1.2.4 a + b - To what extent are the water and carbon cycles linked?

interdependence of water, carbon cycles via atmosphere

- atmospheric CO2 has greenhouse effect (anthropogenic emissions especially). CO2 is absorbed via photosynthesis from atmosphere.

- Roots extract water from soil and transpire it. Water is evaporated from the oceans to atmosphere and CO2 moves between them

HOW MUCH CARBON IS IN THE ATMOSPHERE? (PPM)

- 427

interdependence of water, carbon cycles via cryosphere

- CO2 levels in atmosphere determine intensity of greenhouse effect and ergo melting of ice sheets, glaciers, sea ice and permafrost. Melting exposes land and sea surfaces, which absorb more solar radiation and raise sea temperatures further.

- Permafrost melting exposes organic materials to decomposition thus releasing more CO2

interdependence of water, carbon cycles via oceans

- ocean acidity increase when exchanges of CO2 are unbalanced. The solubility of CO2 in oceans increases with lower surface sea temperatures. less calcification

- Atmospheric CO2 levels influence:

SSTs and the thermal expansion of the oceans; air temperatures; the melting of ice sheets and glaciers; and sea level.

interdependence of water, carbon cycles via vegetation

- water availability influences the rate of photosynthesis, NPP, inputs of organic litter to soils and transpiration. The water storage capacity of soils increase with organic content.

- temperature and rainfall affect decomposition rates and release of CO2 to atmosphere

how has human activity altered availability of water in water stores?

- Rapid population and economic growth, deforestation and urbanisation in the past 100 years have modified the size of water and stores and rates of transfer.

- changes to water cycle is most

evident in rivers and aquifers. Rising demand for water

for irrigation, agriculture and public supply, especially

in arid and semi-arid environments, has created acute

shortages. In the Colorado Basin in the southwest

USA, surface supplies have diminished as more water is abstracted from rivers, and huge amounts are evaporated from reservoirs like Lake Mead and Lake Powell.

how has human activity altered carbon stores?

- fossil fuels provide 84 per cent of its primary energy consumption. The exploitation of them has removed billions of tonnes of carbon from its geological store which has sped up recently with the industrialisation of the Chinese and Indian economies.

- 8 billion tonnes of carbon a year are transferred to the atmosphere by burning fossil fuels

- land use change (mainly deforestation) transfers approximately 1 billion tonnes of carbon to the atmosphere annually.

- The additional carbon is stored primarily as atmospheric CO2 where its concentration increases.

- Forest cover has decreased by nearly 50 per cent. Amount of carbon stored in the biosphere, and fixed by photosynthesis, has declined steeply.

- Increase in acidification of oceans and therefore less calcification

- soil being eroded from deforestation, less C stored

how do increasing climate temperatures affect rates of evaporation?

- Rising global temperatures increase rates of evaporation.

- Increased evaporation leads to higher concentrations of water vapour in the atmosphere.

- Water vapour is a greenhouse gas, creating a positive feedback that enhances warming.

- Greater atmospheric moisture results in increased precipitation.

- Increased precipitation leads to higher rates of run-off and an increased risk of flooding.

how does increased energy levels in the atmosphere affect water vapour levels in atmosphere?

- Water vapour releases latent heat during condensation, adding energy to the atmosphere.

- Increased atmospheric energy intensifies extreme weather events such as hurricanes and mid-latitude storms.

effect of climate change on cryosphere

- Global warming accelerates the melting of glaciers, ice sheets and permafrost.

- This reduces water storage in the cryosphere.

- Meltwater is transferred to the oceans and atmosphere, contributing to sea-level rise.

effects of climate change on carbon stores via decomposition

- Rising temperatures generally increase rates of decomposition.

- Increased decomposition transfers more carbon from soils and vegetation to the atmosphere.

effect of climate change on permafrost

Thawing permafrost releases previously frozen carbon stores.

Decomposition of peat releases carbon dioxide into the atmosphere.

effect of climate change on oceans

- Oceans absorb excess atmospheric CO₂, leading to ocean acidification.

Acidification reduces phytoplankton photosynthesis.

