15. Some of the key global issues of the 21st century which necessitate that humans be responsive to the attendant changes are: (i) atmospheric concentration of CO2 increasing from 280 ppm in pre-industrial era to 385 ppm in 2008 (+ 37.5%), and presently increasing at the rate of ~2 ppm/yr, (ii) soil degradation affecting 2 billion hectares (ha) globally and increasing at the rate of 5 to 10 million ha/yr and desertification affecting 3-4 billion hectares especially in developing countries, (iii) food insecure population of ~1 billion and increasing, and the per capita grain consumption of 300 kg/yr and decreasing, (iv) water scarcity (< 1000 m3/person/yr) affecting population in 30 countries and increasing to 58 countries by 2050, (v) per capita cropland area of 0.22 ha and decreasing to < 0.07 ha by 2025 for at least 30 densely populated countries, and (vi) global energy demand of 475 quads (1 quad = 1 x 1015 BTU) and increasing at the rate of 2.5%/yr. These issues are intertwined at global-scale and are accentuated by human activity (Walker et al., 2009), especially by the increase in world population. It was 6.7 billion in 2008, increasing at the rate of 1.15%/yr or by 70-80 million person/yr, and projected to be 9.2 billion by 2050. Almost all of the increase in world population will occur in developing countries where soils are fragile and under great stress, climate is harsh and changing, and water resources are scarce and getting severely polluted. Addressing the interrelated issues of soil degradation, food insecurity, water scarcity and climate change (CC), necessitates identification and implementation of specific sustainable land management (SLM) options.
