geography: the carbon cycle

what is carbon?

a nonmetallic element found more or less pure in nature (as in diamond and graphite) or as a part of coal and petroleum and of the bodies of living things

what is a carbon store?

a place where Carbon dioxide is held and prevents it from entering the atmosphere

what is a carbon sink?

a natural or artificial process that absorbs more Carbon from the atmosphere than it releases

what is a carbon source?

a process/area/ecosystem that releases more Carbon dioxide than it absorbs

what is GtC?

gigatons of Carbon (1 billion)

what is anthropogenic co2?

enters the natural carbon cycle due to human activity

what is carbon sequestration?

process of capturing and storing co2 from the atmosphere to reduce the amount in the environment and slow climate change

what is a greenhouse gas?

gas in the atmosphere that traps heat and raises the temperature of a planets surface

what are the origins of carbon on earth?

• original source is the earth’s interior

• stored in the mantle when earth formed and escapes at constructive and destructive plate boundaries

• some of the carbon remains as co2 in the atmosphere, some is dissolved in the oceans, held as biomass in living/dead organisms and some is bound in rocks

what is the largest store of carbon?

the lithosphere → most is in sedimentary rocks in the planets crust

over 99.9% of the Earth's carbon, or around 60–100 million billion gigatonnes (Gt).

what are rocks in the lithosphere that store carbon produced by?

1. the hardening of mud into shale over geological time

2. the collection of calcium carbonate particles, from the shells and skeletons of marine organisms into limestone and other carbon containing sedimentary rocks

→ around 4,100 GtC is stored in the earth’s crust as hydrocarbons formed from dead organisms under extreme heat and pressure

fossil fuels (coal, oil, natural gas) together are estimated to store around 15,000 to 20,000 GtC

how does the hydrosphere store carbon?

earth’s oceans catch 38,000 GtC of carbon split into:

• 900 GtC in the surface layers of the ocean - sunlight into water = photosynthesis

• carbon is exchanged with the atmosphere through Co2 dissolving in oceans and biological processes e.g. growth, death, decay of plankton

• most of this surface carbon cycle occurs rapidly, some of it can be transferred by sinking into the deep ocean where it is stored

how is carbon stored in the cryosphere?

• 2 potential stores of methane → 1,400

1. Methyl clathrates are molecules of methane that are frozen into ice crystals → molecules form under high pressure and low temperatures deep in the Earth or underwater. 
   2. Organic matter frozen in permafrost → contains a lot of frozen organic matter. This organic matter is made of dead plants and animals that have been frozen deep in permafrost for thousands of years. The carbon in this organic matter is locked up because it is frozen.  With global warming, if this permafrost melts the organic matter will decay, rand this will release carbon dioxide or methane into the atmosphere.

how does the biosphere store carbon?

3170GtC - plants and soils are the largest soils

1. The Earth’s plants store approximately 560 GtC, with the wood in trees being the largest fraction (woody stems have the greatest ability to store large amounts of carbon, because wood is dense and trees can be large).
2. The world’s soils carbon content is estimated to be 1500 GtC.
3. Peat contains "at least 550 Gigatonnes of carbon globally - more than twice the carbon stored in all the world’s forests."  Peat is an accumulation of partially decayed vegetation or organic matter - created in anaerobic conditions and keeps carbon locked up.
4. Litter – the decaying remains of plants, contain carbon, and this can be released over time via decomposition.

how is carbon stored in the atmosphere?

750 GtC , the majority of which is in the form of CO2, with much smaller amounts of methane (CH4) and various other compounds. 
Despite the small size of the store, carbon in the atmosphere is of great importance because of its influence on the greenhouse effect and climate.  The relatively small size of the atmospheric C pool also makes it more sensitive to disruptions caused by an increase in sources or sinks of C from the Earth’s other pools. 
Carbon in the atmosphere is measured in parts per million. 

• Deforestation and fossil fuel combustion have added to this store

what is the slow carbon cycle?

takes place on a continental scale → slow processes (around 100-200 million years)

a series of chemical reactions and tectonic activity that moves carbon between the ocean, atmosphere, lithosphere, and soil over millions of years

what are the transfers in the slow carbon cycle?

