Scott Foresman Science 5.8 Genre Comprehension Skill Text Features Science Content Nonfi ction Draw Conclusions • Captions • Sidebar • Maps • Glossary Weather Patterns ISBN 0-328-13939-4 ì<(sk$m)=bdjdjc< +^-Ä-U-Ä-U 13939_01-04_CVR_FSD.indd Cover113939_01-04_CVR_FSD.indd Cover1 5/10/05 2:15:13 PM5/10/05 2:15:13 PM Scott Foresman Science 5.8 Genre Comprehension Skill Text Features Science Content Nonfi ction Draw Conclusions • Captions • Sidebar • Maps • Glossary Weather Patterns ISBN 0-328-13939-4 ì<(sk$m)=bdjdjc< +^-Ä-U-Ä-U 13939_01-04_CVR_FSD.indd Cover113939_01-04_CVR_FSD.indd Cover1 5/10/05 2:15:13 PM5/10/05 2:15:13 PM 1. How can a region’s climate make it more likely to suffer from droughts? 2. If seasonal rains are important for crops to grow in a certain country and those rains don’t happen for two years in a row, what may happen to the people of that country? 3. Why do some scientists think that droughts will happen more often in the future? 4. El Niño brings rain to normally dry regions, causes drought in others, and causes extreme weather around the world. Write to explain some of the effects of El Niño. Use examples from the book to support your answers. 5. Draw Conclusions Why should water be conserved when a drought has already started? What did you learn? Extended Vocabulary cover crops deforestation desertifi cation economic famine malnutrition overpopulation resources terracing topsoil Vocabulary air mass anemometer barometer climate convection current front rain gauge Picture Credits Every effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). Opener: A. Ishokon/UNEP/Peter Arnold, Inc.; 1 Anthony Bannister/NHPA Limited; 3 Digital Vision; 4–5 Anthony Bannister/NHPA Limited; 5 (TR) Adrian Arbib/Corbis; 6–7 Dieter Telemans/Panos Pictures; 8 (BL) Yann Arthus-Bertrand/Corbis; 9 A. Ishokon/UNEP/Panos Pictures; 10–11 (B) Ferdinando Scianna/©Magnum Photos; 11 (C) Herbie Knott/Rex Features, Ltd; 12–13 (B) John Maier Jr./Argus Fotoarchiv/Corbis; 14 (B) Reuters/Corbis; 15 Liba Taylor/Hutchison Picture Library; 16–17 Chris Stowers/Panos Pictures; 18–19 (B) Corbis; 20 Ron Giling/Peter Arnold, Inc.; 21 Mark Edwards/Peter Arnold, Inc.; 22–23 Yann Arthus-Bertrand/Corbis. Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson. ISBN: 0-328-13939-4 Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05 13939_01-04_CVR_FSD.indd Cover213939_01-04_CVR_FSD.indd Cover2 5/10/05 2:15:22 PM5/10/05 2:15:22 PM by Beth Parlikar 13939_05-28_FSD.indd 113939_05-28_FSD.indd 1 5/10/05 2:15:51 PM5/10/05 2:15:51 PM Weather is made up of the conditions of the atmosphere at a given moment, and it can change very quickly. Measurements of temperature, air pressure, wind speed and direction, and precipitation are used to describe the weather. The atmosphere is made up of air, which is a mixture of gases such as nitrogen and oxygen. The atmosphere has fi ve layers. Air temperature changes as you go up through the layers. Cool air is heavier than warm air because the gas particles in cool air are closer together. The differences in air temperature cause air to move, and air movement creates currents, which affect weather. When cool air and warm air come together, the cool air sinks and the warm air rises. This looping movement of air is called a convection current. These currents can create clouds, rain, and other weather patterns. What You Already Know 2 When warm air and cool air meet, rain can occur. 13939_05-28_FSD.indd 213939_05-28_FSD.indd 2 5/10/05 2:15:57 PM5/10/05 2:15:57 PM An air mass is a huge body of air that has similar conditions throughout. Air masses move because of winds and can be warm or cold, wet or dry. Fronts are boundaries between air masses. Precipitation often happens when a front moves through an area. Meteorologists use patterns of weather changes from the past to predict future weather. They use many instruments to measure weather conditions. A barometer measures air pressure, an anemometer is used to determine wind speed, and a rain gauge measures how much rain has fallen. Climate is not the same as weather. Climate is the average of weather conditions for an area over a number of years. In this book you will read about a weather condition called drought. You will learn how droughts affect environments and people. area affected by drought, Botswana 3 13939_05-28_FSD.indd 313939_05-28_FSD.indd 3 6/16/05 2:53:54 PM6/16/05 2:53:54 PM What is drought? If you think it’s a period of time with little or no rainfall, you’re partly right. Droughts are long periods of reduced precipitation that usually last for months or even years. Drought is actually a normal part of climate and can occur anywhere on Earth, from deserts to rain forests. Depending upon its location, length, and severity, drought can have many different effects on people and the environment. Agriculture is often affected during a drought; crops might fail, and farm animals might die. People have less food to eat, and they might suffer from hunger, malnutrition, or starvation. Introduction Drought can cause crops to fail. 4 13939_05-28_FSD.indd 413939_05-28_FSD.indd 4 5/10/05 2:16:00 PM5/10/05 2:16:00 PM Drought can have many other effects. Dry conditions can cause wildfi res and dust storms, and wild animals can die from lack of food and water as natural vegetation decreases. Water supplies are lower than usual during a drought, so people might be asked to conserve water. If a drought lasts a long time and is severe, people may even abandon their homes and move to an area with more water. Aid organizations provide food for drought sufferers. 