Sec 1 Chapter 3 Tropical Rainforests

Chapter 3Tropical RainforestHow Can We Save The

Rainforest?

Think about this!

How did the name tropical rainforest come about?

TROPICAL

RAIN

FOREST

Tropical Rainforest

In this section, you will explore these Guiding Questions:1. What are tropical rainforests? 2. Where can they be found?3. What is deforestation and which areas have been

deforested?4. Why does deforestation occur?5. How does deforestation impact people and the

environment?6. How should we manage deforestation?

• Watch a video of the tropical rainforest. Take note of the features of a tropical

rainforest.

1. What are tropical rainforests?

Which photo do you think shows a tropical rainforest?

1. What are tropical rainforests?

1. What are tropical rainforests?Characteristics of tropical rainforest• Thick and luxuriant• Broadleaved (to capture sunlight for

photosynthesis)• evergreen trees – they do not shed all their leaves

at the same time. • Found in areas that experience high rainfall

(about 1,500 – 2,500 mm annually) and high temperature (about 26oC) throughout the year

1. What are tropical rainforests?Characteristics of tropical rainforest• Diversity of plant species• Structure of tropical rainforest

1. What are tropical rainforests?Characteristics of tropical rainforestDiversity of plant species• Hot and wet environment gives rise to rich

biodiversity (range of plant and animal species found in an area)

In Amazon rainforest in South America

In forests in United Kingdom

300 different plant species within 0.01 km2 (1 football field)

40 plant species within 27,000 km2

1. What are tropical rainforests?Characteristics of tropical rainforestDiversity of plant species• Different types of food can be found:– Fruits (e.g. bananas, mangoes)– Spices (e.g. pepper, cinnamon)– Vegetables (e.g. corn, pandan)– Nuts (e.g. Brazil nuts, walnuts)

1. What are tropical rainforests?Characteristics of tropical rainforestStructure of the tropical rainforestA tropical rainforest has primarily three layers:• Emergent layer (above 30 m)

• Canopy layer (20–30 m)

• Undergrowth layer (below 20 m)

• Watch a video that describes the structure of a tropical rainforest.

1. What are tropical rainforests?Characteristics of tropical rainforestStructure of the tropical rainforest• Emergent layer (above 30 m)

– Uppermost layer where some trees rise and tower above other trees

– Can grow up to 50m – 80m– The emergent layer is formed

by the crowns of these trees.– Trees in this layer usually have

tall, straight and smooth trunks with few branches

– E.g. Tualang tree, Kapok tree

1. What are tropical rainforests?Characteristics of tropical rainforestStructure of the tropical rainforest• Canopy layer (20 – 30 m)

– The trees grow to heights of 20 – 30m to reach for sunlight.

– Trees grow close together (dense)

– Crowns interlock to form an almost continuous cover

– This blocks up to 90% of the sun’s rays from reaching the forests floor

1. What are tropical rainforests?Characteristics of tropical rainforestStructure of the tropical rainforestCanopy layer (20 – 30 m)• Lianas: Thick,

woody vines that twine up trees to reach for sunlight.

• Epiphytes: Plants which grow on trees to reach more sunlight(includes ferns, orchids, mosses, lichens)

1. What are tropical rainforests?Characteristics of tropical rainforestStructure of the tropical rainforest• Undergrowth layer (below 20 m)

– Dark because sun’s rays blocked by the canopy.

– Plants are small, thin and widely-spaced due to lack of sunlight.

– Consists of plants such as moss, ferns, some lianas and epiphytes.

– They have much larger leaves compared to those in the other layers

– Thin layer of leaf litter due to rapid decomposition caused by hot and wet environment.

1. What are tropical rainforests?Characteristics of tropical rainforestAdaptation of plants• Leaves– Leaves are broad • Helps trees capture sunlight for photosynthesis

– Leaves have waxy, leathery or hairy surfaces • Helps to minimise the loss of moisture through

transpiration due to the high temperatures

1. What are tropical rainforests?Characteristics of tropical rainforestAdaptation of plants• Leaves– Some leaves have narrow,

downward pointing tips (drip tips) • Allow water to run off easily• Prevents fungi and bacteria

from growing on the leaves

1. What are tropical rainforests?Characteristics of tropical rainforestAdaptation of plants• Fruit and flowers

- colourful and strong-smelling to attract insects and other animals to assist in seed dispersal and pollination Air is usually still (lack of wind)

which is hard for seed dispersal and pollination by wind

Fruit of the cacao plant

Rafflesia, the world’s largest flower

1. What are tropical rainforests?Characteristics of tropical rainforestAdaptation of plants• Roots– Buttress roots which grow

from 1 – 5 m above the ground • To support the heavy

weight of tall trees

1. What are tropical rainforests?Characteristics of tropical rainforestAdaptation of plants• Roots– Shallow roots• Nutrients from the rapid decomposition of fallen leaves

and branches are mostly found in the top layer of the soil• Water is available throughout the year, therefore there

is no need for the roots to grow deep to search for water.

