A STUDYGUIDE by Andrew Fildes

Transcription

1 A STUDYGUIDE by Andrew Fildes 7

2 Overview 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.

3 1 Episode Seven: Great Plains 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. Ninetyeight 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. Web Resources Teacher Links au/pdf/srbi-grasslands.pdf Episode 7: Great Plains (Timings are approximate) Time Log Intro 00:00-01:50 Mongolian Gazelles and Eagles Grassland fire and Recovery Savannah Quelea Flocks 01:50-03:45 03:45-06:00 06:00-07:30 Wildebeest Herds 07:30-08:25 Arctic Grasses 08: Snow Geese 09:50-12:47 Arctic Fox and Geese 12:47-14:35 Arctic Wolf and Caribou 14:35-18:05 Arctic Fox and Geese 18:05-20:52 Prairies and Bison 20: Grasses Flowering 23:21-25:30 Tibetan Plateau and Yak 25:25-27:09 Wild Tibetan Asses 27:09-29:08 Pika (rodents) and Foxes Tropical Indian Long Grasslands African Savannah and Elephants 29:00-31:35 31:35-34:50 34:50-36:50 Elephants and Lions 36:50-38:10 Lion night Hunt 38:10-43:20 Savannah Floods and Baboons 43:20 - end (Australian Grasslands systems) grasslands/pech.htm (Tibetan Pikas assessed as pests as they compete with cattle for feed) Onsite_Grassland.htm Werribee Zoo (Melbourne) excursion - Senior Biology/Environmental Sci. workshop Student Links distancelearning/prairie/build (interactive - junior) exhibits/biomes/grasslands.php (Senior precise definitions of terms like Steppe and Savannah and other ecosystems) Species List Mongolian Gazelle Procapra gutturosa Red-billed Quelea Quelea quelea Wildebeest Connochaetes spp. Snow Goose Chen caerulescens Arctic Fox Alopex lagopus Arctic Wolf Canis lupus arctos Caribou Rangifer tarandus Bison (Buffalo) Bison bison Yak Bos grunniens Wild Ass (Khulan) Equus hemionus hemionus Plateau Pika Ochotona curzoniae Golden Eagle Aquila chrysaetos Tibetan Snow Finch Montifringilla henrici Tibetan Fox Vulpes ferrilata Asian Elephant Elephas maximus Lesser Florican Sypheotides indica Pygmy Hog Sus salvanius African Bush Elephant Loxodonta africana Lion Panthera leo African Buffalo Syncerus caffer Chacma Baboon Papio ursinus

4 1 Blackline Master Planet Earth Episode 7: Great Plains Viewing Questions

5 1a 11 What proportion of the earth s surface is grassland? 2 What climatic conditions are required to create a grassland? 6 Which animal migrates in huge numbers across the African Savannah? 7 Where do the snow geese spend the winter? 3 What animal grazes the Mongolian steppe? 8 How many snow geese migrate each year? 9 What animal is the goose s main predator in the Arctic? 4 How does grass recover from fire? 5 Which species of bird is the most numerous? Where does it live? 10 What do the Arctic wolves hunt?

6 1b 11 What was the original large grazing animal of the American prairie? 12 What is the highest great plain in the world? 13 Why is this plain such a dry place? 16 What is its main predator? 17 What is the advantage of long grassland for the animals? 14 Name the main large grazer of this system. 15 What small animal is the most common inhabitant of the plateau? 18 What techniques do lions use to attack and kill an elephant?

7 2 Case Study Planet Earth Episode 7: Great Plains The Dust Bowl 7

8 2a Ever since humans began to cultivate the land rather than hunt and gather, the grasslands have been threatened. They were the obvious environment to graze animals for meat and wool or to plant dry country crops such as wheat, oats and barley that require rain in their early stages but need a dry, hot summer to dry the seeds on the stem. Of course, many of these cereal crops are just grasses that humans had collected for thousands of years, modified by selective breeding for larger seed heads and heavier yields. The vast grasslands of the Great Plains and the Great Basin in the United States were once inhabited by many different Indian tribes and abundant wildlife who had lived in balance with the ecosystem for thousands of years, taking no more than they needed. Twenty million bison thundered across the plains, which the Indians depended upon for food and clothing. Then as Europeans began to move west in search of farmland to develop, encouraged by the Homestead Act of 1862, 6 million settlers came to the prairies and created one of the worst environmental disasters in world history. As the settlers moved out over the plains, forcing out the Indian tribes, they brought cattle and sheep to graze in the grasslands. They slaughtered millions of bison, almost to the brink of extinction. They were not a useful species as they were migratory and hard to control. Many were killed to feed the workers building the railroads that would bring even more settlers. By 1889 only 541 bison were known to be alive in the U.S. The Indians had been deprived of their main source of food. The settlers farmed the land once covered with native bluestem, buffalo and grama grasses. The topsoil was ploughed up and with it, the extensive root systems of the native grasses. The farmers planted fleshy, introduced feed grasses for their animals and grain crops such as barley, oats and mostly wheat. Early in the 1930s, an eight year drought began, and a series of major