5 13939_05-28_FSD.indd 513939_05-28_FSD.indd 5 5/10/05 2:16:06 PM5/10/05 2:16:06 PM Why do droughts happen? Scientists have found that droughts are usually a result of many factors. Climate is one thing that determines when and where droughts occur. Some parts of the world are more prone to droughts because the weather varies a lot from year to year. Some regions get seasonal rains that are important for animals’ survival and for crops to grow. If those rains don’t come, the drought can kill animals and crops, and people may even die. Climate change can cause droughts to happen more often and turn fertile land into desert. Global weather patterns can also help to cause droughts. Certain weather patterns happen periodically and can lead to drought in different parts of the world. 6 13939_05-28_FSD.indd 613939_05-28_FSD.indd 6 5/10/05 2:16:09 PM5/10/05 2:16:09 PM One such weather pattern that happens every few years is called El Niño. This pattern is caused by a shift in the winds and ocean currents off the coast of South America. The effects of this event can spread across the world, bringing droughts to normally wet regions and fl oods to dry ones. People can cause droughts to be more likely to happen. For example, poor farming practices, such as overgrazing and clear-cutting of trees for fi rewood, can cause the land to lose moisture easily. This can make a drought far worse than usual. If many people move to an area that is prone to droughts, they may have problems. The more people there are, the more water they need to survive. If the rains don’t come, those people may run out of water quickly. Survival in a dry region can be very diffi cult. 7 13939_05-28_FSD.indd 713939_05-28_FSD.indd 7 5/10/05 2:16:15 PM5/10/05 2:16:15 PM An area’s average weather conditions are called its climate. However, the weather at any one time can be very different from the average. For example, the summer in California is usually hot and dry, but sometimes there are big storms that bring rain. Changes from normal conditions can lead to droughts if precipitation is less than normal. These droughts can be devastating if a region needs seasonal rains for crops to grow. Climates don’t always stay the same over time. In fact, they can change drastically and sometimes quickly. For example, sudden volcanic eruptions can block sunlight and change the climate over a large area. Other times, climate changes slowly. Sometimes the cause of slow climate change is natural. One natural cause of climate change is variation in the strength of the Sun’s energy, which warms the Earth. People also cause climate change. Most scientists believe that a process called global warming is happening because cars and factories make gases that warm up the atmosphere. Global warming is changing the patterns of the water cycle. Scientists think that land in the middle of continents will have more droughts, and deserts will grow bigger. Climate As an area becomes drier, some rivers may dry up entirely, as this former river in Argentina has. 8 13939_05-28_FSD.indd 813939_05-28_FSD.indd 8 5/10/05 2:16:17 PM5/10/05 2:16:17 PM 9 Water is very scarce in some parts of India. 13939_05-28_FSD.indd 913939_05-28_FSD.indd 9 5/10/05 2:16:18 PM5/10/05 2:16:18 PM Ethiopia is a country in East Africa with a population of sixty-seven million people. Of these, 90 percent are subsistence farmers, meaning that they make a living by growing just enough food to eat. The soil is good, but there isn’t much rainfall most of the year. The rains usually come between June and September and are very important for farming and for the people’s survival. Case Study: Ethiopia 1981–1985 Most of Ethiopia, a country in East Africa, suffered from drought for several years in a row. Ethiopia Area worst affected by drought AFRICA Ethiopia 10 13939_05-28_FSD.indd 1013939_05-28_FSD.indd 10 5/10/05 2:16:25 PM5/10/05 2:16:25 PM Beginning in 1981, the seasonal rains that are so important for survival in Ethiopia did not come. In most parts of the country, all or almost all of the crops died, and people did not get enough to eat. This continued through the years of 1982, 1983, and 1984, until the drought was so severe that eight million people were in danger of starving to death. Finally the people of the world came to help, bringing food, medicines, and clothing. But it was already too late for many: almost one million people starved to death. Thousands of others left Ethiopia and went to nearby countries in search of food and shelter. Since the terrible famine of 1981–1985, Ethiopia has suffered from two more major droughts. Today the country is trying to conserve water more carefully and educate its people about health, nutrition, and good farming practices. Millions of dollars were spent on food and medical aid for Ethiopians during the drought of 1981–1985. 