Carbon Cycle

Question 1

What percentage of carbon is stored in the lithosphere?

Answer 1

99.9%

Question 2

What percentage of carbon is stored in the hydrosphere?

Answer 2

0.04%

Question 3

What percentage of carbon is stored in the biosphere?

Answer 3

0.004%

Question 4

What percentage of carbon is stored in the cryosphere?

Answer 4

0.1%

Question 5

What percentage of carbon is stored in the atmosphere?

Answer 5

0.001%

Question 6

Processes driving change in the carbon cycle

Answer 6

Respiration
Photosynthesis
Diffusion
Sequestration
Decomposition
Weathering
Compaction
Combustion

Question 7

Stages of succession in the lithosphere

Answer 7

bare rock colonised by pioneer species such as lichens
Dead organic material builds up and the exposed rock is further weathered
Mosses colonise rocks and soil forms when the rock is further weathered
Decomposition of organic matter leads to carbon in the soil
Grasses grow, roots cause biological weathering
Soil respiration improves quality
Larger plants grow due to more nutrients

Question 8

Human causes of change in the carbon cycle

Answer 8

Hydrocarbon fuel extraction and burning
Farming practices
Deforestation
Land use changes

Question 9

Natural causes of change in the carbon cycle

Answer 9

Volcanic activity
Wildfires

Question 10

Today, the concentration of carbon in the atmosphere is the highest it’s been for how many years? What is it’s concentration?

Answer 10

Over 420 ppm (parts per million).

Question 11

Outline the processof photosynthesis

Answer 11

• Transfers carbon stored in the atmosphere to biomass.
• Plants and phytoplankton use energy from the Sun to change CO2 and water into
glucose (carbohydrates) and oxygen. This enables plants to grow.
• Carbon is then passed through the food chain and released through respiration and
decomposition.

Question 12

Outline the process of respiration

Answer 12

• Transfers carbon from living organisms to the atmosphere.
• Plants and animals break down glucose for energy, releasing CO2 and methane (which
contains carbon) in the process.
• This process is essentially the opposite of photosynthesis. Respiration takes O2 from
the atmosphere and replaces it with CO2. These processes are not in balance; the rate of photosynthesis is greater than the rate of respiration.

Question 13

Name decomposers that help break organisms down, releasing carbon into the soil and atmosphere.

Answer 13

Bacteria, fungi and insects such as ants and beetles.

Question 14

What makes decomposition essential for life on earth?

Answer 14

Decomposition ensures that carbon can be continually recycled into the soil and made available for life.

Question 15

Process of combustion

Answer 15

• Transfers carbon stored in living, dead or decomposed biomass (including peaty soils) to the atmosphere by burning.
• Combustion occurs when any organic material is reacted (burned) in the presence of oxygen to give off CO2, water and energy.
• The organic material includes any vegetation or fossil fuel such as natural gas (methane), oil or coal.
• Wildfires cause carbon flow.

Question 16

Weathering in carbon cycle

Answer 16

• Chemical weathering transfers carbon from the atmosphere to the hydrosphere and biosphere.
• Atmospheric carbon reacts with water vapour to form a mildly carbonic acid. When this acid rain falls onto rocks, a chemical reaction occurs which dissolves the rocks. The molecules resulting from this reaction may be washed into the sea. Here they react with CO2 dissolved in the water to form calcium carbonate, which is used by sea creatures, e.g. to make their shells.

Question 17

Processes involved in natural sequestration of carbon

Answer 17

• Carbon from the atmosphere can be sequestered (captured and held) in sedimentary rocks or as fossil fuels. This effectively puts carbon into long-tern storage.
• The process begins with the transfer of carbon from the atmosphere to vegetation during photosynthesis and then to the soil during decomposition. Weathering also transfers carbon to the soil. Once in the soil carbon can transfer to the oceans via the water cycle where is can accumulate of the sea bed and become sedimentary rock through the process of burial and compaction.
• Rocks and fossil fuels form over millions of years when dead animals and plant material in the ocean falls to the floor and is compacted.

Question 18

Identify the main carbon transfers found at the scale of a plant?

Answer 18

Respiration, photosynthesis and decomposition.

Question 19

Identify the main transfers operating at a global scale.

Answer 19

Combustion, sequestration, ocean uptake and loss.

Question 20

Ecological succession

Answer 20

A process in which the mix of plant species and habitat in an area over time. Gradually, plant communities replace one another.

Question 21

Outline the main changes in the storage and cycling of carbon as succession moves from its first stage to the final stage of climatic climax.

Answer 21

At the beginning of a succession, e.g., a lithosere succession on bare rock, carbon is in the rock and the atmosphere. As the succession moves from the pioneer stage to the climatic climax carbon is transferred to biomass as the mass of vegetation increases due to photosynthesis and also to the soil due to decomposition and weathering.

