Five true-or-false statements on the biosphere, food webs, renewable energy, groundwater and noise

(i)True The biosphere is the thin layer of the Earth in which life can exist; it takes in all living organisms, together with the air, water, rocks and soil they live in, working as one global living system.

(ii)False A food web is formed when many food chains are interconnected, because most animals eat more than one kind of food. A web is therefore more complex than any single chain, not less.

(iii)False Renewable sources have lower impacts but not none. Wind power, for instance, has almost no air or water emissions, yet it causes bird deaths and noise, and the turbines needed spread over large areas of land and spoil the view.

(iv)True Falling groundwater levels are a serious problem in India. In West Bengal, intensive irrigation from deep and shallow tube wells has lowered the water table, and this has been linked to arsenic entering the groundwater.

(v)False Noise harms health. Long exposure to loud sound causes temporary or permanent loss of hearing, raises blood pressure, and leads to irritability, anxiety, stress and poor concentration; it also masks warning signals and so increases accidents at work. Traffic noise near a school in a busy city is a common Indian example.