Reduced photosynthesis limits the ocean's ability to store carbon.

effect of climate change on forests

- In tropical regions, climate change may increase aridity.

- Increased aridity threatens tropical forests, reducing carbon storage.

- Replacement of forests by grasslands lowers carbon stored in tropical biomes.

- In high latitudes, warmer temperatures allow boreal forests to expand polewards.

what are voluntary offsets?

firms pay to compensate for their GHG emissions by funding projects that remove an equivalent amount of CO2 elsewhere without a legal requirement to do so

what is carbon trading?

- buying and selling of credits that permit a company to emit a certain amount of CO2 or other GHGs which is legally binding.

- it incentivises firms to reduce their emissions via the governments setting caps on maximum emissions

why has carbon trading, or cap and trade been unsuccessful previously?

- over allocation of permits - political resistance to strong caps often leads government to issue too many free permits in early phases of implementation which dilutes scarcity and thus drives price discovery e.g. EU ETS phase - when stakes granted more permits than actual emissions, ergo market price of carbon collapsed to 0

- requires strict enforcement - financial motive outweighs it

- market manipulation - some firms might wait for credits to go down to sell at a higher price later

advantages of scheme

- in 2019 EU ETS was worth 169 billion euros proving that reducing pollution is becoming more financially rewarding thus incentivising firms to cut down on emissions

- e.g. 1995 US acid rain programme implemented scheme and it successfully reduced S02 emissions from power plants

- not restricted geographically

- mitigation not adapting

- quick to implement unlike afforestations

what was the paris 2015 UN climate convention?

- 1.5 C target push (not 2 degrees) - big difference

- 195 nations involved

- legally binding

- HICs to aid developing countries to reduce their emissions

what was the Kyoto Protocol UN 1997?

- treaty in 1997

- 5% cut below 1990 GHG levels

- introduced cap and trade scheme

- legally binding

- served as a foundation for paris agreement

disadvantages of agreements like these

- compromises developing countries from developing ( requires large amounts of GHG for energy), limiting them from doing so at the expense of HICs utilisation of it

- not every country must enter agreements so could be ineffective. E.g. USA no longer apart of Paris agreement and is world's 2nd largest emitter

- lack of enforcement

- green tech is expensive and may increase debt burden

- global motivations differ from local/regional ones

pros of paris agreement

- political resilience despite USA ditching agreement, others did not follow this nationalistic action displaying unified motivation to tackle climate change and thus interdependence of one another

- normalising 1.5 C - initially thought of as unfeasible but intergovernmental panel showing how much of a difference it would make

- cleaner energy shift

- institutional change, semi enforcement

cons of paris agreement

- despite agreement emissions still continue to rise at about 427 ppm

- billions of tonnes of CO2 from emerging economies in Asia as incumbent energy industries will develop by any means

- rising temps causing more extreme events to occur

- the vulnerable suffer, increases debt burden with green technology as you cannot compensate victims of climate disaster

advantages of international agreements

- encourages global coordination and shared responsibility

- facilitates sharing of successful climate technologies

- semi enforced

why is wetland restoration important?

- Wetlands are important in the carbon cycle: they occupy 6-9 percent of the Earth's land surface and contain 35 per cent of the terrestrial carbon pool.

- destruction of wetlands transfers huge amounts of stored CO2 and CH4 to the atmosphere.

at what rate are wetlands being lost and why?

- around 90% lost in the last century

- Population growth and urbanisation have placed huge pressure on wetland environments, as peat is extremely fertile and yields high yields.

how much carbon can wetlands store?

- Restoration programmes in this area have shown that wetlands can store on average 3.25 tonnes C/ha/year.

examples of wetland restoration programmes?

