Chapter 10 Soil Erosion, Leaching, and Pollution 241 Copyright Goodheart-Willcox Co., Inc. Plants and Erosion Control Conserving soil is a vital component of sustainable farming. Soil that is blown or washed from fields carries away important nutrients that plants need to grow. Some of this soil is deposited in waterways, causing negative impacts on the water and aquatic life. The following experiment illustrates the important role that plants play in erosion control. Materials • 6 plastic soda bottles (1-liter) • Compost for mixing with soil for two bottles • Hole punch • Mulch for covering the soil in one bottle • Permanent marker • Plants for one container • Scissors or knife to cut plastic • Soil (enough to be 6 cm deep in each container) • String • Water • Wood glue • Flat surface that can be lifted on one end, such as a piece of plywood wide enough and long enough to hold all three bottles. Glue the bottles to the wood surface for stability. If plywood is not available, set the bottles up on an available surface so they are stable and elevated at one end. Procedure Goodheart-Willcox Publisherr Cut along dashed lines Remove cap andd leave uncovered 1. Draw 3″ × 10″ rectangles on the side of 3 plastic bottles. Cut the rectangular openings. 2. Glue the bottles to the plywood with the necks hanging over one edge. Discard the bottle caps. STEM Connection 3. Fill the first container with soil and the second and third with a soil and compost mixture. Firmly press the soil into the container. 4. Cover the soil in the second bottle with mulch. 5. Install the plants in the third bottle. Plants should be placed tightly together and the soil should be pressed firmly into the bottle. For best results, allow 7 to 10 days for the plants to take root. 6. Cut the other three bottles in half (horizontally) and keep the bottom halves. 7. Use the hole punch to make two holes (on opposite sides) in each of the bottle bottoms. 8. Cut three pieces of string and feed the string through each hole to make a handle. Make a knot on each end of the string to keep it from sliding through the hole. 9. Hang the bottoms over the necks of the bottles that are glued to the board. These buckets will the water from each of the bottles. 10. Place a wedge under plywood at the end opposite bottlenecks to create a slight slope. 11. Pour amounts of water into each bottle at the end opposite the bottlenecks to simulate flowing water.* 12. Observe the color the water as it fills each (bottle bottoms). 13. Record your observations. 14. Repeat Step 11 each day over the course of a week and record your watering can or perforated milk jug may be used simulate rainfall. The watering can or milk jug must held high enough over to cover the entire surface of the soil at once. To the milk perforate the side opposite the handle with 3 to 6 rows of small holes. Pour the same amount of water the same height for each bottle.. Consider This 1. What type(s) of occurred, sheet, rill, or splash? 2. Would full-size or trees be more effective at holding the soil than the young plants used in the experiment? Explain your answer. 3. Try the experiment with different soil types, sandy clayey Will some be more susceptible to than 4. Does the type of plant species make a difference on how well the soil is retained?? Chapter 4 Ecology and Earth 87 Copyright Goodheart-Willcox Co., Inc. • A carbon source releases more carbon than it stores. Therefore, anything that burns fossil fuels is a carbon source. A campfi re, for example, is a carbon source. Although ash composed primarily of carbon and minerals remains on the ground, the smoke from the burning logs also contains carbon that becomes airborne and drifts into the atmosphere. Automobiles and the combustion of gasoline and diesel fuel continually release millions of tons of carbon into the atmosphere. The Energy Cycle The energy cycle is the movement of energy through the biosphere. The energy cycle involves food chains and food webs in which growing plants are consumed by animals and then larger animals eat the smaller animals. Most energy cycles back to the soil with the decomposition of dead plants and ani- mals. A food chain is a simple model of how energy fl ows from one living organism to another. Much of the trash found in a landfill is carbon. Manmade carbon sinks, such as landfills, are not as efficient or productive as natural carbon sinks. Did You Know? Can Energy Be Created or Destroyed? Energy is defined as the ability of an object to do work. This includes the capacity to produce light, heat, or a type of mechanical response. STEM Connection The law of conservation of energy states that the total energy in a closed system can neither be created nor destroyed it can only be transformed or transferred from one form to another. Fire, for example, is the conversion of chemical energy into thermal and electromagnetic energy through a chemical reaction. The chemical reaction combines the molecules in fuel with oxygen from the air to create water and carbon dioxide (CO 2 ). The energy released is in the form of heat and light. Energy is either kinetic energy or potential energy. Potential energy is untapped or unused energy. Kinetic energy is energy in motion. A yo-yo, for example, has potential energy when it is being held and kinetic energy when it is released. Consider This 1. If energy cannot be destroyed, how can we experience an energy crisis? 2. Is mass considered a form of energy? Explain your answer. 