You might not think that something such as soil could ever be in danger. After all, the soil itself isn’t alive. It can’t get burned or ripped up. But, as you’ve learned, soil contains living organisms and nutrients and is a vital part of the web of life. It is possible to put soil in danger.
WHERE DID THE SOIL GO?
We’ve learned about soil erosion. This is when the top layers of soil are washed or blown away by wind or water. Erosion is a major danger to soil that can be caused by the actions of people. Do you remember the Dust Bowl?
ESSENTIAL QUESTION
How important is soil as a natural resource?
You know that plant roots help hold soil in place. If people remove all the trees and other plants from an area, the soil isn’t held in place anymore. The more exposed the soil, the more likely it is to be carried off by wind and water. Are there a lot of storms where you live? Those storms could hurt the soil.
When soil erodes, that area loses most of its nutrient-rich layer. People who try to plant anything there won’t have much luck because the quality of the soil won’t be good anymore.
WHY DID THE FARMER PLANT LIGHT BULBS?
He wanted to grow a power plant!
EASTER ISLAND
You may have heard about the enormous rock statues on Easter Island in the South Pacific. Some scientists and historians believe that the people of Easter Island caused erosion problems for themselves. They cut down the few trees that were on the island and overworked the land. Because of significant erosion, the inhabitants couldn’t plant enough crops to survive. Half of the native plants died out because they couldn’t grow any more.
You can see pictures of Easter Island here. Does it look like a good place for farming?
KEYWORD PROMPTS
Easter Island Britannica 
With erosion comes another problem, called runoff. Because the quality of eroded soil is so poor, farmers might add artificial fertilizers and pesticides to try to help their crops. But when it rains, some of those chemicals get swept away, along with the soil, into the water table.
This leads to water pollution that affects drinking water and the ecosystems of lakes and wetlands. Fish and wildlife can get sick and die.
With erosion, there is also an increased danger of flooding. When it rains and there’s no soil to soak up and filter the water, the water often ends up rushing into rivers and overflowing the banks.
WORDS to KNOW
runoff: when fertilizers and pesticides leach out of the soil and into the water system.
fertilizer: any substance put on land to help crops grow better.
ecosystem: a community of living and nonliving things and their environment. Living things are plants, animals, and insects. Nonliving things are soil, rocks, and water.
NO DUMPING!
Another threat to soil is contamination. That’s when manmade chemicals or other pollutants get into the soil. This upsets the balance of nutrients and organisms there. Soil contamination can happen at factories and farms or when people dispose of certain kinds of waste by dumping it on the ground. Using containers that aren’t able to hold waste properly also contaminates the soil.
Not only can plants get sick and die from soil contamination, people are affected by it, too. Do you remember the water table? It’s below the layers of soil. As contaminants move downward, they can end up in our drinking water, which makes people sick. Contaminants often don’t break down quickly, so they stay in the environment for a very, very long time.
WASHED UP
So what does it all mean? Why should we be concerned about the dangers to soil? If the soil is destroyed, our ability to grow food for ourselves becomes limited. After all, if you don’t have healthy soil, you can’t plant crops! There are more than 7 billion people on the planet relying on soil for food.
Many scientists also warn that the loss of topsoil contributes to global warming and climate change. Global warming is the slow rise in the planet’s average temperature. This happens partly because fewer plants growing means that less carbon dioxide is absorbed from the atmosphere. More carbon dioxide traps more heat. Just like in a greenhouse, the surface air gets warmer because of all that trapped heat. Higher global temperatures change the climate.
Soil might be in danger from human actions, but there is plenty that you can do to help make sure it stays healthy! Learn what you can do in the next chapter.
ESSENTIAL QUESTION
Now it’s time to consider and discuss the Essential Question: How important is soil as a natural resource?
SOIL RUNOFF EXPLORATION
This project requires you to grow some plants in advance, but it’s a fantastic way to really see the effects of soil runoff. Be sure to have an adult help you with the cutting!
SUPPLIES
scissors
3 plastic milk jugs
3 plastic water bottles
wooden board long enough to hold the milk jugs side by side
books or rolled-up towels
soil
grass seed
water
rocks and leaf litter
string
1 Lay each plastic milk jug on its side and have an adult cut a section away as shown below. Have an adult cut the plastic water bottles in half across the middle, so the top with the cap is in one piece.
2 Take one jug and fill it with soil. Plant plenty of grass seed in it and cover the seed with a layer of soil according to the directions on the package. Put this in a sunny place and water every day or two until you have a full container of growing grass.
3 Put the board in a sunny place and prop it at an angle using the books or rolled towels underneath. You want the higher side of the board near the window, so it tilts away from the sun.
4 Put the milk jugs on their sides on the board with the open cut side facing up and the spout open pointing slightly down.
5 Use the string to tie the tops of the water bottles so they hang just beneath the spouts of each jug. Any runoff is going to drip into these water bottle tops, so be sure they’re lined up right! You might want to put an old rag or towel on the floor underneath in case there’s any splashing.
6 Now you need to prepare the remaining two jugs. The first jug will already have the grass you planted. In the second jug, add a mixture of soil, rocks, and leaf litter. In the last jug, just put plain soil. You’ll end up with three jugs: One with grass, one with a mixture of material, and one with plain soil.
7 Each day, water the containers. Make sure to pour the water in one spot every time, toward the back, away from each milk jug’s spout.
WHAT’S HAPPENING? Watch what happens through time. Look at the color of the water in each of the small water bottles. Which one is clearest? Why? What’s the difference between the jug with the growing grass and the one with bare soil? You can see how much more material ends up in the water bottle without anything to anchor the soil.
EROSION STUDY
In nature, wind and rain contribute to erosion. Even the ice in glaciers push the earth around! With this experiment, you can see for yourself the impact of the weather on erosion. Start a scientific method worksheet.
SUPPLIES
3 shallow pans or trays
books or folded towels
soil
spray bottle with water
straw
ice cube
science journal and pencil
1 Prop one end of each tray up slightly with the books or folded towels. Pile some slightly damp soil at the end of each tray. Form each pile into a little mound, making sure they’re all the same height.
2 Use the spray bottle to squirt one pile with water five times. Using the straw, blow puffs of air on the second pile five times. Slide the ice cube down the third pile five times using a pencil or your finger.
3 What happened to each pile? Is one more affected by “erosion”? Repeat all the steps again and record the results in your science journal. Does one erosion method work faster than another?
4 Keep repeating the steps until you’ve eroded most of the soil in the pans. Notice which pan eroded fastest and which the slowest.
TRY THIS! Find places in your own community that have been impacted by soil erosion. What are people doing to try to stop the erosion? Sometimes little walls or barriers can help keep the soil in place or planting trees or bushes can help keep the soil from eroding.