• weathering

• sequestered in oceans

• physical and biological pumps

• collision of tectonic plates

how does weathering transfer carbon?

Carbon in the atmosphere can dissolve in water and form weak carbonic acids → falls as rain and carbon is transferred out of the atmosphere into water stores such as the oceans.

When carbonic acid comes into contact with limestone it reacts with the rock to form calcium bicarbonate. The calcium bicarbonate is soluble and is carried away in solution, gradually weathering the limestone. Rivers carry the ions to the ocean

how does carbon sequestration transfer carbon?

carbon is sequestered by the oceans = calcium carbonate. 

used for shells, and when these organisms die they sink to the floor of the ocean and form part of the sediment layers.  Over millions of years, these sediments are compressed to form sedimentary rock.

how do physical and biological pumps transfer carbon?

reaches the ocean floor through the biological and physical pumps.

• physical pump is when cooler water sinks and takes carbon from the surface with it.

• biological pump moves organic carbon out of the surface ocean into deeper waters in sinking particles and vertically migrating organisms.

how does the collision of tectonic plates release carbon?

• tectonic plates collide, one sinks beneath the other, and the rock it carries melts under the extreme heat and pressure - heated rock recombines into silicate minerals, releasing carbon dioxide.

• When volcanoes erupt, they vent the gas to the atmosphere and cover the land with fresh silicate rock to begin the cycle again.

• Tectonic uplift also brings marine sedimentary rock to the surface, exposing it to the potential for weathering.

what is the fast carbon cycle?

happens over days, years or decades - because the fast carbon cycle moves carbon through living things.

The fast carbon cycle moves around 1000 times more carbon per year than the slow carbon cycle.

what transfers are involved in the fast carbon cycle?

• respiration

• photosynthesis

• decomposition

• combustion

how does respiration transfer carbon?

The vast majority of living things release carbon dioxide when they breathe. This is a by-product of producing energy in cells → moves carbon from the biosphere to the atmosphere.

• Not all stored carbon from photosynthesis is released by respiration as some is stored in biomass and some is stored in soils.

how does photosynthesis transfer carbon?

Plants absorb carbon dioxide and convert it into sugars during photosynthesis.

Photosynthesis moves carbon from the atmosphere (or the ocean with algae) into the biosphere.

• Animals that eat the plants take in this carbon.

how does decomposition transfer carbon?

important in returning carbon from the biosphere to the atmosphere + the pedosphere (soils) and lithosphere (rocks). 

• break down the dead organisms and return the carbon in their bodies to the atmosphere as carbon dioxide by respiration.

1. Fungi release chemicals to break down dead plants or animals into simple substances. They absorb some of these substances for growth, but others enter the soil.

what conditions can block decomposition?

• if the organic matter is frozen for example, or if it is buried in anaerobic environments such as in peat bogs.

how does combustion transfer carbon?

Combustion moves carbon from the biosphere into the atmosphere by releasing carbon dioxide as a byproduct. This process occurs when fuel, oxygen, and heat combine to create a fire

what happens when carbon is released immediately after a fire?

carbon is released in huge quantities into the atmosphere through combustion.

• Wildfires in forests kill living biomass in forests and reduce carbon gains to near zero.

what happens in the long-term after carbon is released in a fire?

balance between carbon lost through subsequent decomposition and simultaneous carbon gains through growth of new vegetation is changed

decomposition of dead biomass that lasts for several decades post-fire can release up to three times as much carbon as that lost in the initial combustion.

Eventually many decades later, as the forest continues to regrow and decomposition tapers off, carbon storage in trees eventually “catches up,” and the carbon balance equalises. 

how does the carbon cycle occur at plant scale?

Carbon is absorbed by plants for the process of photosynthesis.

Glucose, a product of this, is used as a ‘building block’ for plant biomass and ends up stored in plants.

Some carbon is returned through cell respiration, although there is a net sink of carbon into an individual plant.

Decomposition and respiration in soil also forms part of the cycle at this scale.

how do plants use carbon?

