Five true-or-false statements on environmental studies, ecosystem services, energy flow, soil erosion and renewable energy

(a)False Environmental studies is multidisciplinary, not purely biological. Besides biology it draws on geology, chemistry, physics, engineering, sociology, health, anthropology, economics, statistics, computers and philosophy.

(b)False Ecosystem services are of four kinds: provisioning, regulating, cultural and supporting. The statement leaves out the cultural services, such as the recreation, beauty and spiritual value people find in forests, rivers and sacred groves.

(c)False Energy flows one way in an ecosystem: from the sun to producers and then to consumers at higher trophic levels, with part lost as heat at each step. It is nutrients that are used again and again: dead matter is decomposed and its minerals are released back for reuse by producers.

(d)True Soil erosion is the removal of the surface litter and topsoil from one place to another. It is a natural process, but farming, construction, overgrazing, burning of grass cover and deforestation speed it up greatly; it is treated as a cause of soil degradation under soil (land) pollution, and the soil washed away also pollutes water.

(e)False Renewable resources can be renewed by nature, but not without limit: they too are used up if they are drawn faster than nature can replace them, as when trees are cut faster than they regrow.