earths life support system

Importance of water

• Water is essential for all living organisms.

• Humans use water for drinking, washing, cooking, agriculture and industry.

• Plants need water for photosynthesis and nutrient transport.

• Animals need water for hydration and biological processes.

• Water helps regulate Earth's temperature because it has a high specific heat capacity.

• Water provides habitats for aquatic organisms.

Importance of carbon

• Carbon is the building block of life because it forms the basis of organic molecules.

• Carbon is found in carbohydrates, proteins, fats and DNA.

• Plants absorb atmospheric carbon dioxide during photosynthesis.

• Carbon moves through food chains when organisms consume plants or other organisms.

• Humans use carbon-based fossil fuels for energy.

• Carbon dioxide helps regulate Earth's temperature through the greenhouse effect.

Water and carbon cycles

Water and carbon move continuously between the land, oceans and atmosphere.

The cycles are interconnected because processes in one cycle can affect the other.

For example, plants absorb carbon dioxide through photosynthesis and water through their roots.

Open and closed system

Open system: Allows energy and matter to enter and leave.

Closed system: Allows energy to enter and leave but has very limited exchange of matter.

The global water cycle is approximately a closed system for water because very little water enters or leaves Earth.

The global carbon cycle is also approximately closed, although small amounts of carbon enter and leave Earth.

Individual drainage basins are open systems because water enters through precipitation and leaves through river discharge and evapotranspiration.

Stores in water cycle

Oceans: Largest water store, containing approximately 97% of Earth's water.

Cryosphere: Water stored as ice sheets, glaciers, snow and permafrost.

Groundwater: Water stored beneath the Earth's surface in soil and rocks.

Atmosphere: Water stored as water vapour, clouds and precipitation.

Soil: Water stored in soil pores.

Vegetation: Water stored within plants.

Rivers and lakes: Surface water stores.

Stores in carbon cycle

Sedimentary rocks: Largest long-term carbon store, including limestone.

Oceans: Large carbon store, with carbon dissolved in seawater.

Fossil fuels: Carbon stored in coal, oil and natural gas.

Soils: Carbon stored in organic matter and decomposing material.

Vegetation: Carbon stored in plant biomass.

Atmosphere: Carbon stored mainly as carbon dioxide and methane.

Water cycles input and output

Input – precipitation: Water enters a drainage basin through rain, snow, sleet or hail.

Output – evapotranspiration: Water leaves the land through evaporation and transpiration.

Output – river discharge: Water leaves a drainage basin through rivers.

Input – snowmelt: Snow and ice melt, releasing water into the water cycle.

Carbon cycle input and output

Photosynthesis: Plants absorb carbon dioxide from the atmosphere and store carbon in biomass.

Respiration: Plants, animals and microorganisms release carbon dioxide into the atmosphere.

Decomposition: Microorganisms break down dead organic matter, releasing carbon dioxide and sometimes methane.

Combustion: Burning fossil fuels and vegetation releases stored carbon into the atmosphere.

Weathering: Chemical weathering removes carbon dioxide from the atmosphere and transfers carbon into dissolved forms.

Precipitation: Carbon can be transferred from the atmosphere to land and oceans through rainfall.

Water cycle processes

Evaporation: Liquid water changes into water vapour due to energy from the Sun.

Transpiration: Water evaporates from plant leaves through small openings called stomata.

Evapotranspiration: The combined loss of water through evaporation and transpiration.

Condensation: Water vapour cools and changes into tiny liquid water droplets, forming clouds.

Precipitation: Water falls from the atmosphere as rain, snow, sleet or hail.

Interception: Precipitation is caught by vegetation, such as leaves and branches, before reaching the ground.

Infiltration: Water enters the soil from the ground surface.

Percolation: Water moves downwards through soil and permeable rock.

Surface runoff: Water flows over the land surface towards rivers and streams.

Overland flow: Water travels across the ground when rainfall exceeds infiltration capacity or the soil is saturated.

Throughflow: Water moves sideways through the soil towards a river.

Groundwater flow: Water moves slowly through saturated rock and aquifers.

Baseflow: Groundwater supplies water to a river, helping maintain its flow during dry periods.

Channel flow: Water moves through a defined river channel.

Sublimation: Ice or snow changes directly into water vapour without becoming liquid.

Ablation: The loss of ice or snow from a glacier through processes such as melting and sublimation.

Causes of precipitation

Convectional rainfall: The Sun heats the ground, causing warm moist air to rise, cool and condense.

Relief rainfall: Moist air is forced to rise over high land, cools and condenses.

Frontal rainfall: Warm air rises over colder, denser air along a weather front, cools and condenses.

Carbon cycle processes

Photosynthesis: Plants absorb atmospheric carbon dioxide and use sunlight to convert it into organic matter.

Respiration: Organisms break down glucose to release energy, releasing carbon dioxide.

Decomposition: Bacteria and fungi break down dead plants and animals, releasing carbon into the atmosphere and soil.

Combustion: Burning vegetation or fossil fuels releases carbon dioxide.

Natural sequestration in oceans: Oceans absorb carbon dioxide from the atmosphere and store carbon in dissolved forms.

Vegetation sequestration: Plants absorb carbon dioxide through photosynthesis and store carbon in their biomass.