• use co2 from the air and water from the soil to build carbohydrates

• plants exude carbohydrates through their roots to feed soil organisms

• organisms in the soil feed on decomposing plant material

• soil organisms release co2 through respiration

• plants absorb co2

how do plants and soil act as a net store for carbon?

more carbon is stored in soils than in plant biomass, although this varies by biome.

During photosynthesis, energy is produced. Much of this energy is used in respiration.

However, the remaining energy that is stored as biomass is called the Net Primary Production, or NPP, for that plant.

what does a high NPP mean?

higher the NPP, the faster the rate of growth and the more carbon is being sequestered from the atmosphere.

what is succession?

to the way a landscape or particular environment changes over time with regards to vegetation.

what is the lithosphere?

succession from bare rock

what is the psammosere?

succession on sand dunes

what is the halosere?

succession on salt marshes

what is the hydrosere?

succession in aquatic environments

what is the xerosere?

succession in arid environments

how does carbon cycling occur at sere scale?

Rock is weathered, cracks appear → These species are hardy and break rock down further → Topsoil is known as humus, rich in carbon → layer of humus becomes thicker and can support bigger species → Positive feedback as the cycle continues and soil develops → increase in soil depth enables tree growth

what are the stages of psammosere development?

• Embryo dune

• Foredunes

• Yellow dunes

• Grey dune

• Dune slack

• heath + woodland

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what are embryo dunes?

Upper beach area - Mobile dunes accumulate sand

what are foredunes?

Colonization by hardy species tolerant Of aridity, salt, wind and exposure such as marram and sea sandwort

what are yellow dunes?

A vegetation mat develops on the upper and back dune surfaces - Stabilising the dune system

what is a grey dune?

Fixed dunes where accumulating humus changes sand to develop a soil horizon with more moisture and nutrients.

Plantains, wild thyme and sea buckthorn colonise.

what is a dune slack?

Depression where water table is close to the surface so moisture-loving plants colonise such as flag iris and willow.

what is heath and woodland?

Sandy soils have developed that can support scrub heaths Of willow and birch, pine trees and a climate climax Of alder and oak trees.

what are the stages of halosere succession?

• submerged estuary shore

• mudflat saltmarsh establishment

• low saltmarsh/saltmarsh stabilisation

• high saltmarsh/saltmarsh maturity

• climax vegetation

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what is a submerged estuary shore?

 Marine algae and sea lettuce are early colonizers Of nearly permanently submerged mudflat where tidal water is clear enough to let high light levels through. They help stabilize the estuary mud.

what is a mudflat saltmarsh establishment?

Pioneer species trap sediment and calm tidal waters flowing amongst early colonizers. Plants such as glasswort and cordgrass increasingly raise the surface above low tide.

what is low saltmarsh/saltmarsh stabilisation?

Colonisation by hardy grass species that can tolerate high saline and pH conditions such as plantains, sea aster and thrift. Max 4 hrs. submergence.

what is high saltmarsh/saltmarsh maturity?

Vegetation is dominated by low-growing flowering plants such as scurvy grass and sea lavender, with sedges and rushes in hollows and creek banks.

what is climax vegetation?

Deciduous woodland develops that shades and dominates competition. Species are non- halophytic (non- salt-tolerant) such as alder, birch and eventually, oak.

how does natural change affect the carbon cycle?

- Quaternary period = 2.6 million years ago to present day

Global climates have fluctuated massively between interglacial (warm) and glacial periods - Within each glacial period you have stadial (coldest) and interstadial periods.

We are currently in an interglacial period

how does eccentricity impact the carbon cycle?

change in the shape of the earth's orbit around the sun - 100,000 year cycle, the earth's orbit around the sun changes from a thin ellipse (oval) to a circle

When the Earth orbit is elliptical we spend less time close to the sun in the span of a single year. This means we get less solar energy on an annual basis, and tends to cool the Earth.

Less insolation → Lower temperatures → CO₂ is trapped in ice → lowers greenhouse effect → enhances lower global temperatures

how does the end of a Milankovitch cycle effect the carbon cycle?

