Emergent
The tallest layer of the rainforest. Can reach over 40m high.
Upper Canopy
The second tallest layer of the rainforest. Can ready 30-40m high. This is the densest layer of the rainforest and contains the most species. 75% of rainfall is intercepted in this canopy layer.
Under Canopy
The second layer of the rainforest, reaches around 20m high.
Forest Floor
The smallest layer of the rainforest, around 10m high.
Cattle Ranching
The practise of raising a herd of cattle on an area of land. Deforestation often occurs to provide the field space. Cattle ranching is responsible for 80% of deforestation in the Amazon Rainforest.
Logging
Cutting down trees for sale as timber or pulp. The timber is used to build homes, furniture, etc. and the pulp is used to make paper and paper products. Logging can be either selective or clear cutting.
Clear Cutting
Loggers are interested in all types of wood and therefore cut all the trees down, thus clearing the forest. This is not sustainable.
Selective Logging
The practise of cutting down selected trees whilst leaving the rest unharmed. Often, more expensive hardwoods such as mahogany are felled, leaving fast growing softwoods to continue growing. This is a more sustainable method of deforestation.
Vegetation Breezing
When land is cleared the air warms faster, rises and creates an area of low pressure. Rainclouds form above the cleared area and rainfall occurs at expense of the forested area. This rainfall can lead to desertification of the cleared area, preventing any future regrowth.
National Parks and Forest Reserves
A park in use for conservation purposes, created and protected by national governments/An area of forest set aside and preserved by the government. This area is protected from deforestation.
Reforestation
The processes of replanting an area with trees. Also called afforestation.
Enrichment of Degraded Forest
The introduction of valuable species to degraded forest without elimination of valuable species which already exist at that particular site. It is commonly used for increasing the density of desired species in the forest.
National and International Agreements
Agreements made between countries to reduce the amount of deforestation taking place. This can involve higher income countries offering debt relief if the lower income countries reduce their rates of deforestation.
Amazon total annual rainfall
Over 2000mm
What proportion of the total input of precipitation leaves the Amazon basin as river discharge into the Atlantic. What happens to the rest
1/3 (below average)
Most of remaining leaves via evapotranspiration
Average temperature in Amazon - how does it affect the water cycle
27 degrees Celsius - no seasons
High rates of evaporation
How does the structure of the tropical rainforest effect water cycle in Amazon
Canopy intercepts up to half of precipitation. Some will be evaporated from leaves and rest reaches ground through through fall and stem flow. Relatively little water enters groundwater stores or run off to rivers
Biggest cause of deforestation in Amazon
Agriculture - commercial crops e.g. soy and palm oil
Cattle ranching 80% g
How much of Amazon has already been lost
17% in last 50 years
What proportion of Amazon will be treeless by 2030 if current rates of deforestation continue
More then a quarter
How does deforestation or conversion of forest to crops affect water cycle in Amazon
• Vegetation storage reduces.
• Increased river discharge locally. This is due to:
o Fewer trees to absorb water.
o Less interception.
o Reduced infiltration.
• Lower rainfall locally and regionally. This is due to:
o Less evapotranspiration so less condensation, smaller clouds, and less precipitation.
o Studies by Leeds University suggest that regional rainfall could reduce by up to 20%.
Give a place example to illustrate the impact of deforestation on the water cycle
In Rondônia, one of the most heavily deforested areas of Brazil, data shows an 18-day delay in the rainy season compared to the 1970s.
Explain why local areas next to cleared forest have an increase in rainfall
Air over a cleared area warms faster than air over forest. This creates localised low pressure as the warmer air rises. This results
in localised convectional rainfall.
Explain how burning trees can reduce rainfall
The burning produces ultrafine airborne aerosols (particles). Water condenses around airborne particles, but these are so small that
the droplets formed are too small and light to fall as rain.