1. What are tropical rainforests?Uses of tropical rainforestsa. Water catchmentb. Green lungs of the earthc. Habitat to flora (plants) and fauna (animals)d. Habitat to indigenous peoplee. Source of timberf. Medical application

Uses of tropical rainforestsa) Water catchment• Refers to an area drained by a river and the smaller

rivers that flow into itRain falls in tropical rainforests

Trees stop rain from reaching the ground directly

Water slowly drips from the trees

Contributes to water supply

• Because impurities in rainwater are trapped in the soil before it flows into the reservoirs, forests help to maintain the quality of water.

Seeps into the ground and is stored as groundwater

Flows as runoff into the rivers or reservoirs

b) Green lungs of the earth• Tropical rainforests help the earth to ‘breathe’– More than 20% of the earth’s oxygen is generated by

the Amazon rainforest– Absorb carbon dioxide from the atmosphere and

release oxygen (photosynthesis)– They act as the earth’s natural air purifier as they

absorb 2.4 billion tonnes of carbon dioxide in one year.

• Dense vegetation of tropical rainforests keeps the earth cool

Uses of tropical rainforests

c) Habitat to flora (plants) and fauna (animals)• Home to more than 2 million species (1/2 of world’s

species)


Habitat to flora (plants) and fauna (animals)• Abundance and diversity of flora and fauna– Ample sunlight is converted by the plants into energy

and food (photosynthesis) which allows plants to thrive In turn, the plants are eaten by animals for survival

– Continuous canopy is a habitat where other plants can grow and animals can live in


d) Habitat to indigenous people• 60 million indigenous people

(original inhabitants of a country) are wholly dependent on the tropical rainforest

• been living in tropical rainforests for thousands of yearse.g. Yanomami (Amazon rainforest), Penan (rainforest in Sarawak)

An indigenous group living in the Amazon rainforest


Habitat to indigenous people• Tropical rainforests provide these people with daily

necessities (food, clothing and medicine)• They obtain food by either hunting and gathering

(hunt fish, gather wild fruit and nuts), or agriculture (growing of crops)[As such, they are known as hunter-gatherers or shifting cultivators]


• Yanomami Tribes

e) Source of timber• Timber refers to the the wood (e.g. teak, ebony,

mahogany and meranti) used to build or make things such as doors, window frames and furniture

• Tropical rainforests supply about 1/5 of the world’s industrial timber

• provide fuel wood to people for cooking


f) Medical application• In Amazon rainforest, nearly 3,000 plant species have

been identified to have medicinal properties• Many of the foods (e.g. Brazil nuts) have cancer-

fighting properties


Medical application

25% of all modern medicines come from rainforest plants


• Medicine in the Rainforest

• People value the rainforest for different reasons


World distribution of tropical rainforests

2. Where are tropical rainforests found?

Global distribution of tropical rainforests• Less than 5% of the earth’s land surface• Equatorial climate (between latitudes 20° N and 20°

S) where there is abundant sunlight, high temperatures and heavy rainfall throughout the year

• High annual temperatures (of more than 26oC, with a range of 2–3oC) and high annual rainfall (1,500–2,500mm)

• Main areas : Amazon Basin, the Congo Basin, Southeast Asia.


World distribution of tropical rainforests


Amazon Basin in South America

Congo Basin in Africa

Southeast Asia

Latitudes

• Are imaginary horizontal lines that run in an east-west direction around the Earth.

• The Equator is the longest line of latitude – it divides the Earth into two equal halves (Northern and Southern Hemisphere)

Latitudes

• Latitudes are measured in degrees and minutes from the Equator

• They increase in value as they move northward and southward.

Distribution of tropical rainforests in Singapore• Many parts of Singapore were originally covered with

rainforests• After 1819: Rainforests were rapidly cleared to grow

crops and build infrastructure• 1882: Only 7 per cent of the original rainforests remained• Today: Rainforests occupy an area of about 20 km2 (3% of

total land area) and are mainly found at the Central Catchment Nature Reserve and Bukit Timah Nature Reserve

3a. Where are tropical rainforests found?

