Forests: Changes in the Land
Part A: Changes in Forest Cover
Forest cover...then and now!
Next, examine the two images that each tells a story of changes in forest cover over very different times scales. The first image shows changes in forest cover that has occurred over thousands of years. The second image shows changes in forest cover loss from 2002-2012.
- What has happened to global forest cover over the past few thousands of years? What countries or regions around the world have experienced the greatest change in forest cover? What do you think the causes of these changes might be? List as many as you can.
- Next, look at changes in forest cover from 2000 to 2012. What countries or regions show higher losses in forest/tree cover compared to other countries and regions? Why do you think these countries or regions have higher losses?
- Compare the changes in forest cover in the two images. What patterns or trends in forest cover change do you see when comparing changes over a thousand years to changes over a recent decade?
- Think about how the loss of forest cover over time might affect the global carbon cycle. List as many as you can.
- How can preserving forests help to mitigate the effects of rising atmospherics CO2 and climate change?
- At the end of Lab 4A, you will have the opportunity to use the Global Forest Watch tool to develop and investigate your own research question. But, why should we care about changes in forest cover, especially if these changes are happening far away from where we live? List as many reasons as you can and share with the class.
What causes losses in forest cover over time?
There are many reasons that forest cover can be lost over time. For example, the image on the right shows loss of original, natural forest cover in Indonesia to make way for the planting of palm oil trees. The global market for palm oil as biofuel is one of the many complex factors driving this change in forest cover. Palm trees will be planted in place of the original trees, however the original forest and the creatures that lived there will be lost.
There are both natural causes and man-made causes of forest cover loss.
Natural causes include events such as:
- insect infestations
Man-made causes of forest cover loss include clearing the land for:
- logging for timber
- agriculture - raising crops and cattle, and planting tree plantations
- building roads and towns
Drought and Wildfires
Millions of Trees Die in Texas!Severe tree cover loss can happen right in your own backyard. In 2011, Texas experienced its worst and most resilient drought in recorded history. The ongoing drought set the stage for a more active wildfire season as vegetation dried out. According to State Impact Texas over 3 million trees died from drought and related fires. These NASA satellite images show the burn scar from one of these drought-related fires in Bastrop, Texas in 2011. Over 34,000 acres burned. The false-color image on the right shows a wide-area view of the fire. Vegetation is bright green, and sparsely vegetated or bare land is green-yellow. The burn scar appears in shades of red and orange. Far from uniform, the burned areas are separated by unburned expanses. The area outlined in white in the top image corresponds to the close-up view provided in the natural-color image below. Take a minute to study and compare these two images before moving on to the discussion questions below.
- Which image - false color or natural color- is the most useful to you for determining the extent of damage from this fire? Why?
- What happens to the carbon stored in the 3 million trees that died due to the 2011 Texas drought?? Where will that carbon go?
- Should Texas implement a reforestation project to replace these trees? Why or why not?
Not all wildfires are caused by the same environmental conditions. Watch "Wildfires out West" from ClimateCentral. As you watch, make note of the different environmental conditions that are involved in creating wildfires in Montana versus wildfires in Nevada.
Not all wildfires are bad for forest ecosystems. As a matter of fact, wildfires have always been a natural and important part of forest ecology. For example, after the 1988 wildfires that burned 1.2 million acres in Yellowstone National Park and surrounding areas, fire ecologists found that fires were important to lodge pole pine trees. Read or listen to the article Yellowstone Fires: Ecological Blessings.
Wildfires seen from space - NASA keeps track!
NASA uses satellites, aircraft and ground resources to observe and analyze fires around the world. This research helps scientists understand how fire affects our environment on local, regional and global scales. NASA has created a visualization from ten years of global fire surveillance data taken by the MODIS instruments on NASA's Terra and Aqua's satellites. Take a visual tour of a decade of fires created from these satellite measurements. As you watch, make note of the following:
- Countries or continents where more fires occur.
- Natural event fires (grassland fires, forest fires, peat fires) versus man-made fires (for agricultural and pastoral purposes)
How does the carbon cycle respond to wildfires?
Wildfires in Indonesia provide a clue to this important question. In 1997–98, the growth rate of carbon dioxide in the atmosphere doubled, reaching the highest on record. According to researchers studying the carbon cycle much of this increase in carbon dioxide emissions can be attributed to the forest and peat fires in Indonesia that began in 1997 and lasted into 1998. In addition to releasing higher levels of CO2, these fires spewed carbon-containing smoke particles (black carbon) and spread haze to nearby countries causing air pollution. By the time the 1997-98 forest fires were finally over, more than 8 million hectares of land had burned. According to the researchers, the amount of extra carbon the 1997-98 Indonesian fires pumped into the atmosphere was more than all living things on Earth remove from the atmosphere in one year! That's a lot of carbon!