9 2b wind storms swept over the Great Plains and the southwest creating huge smothering dust storms. The soil in the grasslands had become dry and loose from European style farm techniques such as ploughing and the damage caused by livestock grazing. The roots of the grain crops and introduced grasses could not hold the dry topsoil under such severe winds. Tons of loose fertile topsoil was picked up and carried for hundreds of kilometres. Fences were buried by huge drifts and dirt had to be shovelled out of houses. The dust was so thick that people could not see, lungs were damaged, and some people even became lost in the storms and died. The southern Great Plains soon became known as the Dust Bowl as the drought continued and the land stripped of its topsoil could not recover. Grass could not grow even when there was rain and the clay subsoils continued to create new dust storms every summer. Farms were now worthless. The land became so damaged there was very little to harvest, so thousands of farmers and ranchers walked away to seek their fortunes elsewhere. Many continued west into California, often looking like the lines of refugees seen in wartimes. It is estimated that some 20 million hectares of land were badly damaged and 20 million more threatened. The worst damage occurred in Oklahoma, Kansas, Colorado, Texas and New Mexico. Because of the poor judgement of humans in converting the natural grassland ecosystems into grain crops (monocultures), allowing the remaining grasslands to be overgrazed, and not using proper farming methods, the land was unable to cope with such a long drought and unusually severe wind storms. The government set up programs to help restore the land, and they taught the remaining farmers how to protect the soil and reduce erosion. The settlers began to restore and protect the land, and they planted trees as windbreaks. The land, the Indians, the settlers, and the bison species had all suffered greatly, and harsh lessons had been learned. But around the world in many countries, the same mistakes are being made and climate changes such as global warming are accelerating the process. Great Plains Discussion Questions The grassland plains cover huge areas of the earth and vary considerably depending on climate, some are short grasslands (steppes), some long grass (savannah) and some seasonal as in the Arctic. Each provides a habitat for a complex ecosystem, including soil fauna, grazers and predators. They range from the wet, long grasslands of northern India, which can conceal an elephant, to the arid grasslands of central Australia which were reduced to desert by rabbit infestation. 1. The flowering of the grasses (did you even know that grasses flowered so beautifully?) was done with time-lapse photography. How is that process achieved? 2. The snow goose eggs all hatch within one to two days of each other a million goslings at once. What survival advantage would there be in this close timing? 3. The Tibetan fox must hunt the pika out in the open with very little cover and get close enough to catch it. What physical adaptations and behaviours help it to achieve this. 4. What similarities and what differences are visible in the various grasslands in the documentary. How do you explain these similarities and differences? Extension Tasks Draw up a table or a visual presentation (poster) that compares two different grassland habitats and the numerous differences between the two. Discuss the principle threats to grasslands from human activities such as farming and grazing. Prepare a visual presentation such as a poster or PowerPoint presentation that shows the extent of damage and the possible restoration measures.

10 ANSWER SHEET Viewing Questions 1. One quarter of the earth s surface is grassland 2. Insufficient rain for forest but too much for desert 3. The Mongolian gazelle 4. It re-grows quickly from the protected base of the stem 5. The red-billed quelea of the African Savannah 6. Wildebeest two million herd 7. In the Gulf of Mexico (very sensibly) 8. Five million 9. Arctic fox 10. Caribou 11. The bison (or buffalo) was the original prairie grazer 12. The highest plain is the Tibetan plateau 13. The Himalayas act as a barrier, blocking clouds from the south (rain shadow effect) 14. The wild Asian ass 15. The pika, a relative of the rabbit 16. The Tibetan fox hunts the pika 17. Even large animals like elephants can conceal themselves and feed themselves 18. They attack by night, select an isolated animal of the right size and attack in large numbers Great Plains Discussion Questions 1. A film camera is locked into position on a tripod. It is set to take one shot every few seconds instead of twenty-four shots every second. The film is then shown at normal speed that has the effect of speeding up the motion by up to several hundred times. It makes plants come to life. The same process is used for animating clay models like Wallace and Grommit and is easy to do but very slow. 2. There are huge numbers of goslings and only a few foxes to predate them so the chances of survival are much better for each individual gosling. It is one in a million possible targets for a fox! 3. Its colour and the strange stalking movements help it to get close enough to dig out the pika before it can get too deep. Even the strange square face may make it harder to see when it keeps still. 4. None of them has trees in any numbers. All have grazing animals that rely exclusively on grass as a food source. All have predators which have the ability to hunt out in the open by various means sneaky animals like foxes, birds like eagles, pack hunters like lions. However, some have sparse seasonal grasses so grazers like snow geese migrate for the growing season, others have permanent short grasses that support migrating herds and others have lush, long grasses that support large animals all year around. BBC and Planet Earth are trade marks of the British Broadcasting Corporation and are used under licence. Planet Earth logo BBC BBC logo BBC This study guide was produced by ATOM editor@atom.org.au For more information on Screen Education magazine or to download other free study guides visit For hundreds of articles on Film as Text, Screen Literacy, Multiliteracy and Media Studies, visit Notice: An educational institution may make copies of all or part of this Study Guide, provided that it only makes and uses copies as reasonably required for its own educational, non-commercial, classroom purposes and does not sell or lend such copies. 10