Biomass, which is any material derived from living organisms (plant or animal), is a fundamental natural resource. People use biomass for food, animal feed, raw materials and energy. In 2000, 45 per cent of the global working population was involved in the production of biomass from plant sources (agriculture and forestry), which used two thirds of the world's surface land. Plant-derived biomass also met 9-13 per cent of the world's energy needs.
Humans consume a significant amount of global plant-based biomass. However, only 12 per cent of the 2000 harvest of plant-based biomass was used directly for human food. On average, 58 per cent was used as animal feed, 20 per cent for raw materials and 10 per cent as fuel wood. Wealth and economic development status were not necessarily key factors in plant biomass use. Historical land use patterns and population density were more significant. For example, in North America and Oceania, where population densities are lowest, plant biomass consumption per person is highest. In Asian regions, where population densities are highest, plant biomass use per person is lowest.
Livestock use the majority of plant-based biomass harvested by humans, but there is considerable regional variation: in Latin America, for example 75 per cent of harvested plant biomass is used by livestock, while in South Eastern Asia the figure is only 30 per cent. There is also considerable variation in the amount of feed needed to produce animal products (e.g. milk, meat, wool). In Europe, for example, typically 10kg of animal feed is needed to produce 1 kg of animal products. In contrast, in Sub-Saharan Africa, Latin America and Southern Asia, 50-100 kg of feed are needed to produce 1 kg of animal products. The researchers note that in many regions livestock provide draught power for agriculture and transport, which would increase the amount of feed needed to produce 1 kg of animal products (draught animals are fed but may not produce human food). In addition, ruminants digest biomass unsuitable for humans and in low-input agriculture systems, livestock provide essential plant nutrients (e.g. manure).
Human biomass use is expected to grow as the world population increases, putting significant pressure on land resources. Future approaches include cultivating new territory, but biodiversity in wilderness areas would be affected. Higher yields from more intensive methods require greater resource use, and could also damage established ecosystems. The most promising route may be to reduce meat consumption in high-income countries to encourage more efficient land use.