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The Living World - Tropical Rainforests - Coggle Diagram
The Living World - Tropical Rainforests
Tropical Rainforests
High Biodiversity
Biodiversity is the
variety
of organisms living in a particular area - both
plants
and
animals
Rainforests have extremely
high
biodiversity
- they contain around
50%
of the world's plant, animal and insect species, and may contain around
half
of
all life
on Earth
Rainforests are
stable
and
productive
environments because their climate is constant - its
hot
and
wet
all the time. Plants and animals don't have to cope with changing conditions and there is always plenty to eat
Many organisms have
evolved
to
depend
on just a few other species for survival - they are
specific
to a particular
habitat
and food source. Many species are also found in a small area
Deforestation
and
uncontrolled development
of the rainforest are likely to lead to the
extinction
of many species and the loss of biodiversity. The number of threatened species in Brazil increased from 628 in 2008 to 1182 in 2014
Habitat
Climate
The climate is the
same all year
round - there are no definite seasons
Its
hot
(the temperature is generally between 20-28 degrees and only varies by a few degrees over the year). This is because the
sun's
energy is more intense near the equator as it is
overhead
all year round
Rainfall
is very
high
, around 2000 mm per year. It rains everyday
Plants
Most trees are
evergreen
to help them take advantage of the continual growing season
Many trees are really
tall
and the
vegetation
cover is
dense
- very little light reaches the forest floor
There are lots of
epiphytes
(plants that grow on other living parts and take nutrients and moisture from the air), e.g. orchids and ferns
Soil
Surface soil is high in nutrients however this is only a thin layer and is quickly used up by plants and animals in the rainforest. Underneath the thin layer of nutrients, the soil
isn't
very
fertile
as heavy rain quickly washes nutrients away that are not used.
There are
surface
nutrients
due to decayed leaf fall, but this layer is very
thin
as high rainfall washes the nutrients away quickly. Decay is fast in the warm, moist conditions.
Animals
Rainforest ecosystems are believed to contain more
animal
species
than any other ecosystems. Gorillas, jaguars, anacondas, tree frogs, sloths and howler monkeys are all found here, and there are also many species of insects and birds
People
Many
indigenous
people have adapted to life in the rainforests
They make a living by
hunting
and fishing, gathering nuts and berries, and
growing
vegetables
in small garden plots
Interdependent Ecosystems
All parts of the rainforest (climate, water, soils, plants, animals and people) are dependent on one another - if any
one
of them change,
everything
else is affected. For example:
The
warm
and
wet
climate helps fungi and bacteria on the forest floor to
decompose
dead plant material
rapidly
. This makes the surface soil
high
in
nutrients
, meaning plants can
grow easily
Plants
pass on
their
nutrients
when eaten by animals. The dense vegetation provides lots of
food
, so animal populations are
high
. When the animals
die
, their nutrients are transferred back to the soil, making it richer and encouraging lots of
vegetation
. This is a key part of the
nutrient cycle
Many plant and animal species have formed
symbiotic relationships
(depend on each other for survival). For example: Agouti and Cecropia Trees
Agouti
Agouti
(a rodent) are one of the only animals that can
crack
open the hard seed pod of the
Brazil nut
to eat the nut inside. Sometimes, the agouti
bury
the nuts - these can
sprout
into new seedlings. If the agouti becomes
extinct
, Brazil nut trees numbers would
decline
and so could the populations of all the other animals that depend on Brazil nut trees for food or shelter.
People
who
sell
Brazil nuts to make a living could also be affected
Cecropia Trees
Cecropia trees
have hollow stems and produce an energy-rich
foodstuff
at the base of their leaves. This makes the trees an ideal home for the
Azteca ants
, who rely on the trees for
food
and
shelter
. Without Cecropia trees, the Azteca ants could struggle to survive.