As temperatures start to rise at the end of the glacial periods (triggered by Milankovitch cycles), there is then a surge in CO₂ released into the atmosphere by the melting of ice.

This surging of CO₂ then enhances the greenhouse effect, warming the trend.

Positive feedback loop

how do colder conditions impact the carbon cycle?

Cold rainwater can hold more CO₂ → chemical weathering is more active

Forest coverage would be very different → Affects the significance and distribution photosynthesis and respiration

Decomposers would be less effective → carbon transfer to the soils is reduced.

More water stored as ice → less transferred to the oceans. Less sediment transfer along the rivers and less sediment build up on the ocean floor

Soil is frozen over vast areas → Stops CO₂ soil transfer

how do warmer conditions impact the carbon cycle?

Melting of permafrost → releases previously trapped gases, such as methane which is now being released → enhances greenhouse effect → positive feedback system leading to further destabilisation of systems

how do wildfires influence the carbon cycle?

Can be started naturally by lightning strikes

they can have regional impacts e.g. 1997-8 and in 2003, Indonesia had lots of wildfires that burnt out of control for months → Smoke spread across south-east Asia

Released large amount of CO₂ into the atmosphere – noticeable strike in carbon emissions

Turned forests into a carbon source (compared to a carbon sink) – combustion returns carbon back to the environment

how does volcanic activity affect the carbon cycle?

Returns carbon that has been trapped in the lithosphere for millions of years

Palaeozoic era volcanoes were much more active than they were today → Carbon dioxide was therefore emitted into the atmosphere, where it remained for a very long time.

At present, volcanoes emit roughly 0.1GtC a year

Volcanoes also erupt lava, which contains silicates that will slowly weather - converts carbon dioxide in the air to carbonates in solution = carbon dioxide is absorbed very slowly from the atmosphere.

how does farming impact the carbon cycle?

1. People have cleared vast areas of natural biomes and replaced them with crops and pasture

• farmed plants do take in carbon seasonally, it tends to be far less that the storage in a natural biome

• process of slash and burn releases huge amounts of stored carbon, and the replacement farming of soya and pasture for cattle takes in small amounts. 

  2. Peat lands and wetlands have been drained and used for farmland.  In doing so, methane is released as organic matter that was previously stored and in anaerobic conditions can now decay.
  3. There has been a huge increase in stock densities of animals such as cattle and chickens as global demand for animal products increases - Up to 60% of all agricultural emissions of carbon come from this pastoral farming. 
  4. Rice paddies produce methane.  emitted from flooded rice fields as bacteria in the waterlogged soil

  5. ploughing of fields releases carbon from soil

how does hydrocarbon extraction and burning effect the carbon cycle?

effectively lock up carbon within the lithosphere over long periods of time as carbon enters the oceans from the atmosphere and enters into phytoplankton or animal life. 

rate of extraction and burning has increased over time shifting carbon stores from the lithosphere to the atmosphere - extra carbon dioxide in the air acts as a greenhouse gas and effectively traps heat within the Earth’s atmosphere.

Worldwide emissions of carbon dioxide (CO₂) from burning fossil fuels total about 34 billion tonnes (Gt) per year. About 45% of this is from coal, about 35% from oil and about 20% from gas.

how does cement manufacture impact the carbon cycle?

manufacture of cement creates greenhouse gases both directly through the production of carbon dioxide when calcium carbonate is thermally decomposed, producing lime and carbon dioxide, and also through the use of the energy needed to make cement, particularly from the combustion of fossil fuels. 

• Cement plants account for 5 percent of global emissions of carbon dioxide

how does deforestation effect the carbon cycle?

1. The biomass store of trees and plants is removed
2. Waste from the deforestation process such as any woods not valuable enough to sell, small plants etc. are burned, this releases Carbon directly into the atmosphere as part of the combustion process.
3. Clearing forests speeds up the decay of leaf litter on the forest floor, releasing even more carbon to the atmosphere
4. Soil carbon is exposed to the atmosphere, speeding up soil erosion + the release of stored soil carbon through decomposition into the atmosphere.

how does urban growth effect the carbon cycle?

