4.a. The two cycles are linked and interdependent Flashcards
(9 cards)
How human activities cause changes in the availability of water and carbon?
rapid population + economic growth, deforestation, urbanisation (past 100 years) have modified the size of W + C stores and rates of transfer between.
- impact most apparent at regional + local scale
where/what are human impacts on water cycle most clear?
most clear in rivers + aquifers
- increased demand for water - for irrigation and public supply has created huge shortages
- lake Mead near Las Vegas - reservoir has fallen dramatically due to abstraction - city built in a desert
- over pumping water from aquifers in coastal bangladesh creates salt water incursion - making water supply unfit for irrigation or drinking
how does deforestation and urbanisation affect water cycle?
decrease evaporation thus precipitation, increase surface runoff - decrease throughflow + decrease water table
- in amazon, deforestation has broken the cycle of water transferring between the biosphere and atmosphere - to be returned by precipitation (evapotranspiration-precipitation feedback loop) causing the climate to dry and the forest to degrade
how has human activity altered the carbon cycle?
has altered carbon cycle - depleting some stores and increasing others
- world relies on fossil fuels for 82% primary energy consumption
- exploitation of coal, oil and gas has removed billions of tonnes of carbon from geological/fossil long-term storage and moved the carbon into the atmosphere - creating disequilibrium
how has deforestation affected transfers of carbon into atmosphere + how much is transferred into atmosphere?
deforestation transfers approx 1 billion tonnes of carbon into the atmosphere per year. additional carbon is stored primarily in the atmosphere, where carbon dioxide is increasing yearly. mass deforestation has decreased the earth’s forest cover 50% since historic times thus the amount of carbon stored in the biosphere and fixed by photosynthesis has decreased steeply.
how does human activities affect soil?
it is an important carbon store being degraded by humans via deforestation and agricultural mismanagement
how have carbon stores in wetland been affected by human activities?
carbon stores in wetland have been drained for cultivation or urban development have ben depleted as they dry out and are oxidised.
what is the impact of long-term climate change on the water cycle?
- increased evaporation = increased water vapour in the atmosphere - a natural greenhouse gas which therefore helps raise global temps, increase evaporation and therefore increase precipitation
- meanwhile, increased precipitation creates increased run off and flood risk
- water vapour = source of energy in atmosphere - releasing latent heat through condensation
- increased energy –> more intense hurricanes + mid latitude storms
- global warming increases melting of glaciers, ice sheets eg. permafrost of tundra –> therefore water store in cryosphere decreases as water is transferred to oceans + atmosphere
what is the impact of long-term climate change on the carbon cycle?
- increased global temps = increased decomposition = greater transfer of carbon from biosphere + soil to the atmosphere
- however, humid tropics climate change may increase aridity + threaten forests - forests replaced by grasslands store far less carbon
- contrast / high latitudes boreal forests will expand northwards -> taking in more co2 via photosynthesis
- carbon frozen in permafrost is released as temp increases above freezing
- acidification of ocean thru absorption of excess co2 from atmosphere decreases the absorption of co2 via photosynthesis by the phytoplankton, limiting capacity of the oceans to store carbon
- long term climate change –> increased carbon stored in atmosphere, decreased carbon stored in biosphere = decrease in ocean storage
- movement of carbon in and out of atmosphere will vary regionally, depending on the rates of photosynthesis, decomposition and respiration
