(iv) The SLM technologies must be socially acceptable and ethically grounded. The severe problem of soil degradation can be reversed by creating awareness about the stewardship of land resources. Faith-based and cultural organizations must be involved to teach responsibility, respect, generational/gender/social equity, fairness, and societal values of natural resources through SLM. (v) Political support and acceptibility is extremely important to any SLM technology and strategy. The Green Revolution largely by-passed SSA partly due to lack of political support. It is now taking root in some countries of SSA (e.g., Malawi, Ghana) maily because of political support. Visionary leadership, committed to national progress and economic growth (rather than personal), is essential to relevance and effectiveness of SLM options. (vi) SLM adaptation technologies must be considered as an integral component of the mitigation options. These should be considered neither as policy alternatives, nor as opposite to mitigation. In addition, SLM technologies that have appreciable mitigation benefits should be given the prominence they deserve, relative to other industrial mitigation technologies (e.g., clean coal, CCS). (vii) There must by a minimal of trade-offs in terms of competition for land, water, nutrients, energy, etc. SLM technologies requiring additional inputs, are essential to advancing food security, restoring ecosystesm services, and improving the environment. In comparison, forest plantations would require additional water, nutrients and lands. Increasing food crop productivity through SLM is potentially important to limiting atmospheric CO2 concentrations (Wise et al., 2009). In view of these considerations, SLM technologies for four prominent ecoregions are described in the following sections.
A. Land Use Conversion 59. Land use affects soil quality and the terrestrial/ecosystem C pool through its impact on both the biomass and SOC pools. Land use affects NPP through alterations in soil moisture and temperature regimes, changes in elemental cycling and nutrient availability. In the Loess Valley of China, for example, Gong et al. (2006) documented significant impacts of land use on soil quality, NPP, and ecosystem C pool. Developing strategies that foster SLM in fragile soils (e.g., Loess Plateau in China) is important to enhancing the ecosystem C pool. In Thailand, Gnanaverajah et al. (2008) assessed the ecosystem C pool for 11 different land use systems. The biomass C pool was 247.9 t C/ha for rubber, 189.4 t C/ha for mixed orchard, 159.1 for eucalyptus, 139.2 t C/ha for coconut, and 12.9 t C/ha for rice paddy. The data from Minas Gerais, Brazil, show that conversion of degraded to improved pastures and establishment of plantations on degraded lands can enhance the SOC pool (see Table 12). Thus a perennial land use, established on degraded land, is an important option to adapt to CC while enhancing the ecosystem C pool and NPP. B. No-Till Systems 60. The choice of seedbed preparation, of methods and timing of tillage operations, is important to adaptation to and mitigation of CC. Crop residues constitute more that 50% of the world’s agricultural biomass (Smil, 1999), and are important to recycling of C and nutrients. Effectiveness of NT farming on improving soil quality depends on retention of crop residue mulch. It is widely documented that conversion of conventional tillage (CT) to NT farming, with use of crop residue mulch and cover crops in the rotation cycle along with INM, conserve soil
Table 17. Estimate of annual rate of land degradation in mid latitude drylands (calculated from Mainguet, 1991; UNEP, 1991). Land use Total land area (Mha) Rate of desertification Mha/yr % of total/yr Irrigated land 131 0.125 0.095 Rangeland 3700 3.200 0.086 Rainfed cropland 570 2.500 0.439 Total 4410 5.825 0.132 Mha = 106 ha Table 18. Estimates of land area under different vulnerability classes of desertification and the number of impacted people (Eswaran et al., 2001). Vulnerability Class Area Affected Population 106 km2 % of Global Land Area 106 People % of Global Population Low 14.60 11.2 1,085 18.9 Moderate 13.61 10.5 915 15.9 High 7.12 5.5 393 6.8 Very High 7.91 6.1 255 4.4 Total 43.24 33.3 2,648 46.0
P = Phosphorus POM = Particulate organic matter ppm = Parts per million PT = Plow tillage Quad = Quadrillion BTU (1015 BTU) RMPs = Recommended management practices SA = South Asia SCS = Soil carbon sequestration SIC = Soil inorganic carbon SLM = Sustainable land management SOC = Soil organic carbon SOM = Soil organic matter Spp = Species SSA = Sub-Saharan Africa t = Ton (metric ton) TFE = Tropical rainforest ecosystem TN = Total nitrogen TPG = Temperate prairies and grasslands TRF = Tropical rainforest TSE = Tropical savannah ecosystem U.P. = Uttar Pradesh, India UNEP = United Nations Environment Program UNCCD = United Nation Convention to Control Desertification UNFCC = United Nations Framework Convention on Climate Change yr = Year