What are the effects of deforestation in Brazil?

Make sure that you can distinguish global/local effects of deforestation and environmental/social effects.

Loss of bio-diversity
Large numbers of plants and animals have been destroyed. It is possible that medicines are being lost.

Soil fertility
Once an area has been cleared, lots of rainfall reaches the ground. This washes the nutrients out of the soil and makes it less fertile.

Soil erosion
Clearing trees means that there is no canopy to protect the soil from heavy rain, or plant roots to bind it together. The result is that a lot of the soil gets washed away.

Amerindians
There has been a huge reduction in the number of people in local tribes.

Traditional culture
Many Amerindians have been forced off their land and ways of life have been destroyed.

World climate change
The burning of the forest releases carbon dioxide into the air. This may be linked to an increase in world temperatures. The carbon cycle and water cycle are severely affected.

Decrease in hardwoods
Trees such as mahogany and rosewood are becoming endangered species.

How are we exploiting the Amazon rainforest?

Today is Blog Action Day. Bloggers from all over the world are writing about the environment, which fits rather nicely with today's lesson!

Today's objectives were:

to know that the Amazon has suffered large scale deforestation

to recognise that the rate of deforestation has changed over time

to be able to give reasons for the deforestation of the Amazon

Deforestation is the conversion of forest areas to non-forest areas (i.e. cutting down the forest). In 2005, an area larger than Wales was cut down in the Amazon Rainforest. The rate of deforestation has slowed since 2005.

The main reasons for deforestation are:

Slash and Burn - most commonly for local tribes who need space to plant crops on a small scale. In recent years, only about 1/3 of deforestation can be attributed to shifting cultivators.

Road Building - particularly the TransAmazonian Highway.

Logging - commercial logging is widespread. It has been estimated that 28 trees are damaged for each one that is removed.

Cattle Ranching - an extensive form of farming - beef cattle roam large areas because the land is not fertile enough for them to feed on the grass in a small area. Most people agree that this is now the major reason for large scale forest clearance.

Hydroelectric Power - areas have been flooded when dams have been built for HEP projects. An example is the Balbina Dam.

Farming - soya farming has become big business. Nutrients in the soil are quickly exhausted and the land become infertile.

Mining - eg. gold, tin, copper, bauxite, oil. This can raise large amounts of cash.

New settlements - a significant amount of deforestation is caused by poor farmers who are encouraged to settle. Each squatter acquires the right to continue using a piece of land by living on a plot of unclaimed public land and "using" it for at least one year and a day. After five years the squatter acquires ownership and hence the right to sell the land.

The pie chart below shows the causes of deforestation in Amazon between 2000-2005.

Brazilian deforestation is closely linked to the economic health of the country - periods of lower deforestation (eg. 1988-2001) link to periods of slower economic growth; periods of rapid deforestation (eg. 1993-1998) link to periods of faster growth in the economy. During recessions, ranchers and developers do not have enough cash to rapidly expand their operations, while the government lacks funds to build new roads and settlements and grant tax breaks and subsidies.

How have plants adapted to the conditions in the tropical rainforest?

Lesson objectives:

• To be able to name plants of the tropical rainforest.
• To be able to describe and explain the adaptations that these plants have made to the conditions of the forest.

You should be aware of the following plants:

Lianas
These are thick vines that loop around tree trunks to make their way up to the canopy and the sunlight. They have thick, woody stems and come in various lengths (up to 3,000 ft) and varying shapes. They begin life on the forest floor but depend on trees for support as they climb upwards towards the sunlight they need for survival. They do this by attaching themselves to trees with sucker roots or tendrils and growing with the young sapling, or they climb by winding themselves round the tree's trunk.
When they reach the top of the canopy they often spread to other trees or wrap themselves around other lianas. This network of vines gives support against strong winds to the shallow-rooted, top-heavy trees. However, when one tree falls several others may be pulled down also.
Lianas include rattan palms, philodendron and Strychnos toxifera (from which the deadly poison strychnine is obtained). Rattans, the Asian lianas, have thorny stems and can reach heights of 650 feet (200 m). They are used to make a variety of things including baskets, ropes and wicker furniture.

Epiphytes, or air plants
These plants forget about roots in the soil - they perch high up on branches.
Epiphytes grow everywhere but can be found mainly on the branches, trunks, and even the leaves of trees. The name 'epiphyte' comes from the Greek word 'epi' meaning 'upon' and 'phyton' meaning 'plant'.
Different types of epiphytes may grow on the same tree, including orchids, cacti, bromeliads, aroids, lichens, mosses and ferns. They begin their life in the canopy from seeds or spores transported there by birds or winds.

Ferns
Ferns grow very well on the forest floor as they have adapted to the shady conditions.

Bromeliads
Bromeliads are related to the pineapple family. Their thick, waxy leaves form a bowl shape in the centre for catching rainwater. Some bromeliads can hold several gallons of water and are miniature ecosystems in themselves providing homes for several creatures including frogs and their tadpoles, salamanders, snails, beetles and mosquito larvae. Those that die decompose and furnish the plant with nutrients.

