3.A - human factors influencing the water and carbon cycles

Question 1

what is dynamic equilibrium?

Answer 1

the natural system will respond to changing inputs over time

Question 2

what will plants do after heavy rain?

Answer 2

• after heavy rain, plants will intercept the water
• and this leads to evapotranspiration, returning it to the atmosphere

Question 3

how does dynamic equilibrium deal with rain increases?

Answer 3

• rain increases adding inputs to a system (potential flooding)
• transfer/outputs increase to remove it, restoring equilibrium

Question 4

what happens to oceans when amount of CO2 in the atmosphere increases?

Answer 4

• amount of CO2 in the atmosphere increases
• therefore the physical pump in the oceans which diffuses carbon into the water is enhanced increasing the amount of Co2 dissolved in the ocean to restore equilibrium

Question 5

in the winter, what are deciduous forests?

Answer 5

• deciduous forests will be net sources of Co2 in the winter (respiration > photosynthesis)
• but in the summer there is net NPP gain (photosynthesis > respiration)
• balancing out the two flows over the year

Question 6

what happens as climate change melts the tundra?

Answer 6

• as climate change melts the tundra the active layer thaws
• this results in faster photosynthesis rates of the plants in this layer which removes CO2 from the atmosphere and returns equilibrium

Question 7

what happens to the diffusion gradient as atmospheric CO2 increases?

Answer 7

• as atmospheric CO2 increases the diffusion gradient increases
• plants grow faster the sequester it and take it out, thus lowering atmospheric CO2

Question 8

POSITIVE FEEDBACK LOOPS in the water cycle - temperature

Answer 8

• as temperatures increase, rates of evaporation increase and the ability of the atmosphere to hold more water increases.
• however, as water vapour is a greenhouse gas it will absorb more outgoing long wave radiation and the temperature will increase further, allowing more water vapour to be absorbed

Question 9

NEGATIVE FEEDBACK LOOPS in the water cycle - rainfall increases

Answer 9

• as rainfall increases in a drainage basin, stores such as soil fill up and so flows such as surface run off increase.
• this means there is a greater discharge in river channels and eventually more water leaving the drainage basin as rivers discharge into the sea

Question 10

NEGATIVE FEEDBACK LOOPS in the water cycle - rainfall decreases

Answer 10

• if the rainfall amount falls then trees such as the silver birch become stressed and shed their leaves
• this reduces the amount of water taken in by the tree and so the water balance is restored

Question 11

NEGATIVE FEEDBACK LOOPS in the water cycle - temperature increases

Answer 11

• as temperature increases, more water vapour is absorbed and therefore more clouds are formed
• this in turn reflects more incoming solar radiation, which reduces the temperature

Question 12

NEGATIVE FEEDBACK LOOPS in the carbon cycle - atmospheric CO2 increases

Answer 12

• as CO2 levels increase in the atmosphere, photosynthesis is stimulated (carbon fertilisation)
• this promotes plant growth and so more carbon is held in the biosphere rather than in the atmosphere resetting conditions

Question 13

POSITIVE FEEDBACK LOOPS in the carbon cycle - TEMPERATURE

Answer 13

• as temps increase, the permafrost melts and releases more CO2 and CH4
• these GHGs cause a further increase in temperature and so more CO2 and CH4 is released

Question 14

POSITIVE FEEDBACK LOOPS in the carbon cycle - decomposition

Answer 14

• in a warmer global climate there will be more decomposition of organic material
• and so more CO2 in the atmosphere and therefore further increases in global temperatures

Question 15

what impact does urbanisation have on the water cycle?

Answer 15

• artificial surfaces such as tarmac will be impermeable
• this will reduce infiltration and rapidly increase surface run-off
• guttering will transfer water very efficiently… but ultimately will contribute to flooding if drains become overwhelmed

Question 16

what impact does farming have on the water cycle?

Answer 16

• farm machinery compacts soil
• deforestation = no interception
• very little evapotranspiration
• increased surface run off

Question 17

what is urbanisation?

Answer 17

• the conversion of land use from rural to urban

Question 18

what impact does urbanisation have on the carbon cycle?

