Planet Earth - Episode 07 (Great Plains) (ATOM Study Guide)

Planet Earth is a BBC production with five episodes in the first series (episodes one through five) and six episodes in the second series (episodes six through eleven). Each episode examines a specific environment, focussing on key species or relationships in each habitat; the challenges they face; the behaviours they exhibit and the adaptations that enable them to survive. Recent advances in photography are used to achieve some spectacular 'first sights' – in particular, stabilised aerial photography gives us remarkable views of migrating animals and the techniques used by their predators to hunt them.

As the series examines pristine environments where possible, they are often extreme. These are the parts of the world where few humans have chosen to live as the climate and landscape is too challenging, too difficult and dangerous. The plants and animals that do survive here have made some spectacular adaptations in forms and behaviour to live in these far reaches of the planet.

The series is suitable for middle secondary students studying Science and SOSE, and for senior secondary students of Biology, Environmental Science and Geography.

Grass is the engine that powers all life on land and the great swathes of grass that blanket the plains of the earth are the focus of this second episode. Nothing living on earth can exist without the grass, or at least some similar green species.

Grassland plains cover between one fifth and one quarter of the earth, usually in central continental areas where rainfall is low or highly seasonal. Every continent has its grasslands – the chilled steppes of Asia that extend one third of the way around the planet; the Pampas of South America and the prairies of North America, the tropical central savannah and drier southern veldt of Africa; the spinifex scrub of arid Central Australia. Any area of the world that has some soil but insufficient rains to support forest beyond occasional clumps of small trees supports extensive grassland. Even remote areas of central Europe still have some rare pristine grasslands. All are homes to herds of grazing herbivores and the predators that stalk them, huge flocks of birds that feed on their seeds and burrowing rodents that live nervous lives, fearful of sudden eagles in a treeless landscape.

These are threatened habitats – many have been destroyed or modified beyond recognition as they have been replaced with wheatlands in particular and introduced grasses for grazing huge herds of cattle and sheep. Of course, a wheatfield is technically a grassland as wheat and other cereals are modified grasses, reminders of the times when humans collected grass seeds to make basic breads. Ninety-eight per cent of the North American long and short grass prairies have been lost and the mallee of southern Australia and remote Asian steppes are threatened in the same way as they are converted to food and textile production. However, many of the central Australian 'deserts' returned to arid grassland condition once the rabbits had been removed by introduced diseases in recent years.