The ants
fight
off other insects that try to feed on the tree. They also
attack lianas
, which
compete
with the Cecropia for
sunlight
by winding vines around their stems. Without the Azteca ants, Cecropias would be much more vulnerable to predators
Humans Interfering
Changes
to one part of the rainforest ecosystem can have
knock-on effects
on the whole ecosystem. For example, cutting down trees (deforestation) can contribute to climate change
Trees
intercept
and take up lots of water, and
release
it back to the atmosphere, providing moisture for further rainfall.
Reducing
tree cover may
increase
the risk of
drought
, affecting the plants and animals that live in the rainforest ecosystem
Trees
stabilise
soil with their root and provide some nutrients when they
drop
their
leaves
. With fewer trees, the soil would have less protection from heavy rainfall, the few
nutrients
present would
wash away
more easily and plants would
struggle
to grow
Adaptions
Plants
in the rainforest are adapted to
high rainfall, high temperatures and competition for light
Trees compete for for sunlight by growing tall
Plants have thick waxy leaves with pointed drip tips. These channel rainfall to the point encouraging runoff so the weight of the water doesn't damage the plants
Climbing plants use tree trunks to reach sunlight
Many trees have smooth, thin bark as there is no need to protect them from cold temperatures. The smooth surface also helps water run off easily
Large stable buttress roots, support the trees' trunks
Plants drop their leaves gradually throughout the year, meaning they can go on growing all year round
Animals
are adapted to
finding food and escaping predators
Many animals spend their entire lives high up in the canopy. They have strong limbs so that they can move around their habitat quickly and easily
Some birds have short, pointed wings so that they can easily manoeuvre between the dense tangle of trees
Suction cups help some animals climb. Others have flaps of skin that help them glide between trees
Some animals are camouflaged to look like leaves so they can hide from predators
Some animals are adapted to the low light levels on the rainforest floor. Eg anteaters have a sharp sense of smell so they can detect predators without seeing them
Many animals are nocturnal, they feed at night when it is cooler which helps them save energy
Case Study: The Amazon
The Amazon is the largest rainforest on Earth - it covers an area of around 8 million km2, including parts of Brazil, Peru, Columbia, Venezuela, Ecuador, and Bolivia (9 countries)
Almost 18 million hectares of forest were lost between 2001 and 2012
It is estimated that 30% of the Amazon will have been deforested by 2030 if the current rate of deforestation is not reduced
Most biodiverse ecosystem on the planet - 16,000 tree species
Indigenous tribes
Cattle ranching accounts for 70% of deforestation
Rate of deforestation falling since 2004
Reasons for Deforestation:
Commercial Farming
Forest is cleared to make space for cattle grazing or for huge plantations
Cattle ranching is the main cause of deforestation in the Amazon - In Brazil 200 million cattle on 450 000 km2 of pasture
Soy, rice, corn and sugar cane are also commercially farmed crops
Subsistence Farming
Forest is cleared by small scale farmers who need land to grow crops for themselves and their families
Many indigenous people are subsistence farmers
Commercial Logging
The Amazon is full of valuable hardwood trees such as mahogany which makes logging extremely tempting to both legal and illegal businesses
Mineral Extraction
Gold, iron ore and copper are mined and exported to help boost countries development. Explosives are sometimes used to clear earth and deep pits have to be dug to reach the minerals
Energy Development
Building hydroelectric dams floods large areas of forest
Road Building
The 4000km Trans-Amazonian Highway connects the Brazilian coast to Peru, Columbia, and Ecuador through the Amazon
New roads built for logging have opened up areas that were previously too hard to get to, destroying and threatening more of the forest
Impacts of Deforestation
Climate Change
Trees remove CO2 from the atmosphere. The Amazon stores 140 billion tonnes of carbon. Deforestation releases some of this as CO2 which causes global warming
Up to 75% of Brazil's CO2 emissions come from deforestation
Soil Erosion
Brazil is losing up to 100 tonnes of topsoil per hectare each year because of soil erosion. This may lead to landslides and flooding in the future
With less tree canopy to intercept rainfall and fewer tree roots to absorb it, more water reaches the soil. This reduces soil fertility as nutrients in the soil are washed away