Distribution of tropical rainforests in Singapore


1819

Distribution of tropical rainforests in Singapore


2006

3. What is deforestation? (p86)Spot the difference

An area in the Amazon rainforest

3. What is deforestation?Deforestation• It is the cutting down and removal of all or most of

the trees in a forested area• If not managed properly, it can lead to the

permanent destruction and eventual disappearance of a once renewable resource

1980 1990Tropical Rainforest 19.1 mil km2 17.9 mil km2

3b. Which areas have been deforested?

Global distribution of deforested areas of tropical rainforest• Rainforests are disappearing at alarming rates

because of human activities:– Agriculture– Mining– Logging – Land clearance (for housing and industries)

• Remaining rainforests are smaller and broken up into fragments


Global distribution of deforested areas of tropical rainforest

At least 320 km2 of tropical rainforest disappear each day



Areas of tropical rainforest that have been deforested


Global distribution of deforested areas of tropical rainforest (TB p92)

Tropical rainforest loss in some countries

Do “Let’s try it!” on pg 93



Deforestation estimates of tropical rainforests in Borneo

• If the present rates of deforestation in the world continue, our world’s remaining rainforests could be gone in one hundred years.

• In Borneo, logging is one of the main reasons that caused rapid deforestation.

• Deforestation Video - CNN

4. Why does deforestation occur?• Agricultural activities• Cattle ranching• Logging• Mining

4. Why does deforestation occur?Agricultural activitiesAgriculture is the growing of crops and raising of animals to provide food• Shifting cultivation (a form of subsistence farming

activity)– Have been the traditional cause of deforestation– Shifting cultivators grow crops for their own use and

consumption– They allow land to regain its fertility and for vegetation

to regrow when they move to the next plot of land

As such, does not pose a major threat to the forest

4. Why does deforestation occur?Agricultural activities• Large-scale commercial agricultural activities on

plantations– Burn and clear large areas of the rainforest – Crops are grown for cash and are sold to meet

both local and global needs

As a result, the rate of deforestation has increased greatly!

4. Why does deforestation occur?Agricultural activitiesExample:• By 2010, about 242,000 km2 of

the Amazon rainforest have been converted into soya bean farms– Major ingredient in food for

cattle– Also, processed into products

such as soya milk and tofu Large areas of rainforest are being cleared for soya bean farms in the Amazon Basin

4. Why does deforestation occur?Cattle ranchingInvolves operating large farms to raise cattle• Large areas of rainforest are cleared to create land

for cattle to graze

Large tracts of the Amazon rainforest are being lost to cattle ranching

For example:• 80% of deforestation in the

Amazon rainforest is caused by land cleared for cattle ranching

• 1986: Less than 10 million head of cattle

• 2011: 79 million head of cattle

4. Why does deforestation occur?Cattle ranching• A large amount of beef from cattle in the Amazon is

exported to other countries (e.g. USA, Britain)

4. Why does deforestation occur?LoggingThe cutting down of trees for timber• Commercial logging of tropical hardwoods (teak,

mahogany, rosewood) to make furniture, building materials and charcoal

• Growing demand for timber products Increases logging activities

Commercial logging is responsible for destroying 50,000 km2 of tropical rainforest every year!

4. Why does deforestation occur?Logging• Logging reduces the number of trees and damages

the rainforest as a whole

Why?• For every tree extracted, five are badly damaged

(falling tree will destroy the surrounding trees or smaller-sized plants)

• Also, the soil is exposed to erosion

4. Why does deforestation occur?LoggingExample:• To meet needs in China– Huge demand for timber for making disposable

chopsticks and paper – Caused heavy logging in the rainforests of Congo

and Cameroon in Central Africa, Brazil and Indonesia

4. Why does deforestation occur?Mining• Precious metals and

gemstones (gold, copper and diamonds) are found beneath many tropical rainforests

• Forests are cleared to establish the mines and construct roads to transport the mined materials

NASA satellite image showing the extent of deforestation caused by the Carajás Mine, Brazil

4. Why does deforestation occur?MiningExample:• Carajás Mine in Brazil has a rich variety of mineral

reserves• In 2007: 296 million tonnes of iron ore were extracted

(18 billion tonnes of minerals including gold and copper)

• These minerals are needed to produce electronic products such as computers and telephones as well as electrical wires