11 13939_05-28_FSD.indd 1113939_05-28_FSD.indd 11 5/10/05 2:16:32 PM5/10/05 2:16:32 PM El Niño means “the child,” and it gained its name because it arises around Christmas. It is a weather pattern that causes disruptive events every few years. El Niño starts out in the southern Pacifi c Ocean, where the winds usually blow from east to west. Warm water normally collects along the eastern coast of Australia. Meanwhile, currents of cold water fl ow along the western coast of South America. During El Niño, the warm water current suddenly rushes across the ocean from west to east. The warm, moist air that usually brings the monsoon rains to Southeast Asia is no longer there, so the monsoons don’t come on time. Across the ocean, the desert along the coast of Peru receives heavy rains. The effects don’t stop there, though. El Niño can affect weather patterns from Florida to Africa! Scientists aren’t sure what makes El Niño happen, but they do know something about its effects. The sudden presence of warm, moist air over South America causes convection currents in the atmosphere to shift. These huge currents affect weather throughout the world. El Niño El Niño often causes drought in the Amazon River region in Brazil, increasing the risk of forest fi res. 12 13939_05-28_FSD.indd 1213939_05-28_FSD.indd 12 5/10/05 2:16:36 PM5/10/05 2:16:36 PM El Niño Under normal conditions in the South Pacifi c, warm water collects in the west, and cold water in the east. This makes the air warm and moist in Southeast Asia, while coastal Peru is a desert. During El Niño, a mass of warm water moves across the ocean from Australia and along the equator to the coast of South America. This brings rain to normally dry Peru and can affect the weather around the world. Mexico Mexico Equator NORTH AMERICA SOUTH AMERICA CENTRAL AMERICA Pacifi c Ocean SOUTHEAST ASIA Australia cold currents NORTH AMERICA SOUTH AMERICA CENTRAL AMERICA Pacifi c Ocean SOUTHEAST ASIA Australia warm currents 13 N E S W N E S W 13939_05-28_FSD.indd 1313939_05-28_FSD.indd 13 5/10/05 2:16:43 PM5/10/05 2:16:43 PM The strongest El Niño of the past century struck in 1997. It brought extreme weather that devastated the countries of Central America. Droughts occurred throughout the region, causing many crops to fail. Unusual rains caused fl oods that also hurt food production and endangered people’s lives. There were outbreaks of tropical diseases, which made thousands of people very sick. The worst forest fi res on record destroyed rain forests and polluted the air as far away as the eastern United States. Water levels in rivers and lakes fell so low that the country of Honduras declared a state of emergency. Case Study: Central America 1997–1998 El Niño caused drought, fl ooding, and forest fi res, which overwhelmed Central American countries in 1997–1998. NORTH AMERICA SOUTH AMERICA CENTRAL AMERICA Many farmers in Central America lost their crops due to drought caused by El Niño. Gulf of Mexico Pacifi c Ocean 14 13939_05-28_FSD.indd 1413939_05-28_FSD.indd 14 5/10/05 2:16:48 PM5/10/05 2:16:48 PM Wildlife suffered from the severe weather as well. Fewer sea turtles hatched on beaches in Central America and Mexico because of high tides and drought. Many coral reefs, which are made up of tiny animals called coral polyps, died or were damaged because the water grew too hot. Fishermen also reported that there were very few fi sh to be found in the oceans. As the terrible effects of El Niño continued, thousands of people found themselves without enough food to eat. Aid organizations from around the world stepped in to help, bringing food and other supplies for the people. Unfortunately, relief for the people of Central America did not last long, as Hurricane Mitch devastated the region in 1998. Another drought struck in 2001, and this time three-quarters of a million people were in need of food aid. The people of Central America suffered a great deal from these natural disasters. When terrible events like these happen, it is important for people to work together to help everyone recover. International aid workers gave food to thousands of hungry people. 15 13939_05-28_FSD.indd 1513939_05-28_FSD.indd 15 5/10/05 2:16:56 PM5/10/05 2:16:56 PM People’s actions can affect how bad droughts are and how often they happen. For instance, if too many people decide to live in a region that is prone to droughts, they can put a strain on land and water resources. People need water for cooking, washing, and growing food. The more people that live in an area, the more water they need. The increasing number of people in the world is also a problem. The more people there are on Earth, the more water is required to meet their needs. Overpopulation is therefore one factor that can worsen droughts. Poor farming practices can also increase the risk of drought. In some areas farmers clear land so that they can grow more crops, even if the land is not good for farming. In order to clear land, they burn or cut down forests. This makes the soil dry up easily and blow away or be washed away by storms. This soil erosion makes it very hard to grow crops. Overpopulation and Poor Farming Practices The soil in deforested areas often becomes hard and dry, making it drought-prone and diffi cult to farm. 16 13939_05-28_FSD.indd 1613939_05-28_FSD.indd 16 5/10/05 2:16:58 PM5/10/05 2:16:58 PM Deforestation is also bad for drought prevention because trees help to control global warming by capturing some of the gases that cars and factories release. Animal grazing can also make the land dry. If animals such as cows and goats are allowed to eat too much of the grass in an area, this can have the same effect as burning down forests. Soil erosion and overgrazing can cause areas that used to have plant life to become deserts. This process is called desertifi cation. 