Although wildfires around the world differ from each other in a variety of ways, the processes that drive the carbon cycle will respond to wildfires, but at different time and spatial scales. They are:
- In time scales of minutes to days, burning trees rapidly release large amounts of carbon dioxide(CO2) and smaller amounts of methane (CH4) to the atmosphere via the process of combustion. Carbon-containing smoke particles are also released.
- In time scales of years to decades, dead trees fall to the ground and decompose at different rates based on environmental variables such as temperature and moisture. As these dead trees decompose, CO2 is released into the air via respiration and some carbon stays in the soil as soil organic carbon. For example, bits of burnt charcoal can be stored in the soil for long periods of time.
- In longer time scales of decades and centuries, regenerated forests are again absorbing large amounts of CO2 from the atmosphere. However, the type of forest vegetation that regenerates may be very different from the original forest and this may impact the amount of CO2 that is absorbed.
Activity and Discussion
- Draw two conceptual model diagrams illustrating how the carbon cycle responds to wildfires at different time scales.
Drawing 1 assumes regeneration of the forest will occur after the fire through natural regeneration and/or purposeful planting of trees.
Drawing 2 assumes that no regeneration of the forest will occur after the fire.
- Share your diagrams with each other and the rest of the class. After 100 years, how will atmospheric concentrations of CO2 differ between the two models? Why?
Deforestation: Permanent loss of forest cover
If left to themselves, forests will regenerate over time. We can also plant trees to replace trees lost to fire and drought events such as the 2011 drought and wildfires in Texas. Deforestation is different. Trees are not replaced and the land is converted to a non-forest use. Examples of deforestation include cutting down forests and converting that land to cropland, cattle ranches, urban development, roads, and mining operations. Forests can also be cut down to provide wood to burn for cooking and heating. The largest and most direct cause of tropical deforestation is converting forested land to cropland or pasture for cows and other animals.
DiscussionLet's examine a well known example of deforestation - Haiti and the Dominican Republic. Both these countries share the same island. The NASA satellite image above shows the border between Haiti on the left and the Dominican Republic on the right. Click on the image to make it larger. Then, take a few minutes to carefully look at and think about the image you are viewing.
- What difference(s) in forest cover can you observe in this satellite image? What is the evidence for the difference(s) you observe?
- What do you think might be some contributing causes to the differences in forest cover between these two countries? List all that you can think of.
- Share your ideas with the rest of the class.
Basic stages of deforestation
Click on this link to view the basic Stages of Deforestation. As you view these stages, think about following:
- Undisturbed forests absorb and store more carbon via photosynthesis than they release via cell respiration.
- Trees that have been cut down no longer absorb CO2 from the atmosphere via photosynthesis.
- Trees that are burned release CO2 to the atmosphere via combustion.
- Trees left behind to decompose emit CO2 via the process of soil microbial respiration.
- Agricultural land created from deforested areas emits CO2 to the atmosphere via increased respiration and diffusion from soil that has been turned over (tilled).
Next, watch the CNN movie Planet in Peril and then answer the Checking In questions below.
How much carbon is in tropical rainforests?
How much carbon would be lost in the deforestation of the tropical rainforest? To answer that question, consider the new NASA map of Carbon Storage in Tropical Forests on the right. This map uses NASA satellite data combined with ground measurements to quantify the amount of carbon stored in tropical forest biomass. Remember that a tree's biomass includes all the carbon compounds in the tree's leaves, branches, trunk and roots.
Trouble in the Amazon?
Because the Amazon forest is so large and so much carbon is stored there, deforestation in this region concerns us all. The larger the forest, the greater its impact on the carbon cycle. What impact will deforestation have on the Amazon Rainforest and its ability to remain a strong carbon sink as opposed to a carbon source? To help you answer this question, use a time series interactive Forest changes in Rondônia, Brazil and watch Amazon Deforestation
In the times series interactive, you can:
- Click on the arrow to start the time series to look at forest changes over time.
- When in the pause mode, click on the "view large" tab on the right. Once the large view comes up, you can click on sections of the image to get a closer look at forest changes.
- By 2003, how many square kilometers had been cleared from the Amazonian Forest in Rondônia? How many acres would that be? Use the metric conversion website to help you answer that question. 67,764 sq kilometers = 16,744,849 acres.
- One acre of forests can absorb approximately one ton of carbon dioxide from the atmosphere each year. If deforestation has cleared 16,744,609 acres in just Rondônia, how many less tons of atmospheric carbon dioxide will be stored in the trees every year?16,744,609 tons of carbon dioxide
Stop and Think1. Describe how deforestation can impact the the amount of carbon dioxide in the atmosphere.
Up in Smoke: Deforestation, Fire, Farmers and the Carbon Cycle - a mini case study.
