Socioeconomic aspects of land use change, effects on biogeochemical cycles and greenhouse gas emissions: Intensive agriculture and forestry and associated land degradation, pose an enormous challenge to human society. Overuse of land ecosystems reduces food security, leads to emissions of greenhouse gases and aerosols, drives biodiversity loss, pollutes water, and undermines a wide range of ecosystem services beyond food supply and water and climate regulation. Direct emissions from deforestation, fertilization, rice cultivation, and ruminants currently amount to about 25% of all human greenhouse gas emissions.
Drivers of intensive land use are population growth, together with increases in per capita consumption of calories, wood, and fiber, and a shift towards consumption of meat and dairy products. This chapter briefly summarizes these socioeconomic aspects and introduces the basic processes underlying the emission of CO2, CH4, and N2O. Various chapters in this book revisit these processes and examine them in more detail from different perspectives.