Case Study: Losing the Rainforest, One Tree at a Time
Studying Change over Time
Everything changes over timeincluding people! You might not see a change in yourself from one day to the next, but if you look at a picture of yourself as a baby you can see how much you have changed. Earth's surface changes, too. Some changes are small (a boulder rolls down a hill), or happen quickly (lava flows down the side of a volcano), and we can see a difference from one day to the next. Other changes are too large or too slow to see right away, so we take pictures over time and compare the present to the past, just like you looking at your baby pictures. Information, including pictures, that is collected over time is called "time series" information.
In this chapter, Synthetic Aperture Radar (SAR) satellite images are used to study change in the Amazon rainforest. There are three great reasons for using SAR images to look at the rainforest. First, the rainforest is a cloudy place! Regular cameras cannot take a picture through clouds, but SAR can see right through those clouds – clouds are invisible to SAR. Second, the rainforest is huge! If you were to visit the rainforest in person, it would seem endless. We need to study the "big picture" to tell what changes have occurred, and satellite images give us the biggest picture of all. Third, satellite images are taken of exactly the same places each time the satellite circles Earth, so images from different years match up. You will be able to compare SAR images of the exact same area from three different years to measure how much forest area was lost from a part of the Amazon rainforest between 1994 and 1996. Consider this: Using this technique measures how much forest was lost in just three years. People have been cutting rainforest trees for a long time, with no sign of stopping. What do you think that means for the forest?
Deforesting the Rainforest
Why should anyone care about the Amazon rainforest in Brazil, anyway? Brazil is a long way away, for sure. But today the Amazon River is the source of 20% of all fresh water on Earth, and the Amazon rainforest contains one-third of Earth's remaining rainforests. About 60% of the entire Amazonian rainforest is located in Brazil, and that rainforest affects everybody on our planetincluding you!
Almost all living organisms, including you and me, breathe air and need oxygen. The rainforest plants produce about 20% of Earth's oxygen, and absorb almost 20% of the carbon dioxide we release annually by burning fossil fuels1. The Amazon is home to some incredible animals, including jaguars, poison dart frogs, scarlet macaws, howler monkeys, and millions of other species, including an estimated 30 million species of insects! Maybe you don't like bugs, but what about monkeys? Beautiful parrots? Big cats, or cool frogs?
Do you like tasty food? Many spices we use every day to make our food taste better come from the rainforest, including vanilla, coconut, cinnamon, and pepper. Chocolate comes from the rainforest, too! Let's talk about medicine. Have you or anyone you cared about ever been sick? Gone to the dentist? Everything from quinine, a medicine for malaria, to vincristine, a potent (really strong) cancer medicine, to novocaine, a local anesthetic (numbing agent) that your dentist uses, and lots more medicines come from rainforest plants. Only a small number of rainforest plants have been tested for medicinal uses.
Question: Who knows how many special plants we lose every year because the rainforests are being cut down?
Answer: No one knows. No one at all.
Brazil is not just big trees, lots of bugs, and wild animals. People live there, too! People that cut down rainforest trees are not just inconsiderate or destructive. They want the land for roads and mining and cattle ranches. They sell valuable hardwood trees, like teak, to other countries, including the United States. Poor farmers clear the land so they can grow vegetables to feed their families. People who are pro-development conflict with people, including indigenous (native) people, who want very much to save the rainforest. This is not a simple problem. To learn more about the Amazon rainforest, a great place to start is Raintree.
Forests and Climate Change
In their natural state, forests are a sink, or storehouse, of carbon dioxide (CO2 ). In other words, they store more CO2 than they release. According to Dr Pep Canadell, from the Global Carbon Project and CSIRO Marine and Atmospheric Research, deforestation accounts for approximately 20% of global emissions. This is more than the amount released by 13 years of fossil fuel burning.
Scientists estimate that 5.9 gigatons of CO2 enters the atmosphere every year from deforestation. That destruction amounts to 50 million acresor an area the size of England, Wales and Scotland felled annually. When tropical forests are cut–down and burned they release the CO2 that they had stored back to the atmosphere. Therefore, protecting tropical rainforests is not only important to protect biodiversity it is an important tool in our efforts to mitigate climate change.
In this chapter, you obtain SAR satellite images of an area in the rainforest of northwest Brazil where deforestation has occurred and roads have been built. It is easy to see the roadsthey look like fish bones in the satellite images. After exploring the images, use a scientific analysis software package, ImageJ, to analyze them and determine how much forest has been lost from this rainforest area in just three years.1- (S.L. Lewis et al., Increasing carbon storage in intact African tropical forests, Nature 457, 19 Feb 2009)