1. Cities consume as much as 80 percent of energy production worldwide, due to the many industrial activities that take place within them.

2. As development proceeds, greenhouse gas emissions are driven less by industrial activities and more by the energy services required for lighting, heating, and cooling.

3. A lot of the cement produced creates greenhouse gasses

what is the impact of volcanic activity on processes and flows in the carbon cycle?

• decreases rate of photosynthesis - ash blocks sun light

• eruptions may inject aerosols into the stratosphere, reflecting sunlight and causing temporary cooling - slows down biological carbon sequestration

• volcanic ash deposition can enhance soil fertility - negative feedback

what is the impact of wildfires on processes and flows in the carbon cycle?

• change the species composition of ecosystems which can lead to a long term reduction in ecosystems ability to sequester carbon

• amplification of climate change - increased co2 emissions - temp changes - increased climate for wildfires (positive feedback)

what is the impact of hydrocarbon extraction and burning on processes and flows in the carbon cycle?

• increased co2 may increase photosynthesis - could be negative feedback but limited by nutrient availability and climate

• increased global temps may increase decomposition - leading to the release of carbon

• warming oceans reduce the efficiency of biological pump - limits carbon sequestration

what is the impact of farming practices on processes and flows in the carbon cycle?

crops capture carbon however monocropping limits the health of soil - limits efficiency of carbon sequestration

what is the impact of deforestation on processes and flows in the carbon cycle?

• reduces photosynthesis

• forests cleared - die and release carbon or are burned and release carbon

• forests absorb sunlight and cleared land affects solar radiation

what are the impacts of the carbon cycle on the atmosphere?

most important role of the carbon cycle is the release of carbon dioxide and other gases such as methane into the atmosphere.

• gases absorb long-wave radiation from the earth and lower atmosphere.

Therefore, the greenhouse effect enables life to exist on Earth.

how has anthropogenic activity impacted the carbon cycle in the atmosphere?

Anthropogenic activities have increased the concentration of GHGs - the enhanced greenhouse effect.

Global temperatures have increased 1.1^oC since 1880 – official figure.

2023 was measured as 1.35^oC above 1850-1900 average

how does the carbon cycle effect regional climate?

• Vegetation removes CO₂ and releases water and oxygen

• Regions with dense vegetation (tropical rainforests) experience high rates of photosynthesis and respiration - increases the levels of humidity and cloud cover, which in turn can have regional climate and rainfall implications.

• Widespread deforestation cause areas to become drier and less humid. Less trees = less photosynthesis.

• Volcanic eruptions release CO₂ along with other gases into the atmosphere. This absorbs more incoming radiation from the sun and can lead to a cooling effect.

what are the impacts of the carbon cycle on the land?

• Carbon Cycle is responsible for the formation and development of soil. Carbon in the form of organic matter introduces important nutrients to the soil → for plant growth and production of food.

• Valuable source of energy in the form of wood and fossil fuels

• More CO₂ available results in more photosynthesis and plant growth.

• More CO₂ has also led to an increased growing season for plants

• More CO₂ has increase temperatures which then leads into increased decay of organic matter.

how does the carbon cycle contribute to ocean acidification?

• 30% of the released CO₂ is diffused into the ocean through direct chemical exchange.

• creates a carbonic acid, making the ocean less alkaline

• Since 1750, the pH of the oceans surface has dropped by 0.1.

why is the carbon cycle needed for organisms in oceans?

Carbonic acid reacts with carbonate ions in the water to form bicarbonate → animals like coral and phytoplankton need those ions to make their shells.

Less carbonate = shells become thinner and more fragile.

Coral reefs provide food and livelihood security for 500 million people. A fall in marine biology threatens food security.

negetive feedback: the more acid seawater is, the better it is at dissolving calcium carbonate rocks (chalk and limestone). Over time, this allows the ocean to soak up excess CO₂ because the more acidic water will dissolve more rock.

how does thermal expansion affect the carbon cycle in oceans?

Increased melting of ice and drop in snowfall in shorter winters results in a imbalance → net gain of water entering the ocean.

