Niger, investments in improved traditional planting pits produced an internal rate of return (IRR) of 82 per cent for farmers who already owned the land they were rehabilitating, and 39 per cent even if the land still had to be bought.13
Sustainable agriculture is based on complementarity between plant species and between agriculture systems. It brings together farmers and pastoralists in a win–win situation: agroforestry practices greatly increase the land cover and the availability of fodder for animal feed, and animal dung is used to fertilize fields. Because the benefits are shared along the various users of the resource, this led to a reduction in usage conflicts by 80 per cent.14
Closing the gender gap in agriculture would generate large gains for the agricultural sector and for society as a whole. Studies have shown that 20 years ago women spent an average of 2.5 hours a day collecting firewood, as the natural vegetation was far away and scarce. Under agroforestry systems, women spend an average 0.5 hours a day on this task, as they can prune trees on the family fields.15 These two hours saved can be dedicated to productive tasks, bearing in mind that if women had the same access to productive resources as men, they could increase yields on their farms by 20–30 per cent. This could raise total agricultural output in developing countries by 2.5–4 per cent, which could in turn reduce the number of hungry people in the world by 12–17 per cent.16
1 Provisioning, regulating and cultural services. See “Benefits of Sustainable Land Management”, WOCAT, UNCCD, 2009. <http://www.unccd.int/knowledge/docs/CSD_Benefits_of_Sustainable_Land_Management%20.pdf>.
2 Aagard, 2009, Conservation Farming Unit. Lusaka, Zambia. Personal communication in Garrity DP, FK Akinnifesi, OC Ajayi, SG Weldesemayat JG MowoA Kalinganire 2010.: Evergreen Agriculture: a robust approach to sustainable food security in Africa. Food Sec 2 (3), 197–214.
3 Personal communication. Gray Tappan (US Geological Survey Data Center for EROS, South Dakota).
4 Pretty J, AD Noble, D Bossio, J Dixon, RE Hine, FWT Penning de Vries and JIL Morison, 2006. “Resource-conserving agriculture increases yields in developing countries,” Environmental Science and Technology, 40:4, 1114−1119. in Olivier de Schutter (2010): Report submitted by the Special Rapporteur on the right to food. Agroecology. UN General Assembly. <http://www.srfood.org/images/stories/pdf/officialreports/20110308_a-hrc-16-49_agroecology_en.pdf>.
5 UNEP-UNCTAD Capacity Building Task Force on Trade, Environment and Development (CBTF), Organic Agriculture and Food Security in Africa, New York/Geneva, United Nations, 2008, p. 16. in Olivier de Schutter (2010): Report submitted by the Special Rapporteur on the right to food. Agroecology. UN General Assembly. <http://www.srfood.org/images/stories/pdf/officialreports/20110308_a-hrc-16-49_agroecology_en.pdf>.
6 Garrity DP, FK Akinnifesi, OC Ajayi, SG Weldesemayat JG MowoA Kalinganire 2010.: Evergreen Agriculture: a robust approach to sustainable food security in Africa. Food Sec 2 (3), 197–214.
7 UNCCD Thematic factsheet N°2 – Water scarcity and desertification. <http://www.unccd.int/documents/Desertificationandwater.pdf>.
8 Kaboré D and C Reij. 2004. The emergence and spreading of an improved traditional soil and water conservation practice in Burkina Faso. IFPRI, Washington. EPTD Discussion paper no. 114. 28 pp.
9 Remini, La sédimentation dans les barrages de l’Afrique du Nord. Larhyss Journal, ISSN 1112-3680, n° 02, Juin 2003, pp. 45-54
10 Nkonya E, N Gerber, P Baumgartner, J von Braun, A De Pinto, V Graw, E Kato, J Kloos and T Walter, The Economics of Desertification, Land Degradation, and Drought Toward an Integrated Global Assessment, ZEF- Discussion Papers on Development Policy No. 150, Center for Development Research, Bonn, May 2011, 184 pp.
11 Hassane A, P Martin and C Reij. 2000. Water harvesting, land rehabilitation and household food security in Niger: IFAD’s soil and water conservation project in Illéla District. IFAD/VU Universtity Amsterdam. 49 pp.
12 Towards a green economy. Pathways to sustainable development and poverty eradication (2011). [S. l.]: United Nations Environment Programme. <http://www.unep.org/GreenEconomy/Portals/93/documents/Full_GER_screen.pdf>.
13 Abdoulaye T and G Ibro. 2006. Analyse des impacts socio-économiques des investissements dans la gestion des ressources naturelles : étude de cas dans les régions de Maradi, Tahoua et Tillabéry au Niger. Etude Sahélienne. CRESA, Niamey
14 Dr. Chris Reij, Personal communication, UNCCD Land Day 2, 2010. <http://www.unccd.int/publicinfo/landday/2010/event.php>.
15 Dr. Chris Reij, Personal communication, UNCCD Land Day 2, 2010. <http://www.unccd.int/publicinfo/landday/2010/event.php>.
16 The state of food and agriculture. Women in agriculture : closing the gender gap for development (2011). Rome: FAO. <http://www.fao.org/docrep/013/i2050e/i2050e.pdf>.