Answer 18

• farmland and woodland are replaced by housing, offices, factories and roads

Question 19

what impact does urbanisation have on the water cycle?

Answer 19

• natural surfaces e.g. vegetation and soil give way to concrete, brick and tarmac
• artificial surfaces are largely impermeable so they allow no infiltration and provide minimal water storage capacity to buffer run-off
• urban areas have drainage systems designed to remove surface water rapidly
• as a result a high proportion of water from preciptiation flows quickly into streams and rivers, leading to a rapid rise in water level
• urbanisation also encroaches on floodplains, reduces water storage capacity in drainage basins, ↑ river flow and flood risks

Question 20

what impact does farming have on the carbon cycle?

Answer 20

• harvesting of crops = only small amounts of organic matter returned to soils
• erosion by wind and water is most severe when crops have been lifted and soils have little protective cover
• changes are LESS APPARENT where farming replaces natural grasslands
• however, carbon exchanges through photosynthesis are generally lower than in natural ecosystems
• lack of biodiversity in farmed systems
• deforestation for farming ↓ carbon storage in vegetation
• soil carbon storage also ↓ by ploughing and exposure of organic material to oxidation

Question 21

what impact does farming have on the water cycle?

Answer 21

• crop irrigation diverts surface water from rivers and groundwater to cultivated land. some is extracted by crops and released by transpiration, but most is lost to evaporation and in soil drainage.
• interception of rainfall by annual crops is less than in forest and grassland ecosystems (also evaporation and transpiration from leaf surfaces)
• ploughing ↑ evaporation and soil moisture loss, and farrows ploughed downslope act as drainage channels, accelerating run-off and soil erosion
• infiltration due to ploughing is usually greater in farmed systems which artificial underdrainages ↑ the rate of water transfer to streams and rivers

Question 22

what impact does forestry have on the carbon cycle?

Answer 22

• ↑ carbon stores
• mature forest trees contain on avg 170-200 tonnes C/ha (10x higher than grassland and 20x higher than heathland)
• carbon pool
• plantations have a rotation period of 80-100 yrs before theyre felled, because forest trees only become an active carbon sink for the first 100 yrs.

Question 23

what impact does forestry have on the water cycle?

Answer 23

• higher rates of rainfall interception in plantations than natural forests
• ↑ transpiration compared to farmland
• ↑ evaporation. a larger proportion of intercepted rainfall is stored on leaf surfaces and is evaporated directly to the atmosphere
• ↓ run-off and stream discharge. with high interception and evaporation rates, and the absorption of water by tree roots, drainage basin hydrology is altered
• streams draining plantations typically have long lag times and low total discharge
• clear felling to harvest timber creates sudden but temporary changes to the local water cycle, ↑ run off, reducing evapotranspiration and ↑ stream discharge

Question 24

what are aquifers?

Answer 24

• aquifers are permeable or porous water bearing rocks, such as chalk
• they can be used as a water source by manufacturing a borehole or well

Question 25

what is groundwater?

Answer 25

• the water that is obtained from wells or boreholes is known as groundwater
• it provides a vital source of water for many parts of the UK

Question 26

what is the water table?

Answer 26

• the level of water within an aquifer is known as its water table
• and can vary throughout the year and over longer periods of time

Question 27

what will cause the water table to rise and fall?

Answer 27

• rainfall
• over a long period, cold/glacial periods will cause water table to fall
• plant growth. summer = growth of leaves = photosynthesis = water drawn up = water table falls
• human/domestic water use = falls

Question 28

what is an artesian basin?

Answer 28

• an artesian basin is formed in a syncline, when an aquifer is contained within impermeable layers of rock
• the aquifer which will contain the groundwater can be tapped by a borehole, and water will flow to the surface under artesian pressure

Question 29

the River Kennet?