3. What is the definition of a closed system? Is Earth in a closed system? Explain your answer. VectorMine/Shutterstock.com Potential energy Potential energy Kinetic energy out Kinetic energy in o ntainer) n d, gh and lue bility. If s up on and Willcox Publishe lines ve ca p an uncovered 3 plastic h e necks ottle knot on each end of the string to keep it from slidin g throu gh the hole. 9. Han g the bottoms over the necks of the bottles that ar e glued to the board. These buckets will ccatch atch the water from each of the bottles . 10. Pl ace a we dg e un d er tthee h pl ywoo d at t h e en d opposit e tthee h bottl enec ks to create a sligh t slope . 11. Pour eequal q ual amounts of water into each bottle a t the end opp osite the bottlenecks to simulate flowing water.* 12. O bserve the color of the water as it fills each bbucket ucket ( bottle bottoms ).are 13. Re cord yo ur observations. 14. Repeat Step 11 each da y over the cour se of a wee k an d recor d y our oobservations.. bservaton ions **A A waterin g can or perforated milk ju g may be used tto o simulate rainfall. The waterin can or milk ju g must bbee held hi g h enou gstreams.eachgbottlemodifyy h over each bottle to cover the entire surface of the soil at once. To modif the mil k jjug,, u g perforate the side opposite the handle with 3 to 6 rows of small holes. Pour the same amount of water ffrom rom the same hei g ht for each bottle C onsider Thi s 1. What tySurface?erosion pe of erosion occurred, sheet, rill, ggully, ully, or splash 2. Would full-size pplants lants or trees be more effective a t holdin g the soil than the young plants used in the experiment? Explain ythroughplant our answer . 3. Tr y the experiment with different soil tto y pes, iincludingg ncludin sandy and clayey types. Will some be more susce ptible to erosion than others 4. Does the ty pe of plant species make a difference on how well the soil is retained Chapter 14 Water Quality 333 Copyright Goodheart-Willcox Co., Inc. Surface Tensionof Surface tension exists when molecules on the liquid surface strongly pulling each other. Imagine raindrops falling on a car’s wind- shield. As more water falls the raindrops on the windshield, the stress on the bonds increases and eventually the raindrops burst and fl ow together in The molecules on the water surface behave differently than the molecules below the surface. The molecules on the sur- face are not surrounded by other molecules and cohere more strongly to other molecules on the surface.(s) tension is one of water’s most impor- tant properties. The surface tension of water enables water to travel up stems or enter an organism’s cells blood vessels. Sur- face tension also enables water fl ow freely. See Figure 14-2.anderosiontypes.others?? Surface Tension In this simple experiment, we will observe how different substances exhibit differing surface tension properties. Obtain the following materials: • Tap wateralcohol • Isopropyl (rubbing alcohol) • Liquid soap • Eyedroppers • Pennies 1. Fill the eyedropper with water. Squeeze the dropper over a penny and count the water drops. What happens as you add drops of water? How many drops of water were you able to place on the penny before the bubble burst? 2. Repeat the procedure using the alcohol. Do you get the same results? What is the chemical difference between water and isopropyl alcohol? How does the chemistry of a fluid make the surface tension different? 3. Repeat the procedure with water, but stop before the bubble bursts. Add a drop of dish soap. What happens to the water bubble? Can you explain the result? STEM Connection Consider This 1. Soap is used daily by millions of people in many applications. How might the accumulation of soap in bodies of water affect the environment and surface tension of the planet’s water as a whole? Discuss your ideas of potential impacts with your classmates. 2. Repeat the experiment using other common liquids, such as tea, soda, or carbonated water. Note the surface tension each liquid exhibits. 3. How is surface tension measured and in what instances would it be important to know the measurements? Eric Krouse/Shutterstock.com The molecules at the surface are being pulled by the molecules next to them and below them (cohesion) The attraction between other molecules (the penny) and water molecules is adhesion Pulling forces water surface into a curved shape Bonds between water molecules at surface Molecules in the middle of the water Marek Mierzejewski/Shutterstock.com Figure 14-2. This common pond skater would not be able to s it on the water if the water did not have surface tension. The divots created by hydrogen bonds from the pressure of its feet allow the insect to stay afloat. Environmental Features challenge students to think deeply about environmental issues and encourage them to apply critical thinking skills when discussing natural resources topics STEM Connection features integrate all four components of STEM education as well as the social sciences and language arts 366 Natural Resources Systems Copyright Goodheart-Willcox Co., Inc. Why Are We Losing Coral Reefs? Coral reefs are strong enough to protect our coastlines against erosion and other damage caused by strong ocean waves. They also provide habitat to a great variety of marine life to observe and catch for food. However, these complex, underwater ecosystems are also fragile and extremely susceptible to damage or death from anthropogenic (human-caused) threats. The major threats to our coral reefs include temperature changes, poor water quality, ocean acidification, unethical fishing practices, coastal development, and coral mining. Temperature Changes. The temperature of seawater is rising because of climate change. Warmer water temperatures cause the relationship between water corals