The Amazon - W&C Flashcards
Where are tropical rainforests found
In a band between the tropics and cover parts of South Americs, Central Africa and south-east Asia. A smaller area exists in North-eastern Australia
Where does the Amazon rainforest lay
Mostly Within Brazil, with the remainder mainly in Peru and Columbia
How big is the Amazon rainforest
The largest rainforest and covers 2.1 million square miles
What percentage of the earths surface do tropical rainforests cover
6%
What percentage of global photosynthesis do tropical rainforests account for
30-50%
How much of the worlds oxygen do tropical rainforests emit
28%
What is the annual rainfall in rainforests
2000+mm
What is the average temperature in tropical rainforests
27*C
What do the characteristics of tropical rainforests make ideal conditions for
Plant growth
What do rainforests have
A very high biodiversity
What percentage of the worlds species of plants and animals are tropical rainforests home to
50%
Why are inputs to the water cycle of a rainforest high
Because precipitation is very high, occurring throughout the year and usually in daily torrential downpours. It is a consequence of low pressure and high humidity in the tropics.
How much precipitation does the dense canopy of the rainforest intersect
75%
What happens to the intercepted water
Some is evaporated and some reached the ground via stem flow or drips from leaves.
How much of the available rainwater is used by plants and returned to the atmosphere by evapotranspiration
50%
How much of the available rainwater is infiltrated into the soil
50%
What is critical to the regions water supply
Trees of the forest as, through the process of transpiration, trees ensure water enters the atmosphere and in turn produces rain.
What fraction of its own precipitation does the Amazon Basin produce in the recycling of evapotranspiration
1/3, the other 2/3 arrive as moisture-laden air from the Atlantic Ocean
How do raindrops from tropical storms cause soil erosion
They hit the ground with great force
What does a continuous canopy prevent
Soil erosion because the canopy acts as an umbrella so water is transferred through stem flow so have less force than just rain hitting the ground
How is rain water transferred to the forest floor
By a combination of drip flow and stem flow. Drip-tips help the tree to shed water from each leaf, and the rest trickles down branches and stems
What do most rainforests plants have
Very shallow roots that take rainwater and dissolved nutrients directly from the decomposing leaf litter
What is the estimated loss of the Amazon basin in the last 50 years
17%
What is the primary reason the Amazon basin has lost 17% of its primary rainforest
Cattle ranching (80%)
When is the impact of cattle ranching mostly seen
In the east and south-east parts of the basin (Brazil) and in the north-western arc (Columbia and Ecuador)
How does the removal of trees have a massive impact on the rainforest water cycle
It almost wipes out some of the components and significantly affecting others
What does reduced evapotranspiration from cleared areas mean
The air is less moist, resulting in a reduction in cloud cover and less pricks prion.
With fewer trees, what happens to the rainfall
Most rainfall reaches the frond immediately as there is little compacting it. The water leaves the area as overland flow so less is returned to the atmosphere locally. The increased rates of runoff increase the risk of flooding.
In cleared areas, why does temperature increase
Becsuse more solar radiation is reflected by cleared land (than the darker forest canopy)
What limits the chance of regrowth if the forest has been cleared
Exposed soil is at risk of erosion
In a fully forested area, what usually happens to rainfall
It is recycled within the local region
What are the effects some studies have shown about the replacement of forests by pasture or crops
It leads to a reduced atmospheric humidity and suppressing precipitation. This is because rainforests allow a considerable amount of water to be returned to the atmosphere through evapotranspiration. However, other studies have shown an increase in local rainfall downwind of a deforested area.
What has a recent study suggested that rainfall levels in the wider region are likely to do where there is extensive deforestation
Reduce
What have some studies found about the changing patterns of rainfall
air that has passed over extensive forest produces twice as much run compared to air that has passed over little forest. The study estimates that future deforestation of the Amazon rainforest could lead to a 20% decline in regional rainfall.
