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Could you survive the tropics? Lost in the jungle? Discover how to hang on until help arrives.

Finally, it's summer! And your stellar family trip to the tropics has arrived. You decide to bike up the mountain near the lodge where you're vacationing. But a few hours later, you're deep within the jungle--lost. Can you survive this tropical wilderness until help arrives?

ENERGY DRAIN

A trek through twisty vines and leafy shrubs can take a toll on your body. "You sweat profusely in a tropical forest," says Richard Primack, a biologist at Boston University. Those bullets of sweat signal that your metabolic rate (how fast your body uses energy to function) has spiked, causing your body to heat up. One reason: "If you're hiking in the jungle, your energy requirements go up because of the physical activity. You could easily expend an additional 75 to 100 calories (units of energy) for every mile you walk," says Chris Melby, a nutrition scientist at Colorado State University.

Since most calories come from food, this is no time to start a diet.

JUNGLE FARE

What's on the menu? In the tropics, there's no lack of plants to eat. "It's one of the most productive environments, for one because it's warmer and very humid, so plants grow faster and more lushly," says Primack. But if you're looking for something with more protein, look no farther than the creepy-crawlies scuttling around you. "Nutritionally, insects are an amazing source of food. They're mostly protein, with a little fat," says Tim Smith, an outdoor guide for Jack Mountain Bushcraft and Guide Service in Maine. (He warns though that some insects can be poisonous. Avoid brightly colored insects, which are usually toxic. Their flashy coats keep away hungry predators--including you.)

Don't feel like eating your insects raw? Cook them on a steam pit. They'll taste like salty potato chips, says Smith. Dig a shallow area out of the forest floor and spread twigs over it. Then pile rocks on top. No matches? Use your eyeglasses to focus the sun's rays onto the twigs. In minutes, the sun's heat should spark a fire (chemical reaction between oxygen and fuel). When the twigs burn up, the sizzling-hot rocks will fall into the pit, Place an upright stick in the middle. This will become a heat vent.

Cover the pit with a thick layer of banana leaves to trap the heat. Also, wrap some leaves around your plump insects or fruits, like "hot pockets." Cover the bundles of food with dirt, then pull out the stick. Pour a little water into the hole and--poof--steam (vapor formed from heated water) will pour from the chimney. That's because convection (movement of heat in a liquid or gas) transfers the rocks' heat to the water. When the water reaches a blazing 100[degrees]C (212[degrees]F), it will boil--turn to steam. In just a few hours, you'll have a well-cooked snack.

SLIP 'N SLIDE

You'd better down those steamed insects fast, because in a snap the sunny tropics may turn stormy and violent. Some tropical forests get soaked with up to 10 meters (400 inches) of rain in a year--nearly the height of a four-story building, says Bruce Albrecht, a meteorologist at the University of Miami.

That much rain can do more than drench your clothes. During heavy storms, bucketfuls of water work their way into Earth's surface, loosening soil particles. Then gravity (pull toward Earth's center) takes over. "The surface soil can begin to slide downhill," explains Gerald Wieczorek of the U.S. Geological Survey. Called a mudflow, the wet soil sweeps downhill and picks up everything in its path, including people, he says.

CLOUD WATCH

What can you do to keep from taking an unwanted mud bath? Watching for signs of rain will give you time to seek safety far from mudflow-prone slopes. Without the weather channel, you'll need to become your own meteorologist. "If you look for the development of certain clouds, you can predict an afternoon rainstorm," says Albrecht.

What to watch for: When a thunderstorm is coming, bright, puffy fair-weather clouds will build up into a heaping tower. The cloud's Cool Whip color will turn a charcoal gray. These are known as cumulonimbus, or thunderstorm, clouds. "The clouds get darker as they become thicker because sunlight can't penetrate them," explains Albrecht.

If you suspect a coming storm, Wieczorek says: "You wouldn't want to be near the steep edge of a hillside." The steeper the slope, the less force (push or pull) it takes to unglue the surface soil and send it sliding downhill. Another place to avoid is a channel carved by erosion (wearing away of a substance) from a past mudflow. These areas are more likely to experience another muddy event, Wieczorek says.

OFF COURSE

Now that you've braved the elements, it's time to map a course back to your hut. Normally, the rising sun could tell you which way is east. But, Primack says, "It's very easy to get lost in [some] tropical forests, because they're hilly, so you can't see the sun for part of the day." And don't expect to find any landmarks dotting your path--according to Primack, everything around you looks like a mix of leaf green and tree-trunk brown.

OPPOSITES ATTRACT

How to navigate? "When I'm in a tropical forest, I always carry a compass [a device with a needle that points north]," says Primack. As the Earth spins around on its axis (imaginary line around which an object turns), an ocean of heated iron in the planet's core swirls around. This forms an electric current (flow of electrons)--and in turn creates a magnetic field. The field is like a giant magnet (substance that attracts iron and some other metals) jammed through Earth's center, with a north and south end. The ends of Earth's magnet tug at a compass needle.