Thermal expansion: When water heats up, it expands.

• About half of the past century’s rise in sea level is attributed to the oceans having a greater volume.

• oceans are expected to rise between 0.8 and 2mm PER YEAR by 2100

how does the carbon cycle impact ocean salinity?

Decrease in salinity in the deep North Atlantic

More freshwater being added to the ocean

Slowing down of the large-scale oceanic circulation in the NE Atlantic.

what is international mitigation?

Limiting warming requires substantial technological, economic and institutional challenges.

Delaying emissions reduction increases the difficulty and narrows the options for mitigation.

Climate change mitigation requires international cooperation. Effective mitigation will not be achieved if individual countries or groups advance their own interests independently.

what are some significant climate change conferences?

• 1997: Kyoto protocol to reduce emissions of greenhouse gases → agreement

• 2012: extended Kyoto protocol and tried to force countries to legally set binding targets

• 2015: Cop 21 (paris) to limit global warming to below 2c pre-industrial level - preferably 1.5c

• 2022 - cop 26 - agreed to establish a loss and damage fund as a result of climate change

what are the limitations of the Paris climate agreement?

Only three countries out of 197 have not signed the agreement.

However, one of these was USA, which accounted for roughly 15% of all global carbon emissions.

what was in the UAE cop 28?

what are some issues with cop 28?

• Disagreement over phasing out fossil fuels – important for industrialisation

• Trust – countries responsible for reporting their own progress

• Involvement of fossil fuel industry – chair of COP28

• Who is responsible for climate change? Disagreement over loss funding.

what is an example of a regional agreement?

the EU emissions trading scheme

what is the eu emissions trading scheme?

covers over 2 Gt (45%) of annual CO₂ emissions.

• puts a cap on the carbon dioxide (CO₂) emitted by business and creates a market and price for carbon allowances, allowing some businesses to pay to emit more than their quota.

The cost of buying emissions should drive investment in mitigating technology → emissions are estimated to have fallen by 2–5% relative to business‐as‐usual in the first pilot phase from 2005–2007.

In the last phase of the scheme (2013-2020), more industries were included such as flights within Europe, and the cap on emissions is being reduced year by year.

This target was reached 6 years early

Starting in 2027, a new system known as ETS2 will cover emissions from road transport and buildings.

what is Germany’s national mitigation strategy?

Between 1990 and 2014, most major German sources of emissions achieved CO₂ reductions.

half of German electricity is still produced in coal- and gas-fired power plants

• In 2015 the share of renewables in the country’s domestic energy mix increased to 33%.

• Germany managed to cut down its power consumption in the past year by 3.8% by using LED technology and energy saving measures. CO₂ emissions correspondingly fell by 5%.

• Germany aims to cut greenhouse gas emissions 95% in 2050.

what is China’s national mitigation strategy?

China’s emissions started to climb in the 1950s as its economy grew – at an average rate of 10% per year during the period 1990–2004.

China’s total emissions overtook those of the USA in 2006 and its emissions per head of population overtook those of the EU in 2014.
- manufacturing and construction account for two thirds of emissions by source

2015, China dramatically cut its carbon dioxide emissions, with its reduction equalling the UK’s total emissions for the same period.→ due to the closure of more than 1,000 coal mines; coal output is down 7.4% year on year.

By 2020, China hopes to reduce coal from around 66% of its energy consumption to 62% which should also improve air quality.

said it would increase the share of non-fossil fuels (wind and solar) as part of its primary energy consumption to about 20% by 2030

what is adaptation?

process of adjustment to actual or expected climate change and its effects.

In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities.

In some natural systems, human intervention may facilitate adjustment to expected climate and its effects.

how does adaptation help climate change?

Adaptation is becoming embedded in some planning processes, with a focus on incremental adjustments and co-benefits.  In particular, Governments are starting to develop adaptation plans and policies and to integrate climate change considerations into broader development plans.

