Save
the Trees, PleaseSave
the Trees, Please
Lesson
Plan
Overview
There
has been much debate in recent years regarding the rapid pace at which forests
of the Earth are disappearing.
Widespread deforestation in places like the Amazon rain forest,
southeast Asia, Africa, and even the Pacific Northwest of the United States
continues to have a large impact on the Earth's systems. Yet human beings
across the world use forests for many reasons as they often harvest wood as a
means for survival, or for economic development and stability. How do
scientists help us understand this delicate balance between sustaining
resources of the Earth over the long term, and providing for human needs over
the short term? In this 4-part
lesson, students will explore the impact of deforestation on the Earth. Satellite imagery is used to show the
vast devastation that humans have inflicted upon the Earth - the loss of
forests and its impact on animal habitat, erosion, and sediment flow in oceans
and rivers, etc. Students are
encouraged to examine the role that humans play in deforestation (and
reforestation), as well as the way that forests provide important resources for
humans.
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Suggested Lesson Sequence |
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Assessment
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Materials
There are four
individual lessons within "Save the Trees," each requiring its own
activity sheet:
Vocabulary
Note
During this lesson, students will read passages of
text on the activity sheets. Students
may be unfamiliar with some of the vocabulary presented in this lesson. This is done intentionally, to build
reading skills and to spur additional conversations and discussion about these
words and their meanings.
Encourage your students to ask about (or look up the meanings of) words
they may be unfamiliar with that occur in the readings.
Background Information for Teachers
There has been
much debate in recent years regarding the rapid pace at which forests of the Earth
are disappearing. Widespread
deforestation in places like the Amazon rain forest, southeast Asia, and even
the Pacific Northwest of the United States significantly impacts the Earth's
systems. Deforestation greatly
affects surrounding ecosystems. It
alters the habitat of many animals that depend on trees for survival, it can
lead to erosion of soil that then clogs up rivers with sediment, and it can
destroy plant species that cannot survive outside the protection of the
forest.
Equally
importantly, trees are essential for life as they absorb carbon dioxide (a "greenhouse" gas that can affect climate), emit oxygen, and are a primary agent
in sustaining the water cycle. In
fact, the burning that accompanies tropical deforestation is estimated to
annually release 15-50% of the amount of carbon dioxide released in the burning
of fossil fuels. Sustainable
management of the forests of the Earth, therefore, is not only critical for the
health of plants and animals, but for humans as well.
Yet, on the other
hand, human beings throughout the world use forests for many reasons such as
harvesting wood as a means for survival, or for economic development and
stability. Science is being looked upon as a way to help us understand this
delicate balance between sustaining resources of the Earth over the long term,
and providing for day-to-day human needs.
Save the Trees,
Please and other ESC
lessons (e.g. Plants and the Water
Cycle and Urban
Changes) address several of these important issues, focusing in particular on
the ways that trees, and leaves in
particular, are essential for life.
The primary intent
of this lesson is to increase students' awareness of the widespread
deforestation that is occurring in various parts of the world, and the impact
it can have on the systems of the Earth.
Four series of images (from Brazil, Bolivia, Madagascar, and the Pacific
Northwest) help illustrate various instances of deforestation, and the
ecological effects of such deforestation.
Each of these themes is designed to last at least one full class period.
Discussion questions and images are found on the activity sheets that accompany
each lesson. Information
about each series as described in the notes below will help you lead
discussions about these images and what they reveal about the Earth.
Many large, color
images are used in this lesson.
Teachers may wish to project these images with the use of a computer (or
have students observe the images on a computer themselves) in order to reduce
the amount of printing necessary for these lessons, as well as to be able to
illustrate these powerful images in full color. For each lesson, an activity sheet (without images) is
provided for students to record answers.
Note:
This lesson contains content that can become controversial. This lesson tends to highlight the need
for forest conservation with respect to the ecological impact of deforestation
rather than the many reasons that forests are harvested for economic
development. Scientists are
continuing to learn that the ecological services (e.g. clean air, clean water,
pollinator diversity) of healthy ecosystems are very important to the long term
(decades or even centuries) well-being of people, and it is in this vein that
this information has been presented.
You may have families in your school community that depend on harvesting
trees for their own economic sustenance.