At a local level, why have some cleared areas experienced an increase in rainfall
Due to ‘vegetation breezes’
What are vegetation breezes
Air over cleared land warms faster, rises quicker and creates localised low pressure, drawing moist air from forested areas. The result is an increase in cloud coverage, thunderstorms and rainfall over the cleared , at the expense of forested areas.
Why is there less rain in places that have been deliberately burned to clear for agriculture
The burning produces airborne aerosols around which water vapour condense. As a result, smaller droplets occur in clouds, which are too small to precipitate, resulting in less rain
Why do tropical rainforests account for between 30-50% or global photosynthesis
Because the warm, humid tropical climate is ideal for plant growth
Why are tropical forests sometimes called the ‘Lungs of the Earth’
Becsuse the forest absorbs huge amounts of carbon from the atmosphere and emit a great deal of oxygen
What percentage of wood is carbon
50%
Rainforests are carbon sinks, why is this good
They help mitigate the effects of climate change
In a typical year, how much carbon dioxide does the Amazon rainforest absorb
2.2 billion tonnes
In a typical year, how much carbon dioxide does the Amazon rainforest emit through decomposition and organism respiration
1.9 billion tonnes
What can be the outputs of carbon in a rainforest
Decomposition
Organism respiration
Soil removed by streams
What do rainforests store more of than any other type of ecosystem
Carbon (as sugar and starches)
What percentage of the terrestrial biomass is though to be stored in rainforests
40-50% , which has been estimated as more than 17 kilograms of carbon per square metre
How much carbon does the Amazon rainforest contain per square meter
Between 14 and 40 kilograms , the soil lying under rainforests also contain substantial amounts of carbon
Where does soil contains its carbon
In roots, microorganisms, soil fungus and plants
What percentage of global soil carbon is stored in the Amazon
27%
What percentage of all carbon in tropical rainforests is found in below ground root systems and soil organic matter
40%
How much carbon in the upper 50 centimetres of the soil level does Amazonian soil confirm
Four to nine kilograms
How much carbon in the upper 50 centimetres of the soil level does pastureland soil confirm
One kilogram
Why are tropical rainforests capacity to recycle the worlds increasing carbon dioxide emissions beginning to appear in doubt
As human activity alters their extent and dominant processes
What is the second largest anthropogenic source of carbon dioxide to the atmosphere
Deforestation
Of global carbon emissions, what percentage does deforestation in tropical rainforests create
6%-17%
When forests are cleared and burned, whether for farming, mining, rocks or settlements, what percentage of carbon is lost to the atmosphere
30-60%
What happens to unburned vegetation
It decays and is lost within 10 years
At what rate has the size of the Amazon been decreasing per year since 2000
0.3%
What are the pros and cons of burning
It is cheap and effective but can burn out of control for weeks
Why does deforestation mean that photosynthesis rates drop
Because there is less vegetation, especially if it is brunt as it will only start again once new plants start to colonise the area
Due to deforestation, what does plant and animal respiration drop to
Almost zero
Due to deforestation, what happens to de composers
They become largely absent from the environment
Due to the slash and burn technique, what increases the carbon content in the soil
Becsuse the rain will wash the ash into the ground so that, in the short term, the carbon content increases
In the past (1990) how much carbon dioxide did the Amazon absorb
2.2 billion tons
In the Amazon, what is declining
Its capacity to operate as a major carbon sink
In 2015, how much carbon dioxide did the Amazon absorb
1 billion
Why does the Amazon basin no longer represent a continental carbon sink
Because the recent absorption of carbon is less than the total co2 emitted by Latin America counties each year
What is the reason for the decline of carbon capture in the Amazon thought to relate to
Substantial tree death within the Amazon basin - it has been assumed that increased atmospheric carbon dioxide levels would stimulate biomass growth (carbon fertilisation) and regulate the emission rise. However it appears that while rainforest plants do grow faster, they die sooner. This has increased metabolic stress that has been compounded but recurrent drought, unusually high temperatures, continued illegal logging and conversion to agriculture.
What does it appear the rainforest is under threat from
Both direct human activity and climate change arising from indirect action in releasing stored hydrocarbons in such massive quantities