4. Why does deforestation occur?Although human activities have led to deforestation, some may view these activities as key to development:• The clearing of forests provides land for communities

to build houses, factories, offices• Roads can be built and this makes trade and

transport easier• Also, the land can be converted to agricultural land

to allow the production of more food

5. How does deforestation impact people and the environment?

Environmental impact• Loss of biodiversity• Loss of water catchment areas• Increased risk of flooding, soil erosion and

sedimentation• Enhanced greenhouse effectEconomic impact• Depletion of natural resourcesSocial impact• Effects on indigenous people

Environmental impactLoss of biodiversity• Deforestation destroys the habitats of plants and

animals• Loss of biodiversity = Loss of the variety of plants and

animals -> extinction of plant and animal species -> lesser variety of resources (eg. Food, medicine, timber)

• Changes in biodiversity may increase the occurrence of insect-borne diseases (e.g. malaria, dengue fever)

• lack of nutrients in the soils may not be able to support the biodiversity that once existed on that land


Environmental impactLoss of watch catchment areas• Forests play an important role in maintaining our

water supply• They enable water to be collected and stored within

a water catchment area


Environmental impactLoss of watch catchment areas

The Amazon Basin has 7,000 tributaries

Countries surrounding the Amazon rainforest depend on water from the Amazon Basin, especially during dry seasons


Environmental impactLoss of water catchment areas• Clearing of trees disrupts the water cycle Less

transpiration happening, less rain drier climate and drier soils as the ground no longer contains and receives as much water decreased water supply higher water prices


Environmental impactIncreased risk of flooding, soil erosion and sedimentation• When trees are cleared, the ground is left bare• No trees, moss and leaf litter to intercept and reduce

the impact of rain on the ground. • More surface runoff, less infiltration • This causes flooding in the surrounding areas


Environmental impactIncreased risk of flooding, soil erosion and sedimentation


Environmental impactIncreased risk of flooding, soil erosion and sedimentation• Soil erosion is the removal of the top layers of soil by

rainwater, wind and destructive human activities (logging)• When trees are removed no roots to hold the soil, no trees

to intercept the rain land becomes exposed soil erosion rain washes the soil into rivers increases the amount of sediments in the rivers affects water quality and aquatic life

• Increased amount of sediments smothers fish eggs, resulting in lower hatch rates

• Turns water cloudy and prevents sunlight from penetrating the water suffocates coral reefs.


Environmental impactIncreased risk of flooding, soil erosion and sedimentation

Sediments enter the sea

Coral reefs get suffocated

Sediments will eventually settle and accumulate


Environmental impactEnhanced greenhouse effect• The gases (eg. Carbon dioxide, methane, water vapour and

others) in the atmosphere help keep the earth warm. These are known as greenhouse gases. The warming of the atmosphere is known as the greenhouse effect.

Without the greenhouse effect, the earth’s average temperature will be −18°C rather than the current 15°C• Human activities such as setting up of industries, transport

network and power station have increased the amount of greenhouse gases in the atmopshere more heat trapped in the atmosphere increases the earth’s temperature Enhanced greenhouse effect


Environmental impactEnhanced greenhouse effect• Deforestation contributes to enhanced greenhouse

effect increased amount of carbon dioxide in the atmosphere

• Less trees means that less carbon dioxide is absorbed and more of it remains in the atmosphere.

• The burning of rainforests also releases carbon dioxide into the atmosphere. Branches and logs that are left behind become fuel for forest fires.


Environmental impactEnhanced greenhouse effect

Deforestation of tropical rainforest contributes significantly to the total amount of carbon dioxide released into the atmosphere


Environmental impactEnhanced greenhouse effect• The enhanced greenhouse effect affects people and

the environment

For example• Increased temperatures can cause ice caps to melt• Results in a rise in sea levels and flooding of low-lying

coastal areas• Low-lying islands (Kiribati and Vanuatu in the Pacific

Ocean) may be submerged and disappear into the sea• As such, people living on these islands may lose their

homes


Economic impactDepletion of natural resources• Natural resource: Anything from the natural environment

that people can use to satisfy their needs such as food, shelter, clothing, air and water

• Tropical rainforests provide important natural resources (timber, food and water) for human needs, and they contribute greatly to the economic growth of many countries

• Rapid deforestation often destroys the rainforest faster than it can replenish itself depletion of natural resources affects earnings of industries that rely on rainforest resources.