It is our intent in this lesson to provide ecological information about deforestation in a way that does not
cast judgment on people who have, for various reasons, harvested trees.
I.
Assessing Prior Knowledge
Begin this lesson
by asking students to brainstorm a list of all the ways that humans have used trees and forest
products throughout history. They
will generate a long list if given time.
They may not be aware of the unique ways that humans have used trees - for protection, for medicine, and even to refrigerate food as African peoples
have done for centuries. (The
Baobab tree has a huge trunk.
Caves and compartments are carved into the trunks of these trees, and
food can be safely stored as though in a cooler!)
II.
Contextual Preparation
After completing
the previous activity about ways in which humans benefit from trees, prepare
the students for this series of lessons by asking a similar question: Why are trees important for the natural
(non-human) world? How do trees
interact with the various biotic (living, e.g., plants and animals) and abiotic
(non living, e.g., water, wind, rock) elements we find on Earth? Students may struggle at first when
generating this list. Here is a
short list of ideas to generate some discussion:
-
Protection,
shade, and shelter for animals
-
Protection
for other plants
-
Food for
animals
-
Roots hold on
to soil to prevent erosion
-
Recycling
water
-
Uptake and
release of gases in the air (take up CO2, release water vapor and O2)
It is this focus
on the role of trees as a vital element of ecosystems throughout the world that
will be prevalent in this series of lesson activities.
III.
Student Activities
Lesson One: The Amazon Rain Forest
This lesson
introduces the notion of deforestation by looking at satellite images of the
Brazilian rain forest. Distribute
the Amazon Rainforest Activity Sheet. This activity sheet is self-guiding, and answers to
the questions are provided below. Teachers may wish to project the images on
this activity sheet, or allow students to see pictures on a computer screen and
record their answers on the activity sheet. It is important
that teachers read the following information before beginning this lesson with
students. Teachers may wish to use the information below as in introduction to
this activity, and to the Amazon region of Brazil in general.
Teacher Background Information and Discussion Topics:
In these images, one can observe the vast impact of deforestation in an
area of a Brazilian portion of the Amazon Rain Forest. It is important to help the students
understand what they are seeing in the images. First, in the satellite image, red in the image corresponds
to green on the ground. Hence, the
darker the red observed in the image, the darker the green would be if we were
observing this land with the naked eye. (This has to do with how some
satellites use infrared wavelengths to capture imagery. The colors are then projected on the
screen differently from how our eyes can detect colors.) Likewise, the lighter colors
(blue/gray) indicate a lack of green -
i.e., deforested regions. In the
first image, one can see roads, a river, and a small village as depicted by the
gray/white colors. In the
corresponding image 17 years later, the spread of the gray/white colors is
quite evident. This grid of lines
illustrates the deforestation taking place in the forest. This particular pattern illustrates
what is called a "Herring Bone" logging practice, where one road (which can be
seen in the 1975 image) is used as a main thoroughfare from which many
additional perpendicular roads originate.
Students can observe the vast deforestation that has taken place in this
region over 17 years by comparing the increase in the gray/white areas.
It is important to
recognize that humans have harvested trees in the rain forest for a number of
reasons, many of which are linked to their very survival. Logging timber is a form of income for
many individuals, whether that means selling the logs for lumber, or clearing
land to raise cash crops or herd cattle.
Because the reasons for deforestation are varied, it is also important
to realize that not all tropical deforestation is carried out in the same
way. For example, lumber companies
often carry out "selective harvests" where the most desirable species of trees
are sought and individually cut for their highly valuable wood, prized for
building fine furniture or strong structures. Other non-selective logging also occurs where many more
species are cut for general lumber production. Agriculture here has traditionally been small homesteads in
the forest, where people established
vegetable/fruit gardens and small woodlots for their own sustenance. But increasingly,
individuals,
small communities, and large corporations have begun to practice "slash and burn" clearing where all trees in the forest are cut, left to dry in the hot
tropical sun, and then burned in order to clear the land for crops and
grazing.
Clearcutting of
forests in tropical ecosystems, in many locations, leads to an unstable
landscape and high-risk agriculture.
