The Amazon Rainforest - case study

How much of South America does the Amazon cover?

40% of the landmass

Climate and vegetation

Hot, wet climate with lots of dense vegetation

Which groups of people live in the rainforest?

Indigenous people

Plant, fish and mammal species

1 million plant species, 500 mammal species, 2000 fish species

Endangered species

Amazonian manatee, black caiman and the pirarucu

Why does the water cycle cause the Amazon to be very wet?

There is a lot of evaporation over the Atlantic Ocean, and the wet air is blown towards the Amazon. This contributes to the Amazon’s very high rainfall

Warm temperatures

Evaporation is high in the rainforest, increasing precipitation

Dense canopy

Interception is high, this means less water flows into rivers than might otherwise be expected, and it does so more slowly

How does the water cycle affect the Amazon environment?

Populated by species that are adapted to high humidity and frequent rainfall

Why is the Amazon Rainforest a carbon sink?

It stores lots of carbon in its vegetation and soil

Why has the Amazon seen increased productivity?

Increasing concentration of atmospheric carbon dioxide- the vegetation can access more carbon dioxide for photosynthesis- amount of biomass is increasing

What is happening to trees as a result of increased atmospheric carbon?

Trees are growing more quickly but dying younger

Effects of deforestation on the water cycle

• No tree canopy to intercept rainfall- more water reaches ground surface. Too much water to soak into the soil. Water moves to rivers as surface runoff- increased flood risk

• Reduced evapotranspiration- less water vapour reaches the atmosphere, fewer clouds, less rainfall- increased drought risk

Effects of deforestation on the carbon cycle

• No roots to hold soil together. Rain washes away nutrients in top soil, carbon from soil to hydrosphere

• Less leaf litter, no humus. Soil can’t support growth, limits carbon absorption

Climate change impacts

• More drought- severe droughts in 2005, 2010, and 2015-16

• Many species die in dry weather. Long periods of drought could lead to extinction of some species

• Drought can lead to forest fires - releasing CO2 into atmosphere

• 4 degree temp increase could kill 85% of the rainforest. Increased atmospheric carbon due to decomposition, less CO2 being taken in for photosynthesis

Selective logging

• Only some trees felled

• Less damaging than felling all the trees

• Forest structure is kept- soil isn’t exposed

• Forest can regenerate, impact on water and carbon cycles is small

Replanting

• E.g. project in Peru replanted 115 acres between 2016 and 2019

• Same types of tree planted that were cut down

• Variety of trees kept for future, local water and carbon cycles return to their initial state

Environmental law

• Laws that ban use of wood from forests that aren’t sustainably managed

• Laws that ban logging

• Laws that control land use, e.g. Brazilian Forest Code says landowners have to keep 50-80% of their land as forest

Protection

Some countries have set up national parks / nature reserves

Central Amazon Conservation Complex in Brazil set up in 2003 and protects biodiversity in an area of 49,000 km2 while allowing local people to sustainably use the forest

Damaging activities such as logging can be monitored and prevented