Our EnvironmentIntroduction
In 1960 a gardener in England put a little compost and one tiny spiderwort seedling into a large glass bottle. In 1972 he watered it one last time, pushed the cork in, and never opened it again. More than forty years later the bottle was a small green jungle, still growing quietly on his windowsill.
Nothing went in and nothing came out: no fresh air, no water, no fertiliser. Or did something get in after all?
What does the sealed bottle need from outside to stay alive?
Only sunlight goes in. Everything else inside the bottle goes round and round. The plant uses the energy of sunlight to make its food and gives out oxygen and water vapour; the water condenses on the glass and trickles back into the soil; and bacteria and fungi in the compost break down fallen leaves into minerals that the roots take up again. The bottle is a tiny ecosystem: living things and their non-living surroundings, working together.
The Earth works the same way, on a giant scale, and we live inside it. We hear the word "environment" all the time: on television, in newspapers, from our elders, who tell us it is not what it used to be. Countries hold global summits to discuss environmental problems. In this chapter we study how the different parts of the environment interact with each other (who eats whom, where the energy goes, how a poison can travel) and then how our own activities are changing the environment around us.