In general, tropical soils are quite poor in nutrients due to high
amounts of rainfall that washes nutrients out of the soil through a process
called leaching. Scientists have learned that the
nutrients contained within leaves of tropical trees are almost immediately
taken up by the roots when the leaves fall. When trees are clearcut and burned for agricultural
purposes, often the resultant field can sustain crop agriculture for fewer than
5 years, after which time the land is converted to less productive
pasture. After pasture land is
finally abandoned, the re-growing vegetation is vastly different from the
original forest type that occurred because the soils are so depleted in
nutrients. (It should be noted,
however, that due to climate and soil type differences, in most temperate
forest ecosystems soil productivity does not decline in the same way as in
tropical soils following clear-cuts.)
Sample Responses for Amazon Rainforest Questions
1.
What kinds of plants and animals do you think you would find in a forest
like this?
Answers will vary. As the photograph illustrates, vegetation
in this
ecosystem is quite thick.
Thousands of plant, animal, and insect species live in forest regions
such as the one captured in this photograph.
2. What are the main differences you can
see between this image and the first satellite image? What could those white lines be?
Answers will vary. Students should notice an increase in
the blue color (i.e., deforestation) both in terms of lines (roads) and various
shapes (clear-cuts or villages), the pattern of deforestation (parallel lines),
or other general observations.
3.
The road ends at a large river.
What do you think might happen to the logs after the truck drops them off
at the end of the road?
The logs are floated to
lumber mills where they are processed for various purposes.
4. What colors do you see in the
stump? How do you think it became
colored in this way?
This tree stump is discolored
and blackened because it was burned.
This is an example of the effects of "slash-and-burn" practices.
5. Those stumps we saw earlier were
burned! What are some reasons that
a person might want to cut down a forest and clear the land by burning it?
To create open space for planting
crops or raising livestock.
6.
What are the pros and cons of using this wood for furniture?
Answers will vary. The wood provides for beautiful and
sturdy furniture, yet it also depletes the forests of the trees that are vital
to the ecosystem.
7. a) What do you now see in this field
that wasn't there before?
Grazing animals
b) What do you think this field is being used
for now that the forest has been cleared?
Cows are grazing on the
field.
c)
Do you think
that there are more or fewer kinds of plants located on the land now compared
to when the land was a forest?
Far fewer plants.
d) Do you think there are more or fewer
animals that use this land now, compared to when the land was a forest? Why?
Far fewer animals use this
landscape. There is far less plant
growth for food, shelter, shade, etc., that animals need.
Distribute the Deforest
Bolivia Activity Sheet, and the Area Investigation Activity Sheet. The activity sheet is self-guided. Teachers
may wish to project the images on this activity sheet, or allow students to see
pictures on a computer screen and record their answers on the activity
sheet. Answers to the questions on
the activity sheets are provided below.
Teacher Background Information and discussion topics:
As noted in the
activity sheet, these images illustrate a relatively new, governmentally
sponsored relocation project in Bolivia.
These small communities have been carved into the Bolivian forests and
designed to provide both a place and a means for Bolivian citizens to live in
relative stability.
Sample Responses for Deforestation in Bolivia Questions
1. What objects or features on the land
can you identify in this picture?
Students may
identify trees, roads, fields, buildings, etc.
2. Make an estimate - How
big is the area captured in this image?
That is, how many kilometers wide do you think this image is from side
to side?
Answers
will vary. Encourage students to
elaborate on how they made their estimates. They
should use informal reasoning and clues from the image to help them think about
the size of the region of land. It
is not necessary for students to have an exact answer, or even an answer that
is close to accurate. Rather, the
intent of this question is to encourage students to use their intuitions as
they become more familiar with the breadth and depth of these images.
3. Why do you
think they chose to cut into the forest in a circular pattern?
If given a
fixed perimeter, a circular region will allow for the greatest area. Hence, expanding in a circular fashion
affords them the most land while at the same time minimizing the distance
between the outside edge of the border to the center of the circle (i.e., the
village).
4. What can you identify in this picture of a Bolivian
community?
Similar to #1: roads, trees, plants, fields, soil,
roads, buildings, etc.
5. There are a number of straight lines that seem to start at
the center of the image and extend out like a radius of a circle. What
might these lines be?
Answers will
vary: roads, paths, field
dividers, irrigation canals.
6. The image reveals smaller, rectangular plots of land within
the circles. What do you think the
people are doing with these small plots of
land?
Answers will vary: Growing crops, grazing cattle or sheep
or goats, etc.