Cutting down trees is only one part of the complex "carbon cycle" story in areas of deforestation. When rainforest trees are cut, burned, or left to decompose, what happens to the carbon contained in those trees? What happens to the land left behind? Answers to this last question are often dependent on the local economy and the needs of small communities to provide for their families. Small farmers and ranchers use a very old technique called "slash and burn" to clear and prepare the land for agriculture and cattle. In slash-and-burn agriculture, farmers will typically cut forests months ahead of the dry season. During the dry season, the "slashed" trees dry out and are then burned. The ash from the burned trees fertilizes the soil to support crops such as as rice, corn and soybeans and grass for cattle. Unfortunately, soil nutrients such as nitrogen are used up fairly quickly, the land becomes barren and farmers then move on to slash-and-burn other parts of the rainforest. In this way, fire and soil become part of this complex carbon cycle, the economy of the rainforest and the people who live there. So, what can be done to mitigate the impact of slash and burn farming on the carbon cycle? Read about the work of Mike Hand, a British ecologist, and Inga trees to find out!
Model and Discussion
Watch the five Oxfam short videos or the documentary linked above. As you watch, take notes that will allow you to compare and contrast the "slash and burn" farming with sustainable "crop alley" farming in terms of:
- Impact on the community
- Pros and cons of each method
- Impact on the carbon cycle
Use your notes to create a conceptual model diagram that describes how the carbon cycle differs when "slash and burn" methods are used versus sustainable "crop alley" methods. Describe as many changes to the carbon cycle and the community that are part of this carbon cycle story.
Stop and Think
2. Think about the complex story of deforestation, slash and burn agriculture and the carbon cycle in the Central American and Amazon rainforests. Describe how deforestation, combustion and decomposition all impact the amount of carbon dioxide in the atmosphere.
Global Forest Watch - Keeping track of forests in real time!
At the beginning of this lesson, you examined a "Global Forest Watch" map to identify regions of the world that were experiencing forest cover loss from 2000 to 2012. You were also asked to think of some reasons why should we care about changes in forest cover - especially if these changes are occurring far away in other places in the world. Take a few minutes to revisit the list of reasons you made. Would you add any new reasons to your list? Why?
- Discover the types of information available using Global Forest Watch.
- Spend time pulling down menu tabs, clicking on icons, zooming in and out!
- Explore the information at different spatial scales.
- Watch the Overview video and the Tutorial video from the "HOW TO" tab in the top menu.
- Share out all that you have discovered with the rest of the class.
- What is the relationship between logging and changes in forest cover in Washington state?
- Which country has the biggest forest changes related to mining?
- How are reforestation projects working - for example in Haiti and Brazil?
- What forest cover changes are happening or have happened locally in your area? Perhaps phenomena such as wildfires, drought or insect invasions have impacted forest cover in your neighborhood! If you think you have an interesting story to tell about forest changes in your local area, write the story and submit it to Global Forest Watch according to their specifications.
- Create an infographic using one of the new free tools on the Internet or in apps. Ten free tools for creating infographics
- Film a Public Service Announcement (PSA)
- Give a scientific poster.
RESEARCH TASK: You will use Global Forest Watch to generate an original research question about changes in forest cover. You will use data, information, patterns and maps from Global Forest Watch and background research from the Internet to create a product that informs the public about your research question. You can use Global Forest Watch to examine data and patterns from different spatial scales - global, hemisphere, by country, state, regional, local. For example, if you are interested in changes in Texas forest cover, you can drill down to that spatial level.
1. Open and explore the Global Forest Watch mapping tool.
2. Generate a research question.
3. Use the Global Forest Change interactive to gather data and images that allow you to answer your research question.
4. Determine the rate of change and % change in forest cover for the area(s) and time period you are studying for your research question. Graph these values and any other values you have collected in your research and include them in your presentation product.
5. Use the Internet to research the causes of the changes in forest cover in your research area. Causes of changes in forest cover can be economic, environmental, social, and/or geopolitical and often can be varied, interconnected and complex.
6. Prepare and present your product. Think about what your presentation product will look like and and any technology you might use to create this product.
7. Before completing final presentations, you may wish to critique each others presentation product and offer feedback. Share your products with the class and perhaps a wider audience.
Background reading on wildfires:
The Ecology of Fire from The Knowledge Project: Nature Education.
- ESRI latest fire map
Background reading and activities on deforestation:
Tropical Deforestation from NASA.
- Margarito Don Margarito talks about farming life in his village and why he is content to be alive, in this excerpt from "Burning Paradise," a film about indigenous peoples in the heavily deforested state of Oaxaca, Mexico, who must illegally burn their forests into charcoal to survive - or migrate.
- Hold a "PSA (Public Service Announcement) Deforestation on Vimeo Film Festival." PSA's are supposed to inform and to get people to change behavior. In pairs or groups, review the wide variety of deforestation PSAs available on Vimeo and YouTube. Choose one to enter into your class's film festival. Develop a rubric for scoring the PSAs.
Back ground information on Reforestation and Afforestation -
- Research and evaluate reforestation and afforestation projects around the world such as the afforestation project in China - The Green Wall of China or the Nature Conservancy's Plant a Billion Trees Campaign in the Atlantic Forest