Strangler Figs
Most stranglers are members of the fig family. In Spanish they are known as matapalo - 'killer tree'. The seed of the strangler fig starts life as an epiphyte high in the trees, borne by birds and monkeys which eat the fig fruit. The seedling fig sends down long roots to the ground from where it begins to surround the host tree. It grows quickly and eventually suffocates the host: when the host tree dies it leaves an enormous upright strangler with a hollow core.
By using an adult tree as its host, the strangler fig avoids competition for light and nutrients at ground level.

Adaptations

You should be familiar with the following adaptations:

1. Buttress Roots - above-ground root system to ensure stability for the tallest trees and to increase the surface area over which the plant can draw its nutrients.
2. Drip Tips - the leaves are shaped to shed the heavy rainfall.
3. Branchless Trees - the trees put their energy into climbing upwards towards the canopy rather than growing branches at intervals along their trunks.

How have animals adapted to the conditions of the Tropical Rainforests?

Lesson Objectives:

• To know the names of at least one one animal that you could find in each layer of the tropical rainforest.
• To be able to give a detailed summary of the ways in which at least two animals have adapted to life in the Tropical Rainforest.

You did some independent research about a variety of rainforest animals - as soon as I receive your PowerPoints, I'll post them here! To keep us going until then, here are a few notes about some of the plants and animals of the rainforests...

Parasol Ants (forest floor)

Leaf-cutter, or parasol ants, climb trees up to 100-feet tall and cut out small pieces of leaves. They then carry these fragments, weighing as much as 50 times their body weight, back to their homes. Sometimes they must travel 200 feet, equal to an average human walking about 6 miles with 5,000 lbs. on his/her back!

These ants don't eat the leaves they have collected, but instead bury them underground. The combination of leaves and substances that the ants produce such as saliva allows a type of fungus to grow. This fungus is the only food that the ants need to eat.

The Jaguar (forest floor and undercanopy)

The Jaguar is both a good climber and a good swimmer. It pounces from trees on its prey, and is at home both in the understorey and on the forest floor.

Toucans and Parrots (canopy)

Toucans and Parrots have large beaks. These beaks give them a great advantage over other birds with smaller beaks. The fruits and nuts from many trees have evolved with a tough shell to protect them from predators. In turn toucans and parrots developed large strong beaks, which serves as a nutcracker and provides them with many tasty meals.

The three-toed sloth (canopy)



The three-toed sloth is born with brown fur, but you would never know this by looking at it. The green algae that makes its home in the sloth's fur helps it to blend in with the tops of the trees, the canopy, where it makes its home. But green algae isn't the only thing living in a sloth's fur; it is literally "bugged" with a variety of insects. 978 beetles were once found living on one sloth!

The sloth has other clever adaptations. Famous for its snail-like pace; it is one of the slowest-moving animals on earth. (It can even take up to a month to digest its food!) Although its tasty meat would make a good meal for jaguars and other predators, most do not notice the sloth as it hangs quietly in the trees, high up in the canopy.

The Woolly Spider Monkey (canopy)

The spider monkey is a wonderful acrobat which can leap six metres from tree to tree. It has a special tail that can be used like a hand to hang from trees or to reach out for fruit (this is called a prehensile tail).

The Harpy Eagle (emergent trees)

The Harpy is the largest eagle in the world. It hunts monkeys, sloths and snakes by swooping low over the canopy. When its sharp eyes spot prey, it dives into the branches and quickly snatches up its next meal.

Introduction to the Tropical Rainforest

The lesson objectives were:

• To know where the tropical rainforest biome is found.
• To practice describing the distribution of the tropical rainforest.
• To know that the tropical rainforests can be divided into four distinct vertical layers and to be able to name the layers.
• To understand that the climate affects the nutrient cycle of the forest.

Tropical rainforests are found in equatorial areas, between the tropics (concentrated between 10 degres north and south of the equator). They cover about 6% of the earth's surface. The main areas covered by rainforests are: Central America; the Amazon Basin (in South America); Central Africa; Madagascar (much of this has now gone); Southern Asia; Australasia. This is shown on the map below.


You may well get a question along the lines of 'Describe the location of the tropical rainforests' in your final exam. This type of question is usually worth 2 marks. Make sure you mention the general pattern (equator/tropics) and specific rainforests in your answer.

Express Yourself with Gizmoz Video Clips

We watched a video about the structure of the rainforest and the way in which nutrient cycles work. Unfortunately, the video is not available online... here's an alternative for you...


The key things to remember are:

• In general, the rainforest is a hot and humid environment. There is relatively little variation in temperature throughout the year (approx. 2 degrees). There is a wet season and a dry season. The growing season is very long.

• The rainforest has four main layers: shrub layer, under-canopy, canopy and emergents.

• The shrub layer (ground level) is dark and gloomy because the trees of the canopy block out 95% of the sunlight. There's not much growth here.

• The under-canopy has limited sunlight. Saplings wait here for a spot in the canopy to become available for them!

• The canopy is like a vast green ocean when viewed from above! Its full of life.

• The emergent trees can be up to 50 metres high.

• The nutrient cycle operates very quickly due to hot, humid conditions in which dead plant matter decays very quickly. There are very few nutrients stored in the soil because they are quickly absorbed by plant roots.

The diagram below shows the structure of the rainforest. The examiners often ask you to describe the structure of an ecosystem, so make sure that you are able to draw a fully labelled diagram to show the layers of the forest.