7. Do you think windbreaks are necessary to keep the topsoil
in the forested regions adjacent to
the rectangular fields from blowing away?
Why or why not?
No,
the soil is protected from wind by the many trees and plants in the
undergrowth. The soil also clings
to the roots of small plants and trees.
8. What might trees have to do with preventing erosion?
Their roots help protect soil
from the forces of erosion.
Area
investigation: This activity provides a rich context
for students to explore notions of area and perimeter. As students look at
these images, it might be a good opportunity to ask questions related to the
mathematical tools that might be employed by scientists to determine exactly
what percentage of the world's forests are being cut. Specifically, using area concepts, students might be able to
draw comparisons between the amount of clear-cut land, and naturally forested
(or reforested) regions in this image.
On
the Area Investigation Activity Sheet, a grid has been placed over the
enlarged image. You may also wish
to give the students various manipulatives including string, cubes, tracing
paper, overhead transparencies and pens, etc., for those students who would be
challenged to find the areas using other strategies. The most direct way to calculate the area is to count
squares and record those that are completely forested, deforested, and
partially deforested. Students
will need to do some estimating and combining of the partial squares in order
to come to a final estimation.
This approximation activity is an excellent opportunity to develop both
spatial sense and estimation skills.
Allow students to share both their solutions and their solution
strategies.
Distribute the Red
Island Activity Sheet. This
activity sheet is self-guided.
Teachers may wish to project the images on this activity sheet, or allow
students to see pictures on a computer screen and record their answers on the
activity sheet. Answers to the
questions follow below.
Teacher Information and Discussion Topics:
Students should notice the portions of the island that have been
deforested (as evidenced by the visible red soil), as well as the red sediment in
the ocean that surrounds portions of the island after having been washed away
via river flow. As explored in the
lesson entitled Hold on
Tight, the root
systems of plants and trees are vital to preventing the erosion of soil. On the Island of Madagascar, heavy
deforestation has resulted in the loss of millions of cubic meters of soil into
the drainage systems of the island and, ultimately, the ocean.
Sample responses for The Red Ring questions
1. Describe the close-up image of Madagascar
(above) in as much detail as possible.
What do you see?
Answers will vary. Students should identify the forested
and deforested regions of the island, as well as differences in the coasts on
respective sides of the island.
2.
There are some notable differences between the two sides of the island
in the circled area. Describe
those differences.
Answers will vary, and may
overlap with answers from question 1.
3.
In the circled portion of the image, there appears to be a green section
of land on the island. Describe the
color of the ocean water near this green section of the island.
The water is dark blue.
4.
How is the water along the coasts on the red side of the island
different than on the green side?
The water is dark blue on the
green side of the island, and has red/yellow tones on the other side.
5.
What might cause this difference in the color of the water?
Answers may vary. Hopefully students recognize that the
forested side of the island does not have visible sediment in the ocean. Help students make the connection
between deforestation, erosion, and sediment in the water.
6.
It is clear
to see that a lot of red sand or dirt is being washed into the ocean
water. Another name that
scientists use to describe this soil or dirt is sediment. Where do you
think this red sediment in the water came from, and how did it get to the
ocean?
Topsoil from the interior of
the island. It was carried by
rivers and streams to the ocean.
7. What might trees have to do with the
red ocean water?
Answers may vary. Soil tends
to cling to root systems of plants.
8. To be able to see such clear evidence of
sediment in the ocean water from a satellite (600 kilometers above the Earth!)
indicates that thousands and thousands of tons of topsoil have washed off the
island. One of the sad things
about the deforestation in Madagascar is that the topsoil that is now in the
ocean can no longer support life on land.
How are plants and animals affected if there is no topsoil?
Plants cannot grow well without
topsoil. Animals depend on plants
for shelter, food, and shade.
Also, streams and rivers clogged with sediment can lessen water supply
for animals.
Distribute
the Deforest-Reforest Activity Sheet. This activity sheet is self-guided. Teachers may wish to
project the images on this activity sheet, or allow students to see pictures on
a computer screen and record their answers on the activity sheet. After students work through the photos
and questions on this activity sheet, distribute the Deforest Reforest
Questions worksheet. The
questions on this sheet refer to the pictures and images in the activity
sheet. Answers to these questions
follow below.
