Human Interventions in the Carbon Cycle

Human activities have accelerated climate change by transferring carbon from long-term geological stores into the atmosphere. In response, governments, scientists and industries are developing strategies to reduce carbon emissions, remove carbon from the atmosphere, and enhance natural carbon sinks. These interventions aim to influence transfers within the carbon cycle and slow down global warming.

1. Land-Use Change and Forestry

Afforestation and Reforestation

• Afforestation: planting trees where no forest previously existed.
• Reforestation: planting new trees in areas that have been deforested.

How it works in the carbon cycle:

• Trees absorb CO₂ through photosynthesis.
• Carbon is stored in biomass (wood, leaves, roots) and soils.
• When forests expand, the biospheric store increases and atmospheric CO₂ decreases.

Example interventions:

• China’s “Great Green Wall” project has planted billions of trees to combat desertification and increase carbon uptake.
• In the UK, tree-planting schemes are expanding woodland cover to offset emissions.

Strengths:

• Restores habitats and biodiversity
• Low cost compared to industrial removal
• Improves soils and reduces flood risk

Limitations:

• Forests take decades to mature
• Vulnerable to wildfires, disease, drought and future deforestation

Protecting and Restoring Peatlands

Peat stores large amounts of carbon due to very slow decomposition.

Human interventions:

• Blocking drainage channels to re-wet peatlands
• Ending commercial peat extraction
• Restoring vegetation such as sphagnum moss

Carbon impact:

• Reduces oxidation and CO₂ release
• Re-establishes long-term soil carbon storage

2. Ocean-Based Interventions

Blue Carbon and Coastal Wetlands

Mangroves, salt marshes and seagrass beds trap carbon in biomass and sediment.

Interventions:

• Coastal wetland restoration
• Protection from development and aquaculture
• Creation of artificial salt marshes

Carbon impact:

• Coastal wetlands store carbon up to 4 times faster than tropical forests
• Sediments lock away carbon for thousands of years
• Also protect coasts from storm surges and sea-level rise

Ocean Fertilisation (experimental)

Adding nutrients like iron to the ocean to stimulate phytoplankton growth.

Carbon impact:

• Phytoplankton absorb CO₂ through photosynthesis
• Some organic matter sinks to the deep ocean, storing carbon

Concerns:

• Still experimental
• May disrupt marine ecosystems
• Limited international agreement

3. Carbon Capture and Storage (CCS)

How CCS Works

• CO₂ is captured from power stations or factories.
• It is compressed and transported by pipeline or ship.
• The CO₂ is injected deep underground into former oil and gas fields or porous rocks.

Carbon impact:

• Prevents carbon entering the atmosphere
• Can store millions of tonnes of CO₂ for thousands of years

Examples:

• Sleipner CCS project in Norway stores CO₂ beneath the North Sea.
• The UK is developing CCS in the Humber and Teesside industrial regions.

Limitations:

• Expensive to build
• Energy-intensive to operate
• Long-term safety depends on geological stability

4. Carbon Capture and Utilisation (CCU)

Instead of burying CO₂, some industries reuse it:

• Carbonated drinks
• Concrete production
• Manufacturing building materials
• Synthetic fuels

Carbon impact:

Slows the transfer of carbon to the atmosphere
Still limited by scale and energy costs

5. Energy Transition

Renewable Energy

Replacing coal, oil and gas with wind, solar, hydroelectric, geothermal and tidal power.

How it changes carbon transfers:

• Stops carbon from being removed from geological store
• Reduces CO₂ emissions from combustion
• Decreases atmospheric store size over time

Nuclear Power

• Low-carbon electricity generation with high energy output.
• No CO₂ released at the point of use.

6. Carbon Taxes and Emissions Trading

Carbon Taxes

Governments place a cost on carbon emissions.

• Encourages businesses and consumers to reduce consumption of fossil fuels
• Revenues can be reinvested in renewable energy or adaptation projects

Cap-and-Trade Schemes

• Companies receive emission allowances
• Those who cut emissions can sell their unused allowances
• Those who exceed must buy more or pay fines

Carbon impact:

• Creates a financial incentive to emit less
• Used in the EU Emissions Trading System

7. Lifestyle and Behavioural Changes

• Reduced meat consumption lowers methane emissions from livestock
• Increased use of public and electric transport reduces fossil fuel demand
• Energy-efficient homes reduce heating and electricity use
• Circular economy (reuse, repair, recycling) reduces industrial emissions

8. Bioenergy with Carbon Capture and Storage (BECCS)

• Biomass (e.g., wood pellets, crops) is burned to generate electricity
• CO₂ produced is captured and stored underground

Why does it remove carbon?:

• Plants absorb CO₂ as they grow → carbon captured → stored below ground
• Results in net negative emissions

Concerns:

• Requires large areas of land
• Could compete with food production
• May reduce biodiversity

How effective are these interventions?