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A Level Physical Geography > WCC: Carbon Cycle - Human Causes of Change in the Carbon Cycle > Flashcards

WCC: Carbon Cycle - Human Causes of Change in the Carbon Cycle Flashcards

Changes in the carbon cycle over time, to include human impact: hydrocarbon fuel extraction and burning, farming practices, deforestation and land use changes.

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1
Q

What are the 4 major human causes of change in the carbon cycle?

A

Extraction and burning of hydrocarbons
Farming practices
Deforestation
Land use change

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2
Q

How are hydrocarbons formed?

A

Dead plants and animals are buried. The pressure from multiple layers of sediment leads to an anoxic environment that allows decomposition to take place. Combined with heat from the Earth, the carbon is rearranged to form other compounds.

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3
Q

What type of remains does crude oil tend to be formed from?

A

Animal remains

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4
Q

What type of remains do coal and natural gas tend to be fromed from?

A

Plant remains

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5
Q

For the majority of current fossil fuel sources, how long ago did the plants they are made from live?

A

80 million years ago

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6
Q

How have humans used fossil fuels?

A

As a source of energy to power industry, transport and domestic purposes

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7
Q

How does the extraction and burning of hydrocarbons cause change in the carbon cycle over time?

A

Extraction removes carbon from long term storage in sedimentary rocks.
Burning releases this carbon back into the atmosphere through gases such as CO2 and methane

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8
Q

Name an industry that releases a significant amount of CO2 to the atmosphere.

A

The cement industry

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9
Q

What are the 2 major ways cement manufacture contributes to the increase in atmospheric CO2?

A

It involves the heating of calcium carbonate, producing lime and CO2.
Fossil fuels are burned to provide the heat needed in the cement manufacture process.

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10
Q

What percentage of global anthropogenic CO2 emissions is from the cement industry?

A

5%

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11
Q

In 2013, what were the top 3 countries in CO2 emissions?

A

China
USA
India

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12
Q

How has the extraction and burning of hydrocarbons affected global CO2 emissions since 1990?

A

Between 1990 and 2013, global CO2 emissions from fossil fuels and cement production increased by 61%

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13
Q

What are 5 significant agricultural causes of change in the carbon cycle?

A 
Ploughing
Machinery
Artificial fertilisers
Enteric fermentation
Arable farming
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14
Q

How does ploughing cause change in the carbon cycle?

A

Ploughing causes soil layers to invert, mixing in air and dramatically increases soil microbial activity. This increases the rate of soil respiration, releasing carbon to the atmosphere.

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15
Q

How does farm machinery affect the carbon cycle?

A

Heavy machinery is powered by fossil fuels, so emit CO2 into the atmosphere

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16
Q

How do artificial fertilisers cause change in the carbon cycle?

A

Most artificial fertilisers are made from fossil fuels. The spread of these on land means carbon runs into rivers as surface runoff and is transferred back into the atmosphere.

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17
Q

What is enteric fermentation?

A

The release of methane by livestock during digestion

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18
Q

What is the largest source of carbon emissions within agriculture?

A

Enteric fermentation

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19
Q

What percentage of the agricultural sector’s total greenhouse gas emissions in 2011 was through enteric fermentation?

A

39%

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20
Q

How much have carbon emissions by animals increased between 2001 and 2011?

A

11%

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21
Q

How does arable farming affect the carbon cycle?

A

Bacteria release methane during decomposition, making it a by-product of some arable farming.

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22
Q

Which example of arable farming produces significant amounts of methane?

A

Rice paddies

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23
Q

What percentage of the world’s population relies on rice as their primary source of food?

A

50%

24
Q

What percentage of global methane emissions may be generated by rice paddies?

A

20%

25
Q

Why do rice paddies release so much methane?

A

Rice grows in water, providing the perfect environment for methane-releasing bacteria during anaerobic digestion.

26
Q

Describe the global distribution of agriculture-related greenhouse gas outputs.

A 
The regional distribution has been constant over the last decade:
Asia - 44%
Americas - 25%
Africa - 15%
Europe - 12%
Oceania - 4%
27
Q

Give 4 reasons deforestation may occur.