- The UK is actively restoring wetlands, with major goals like the Wildlife Trusts' (WWT) target to restore 100,000 hectares by 2050

- London Wetland Centre 44 acres of protected Wetland

pros of wetland restoration

- quicker to implement than trees, almost immediate as carbon sinks

- cheap and accessible to all countries

- locally managed and scalable

cons of wetland restoration

- site specific, geographically restrictive

- only offsets CO2 emissions

- requires large areas of land conflicting economic development

example of afforestation and why its needed

- Amazon rainforest deforestation, 17k km of forest deforested annually from 1970 to 2013, 1/5 of primary forest has been destroyed

- single tree sequesters 22kg of C annually

- 390 billion trees in Amazon

- 427 ppm

- Parica Project planting over 20 million trees over 100k hectares of land

- UN project to incentivise developing countries to conserve rainforests by placing monetary value on conservation - UNREDD

pros of project

- accessible to LICs aswell

- inexpensive

- multi benefits, reduces flood risk and erosion, incs biodiversity

cons of afforestation

- time lag - tales 10 years for a tree to become an effective carbon sink

- project conserves, doesnt plant more

- limited space

- firms might cheat and use monocultures with fertilisers for financial benefit to create profit

- overgrazing or overcultivation might occur instead increasing CO2 levels and methane

- offsets, does not reduce co2 emissions directly

what are agricultural practices as a solution and why are they needed?

- sustainable farming techniques

- intensive livestock farming produces 100 million tonnes a year of methane

example of sustainable technique

- use non-continuous flooding (alternate wetting and drying) instead of continuous flooding, methane release from anaerobic soil conditions is dramatically reduced

- nturient management - avoids excess fertiliser and associated nitrous oxide emissions which lower GHG emissions without compromising yield

- serves 9% of human-linked methane

pros of sustainable techniques

- inexpensive mostly

- accessible to all countries

- doesnt always compromise yield

cons of sustainable techniques

- would require many to work e.g. rice on would only account for 0.17% of global emissions

- if there's no profit motivation ppl likely wouldnt do it without legal obligation

- perhaps would have to be a mix

- higher labor costs initially

where is the colorado river basin?

- The Colorado River Basin covers parts of seven U.S. states and extends into northwestern Mexico.

- The river originates in the Rocky Mountains and historically flowed to the Gulf of California, although reduced flows often do not reach the sea today.

key facts

- Supplies water to about 40 million people and large agricultural areas.

- Critical for cities like Phoenix, Los Angeles, Las Vegas, and for irrigating millions of acres of farmland.

- Basin water resources are stressed by population growth, drought, climate change, and over-allocation of water right

what is the law of the river and some of its conditions (clue 1922 and more recently)?

- bundle of treaties, compacts, federal laws, court decisions, and regulatory guidelines that together govern how Colorado River water is allocated and managed among the seven basin states and Mexico.

- Colorado River Compact (1922): Divided the river into Upper Basin (Colorado, New Mexico, Utah, Wyoming) and Lower Basin (Arizona, California, Nevada), each allocated 7.5 million acre-feet per year

cons of law of the river

- conditions decided during one of the wettest years, 1922, thus allocating more surface water than in the system in average years, contributing to over extraction

example of surface water management

Reservoirs like Lake Mead and Lake Powell store and regulate flows to meet allocated water demands and support hydropower, agriculture, and urban supply

example of groundwater management

- Groundwater supplies between 13%–50% of water portfolios depending on the state (e.g., high reliance in New Mexico and Arizona).

- Some states like California have implemented groundwater management (e.g., Sustainable Groundwater Management Act) to regulate extraction.

- Large parts of Arizona, still have limited regulation, leading to unmonitored pumping.

challenges in management

- Declining surface flows due to climate change increase pressure on groundwater reserves, complicating allocation and management strategies.

- Surface water agreements don’t fully account for connected groundwater resources (often managed differently)

impacts of groundwater extraction

- In the last two decades, the basin has lost 27.8–34 million acre-feet of groundwater, equal to vol of lake mead

- Groundwater loss is occurring faster than surface water loss, especially in the Lower Basin (Arizona, California, Nevada)

- Agriculture: Heavy pumping to irrigate water-intensive crops, like alfalfa, drives much of groundwater decline, raising concerns about long-term farm viability and food production.

Urban Supply: Cities often rely on groundwater when river allocations are cut, making groundwater integral to water security.

Policy and Management Impacts

- States with groundwater regulation show more stable levels in managed zones, but unregulated areas continue to decline,

- this highlights the need for policy reform and integrated surface–groundwater management.