Teacher
Information and Discussion Topics: This series again raises questions of
deforestation, and includes photographs from hand-held cameras as well. An important contribution of this
sequence is the notion of reforestation. As suggested in the activity sheet,
forests can grow back both by natural means, as well as with the assistance of
humans.
This
sequence of images and questions encourages students to think again about loss of habitat that accompanies
deforestation, and the ways that it may impact animals with respect to loss of
food sources, loss of shade and protection, loss of nests and dens, etc. With these ideas in mind, then, it is
important to illustrate the positive benefits of reforestation. Even if the trees that are planted do
not replace the old growth forests in terms of their size and stature, they do provide
habitat for animals.
Initiating
Discussion with Students
There
are several general discussion questions interspersed among the opening images
of this sequence. These points for
discussion have been underlined on the activity sheet. Engage students in these questions as
preparation for the more formal questions that will follow. Encourage students
to discuss their opinions and hypotheses with each other as they continue to
build their understandings of deforestation. For the first discussion topic, they should notice that the
forests within the Olympic National Park have been protected unlike those in
surrounding areas. Teachers should
also discuss the idea of forest fragmentation
to the children. When forests are
fragmented (clear cut in some areas and not others), the habitats of animals
and other plants in the ecosystem is greatly altered.
Sample responses for the Deforestation/Reforestation Questions
1.
Answers will vary.
2a.
Birds, deer, elk, bear, ground squirrels, etc.
2b.
Loss of habitat, food sources, protection, nests, etc.
2c.
More sunlight available, exposed to animals, erosion of soil that
supports root systems, drying of soil, etc.
3.
Answers will vary. Examples
might include: loss of habitat,
loss of nests, impact on food sources, protection from predators, etc.
4.
Answers will vary. Students
will likely compare prominent features of the map. For example, the parallel
ridges in the lower left hand corner of the image, etc.
5.
Much less pink in the second image means much less barren land.
6.
The dark green probably indicates larger tree growth. The light green is re-growth that
likely includes small trees and lots of green ground cover.
Summary
question: Answers will vary.
At the end of this
series of lessons, students should be able to describe what deforestation is,
as well as its impact on plants and animals in the ecosystem. Students should also recognize the role
humans in both deforestation and reforestation. The summary questions on each of the lesson activities
provide good assessment measures.
As a final assessment for this lesson, have students respond to the
following questions:
1) What are some reasons that people cut
trees down?
2) How can satellite imagery help us study
deforestation?
3) Why should we be concerned about
cutting down too many trees?
4) How can humans use forests and trees
responsibly?
Lesson Extension for Authentic Assessment
Made in the Shade
Conversion of tropical forest land to agricultural use by people can be done in many ways. Each of these different ways has different environmental effects--some of which have broad impact. For example, one of the richest cash crops throughout the tropics is the production of coffee beans. Coffee plantations come in many shapes and sizes, from small single-farmer operations to large, corporate farms. Traditionally, coffee has been grown in semi-cleared areas, under the shade of large rainforest canopy trees, by individual farmers. Today, however, to meet heightened demand and to maximize profits, coffee is increasingly grown on plantations that have been wholly cleared of the native canopy. These two styles of coffee production have great impacts upon the local wildlife community. In particular, the concentrations and diversity of bird species (many of which migrate to North America in the spring) decline markedly as the structure of the forest is altered from a multiple-layer structure (including existing canopy trees as well as low-growing coffee plants) to a single-layer structure (coffee plants only).
As an
extension activity for this series of activities, encourage students to explore
the connections among coffee production methods, biodiversity, and even
economics. Specifically, have
students research "shade-grown" coffee that was produced without the harmful
effects of clear-cutting deforestation.
Students could interview employees at coffee shops to see where their
coffee beans come from, and they could examine the labels of the coffee that is
on sale at their local supermarket.
What are the prices of these different kinds of coffee? Where do the proceeds go from the
coffee sales? Some coffee
cooperatives have been established such that a maximum amount of return comes
to small, individual producers, allowing them to compete with large-scale coffee
plantations that arise when large tracts of rainforest have been clear
cut. Have students research
shade-grown coffee on the Internet to accompany their first-hand research at
the marketplace, to give them a more complete appreciation of what is "behind
the label" of various products sold at the market.