6.7 human activity threatens the carbon cycle

Question 1

6.7a why is there growing demand for resources? (&what is it affecting?)

Answer 1

rapidly increasing population growth and economic development has led to the rising standard of living and emergence of middle class in emerging countries like China.
(increase in meat consumption etc.)

this growing demand is affecting land use cover (= a change in the primary usage/ change in veg cover) which has subsequent affects on the carbon store with wider implications for the water cycle and soil health

Question 2

6.7a why is deforestation increasing?

Answer 2

(forests cover 30% of earths land area
…… their role? intercept rainfall and increase groundwater storage)

!! more than half of forested land is being cleared due to increased demand for commodity production: soy, palm oil, beef and paper production !! (land needed for FOOD)

land is also being converted to build dams and reservoirs therefore clearing may increase as energy demands increase or water supplies decrease

Question 3

6.7a impacts of deforestation (carbon s, wc&soil h.)

Answer 3

impacts on soil health:
- reduced quality and increased erosion leading to loss of nutrients
- CO2 released from decaying material

impacts of water cycle:
- less interception, inc. surface run off & shorter lag time
- infiltration rates decrease (reduced capacity of soil)
- less evapotranspiration from trees/ plants (reducing moisture in atmosphere… risk of drought)

impacts on terrestrial carbon stores:
- less absorption of CO2 through photosynthesis = reduced carbon stored
- more CO2 released from combustion

90% of forests in the UK and USA were lost though deforestation by the c19th!!!!!!!!!!

Question 4

6.7a role of grasslands

Answer 4

• traps moisture and floodwater
• absorbs toxins from soil
• provides cover for dry soils
• maintains natural habitats for wildlife and healthy soils
• acts as a carbon sink

Question 5

6.7a impacts of converting grassland to farmland

Answer 5

• removal releases CO2 into atmosphere initially and ploughing will annually release CO2.
• crops are heavy consumers of water
• soil health decreases: cultivated soils susceptible to erosion and wind… surface run off increases as infiltration rates decrease.

Question 6

6.7a afforestation

Answer 6

not all bad news!!! afforestation is underway in temperate latitudes which is helping to offset the loss of tropical rainforest ‘services’ (negative impacts of deforestation)

the EU Afforestation grant Scheme encourages the planting of forests for their value as terrestrial carbon stores and for their eco system services
a net gain of 50,000 to 250,000 ha of forest was experienced in Russia, Turkey, Italy France and Spain

a net gain was also experienced in China (1990- 2015: +500,000 ha of forest area)

Question 7

6.7b what is ocean acidification?

Answer 7

decrease in the pH of the earths ocean.
….. as more CO2 is released into the atmosphere from fossil fuel combustion, oceans absorb this increasing the acidity (thus decreasing pH)

!!!!! since industrial revolution oceans have absorbed 30- 40% of anthropogenic emissions !!!!!!

Question 8

6.7b what is ecosystem resilience and critical threshold?

Answer 8

ecosystem resilience= the level of damage/ disruption an ecosystem can cope with in its original state
critical threshold= an abrupt and irreversible ecological change (positive feedback loop often kick in when this has been passed)

Question 9

6.7b ecosystem service definition

Answer 9

benefits provided by ecosystems that contribute to making human life both possible and worth living.
—> helps us to understand use and management of natural resources

Question 10

6.7b four types of ecosystem service

Answer 10

1. provisioning service (provision of goods: fuel, food, medicine etc)
2. regulating service (benefits people get from the regulation of ecosystem processes : water/ air cleanliness and flood protection)
3. cultural service (non material benefits: lifestyle, well being, tourism, education, science)
4. supporting service (functioning of healthy ecosystems means the other three services can be provided)

Question 11

6.7c impacts of climate change more info needed

Answer 11

enhanced greenhouse gas effect will lead to increased evapotranspiration and climate zones moving polewards. this will lead to less soil moisture and thus hydrological drought. drought frequency may increase as a result as increased temperatures alters circulation cells.