and their symbiotic microalgae to break down and the coral loses its color and appears bleached. A difference of only 1° higher than the normal temperature for an extended period will kill the coral reef. Warmer water temperatures also allow disease-causing organisms that attack coral to grow faster. Poor Water Quality. Coral reefs need clean water to live and support the wetland ecosystem. Pollution from sources, such as sewage, land-based runoff, and industrial discharge, enters the waters surrounding coral reefs through point-source discharge and waterways that feed into the ocean. Some pollutants, such as fertilizer, increase the rapid growth of algae that can smother corals. Ocean Acidification. Seawater absorbs anthropogenic carbon dioxide (CO 2 ) from the atmosphere. Although the oceans naturally absorb carbon dioxide, the higher levels of CO 2 absorption are making the water more acidic. This is especially harmful to calcifying organisms, such as coral reefs, clams, oysters, and crabs. The excessive amount of CO 2 prevents the exoskeletons from absorbing sufficient carbonate from the water, causing the exoskeletons to weaken. Unethical Fishing Practices. Unethical fishing practices, such as blast fishing with dynamite, cyanide fishing, and deepwater trawling cause physical damage to coral reefs and contaminate the surrounding water. Overfishing diminishes species and causes an imbalance in the food chain, which causes other organisms to overpopulate or die due to lack of food. Marine Ecosystems Coastal Development. Construction along coastlines and inland increases the amount of sediment that flows to the ocean. This sediment clouds the water, which deprives the coral of sunlight, and often contaminates the water with runoff pollutants. The destruction of other coastal wetlands, such as mangrove forests, also allows more sediment to reach the coral reefs. Coral Mining. Corals are harvested for use in aquariums, sold as souvenirs, and even for use as bricks or road fill. The removal of reef fishes and other reef life for aquariums also endangers coral reefs. Other threats include changes in salinity, outbreaks of predatory species, introduction of invasive species, leaking fuels, abandoned fishing nets, and careless boating, diving, and snorkeling. Many natural diseases become deadly to coral reefs because the cumulative effect of threats weakens a coral reef’s natural ability to recover. It is estimated that 25% of our coral reefs have been destroyed and two-thirds of the remaining coral reefs are threatened. The death of a coral reef is not just the death of one animal or one plant, it is the death of an entire ecosystem. Keep in mind that all of our actions, no matter how small, can contribute to coral reef destruction or help protect coral reef wetlands. Consider This 1. Which of the threats to coral reefs indicated in the summary would be the most practical to counteract? How would you propose repairing the situation? 2. How does the loss of coral reefs affect humans and the wildlife that depends on the coral? Rich Carey/Shutterstock.com Chapter 6 Habitat Destruction 147 Copyright Goodheart-Willcox Co., Inc. Tropical Rain Forest Biome Tropical rain forest biomes exist in areas with annual rainfalls of at least 100″ (254 cm) and temperatures averaging around 80 °F (27°C). Today, tropical rain forests cover about 6% of Earth’s total land surface and contrib- ute greatly to global air quality. The Amazon rain forest alone is responsible for nearly 20% of the oxygen turnover on the planet. Habitat degradation is caused primarily by humans clearing land for raising livestock and plant- ing crops. The continued loss of forest in this biome will signifi cantly affect global air quality. The continued destruction of this habitat is also one of the greatest threats to nearly half the plant and animal species on Earth. Steppe Biome A steppe biome may be described between a forest and a des- ert. Steppes are semiarid and receive 10″astohalfway 20″ (25.4 cm to 51 cm) of rain annu- ally. The average temperature range is between 70°F and –4°F (21°C and –20°C). In the United States, the steppe region ranges from the Great Plains to Canada. This biome is typically treeless prairie or grasslands that experience seasonal changes. It is common for this biome to experience extreme temperatures in both the summer and winter. The actions of human beings are the greatest cause of habitat degradation. The black-footed ferret and its population decline is an example of a species nearly driven to extinction by habitat loss and deg- radation. The ferrets feed primarily on prairie dogs whose numbers decreased as land was plowed and homes were built. Rain forests once covered 14% of Earth’s land surface but currently cover approximately only 7% of Earth’s dry land surface. Did You Know? Rabbits and Habitat Degradation The introduction of rabbits in 1859 as hunting game in Australia is a prime example of degradation caused by human beings. The rabbit population quickly grew from 24 rabbits into millions of rabbits . It is said to be the fastest spread of an invasive species ever recorded. As an invasive species, the rabbits had few natural predators and quickly decimated natural grasses and other wildlife food sources. Many control measures have been applied but there has been little success. To this day, rabbits remain a problem in Australia by consuming crops and contributing to soil erosion. Consider This 1. What measures have been taken to reduce the rabbit population? 2. How could these measures be more effective? Invasive Species Lakeview Images/Shutterstock.com Guided Tour