Humans need plants for a number of reasons, with the two most important ones being to provide oxygen and food. Additionally, plants give fuel, fiber, medicine and materials for shelter. They can also be useful in cleaning toxic soils, filtering particles from the air, stabilizing soils and acting as an insecticide.
The majority of the world's oxygen supply is produced by plants, both marine and land-based. Plant foods make up 90 percent of the calories eaten worldwide, with most of the remaining calories produced by plant-eating animals such as cattle and chickens. The main sources of fuel for heating and cooking in the developing world, including Africa, Asia and Latin America, are wood and charcoal.
Many textiles are made from plant fibers, including cotton, hemp and bamboo. Cotton accounts for approximately 36 percent of the world textile market. Plant fibers are also used in the manufacturing of paper products and rope. Plant-based medicines have been used by humans for centuries. Quinine, an anti-malarial drug, is still harvested directly from the bark of the Cinchona tree. Others, such as aspirin, originally derived from the bark of the willow tree, were once harvested from trees, but are now synthetically manufactured.
Pyrethrin pesticides, derived from chrysanthemums (Chrysanthemum cinerariaefolium), are used worldwide as insecticides, due to their neurotoxic effects on insects and their low toxicity on humans and other mammals.