Question 22

Outline the main way in which wildfires change the carbon cycle (refer to the transfers and stores involved).

Answer 22

Wildfires rapidly transfer carbon from vegetation (and soil) to the atmosphere through combustion. Immediately, less photosynthesis occurs so less atmosphere is removed from the atmosphere. In the short-term atmospheric concentrations of carbon therefore increase.

Question 23

Explain why fires may have a neutral effect on amount of atmospheric carbon in longer urn

Answer 23

In time vegetation will start to grow again and recolonise the area with vegetation (secondary succession). During this process photosynthesis will increase as plant communities develop, removing more carbon from the atmosphere, returning the system to equilibrium.

Question 24

Identify a regional area that has been significantly affected by wildfires this century.

Answer 24

Indonesia, SE Asia (2013) or California, USA (2018).

Question 25

Large wildfires can turn forests from being a carbon sink to being a carbon source.’ Explain this statement by referring to carbon cycle stores and transfers.

Answer 25

Natural forests, such as the Amazon, are large carbon sinks (as photosynthesis exceeds respiration each year increasing carbon stored in vegetation (biomass). However, if wildfires are extensive and intense (as is occurring more frequently as global temperatures increase), combustion returns large amounts of carbon to the atmosphere. This can have a lasting effect on the ecosystem, soils may be critically damaged and large- scale loss of trees may dampen rainfall to the extent that the forest never recovers. Through this positive feedback the area may become a carbon source.

Question 26

Name a geological era when volcanos were more active than today, releasing large amounts of CO2 into the atmosphere.

Answer 26

Palaeozoic

Question 27

Explain how the extraction and combustion of hydrocarbons impacts the carbon cycle.

Answer 27

Fossil fuels are hydrocarbons and form part of the huge stores of carbon locked away in the lithosphere. By mining and burning fossil fuel for energy and in industrial processes, this carbon is removed from long-term storage and enters the atmosphere, where is become part of the fast carbon cycle and increases the concentration of carbon in the atmosphere.

Question 28

The burning of fossil fuels can be dated from the beginnings of the Industrial Revolution in 1750, but the rate of burning has increased since 1950. Give reasons why.

Answer 28

This is due to the rapid industrialisation of developing nations (such as India and China) as well as the continued demand from the world’s industrialised nations such as the USA.

Question 29

According to the Intergovernmental Panel on Climate Change (IPCC), what percentage of human related global CO2 emissions come from burning fossil fuels?

Answer 29

90%

Question 30

Outline impact of cement manufacture on carbon cycle

Answer 30

Cement manufacture involves the heating of calcium carbonates (e.g. limestone). This produces CO2 and lime. CO2 is also produced by burning fossil fuels to provide the heat for the cement manufacture process. It is estimated that the cement industry produces 5% of global anthropomorphic CO2 emissions.

Question 31

Agriculture is responsible to significant carbon emissions. Outline three farming activities responsible for emissions.

Answer 31

• Livestock release CO2 and methane when they respire and digest food. This is the largest source of CO2 within agriculture. • Ploughing can release carbon stored in the soil. When soil is turned over, air mixes in and soil microbial activity increases. This results in soil organic matter being broken down more rapidly, and carbon is lost from the soil and transferred into the atmosphere as CO2. • Growing rice in rice paddies releases a lot of methane.

Question 32

Rice paddies + emissions

Answer 32

accounts for over 40% of agriculture-related greenhouse gas outputs occur in Asia.

Question 33

Give two reasons why agricultural activities are having an increasing impact on the carbon cycle.

Answer 33

• As the world’s population has risen, so has food production. As a result, carbon emissions from farming practices have increased. • Mechanisation of farming has also increased CO2 emissions as more tractors and other farm vehicles are used across the globe.

Question 34

Give three reasons why deforestation may occur.

Answer 34

Forests may be cleared for agriculture, logging, or to make way for development and urban sprawl.

Question 35

Outline the impact of deforestation on the carbon cycle (identify changes in stores and the transfers involved)

Answer 35

Clearance reduces the size of the carbon store and, if the cleared forest is burned, there is a rapid flow of carbon from the biosphere to the atmosphere. In a natural system, when a tree dies it decomposes very slowly and releases carbon over a long period of time. During that time, new vegetation starts to grow that quickly compensates for the carbon being released by the dead tree (the system is carbon neutral). However, when deforestation by burning occurs, carbon is immediately released into the atmosphere. If the land is then used for farming e.g. cattle ranching, the future absorption of carbon will be reduced. The system has now become a carbon source rather than a sink. This is extremely significant in terms of the carbon cycle both globally and regionally, as forest ecosystems are limited to certain regions of the world.

Question 36

Identify global locations experiencing significant deforestation.

Answer 36

Tropical regions, for example, Indonesia and the Amazon Basin.