Responding to climate related risks involves decision making in a changing world, where the timing and severity of climate change impacts are uncertain and there are limits to the effectiveness of adaptation.

what are some natural methods of adaptation?

planting trees and restoring peatlands

what are some human methods of adaptation?

carbon capture - when co2 produced in power stations or other industrial processes is captured before it is released into the atmosphere and stored underground

how has the UK adapted to climate change?

• achieving fully ‘clean’ electricity by 2035, by rapidly increasing wind, solar and nuclear power

• making 80% of new car sales ‘zero emission’ by 2030

• capturing and storing between 20 and 30 million tonnes of co2 a year by 2050

how has Kenya adapted to climate change?

Kenya: Climate-Smart Agriculture

• Challenge: Kenya's agriculture, which is critical to its economy, is vulnerable to changing rainfall patterns and drought.

• Adaptation: The adoption of climate-smart agriculture practices, such as conservation tillage, agroforestry, and water harvesting, helps farmers maintain productivity. Crop diversification and planting drought-resistant crops, like sorghum and millet, are also common.

what are some climate change mitigation strategies?

• Carbon Capture and Storage (CCS) – Capturing CO₂ emissions from power plants and storing it underground prevents it from entering the atmosphere.

• Afforestation & Reforestation – Trees act as carbon sinks by absorbing CO₂ through photosynthesis, reducing greenhouse gas concentrations.

• Renewable Energy Adoption – Wind, solar, hydro, and bioenergy reduce reliance on fossil fuels, cutting carbon emissions.

• Soil Carbon Sequestration – Conservation agriculture, such as no-till farming and cover cropping, enhances soil carbon storage, preventing CO₂ release.

• Reducing Deforestation – Protecting forests (e.g., through REDD+ programs) prevents carbon stored in trees from being released into the atmosphere.

• Blue Carbon Ecosystems – Coastal habitats like mangroves, seagrasses, and salt marshes absorb large amounts of CO₂, making their conservation a priority.

how many carbon emissions come from fossil fuels?

70-75%

how does burning of fossil fuels lead to imbalances in systems?

as fossil fuels are extracted and burned, carbon is being artificially moved from the slow carbon cycle to the fast carbon cycle, causing imbalance in the system and accelerating the transfer from lithosphere to atmosphere -> when fossil fuels are burned, the process of combustion releases energy and carbon dioxide.   

what is the link between fossil fuels and climate change?

burning fossil fuels since the Industrial Revolution, around 1800.  

• In this time, combustion has increased exponentially, particularly after 1950 – the great acceleration of globalisation   

• Coal has always accounted for the greatest emissions of CO₂  

• Total human emissions are nearly 10GtC annually -> Coal and oil between them make up around 75% of emissions.  

how do land use changes (urbanisation) impact the carbon cycle?

-> Over half for the world’s population lives in urban areas.  This is expected to reach 60% by 2030 (urban areas grow 1.3 million people per week).  

• As cities grow, land use changes from natural vegetation/agriculture to concrete, brick and tarmac surfaces -> has significant impact on the local carbon cycle as important stores are either replaced (vegetation) or covered up(soils) with impermeable surfaces.  

• Reduces carbon sinks and stores and means that surfaces will not absorb carbon and will increase localised warming  

Globally, urban areas occupy about 2% of the total land area, yet account for 97% of all anthropogenic CO2 emissions.  

Cement manufacture contributes CO₂ to the atmosphere when calcium carbonate is heated, producing lime and CO_{2 -> t}otal 2-5% of global carbon emissions. 

-> For every 1000kg of cement produced, 900kg of CO₂ is released into the atmosphere. 

 

how does land use change (agriculture) impact the carbon cycle?

Around 13 million hectares of forest are cut down and changed to other land uses every year -> Humans have removed nearly 50% of all forested areas in the world.  

Trees are removed, either by burning or felling . Burning produces additional carbon emissions.  Felling accelerates decomposition and decay -> causes forests to become carbon sources rather than sinks. 

land is for building, ranching, mining or growing commercial crops + Timber is a valuable product for furniture and firewood. Deforestation is particularly concentrated in tropical regions – EG Brazil, Indonesia. Indonesia accounts for 20% of all deforestation CO₂ emissions.  

• Large decrease in surface runoff