Since you don't have a compass handy, make your own navigating device: Remove the metal pin from a souvenir button, and rub it in one direction with a silk scarf. The friction between the scarf and the pin sparks an electric charge--turning the pin into a magnet.

To figure out which way is north, float the needle on a blade of grass inside your water bottle. Since opposite poles attract, your needle will spin until it lines up with Earth's magnetic field--pointing in a north-south direction.

SENDING SIGNALS

Look--an airplane is flying overhead! Signaling for help could be a lifesaver. One option: Flash beams of light at the plane using the sun and something shiny. Your Beyonce CD should do the trick. Hold it up to the sun and peek through the hole. Now, maneuver it so sunlight reflects (bounces) off the mirror side of the CD toward the aircraft. Good thing you spied the plane. Now you can get back to the sun and fun of your tropical vacation!

IT'S YOUR Choice

1 Why would you need a lot of food during a long hike in the jungle?

A. So you don't get dehydrated.

B. You store more calories when you sweat.

C. Your body's metabolic rate would increase.

D. Jungle animals steal food.

2 Why do clouds look darker before a storm?

A. They get thicker and the sun can't penetrate them.

B. Dirt particles collect inside.

C. They're higher in the sky and harder to see.

D. They are thinner.

3 The rocks in a steam pit

A. help keep the food from getting muddy.

B. trap heat and transfer it to the water to make steam.

C. hold in water to keep the food moist.

D. get so hot that they char the cooking food.

4 All of the following are true about a mudflow, EXCEPT:

A. It takes less force to sweep soils down a steep hillside.

B. Heavy rainfall can trigger a mudflow.

C. A mudflow can carve a channel in the soil.

D. Mudflows never happen In the same place twice.

ANSWER

1. c 2. a 3. b 4. d

Cross-Curricular Connection:

Health/Math: Research how physical activity increases your metabolic rate. Then, calculate the number of extra calories you'd need for a half-day hike through a hilly tropical area. Make a list of some possible food items that would be important to bring with you on this trek. For information to help you calculate the extra calories, visit this Tufts University Web site: http://nutrition.tufts.edu/news/matters/2001-11-19.html

Critical Thinking: Tropical forests teem with plants and animals. What causes such high biodiversity in the tropics? Here's a helpful Web site to find out: www.szgdocent.org/ff/f-rain1.htm

Did You Know?

* Clouds are made up of water droplets. When the droplets get big enough, rain falls. Since cumulonimbus clouds can build into heaping towers high in the atmosphere, instead of water droplets, these clouds can be made of pure ice crystals. But that doesn't mean an ice shower. Meteorologist Bruce Albrecht of the University of Miami explains: When the ice crystals fall in tropical latitudes, the warm climate heats the ice crystals to form rain.

* Insects can contain more protein than the same weight of steak. Whereas a steak is about 15 percent protein, many insects are made of 50 percent protein, says Gary Hevel of the Smithsonian Institution's National Museum of Natural History.

CORRECTION: According to Tim Smith, outdoor guide for Jack Mountain Bushcraft and Guide Service, insects would only taste like salty potato chips if fried. If they were steamed, like in the article, the insects would be gooey and mushy.

Resources

For a fun and in-depth guide to outdoor survival, read The Complete Wilderness Training Book by Hugh McManners, DK Publishing, Inc., 1994.

Check out this Web site to find out more about different types of clouds--even how much these rainmakers weigh: www.usatoday.com/weather/wcloud0.htm

Visit the University of Kentucky Department of Entomology's Web site to learn more about bug eating: www.uky.edu/Agriculture/Entomology/ythfacts/entyouth.htm

CHECK FOR UNDERSTANDING

Directions: Match the word(s) in the left column with the correct phrase in the right column.
-- 1. fire a. how fast your body uses energy
 to function

-- 2. reflects b. wearing away of a substance

-- 3. heliograph c. chemical reaction between oxygen
 and fuel

-- 4. biodiversity d. number of different plants and
 animals

-- 5. mudflow e. flow of electrons

-- 6. erosion f. wet soil sweeping down a slope

-- 7. metabolic rate g. vapor formed from heated water

-- 8. cumulonimbus h. bounces

-- 9. electric current i. device for sending messages by using
 sunlight

-- 10. steam j. type of thunderstorm cloud


ANSWERS

1. c 2. h 3. i 4. d 5. f 6. b 7. a 8. j 9. e 10. g
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Title Annotation:Earth: ecosystems
Author:Bryner, Jeanna
Publication:Science World
Date:May 10, 2004
Words:1773
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