Question 37

Outline the ways in which the processes of urbanisation drives change in the carbon cycle.

Answer 37

• Vegetation is removed, or covered up, to make way for buildings – this reduces carbon storage in the biosphere. Concrete production releases lots of CO2 and concrete is used when urban areas expand.

Question 39

What proportion of human related CO2 emissions come from urban areas and what are the main sources?

Answer 39

• 97% of all anthropomorphic CO2 emissions come from urban areas. Over half of the world’s population now lives in urban areas; a proportion that is set to grow over the coming decades. • The major sources of these emissions are transport, energy generation, the development of industry, land use conversion from rural to urban and cement production for the building sector.

Question 40

Define‘carbonbudget’.

Answer 40

The difference between the inputs of carbon into a subsystem and outputs of carbon from it. The focus is on carbon emissions into the atmosphere compared to the amount of carbon removed each year.

Question 41

List the carbon transfers that cause an input of carbon into the atmosphere (natural and human).

Answer 41

Volcanic eruptions, burning fossil fuels, respiration and ocean loss.

Question 42

List the carbon transfers that cause an output of carbon from the atmosphere (natural and human).

Answer 42

Photosynthesis, sequestration, decomposition, chemical weathering and ocean uptake.

Question 43

Naturalsystems,suchasbiomass(includingvegetation)andtheoceanshaveoperated as carbon sinks. What does this mean and what transfers are involved?

Answer 43

A carbon sink ‘banks’ carbon. Each year inputs of carbon are greater than outputs. Forests (through photosynthesis) and the oceans (through dissolution or uptake) have been major carbon sinks.

Question 44

In recent decades human processes have turned carbon sinks into carbon sources. Which human activities are driving this change in the carbon cycle? Which transfers/processes are being affected?

Answer 44

Large scale and rapid release of CO from a combination of combustion of fossil fuels and changes in land use patterns are occurring at rates beyond the capacity of natural systems to compensate. This results in rapid increases in CO concentrations the atmosphere.

Question 45

Changes in the carbon budget (essentially the increase in inputs of carbon to the atmosphere and the reduction in carbon stored on land) are having an impact on the land, oceans, atmosphere and global climate. Identify impacts on land

Answer 45

More CO2 is available to plants and longer growing seasons, result in more photosynthesis and plant growth. Growth limits will depend on water and nutrient availability. (Negative feedback) Increased temperatures have led to warming in Tundra regions and the melting of permafrost, releasing carbon stored into the soil into the atmosphere as CO2 and methane. (Positive feedback)

Question 47

Changes in the carbon budget (essentially the increase in inputs of carbon to the atmosphere and the reduction in carbon stored on land) are having an impact on the land, oceans, atmosphere and global climate. Identify impact on oceans

Answer 47

Warmer water is less able to absorb CO2, so as temperatures increase the amount of CO2 that can potentially be dissolved in the sea decreases. (Positive feedback) Warmer ocean temperatures are adversely affecting other marine organisms. For example, phytoplankton may not survive at higher temperatures, so numbers may decline. This means less will be used for photosynthesis, leaving more CO2 in the atmosphere. (Positive feedback)

Question 48

Changes in the carbon budget (essentially the increase in inputs of carbon to the atmosphere and the reduction in carbon stored on land) are having an impact on the land, oceans, atmosphere and global climate. Identify impact on atmosphere

Answer 48

The increasing concentration of greenhouses gases in the atmosphere increases temperatures. Greenhouse gas emissions have increased significantly in recent decades due to human activities such as deforestation and fossil fuel combustion. This has led to an enhanced greenhouse effect. Global warming will affect other aspects of the climate, including global atmospheric winds, rainfall distribution and intensity and the frequency of storms.

Question 49

What is the IPCC and what is its primary aim?

Answer 49

The Intergovernmental Panel on Climate Change (IPCC) is an international organisation set up by the UN to share knowledge about climate change. The IPCC states that countries need to reduce the amount of CO2 emitted by human activities, to prevent large temperature rises.

Question 50

Outline how carbon capture and storage (CCS) could help mitigate climate change.

Answer 50

CO2 emitted when burning fossil fuels is captured and liquified then transported to be stored, often deep underground

Question 51

What is a disadvantage of CCS?

Answer 51

It doesn’t discourage fossil fuel burning or the extraction of fossil fuels and is also relatively expensive.

Question 52

Name an international agreement to reduce emissions.

Answer 52

Kyoto Protocol (1997) or the Paris Agreement (2015)

Question 53

Atmospheric carbon levels historically compared to now.

Answer 53

Past 800,000 years levels have fluctuated between 180-300ppm From 1950 risen to over 400ppm

Question 54

Natural changes to atmospheric carbon before human intervention

Answer 54

1000-1800 Stores increased from 180ppm to 260ppm