AMAZON RAINFOREST

Question 1

LOCATION

Answer 1

• In South America
• occupies area of more than 6 million km2
• 70% of rainforest in BRAZIL, but also extends into parts of Peru, Ecuador, Venezuela, Colombia, Bolivia, Guyana
• Amazonia is world’s largest rainforest
• Dominated by tall, evergreen, hardwood trees

Question 2

WATER CYCLE: CLIMATE/CLIMATIC FEATURES

Answer 2

• high average annual temperatures between 25 °C + 30°C
• small seasonal variation in temperature
• high average annual rainfall (>2000 mm) with no dry season

Question 3

High average temperatures are response to…

Answer 3

intense insolation throughout year
~ But, significant cloud cover ensures maximum temperatures do not reach extremes of subtropical desert climates.

Question 4

Seasonal differences in temperature are…

Answer 4

small + convectional rain falls all year round, though most areas experience at least 1 drier period.

Question 5

How much precipitation recycled by evapotranspiration in Amazonia

Answer 5

• Between 50 + 60%

Question 6

Water losses from Amazon Basin result from

Answer 6

river flow + export of atmospheric vapour to other regions.
~ this loss made good by inward flux of moisture from Atlantic ocean

Question 7

flows + stores in Water cycle in Amazon rainforest

Answer 7

Precipitation
Evapotranspiration
Run-off
Atmosphere
Soil/groundwater
Vegetation

Question 8

1. Precipitation

Answer 8

High average annual rainfall (>2000 mm)
Rainfall fairly evenly distributed throughout year though short drier season occurs in some places.
High-intensity, convectional rainfall
Interception by forest trees is high (around 10% of precipitation). Intercepted rainfall accounts for 20-25% of all evaporation

Question 9

2. Evapotranspiration

Answer 9

• High rates of evaporation + transpiration due to high temperatures, abundant moisture + dense vegetation
• Strong evapotranspiration-precipitation feedback loops sustain high rainfall totals
• Around half of incoming rainfall returned to atmosphere by evapotranspiration
• Most evaporation from intercepted moisture from leaf surfaces
• Moisture lost in transpiration is derived from soil via tree roots

Question 10

Run-off

Answer 10

Rapid run-off related to high rainfall, intensive rainfall events and well-drained soils. Depending on seasonal distribution of rainfall, river discharge may peak in one or two months of the year.

Question 11

atmosphere

Answer 11

High temperatures allow atmosphere to store large amounts of moisture (i.e. absolute humidity is high). Relative humidity is also high.

Question 12

soil/groundwater etc

Answer 12

Abundant rainfall and deep tropical soils lead to significant water storage in soils and aquifers.

Question 13

vegetation

Answer 13

Rainforest trees play crucial role in water cycle, absorbing + storing water from soil + releasing it through transpiration.

Question 14

rainforest carbon cycle

Answer 14

Amazonia’s humid equatorial climate creates ideal conditions for plant growth.

Amazon rainforest is major global reservoir of stored carbon, absorbing 2.4 billion tonnes a year.
Compared to other forest ecosystems, RAPID exchanges of carbon between atmosphere, biosphere + soil

Warm, humid conditions ensure speedy decomposition of dead organic matter + quick release of CO2

Meanwhile, HIGH rates of carbon fixation through photosynthesis
Amazonia’s leached + acidic soils contain only limited carbon + nutrient stores.
fact that such poor soils support biome with highest NPP + biomass of all terrestrial ecosystems, emphasises speed with which organic matter is broken down, mineralised + recycled.

Question 15

NPP, biomass, storage of carbon from large trees + soil

Answer 15

Net primary productivity (NPP) is high, averaging 2500 grams/m3/year
biomass is between 400 and 700 tonnes/ha.
Large forest trees typically store around 180 tonnes C/ha above ground, + further 40 tonnes C/ha in their roots.
Soil carbon stores average between 90 + 200 tonnes/ha.

Question 16

Physical factors such as…affect flows + stores of water in Amazon rainforest + other environments.

Answer 16

geology, relief + temperature

Question 17

Geology + effect on flood hydrograph

Answer 17

Impermeable catchments (e.g. large parts of Amazon Basin are ancient shield area comprising impermeable, crystalline rocks) have minimal water storage capacity resulting in rapid run-off
Permeable + porous rocks (e.g limestone + sandstone) store rainwater + slow run-off

Question 18

Relief (slopes)

Answer 18

Most of Amazon Basin comprises extensive lowlands. In areas of gentle relief, water moves across surface (overland flow) or horizontally through soil (throughflow) to streams + rivers.
In the west the Andes create steep catchments with rapid run-off. Widespread inundation across extensive floodplains (e.g. Pantanal) occurs annually, storing water for several months + slowing its movement into rivers.