Answer 29

• the river kennet, which flows through southern england, is underlain by porous chalk in its upper catchment, and is therefore supported by groundwater flow
• water is extracted by Thames Water both from the surface water of the river and its tributaries and local boreholes

Question 30

water uses and their impact on the water cycle: TROUT FARM (river kennet)

Answer 30

• will extract water directly from river
• ironically wild trout are under threat as a result of lower flows in the Kennet

Question 31

water uses and their impact on the water cycle: FARMS (river kennet)

Answer 31

• land is compacted - less infiltration
• pesticides = eutrophication
• irrigation
• run-off from farmland, as well as road surfaces, containing pollutents reaches the main river channel.
• this reduced channel flow in the Kennet is now unable to dilute this

Question 32

water uses and their impact on the water cycle: HOUSES (river kennet)

Answer 32

• domestic water demand is high
• will indirectly come from river kennet
• in areas such as SE england, supply is low and so groundwater aquifers (like the chalk here) are often used
• so called use of “fossil water” is not sustainable, springs are drying up

Question 33

water uses and their impact on the water cycle: RAILWAY (river kennet)

Answer 33

• the railway is protected from flooding as it is raised up on embankments
• this will interfere with and prevent the natural flooding regime of the river which would flood every couple of years, replenishing the flood plain w/ alluvium

Question 34

water uses and their impact on the water cycle: GOLF COURSE (river kennet)

Answer 34

• golf course requires irrigation in warm months
  = water is taken away from surface stores and ultimately ↓ flow in the main river kennet channel.

Question 35

why is global energy consumption going up?

Answer 35

• ↑ population globally
• ↑ need for energy as more countries develop

Question 36

fossil fuels and the carbon cycle …

Answer 36

• fossil fuel consumption releases 10 billion tonnes of CO2 to the atmosphere every year
• this has resulted in an increase in atmospheric carbon from 280ppm to 410 ppm

Question 37

are alternative energy sources making a significant contribution?

Answer 37

no
- they have increased over time but compared to oil it is very insignificant

Question 38

what could be the effect of increasing CO2 on the terrestrial carbon cycle?

Answer 38

• natural negative feedback loop
• ↑ CO2 in the atmosphere can stimulate photosynthesis if conditions are right, and therefore the movement of carbon stores away from the atmosphere are ↑

Question 39

what may be a solution to the increasing levels of CO2 in the atmosphere?

Answer 39

• sequestration of waste carbon from the burning of fossil fuels may present a solution to the increasing levels of CO2 in the atmosphere

Question 40

what is the limitation of Carbon Capture and Storage schemes?

Answer 40

• although the technology of CCS is feasible, its effectiveness is limited by economic and geological factors:

1. involves big capital costs - the Drax project will cost at least $1 bill
2. uses large amounts of energy - typically 20% of a power plant’s output is needed to separate the CO2 and compress it
3. requires storage reservoirs with specific geological conditions i.e. porous rocks overlain by impermeable strata

Question 41

what is the limitation of carbon sequestration?

Answer 41

• just slowing climate change down
• not doing anything to the CO2 already in the atmosphere

Question 42

OCEANIC carbon sequestration

Answer 42

• OCEAN FERTILISATION
• adding iron filings to the ocean
• this encourages the growth of phytoplankton = ↑ photosynthesis = carbon sequestration
• ↑ productivity of marine food production (accelerates food chains)
• 25% of atmospheric carbon is currently removed this way
• however, its not that efficient as it relies on natural processes BUT scale of oceans is large
• negatives = could imbalance ocean food chains/habitats. nothing stopping it being released in the future

Question 43

limitations of OCEANIC carbon sequestration

Answer 43

• its not that efficient as it relies on natural processes BUT scale of oceans is large
• negatives = could imbalance ocean food chains/habitats. nothing stopping it being released in the future

Question 44

TERRESTRIAL carbon sequestration

Answer 44

• ARTIFICIAL TREES
• first encourage trees to grow naturally
• but there are “fake” trees which can trap CO2 being blown in the wind into a giant filter
• the CO2 is then chemically bonded to the filter and this can then be buried to remove it
• Can be 1000x more efficient than regular trees
• NOT SEASONAL therefore work all year round
• can absorb 1 tonne of carbon per day

Question 45

SUBTERRANEAN carbon sequestration

Answer 45

• CCS
• as CO2 emissions are released from power stations due to burning fossil fuels, the emissions are “captured” through a large filter
• the CO2 is then removed from these emissions through chemistry and stored in a solid manner
• this is then buried underground in geological storage i.e. in the spaces where oil and gas used to be
• stops the flows of CO2 from power stations