Economic impactDepletion of natural resources

Earnings of industries that rely on rainforest resources get affectede.g. timber trade


Social impactEffects on indigenous people

The Guarani community (Brazil) is living in makeshift camps because parts of the forest were cleared for sugarcane plantations, displacing these people from their homes in the tropical rainforest


Social impactEffects on indigenous people• Indigenous people live in harmony with the forest and

obtain their needs, such as food and shelter, from it. • Cutting down rainforests affects the lives of indigenous

people• They lose their homes and are forced to adapt to a new

ways of living to survive causes indigenous tribes to disperse and cultures to disappear


6. How should we manage deforestation?

The worrying state of our world’s rainforests signals a need for action!

The blue line shows the amount of forests that will be lost from 2012 onwards if we do nothing and continue with deforestation. The red line shows a target we can meet if we take action.

• Conservation: It is the protection of the environment and its natural resources from harm . It involves maintenance, restoration and wise management of resources to avoid permanent depletion of resources


International Year of Forests (IYF) 2011

• Sustainable resource management: It refers to the careful use of resources to ensure their availability in the future

• To achieve this, laws need to be passed & everyone needs to play his part.


4 strategies of managing deforestation• Protection of forested areas• Reforestation• Controlled logging• Public education


Managing deforestation in the AmazonProtection of forested areas- Laws are passed to protect the tropical rainforests

from unfavourable activities that might endanger the biodiversity and natural resources.

- The indigenous tribes living in these areas are also preserved.

- The Central Amazon Conservation Complex is the largest protected area in the Amazon Basin. It is set aside for the conservation of the biodiversity, education and research


BenefitsProtection of forested areas • Important in the conservation of our indigenous

ecosystems and native biodiversity• Useful for educational and recreational purposes,

and scientific study• Has helped to reduce deforestation in the Amazon


ChallengesProtection of forested areas • - Protected areas are not fenced and are still vulnerable

to human impact• In the Amazon, officers responsible for monitoring the

protected areas may give in to corruption and allow loggers and miners to illegally enter protected areas

• - There are not enough forest rangers to patrol the huge areas of the Amazon rainforest families illegally settling in the protected areas


Managing deforestation in the AmazonReforestation- Non-profit organisations,

companies and local communities are involved in the reforestation projects in the Amazone rainforest.

Eg. Reforestation in Peru• Organised by LATA (Latin America

Travel Association) Foundation• Buy seedlings from and pays local

communities to plant trees. 70,000 trees were planted in 2011


BenefitsReforestation • Reforestation improves soil fertility sustained plant

growth.• Reduces erosion, maintains the water cycle, and

preserves the rainforest habitat and biodiversity• Creates more jobs for local communities e.g.

producing seedlings to plant, tour guiding


ChallengesReforestation • Can be expensive and time-consuming• Depends on the availability of native plants for

reforestation


Managing deforestation in the AmazonControlled logging• Allows logging only in certain areas and in sustainable

manner (eg. Only selected plant species can be logged)• Ways to control logging:-impose penalties (fines & imprisonment) on irresponsible timber companies-through education & research programmes, timber companies are informed of the damage done and the necessary measures need to be taken to manage the damage.


BenefitsControlled logging • Greater control of illegal logging has led to a decrease in

deforestation in the Amazon• In recent years, Brazil’s environmental enforcement

agency has stopped several illegal loggers

The Brazilian Institute of Environment and Renewable Natural Resources • Programme: Every tree that is logged is accounted for• Prevents total clearance of a forest• Benefits shared with locals who help run this programme


ChallengesControlled logging • Identifying and logging selected trees is time-

consuming and difficult to implement• Areas designated for controlled logging in the

Amazon still face threats from illegal loggers as the rainforest covers a large area, making it difficult to track illegal loggers


Managing deforestation in the AmazonPublic Education1. Publications – magazines published by World Wide Fund for Nature (WWF) informing people about rainforests. 2. Ecotourism – activities organised by MT Amazon Expeditions to the Amazon rainforests. 3. To people of other countries - Embassy of Brazil in Singapore launched an “Amazonia in Singapore Exhibition” which showcased the biodiversity of the rainforest and raised awareness of management and conservation strategies


BenefitsPublic education • Helps to change people’s mindsets, and increase

awareness, understanding and appreciation of forests

• Knowledge and awareness can lead to action and participation from the community


ChallengesPublic education • Turning environmental awareness into personal

behaviour and action is difficult• Raising awareness is difficult in some countries with low

literacy rates• Many of the countries around the Amazon rely on the

rainforest and these countries obtain income from exports derived from the rainforest


DiscussionWhat can you, as an individual, do to contribute to the global/local efforts to save the rainforest?