Question 19

temperature

Answer 19

High temperatures throughout year generate high rates of evapotranspiration
Convection is strong, leading to high atmospheric humidity, development of thunderstorm clouds + intense precipitation.
Water cycled continually between land surface, forest trees + atmosphere by evaporation, transpiration + precipitation.

Question 20

Physical factors affecting stores and flows of carbon

Answer 20

Forest trees dominate the biomass of Amazon Basin + are principal carbon store. In total approximately 100 billion tonnes of carbon locked up in Amazon rainforest.
Absorbing around 2,4 billion tonnes of CO, a year + releasing 1.7 billion tonnes through decomposition, rainforest is a carbon sink of global importance.

Carbon CYCLES between forest + other living organisms, soil + atmosphere.

Photosynthesis connects rainforest to atmosphere carbon stores.

Question 21

% of rainforest carbon stored in above ground biomass of tree stems, branches and leaves.

Answer 21

60%
remainder is below ground, mainly as roots and soil organic matter.

Question 22

High temperatures, high rainfall and intense sunlight stimulate…

Answer 22

primary production.
NPP averages about 2500 grams/m2/year. Amazonia alone accounts for
15-25 per cent of all NPP in terrestrial ecosystems.
Leaf litter + other dead organic matter accumulates temporarily at soil surface + within rainforest soils.

Question 23

High temperatures + humid conditions promote

Answer 23

rapid decomposition of organic litter by bacteria, fungi + other soil organisms.
Decomposition releases nutrients to soil for immediate take-up by tree root systems, + emits CO2 which is returned to atmosphere.

Question 24

geology of Amazon Basin is dominated by

Answer 24

ancient igneous and metamorphic rocks. Carbonates are largely absent from the mineral composition of these rocks.

However, in western parts of basin, close to Andes, outcrops of limestone occur. In context of slow carbon cycle they are significant regional carbon stores.

Question 25

Human factors affecting stores and flows of water

Answer 25

Deforestation in Amazonia averaged around
17,500 km2/year between 1970 and 2013. Since 1970
almost one-fifth of the primary forest has been destroyed or degraded (Figure 4.14). Since 2009 annual rates have been lower than the average but have started to rise again in recent years

In April 2014 devastating floods occurred on the Madeira River, the largest tributary of the Amazon River (Figure 4.14).
At Porto Velho the river reached record levels of 19.68 m above normal. Vast expanses of floodplain were inundated; 60 people died; 68,000 families were evacuated; and there were outbreaks of cholera and leptospirosis.
In the Upper Madeira drainage basin human activity has modified stores and flows in the water cycle. Deforestation has reduced water storage in forest trees, soils which have been eroded), permeable rocks (due to more rapid run-off) and in the atmosphere. At the same time fewer trees mean less evapotranspiration and therefore less precipitation.
Meanwhile, total run-off and run-off speeds have increased, raising flood risks throughout the basin.
Despite torrential rains in the upper basin of the Madeira River, the main driver of the floods was deforestation in Bolivia and Peru. Between 2000 and 2012, 30,000 km? of Bolivian rainforest was cleared for subsistence farming and cattle ranching. Much of this deforestation occurred on steep lower slopes of the Andes. The result was a massive reduction in water storage and accelerated run-off.

Question 26

Deforestation has a huge impact on the water cycle and has the potential to change the climate at local and regional scales.

Answer 26

Converting rainforest to grassland increases run-off by a factor of 27, and half of all rain falling on grassland goes directly into rivers. Rainforest trees are a crucial part of the water cycle, extracting moisture from the soil, intercepting rainfall and releasing it to the atmosphere through transpiration, as well as stabilising forest albedo and ground temperatures. This cycle sustains high atmospheric humidity which is responsible for cloud formation + heavy conventional rainfall Deforestation breaks this cycle and can lead to permanent climate change

Question 27

However, the impact of deforestation on water cycles is not just local.

Answer 27

Projections of future deforestation in Amazonia predict a 20 per cent decline in regional rainfall as the rainforest dries out and forest trees are gradually replaced by grassland.

Nor is it just deforested areas that experience a reduction in rainfall: disruption of the regional water cycle means that forests hundreds of kilometres
downwind of degraded sites are affected too.

Question 28

Human factors affecting carbon and nutrient flows and stores

Answer 28

Present-day deforestation is most severe in the tropical rainforest. In primary rainforest, unaffected by human activity, the biomass of trees represents about 60 per cent of all the carbon in the ecosystem. The above ground carbon biomass in the rainforest is approximately 180 tonnes/ha. Most of the remaining carbon is found in the soil as roots and dead organic material.

Question 29

Deforestation exhausts the carbon biomass store.

Answer 29

Croplands and pasture contain only a small amount of carbon compared to forest trees. For example, the biomass of grasslands in areas of former rainforest is 16.2 tonnes/ ha; and for soya cultivation it is just 2.7 tonnes/ha. At the same time, deforestation drastically reduces inputs of organic material to the soil. Soils, depleted of carbon and exposed to strong sunlight, support fewer decomposer organisms, thus reducing the flow of carbon from the soil to the atmosphere

Question 30

In tropical rainforests, principal store of plant nutrients such as calcium, potassium + magnesium is forest trees.