Economic
Economic development, farming in particular, has brought wealth to many Amazonian countries. Eg in March 2018, Brazil exported almost $600 million of beef. Brazil is also the second largest exporter of soy beans
The mining industry creates jobs for lots of people
Logging contributes a huge amount to Brazil's economy but destroys resources that countries depend on and makes the area less attractive to tourists
Sustainable Management
Replanting
This is when
new trees
are planted to replace the ones that have been cut down
It's important that the
types
of trees replanted match those that were cut down
In some countries there are
laws
to make logging companies
replant
when they clear an area
Selective Logging
Only
some
trees (e.g. old ones) are felled -
most
trees remain
This is
less damaging
to the forest than clearing a whole area. If only a few trees are taken from an area the overall forest
structure
is
kept
- the canopy remains and the soil isn't exposed. This allows the forest to
regenerate
The least damaging forms are
'horse logging'
and
'helicopter logging'
- dragging felled trees out of the forest using horses or removing them with helicopters instead of huge trucks
Ecotourism
Ecotourism
minimises damage
to the
environment
and
benefits local people
Only a
small number
of visitors are allowed into an area at one time and rules are imposed to minimise environmental impacts
Ecotourism provides a source of
income
for local people. Eg guides or in transport
If local people are
employed in tourism
then they d
on't have to log or farm
to make money meaning fewer trees are
cut down
Education
Educating the international community about the
impacts
of deforestation can encourage people to buy
products
from sustainable sources
Local people might damage the forest (e.g. by logging illegally) to overcome their poverty,
without realising
the long-term effects of their actions
Educating local people about the
impacts
of deforestation can help to reduce
damage
to rainforests
Teaching local people about
alternative
ways to make
money
that dont damage the environment as much, means they wont be dependent on
unsustainable
options in order to make a living
Conservation
Many countries have set up
national parks
and
nature reserves
within rainforests. In those areas damaging activities such as logging are
restricted
, however a
lack of funds
means policing is hard
As a result some countries have set up
funds
which
overseas governments
and businesses can
invest
in. The countries get the money in exchange for rainforest conservation
The money can be used to
enforce restrictions
on damaging activities and to
promote sustainable
use of the rainforests
Reducing Debt
Many tropical rainforests are found in
lower income countries
which often
borrow money
from wealthier countries or the World Bank
This money must be
paid back
with interest, so poorer countries
log, farm and mine to make the money to pay back
Reducing debt means countries don't have to do this so the rainforest can be conserved
Debt can be cancelled by countries or organisations, but there's no guarantee that the repayment money will be spent on conservation
A better solution is conservation swap, where part of a country's debt is paid off in exchange for a guarantee that the money will be spent on conservation
International Hardwood Agreements
Hardwood is a general term for wood from certain tree species e.g.
mahogany or teak
. The wood tends to be dense and hard, so its often used to make furniture
High demand
for hardwood from consumers in richer countries means that some tropical hardwood trees are becoming increasingly
rare
as more are cut down
There are
international agreements
in place to try and prevent illegal logging, and to
promote
the use of hardwood from
sustainably managed
forests e.g.
logos
are used to show
sustainably-sourced timber
Tropical rainforests and very
valuable
to
people
and the
environment
:
Many
products
including rubber, coffee, chocolate and medicines, are
sourced
from the rainforest. If species become
extinct
, its harder to discover new
medicines
and develop new products
Sustainable development can offer long-term
economic benefits
e.g. ecotourism
Protecting the rainforests may
reduce
the
greenhouse effect
by reducing CO2
emissions
(from burning, etc), and allowing the trees to continue
absorbing
CO2
Some of the
impacts
of the rainforest destruction, e.g. climate change, could affect
all countries
, not just the countries where deforestation is happening
Rainforests also help
regulate
the
climate
and
water cycle
- without them the risks of drought and flooding in certain areas can increase