17 13939_05-28_FSD.indd 1713939_05-28_FSD.indd 17 5/10/05 2:17:04 PM5/10/05 2:17:04 PM [...]... Bowl drought 18 19 Prevention and Aid There are many aid agencies that help people in areas suffering from drought Some agencies provide money and other resources to farmers whose crops suffer because of drought Other agencies, such as the Red Cross, give food and water to people in drought- stricken areas who are sick and malnourished There are many things people can do to lessen the effects of a drought. .. more droughts, as well as storms and extreme temperatures El Niño caused droughts in Central America in the 1990s Human actions can also contribute to droughts The world’s growing population puts a strain on water resources Some types of farming practices also make the land prone to drought Activities such as teaching people about water conservation and planting trees are ways you can help prevent droughts... many parts of the world 21 Summary Drought occurs when a region receives less rain or snow than usual Drought can be very bad for people and the environment Crops can fail and animals can die, leading to food shortages If the drought lasts very long, people may become malnourished and even die of starvation People may also decide to leave the area suffering from drought, abandoning farms or entire... trees, polluting the air and killing wild animals Droughts usually have more than one cause One factor is climate If the weather tends to vary quite a bit, with some years being much drier than others, then droughts are more likely to happen 22 Most scientists believe that global warming is changing climates all over the world They think that this may make droughts happen more often in the future El Niño... Even before a drought starts, there are many things people can do to help prevent problems Planting native plants and trees helps to hold moisture inside the soil and anchor it Using smart farming and ranching techniques is also important Finally, people can help others learn why conserving water is important and what they can do to help Planting trees can help to prevent soil erosion and drought 20 Clean... states during be swept away Therefore, when the great Dust Bowl of the 1930s a drought came and the soil became dry, winds created great clouds of dust Sometimes these dust storms blocked out the sunlight for days For this reason, this disaster is known as the American Dust Bowl The social and economic effects of the Dust Bowl drought were enormous Thousands of farmers ran out of money and had to sell...Case Study: American Dust Bowl, 1930s During the 1930s the Area affected by dust storms United States suffered from a severe and long-lasting drought Area of greatest soil erosion Dodge City that in its worst year affected 70 percent of the country The drought was centered in the Dodge Great Plains, including Kansas, City U.S Oklahoma, and northern Texas Over the years, cattle grazing and poor farming... are sick and malnourished There are many things people can do to lessen the effects of a drought If the drought has already started, one of the most important things is to conserve water Nonessential uses of water, such as for recreation, watering lawns, and washing cars, should be reduced during a drought Cities and towns may actually require their residents to stop or limit these activities People... malnutrition What did you learn? 1 How can a region’s climate make it more likely to suffer from droughts? 2 If seasonal rains are important for crops to grow in a certain country and those rains don’t happen for two years in a row, what may happen to the people of that country? 3 Why do some scientists think that droughts will happen more often in the future? a lack of some important nutrients in the diet... (Bkgd) individuals are living in an area 4 El Niño brings rain to normally dry regions, causes drought in others, and causes extreme weather around the world Write to explain some of the effects of El Niño Use examples from the book to support your answers 5 Draw Conclusions Why should water be conserved when a drought has already started? overpopulation Opener: A Ishokon/UNEP/Peter Arnold, Inc.; 1 Anthony . book you will read about a weather condition called drought. You will learn how droughts affect environments and people. area affected by drought, Botswana 3 13939_05-28_FSD.indd 313939_05-28_FSD.indd. or even years. Drought is actually a normal part of climate and can occur anywhere on Earth, from deserts to rain forests. Depending upon its location, length, and severity, drought can have. provide food for drought sufferers. 5 13939_05-28_FSD.indd 513939_05-28_FSD.indd 5 5/10/05 2:16:06 PM5/10/05 2:16:06 PM Why do droughts happen? Scientists have found that droughts are usually