Answer 30

Rainforest soils contain only small reservoir of essential nutrients + forest is only sustained by rapid nutrient cycle.
Deforestation destroys main nutrient store (forest trees) + removes most nutrients from ecosystem. Nutrients no longer taken up by root systems of trees are washed out of soils by rainwater; and soils, without protective cover of trees, are quickly eroded by run-off.

Question 31

Strategies to manage tropical rainforests: positive effects on water + carbon cycles

Answer 31

degrading or outright destruction of large areas of Amazon rainforest is an issue of international as well as national concern. This is because deforestation has implications for global climate change. Brazil is committed to restoring 120,000 km2 of rainforest by 2030.
Indigenous people have lived sustainably in the rainforest for thousands of years, maintaining the water balance, carbon cycle and the forest’s biodiversity. These people survived as hunter-gatherers and shifting cultivators
- in contrast to exploitative commercial farming, logging + mining of past 50 years, indigenous people pursued way of life, perfectly adapted to limited resources + fragility of rainforest

Question 32

Modern strategies to manage the Amazon rainforest sustainably fall into 3 categories:

Answer 32

• Protection through legislation of large expanses of primary forest so far unaffected by commercial developments.
• Projects to reforest areas degraded/destroyed by subsistence farming, cattle ranching, logging + mining.
• Improving agricultural techniques to make permanent cultivation possible.

Question 33

Since 1998 Brazilian government has established many forest conservation areas.

Answer 33

These Amazon Regional Protected Areas now cover an area twenty times the size of Belgium.
By 2015, 44 per cent of the Brazilian Amazon comprised national parks, wildlife reserves + indigenous reserves where farming is banned.

Question 34

Several reforestation projects, sponsored by local authorities, non-governmental organisations (NGOs) and businesses, are underway but so far progress has been slow

Answer 34

One such example is Parica project in Rondônia in the western Amazon. This sustainable forestry scheme aims to develop a 1000 km? commercial timber plantation on government-owned, deforested land. The plan is for 20 million fast-growing, tropical hardwood seedlings, planted on 4000 smallholdings, to mature over a period of 25 years.
Financial assistance is given to smallholders for land preparation, planting and the maintenance of plots. Tree nurseries provide them with seedlings. Timber will be exported along the Amazon and its tributaries through Manaus or Port Velho.
Although this project is a monoculture and cannot replicate the biodiversity of the primary rainforest, it is sustainable. It also sequesters carbon in the trees and soil; reduces CO, emissions from deforestation; re-establishes water and carbon cycles; and reduces
life support systems
run-off and the loss of plant nutrients and carbon from the soil.

Question 35

Also in Rondônia, the indigenous Suruí people participate in a scheme that aims to protect primary rainforest on tribal lands from further illegal logging and reforest areas degraded by deforestation in the past 40 years.

Answer 35

The Suruí plant seedlings bred in local nurseries in deforested areas around their villages. The native species planted are chosen to provide them with timber for construction, food crops and, through logging, a sustainable source of income.

Question 36

In 2009 the Surui were the first indigenous group in Amazonia to join the UN’s Reducing Emissions from Deforestation and Degradation (REDD) scheme.

Answer 36

This scheme provides payment to the tribe for protecting the rainforest and abandoning logging. It is a market-based approach involving granting of carbon credits to the Suruí. These credits can be purchased by international companies which have exceeded their annual carbon emissions quotas. In 2013, Natura, a large cosmetics transnational corporation (TNC), purchased 120,000 tonnes of carbon credits from the Surui. This was the first carbon credit sale by indigenous people in Amazonia.

Question 37

Improved agricultural techniques

Answer 37

Farming has been the main cause of deforestation in Amazonia. However, low fertility of soils meant that permanent cultivation proved unsustainable. After a few years, smallholders abandoned their plots which were then converted to low quality grassland. Extensive ranching enterprises could scarcely support stocking levels of one head of cattle per hectare.
One response to improve agriculture has been diversification. Soil fertility can be maintained by rotational cropping and combining livestock and arable operations. Integrating crops and livestock could allow a fivefold increase in ranching productivity and help slow rates of deforestation.
European explorers observed that the Amazon rainforest, as late as the sixteenth century, supported high population densities, and many large urban centres. This appears to contradict the view that natural resources for farming in the region are too poor to support settled, permanent cultivation. The explanation is thought to be human-engineered soils: so-called dark soils made from inputs of charcoal, waste and human manure. Charcoal in these soils attracts micro-organisms and fungi and allows the soils to retain their fertility long-term. Scientists are currently investigating these dark soils. If they can be successfully recreated they would allow intensive and permanent cultivation which would drastically reduce deforestation and carbon emissions.