15 Amazon Case Study - Carbon Cycle

Question 1

What is GPP (Gross Primary Productivity)?

Answer 1

• Gross Primary Productivity (GPP) is the total amount of organic matter produced by photosynthesis by plants in an ecosystem over a given period of time, typically one year. It represents the total energy that is fixed by plants in an ecosystem, and is an important measure of the productivity and health of ecosystems.

Question 2

What is NPP (Net Primary Productivity)

Answer 2

• how much carbon dioxide vegetation takes in during photosynthesis minus how much carbon dioxide the plants release during respiration

Question 3

What is the formula for NPP?

Answer 3

Question 4

Why are there so few nutrients in the soil of the tropical rainforest?

Answer 4

• Nutrients are stored in the vegetation rather than the soil
• The high temperature and moisture of tropical rainforests cause dead organic matter in the soil to decompose more quickly than in other climates, thus releasing and losing its nutrients rapidly.
• Constant leaching of nutrients by heavy rainfall also contributes to poor nutrient content of the soil

Question 5

How much carbon does the Amazon rainforest absorb a year?

Answer 5

• 2.4 billion tonnes a year

Question 6

What is the Amazon’s NPP?

Answer 6

2500 grams/m2/year

Question 7

What are the physical factors that affect stores and flows of Carbon

Answer 7

• Temperature
• Geology

Question 8

How does temperature affect stores and flows of carbon?

Answer 8

• High temperatures, high rainfall, and intense sunlight stimulate primary production in the Amazon rainforest, which is responsible for absorbing around 2.4 billion tonnes of CO2 a year.
• Net primary productivity (NPP) in the Amazon averages about 2500 grams/m2/year, which accounts for 15-25% of all NPP in terrestrial ecosystems.
• High temperatures and humid conditions promote rapid decomposition of organic litter by bacteria, fungi, and other soil organisms, which releases nutrients to the soil for immediate take-up by tree root systems and emits CO2 which is returned to the atmosphere.

Question 9

How does geology affect stores and flows of carbon?

Answer 9

• The geology of the Amazon Basin is dominated by ancient igneous and metamorphic rocks, with carbonates largely absent from the mineral composition of these rocks.
• However in the western parts of the basin, close to the Andes, outcrops of limestone occur, which represent a significant regional carbon store. These rocks weather over time and release carbon into the atmosphere.

Question 10

Land Use Change

How does human activity affect the stores and flows of carbon?

Answer 10

• 4/5th of deforested land in the rainforest is converted to pastures for cattle farming, however croplands and pastures contain only a small amount of carbon compared to forest trees.
• When a forest is cut and burned to establish cropland and pastures, the carbon that was stored in the tree trunks (wood is about 50% carbon) joins with oxygen and is released into the atmosphere as CO2
• Converting forests to other land uses, such as soybean or cattle production, alters the carbon cycle in the Amazon.
• Croplands and pasture only contain 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.

Question 11

Deforestation

How does human activity affect the stores and flows of carbon?

Answer 11

• Present-day deforestation is most severe in the tropical rainforest.
• In primary rainforest, unaffected by human activity, the biomass of trees represents about 60% of all the carbon in the ecosystem.
• The above ground carbon biomass of trees in the rainforest is approximately 180 tonnes/ha. Most of the remaining carbon is found in the soiul as roots and dead organic material
• Deforestation exhausts this carbon biomass store
• Soils, depleted of carbon and exposed to strong sunlight (due to deforestation), support fewer decomposrt organisms, thus reducing the flow of carbon from the soil to the atmosphere.

Talk about how it affects Evapotranspiration and hence interception. Tal

Question 12

How much carbon does the Amazon Rainforest release every year?

Answer 12

• 1.7 billion tonnes

Question 13

Nutrient cycle

How does human activity affect the stores and flows of nutrients?

Answer 13

• Deforestation exhasuts main nutrients which are in the forest tree store (e.g. potassium, magnesium and calcium)
• Soils - nutrients no longer taken by root systems of trees washed out of soils by rainwater
• Soils - without protective cover of trees are quickly eroded by run-off

Question 14

Mining

How does human activity affect the stores and flows of carbon?

Answer 14

• Deforestation: Large-scale mining operations can cause significant deforestation through forest clearing and the construction of roads which opens remote forest areas to settlers and small-scale miners. This can have a significant impact on the carbon cycle as trees absorb carbon dioxide during photosynthesis.
• Release of mercury: Both large-scale and small-scale mining operations rely heavily on hydraulic mining techniques which involve blasting away at river banks and clearing floodplain forests. The process of extracting gold involves the use of mercury, which can end up in rivers, releasing an estimated (1.32 kg) of mercury into waterways for every (1 kg) of gold produced. Mercury is a potent neurotoxin and can have severe effects on the health of people and wildlife.
• Release of carbon dioxide: The process of mining also releases carbon dioxide into the atmosphere, both locally and globally, from machinery involved. Dynamite is often used to blow up large areas of land, which can release pockets of methane stored within the soil, further contributing to global warming.

Question 15

Forest Fires

How does human activity affect the stores and flows of carbon?

Answer 15

• Forest fires in the Amazon can release large amounts of carbon dioxide into the atmosphere, and reduce the forest’s ability to store carbon. Forest fires can also impact local communities, air quality, and biodiversity.
• This is mainly fuelled by global warming caused by human activities resulting in the release of fossil fuels
• According to a study by the National Academy of Sciences, there has been an 84% increase in the frequency of forest fires in the Amazon Basin since the year 2000 due to climate change and deforestation.
• According to a study published in the journal Nature Communications in 2020, forest fires in the Amazon Basin could release as much as 8 billion metric tons of carbon dioxide into the atmosphere annually by 2050, exacerbating global warming.