A

Land for subsistence farming
Logging
Growing urban sprawl
Wildfires

28
Q

Why does subsistence farming lead to deforestation?

A

Subsistence farmers will often clear a few hectares of land through slash and burn agriculture

29
Q

What is slash and burn agriculture?

A

A farming method that involves the cutting and burning of plants in a forest or woodland to create a field

30
Q

What is subsistence farming?

A

A self-sufficiency farming system in which the farmers focus on growing enough food to feed themselves and their entire families

31
Q

How can logging operations lead to further deforestation?

A

Loggers build roads to access more remote forests

32
Q

Name 4 land uses that forests may be cleared for.

A

Commercial farming
Mining
Hydroelectric power
Cattle ranching

33
Q

Where is deforestation occurring particularly quickly?

A

The tropics

34
Q

What percentage of global CO2 emissions does deforestation account for?

A

20%

35
Q

How much of the world’s forests are cut down and converted to other land uses every year?

A

13 million ha

36
Q

What is reducing the net loss of total forest area?

A

Afforestation

37
Q

Give evidence to show that the rate of net loss of forest areas is decreasing.

A

Between 1990 and 2000 there was a net loss of 8.9 million ha/year of forest areas, but between 2000 and 2005 this decreased to 7.3 million ha/year.

38
Q

How much forest are we losing a day?

A

About 200km^2

39
Q

Which carbon cycle stores and transfers does deforestation directly impact?

A 
Photosynthesis
Respiration
Vegetation store
Soil store
Atmospheric store
40
Q

How does deforestation impact photosynthesis? Give evidence.

A

Photosynthesis is significantly reduced, for example even 10 years after deforestation, photosynthesis rates are still less than half of what they were.

41
Q

How does deforestation impact respiration? Give evidence.

A

Respiration is significantly reduced, for example even 10 years after deforestation, respiration rates are around a quarter of what they were.

42
Q

How does deforestation impact soil and below-ground biomass stores? Give evidence.

A

Soil and below-ground biomass stores are significantly reduced, for example even 10 years after deforestation, they are only around 2/3rds of what they were.

43
Q

How does deforestation affect the magnitude of carbon emissions from the forest? Why?

A

Total carbon emissions only slightly increase after deforestation, as the emissions from burning, decay of slash and soil erosion are balanced out by decreased respiration rates.

44
Q

If total carbon emissions only slightly increase after deforestation, how is it such a significant contributor in the rise of atmospheric CO2?

A

Major reductions in carbon absorption, mainly through photosynthesis, results in net carbon emissions being much higher than before deforestation.

45
Q

Why do deforested soils store less carbon?

A

The exposed soil is more prone to erosion, becomes less fertile and so can hold less CO2.

46
Q

Name 4 land use changes that cause significant change in the carbon cycle.

A

Urbanisation
Draining of wetlands
Change from extensive to intensive farming
Deforestation

47
Q

What is a major factor leading to recent land use changes?

A

The industrialisation and development of developing nations

48
Q

What are the 3 main reasons for the change from extensive to intensive farming?

A

Increased demand for food from a growing global population

Increased demand for meat from new middle classes in developing countries

49
Q

How does the draining of wetlands cause change in the carbon cycle?

A

Draining wetlands reduces the land’s ability to be a carbon sink

50
Q

Why are wetlands such massive carbon sinks?

A

Organic matter falls into the water and decomposition is very slow so the carbon is locked away

51
Q

What is the most important land use change causing change in the carbon cycle?

A

Urbanisation

52
Q

What is urbanisation?

A

The proportional increase in the number of people living in urban areas

53
Q

How quickly are urban areas growing?

A

At a rate of 1.3 million people per week

54
Q

How does urbanisation change the land use?

A

Areas of natural vegetation or agriculture change to built up areas

55
Q

How does urbanisation remove carbon sinks?

A

Soil and vegetation are replaced by concrete and tarmac

56
Q

In what ways does urbanisation increase CO2 emissions?

A

Increased energy consumption for transport, industry and domestic use
Increased cement manufacture for buildings and infrastructure

57
Q

What percentage of global carbon emissions were cities responsible for in 2012?

A

47%

A Level Physical Geography (43 decks)

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