Sediment sequestration: Carbon becomes stored in ocean sediments and can eventually form sedimentary rocks.

Chemical weathering: Carbon dioxide dissolves in rainwater, forming weak carbonic acid, which reacts with rocks and transfers carbon into rivers and oceans.

Chemical main forms

Carbonation: Carbonic acid reacts with calcium carbonate in rocks such as limestone, dissolving the rock.

Hydrolysis: Water reacts with minerals in rocks, chemically altering them and forming new minerals such as clay.

Oxidation: Oxygen reacts with minerals, particularly iron-bearing minerals, forming oxides.

Dynamic equilibrium

Dynamic equilibrium occurs when inputs and outputs are balanced over time.

Stores and flows continue to change, but the overall system remains relatively stable.

A change in one part of a cycle can affect other stores and flows.

Human activity can disrupt the balance, causing stores and flows to change.

What Human factors can disturb and enhance the natural processes and stores in the water and carbon cycles.

Land-use changes

Urbanisation

Vegetation is removed, reducing interception and transpiration.

Impermeable surfaces such as roads and buildings reduce infiltration.

Surface runoff increases.

River discharge may increase more quickly after rainfall.

Increased combustion from transport and buildings releases carbon dioxide.

Construction removes vegetation and can disturb soil carbon stores.

Farming

Ploughing exposes soil organic matter to decomposition.

Deforestation for agriculture reduces vegetation carbon stores.

Irrigation increases water extraction and evaporation.

Fertilisers can cause nutrient pollution in rivers.

Livestock release methane.

Forestry

Deforestation reduces interception, transpiration and carbon storage.

Afforestation increases carbon sequestration and can increase interception.

Trees can improve infiltration by increasing soil structure and root pathways.

Water extraction

Surface water extraction

Water is removed from rivers, lakes and reservoirs.

Reduces water available for ecosystems and downstream users.

Can lower river discharge.

Excessive extraction can cause water shortages.

Groundwater extraction

Water is pumped from underground aquifers.

Excessive extraction lowers the water table.

Can reduce groundwater flow into rivers.

May cause land subsidence in some locations.

Can lead to saltwater intrusion in coastal aquifers.

Aquifers

Permeable rocks that store and transmit groundwater.

Examples include sandstone and chalk.

Artesian basins

Groundwater is stored in a confined aquifer between impermeable rock layers.

Water is under pressure, so it can rise naturally when a well is drilled.

Fossil fuel combustion

Burning coal, oil and natural gas releases carbon dioxide.

This transfers carbon from long-term geological stores into the atmosphere.

Increases atmospheric greenhouse gas concentrations.

Enhances the greenhouse effect and contributes to global warming.

Climate change can alter precipitation, evaporation and river flows.

Carbon sequestration

Carbon sequestration is the capture and long-term storage of carbon dioxide.

Natural sequestration occurs in vegetation, soils and oceans.

Artificial methods include carbon capture and storage (CCS).

Afforestation increases carbon storage in vegetation.

Wetland restoration can increase carbon storage in soils and vegetation.

Positive and negative feedback loop between water and carbon cycle

Positive feedback

Amplifies an initial change.

Example: Rising temperatures cause permafrost to thaw.

Thawing releases carbon dioxide and methane.

These greenhouse gases increase global warming.

Further warming causes more permafrost thaw.

Negative feedback

Reduces or counteracts an initial change.

Example: Rising atmospheric carbon dioxide can increase photosynthesis if water, nutrients and other conditions are suitable.

More plant growth can remove additional carbon dioxide from the atmosphere.

This can help reduce the initial increase in atmospheric carbon dioxide.

Short term changes of cycles

Short-term changes

Diurnal changes

Changes that occur over a 24-hour period.

During daytime, higher temperatures and sunlight increase evaporation and transpiration.

Photosynthesis occurs during daylight, removing carbon dioxide from the atmosphere.

At night, photosynthesis stops or greatly decreases.

Respiration and decomposition continue.

Seasonal changes

Changes that occur throughout the year.

Summer generally has higher temperatures and more sunlight, increasing evaporation and photosynthesis.

Winter generally has lower temperatures, reducing evaporation and plant growth.

In deciduous forests, leaf fall reduces transpiration during autumn and winter.

Snow accumulation stores water during winter.

Spring snowmelt releases water into rivers and soils.

Long term changed in water carbon cycle including changed to store and flows

Long-term changes – millions of years

Water cycle

Changes in global temperatures affect evaporation and precipitation.

Ice ages increase the amount of water stored in glaciers and ice sheets.

Sea levels fall as more water is stored as ice.

During warmer periods, melting ice increases ocean water stores and sea levels.

Carbon cycle

Volcanic activity releases carbon dioxide into the atmosphere.

Chemical weathering removes carbon dioxide over long periods.

Carbon can become stored in sedimentary rocks.

Fossil fuel formation stores carbon over millions of years.

Changes in vegetation and ocean conditions alter carbon storage.

The importance of research and monitoring techniques to identify and record changes to the global water and carbon cycles; reasons why this data is gathered.

Research and monitoring

Satellites: Monitor vegetation cover, ice sheets, sea levels and atmospheric gases.

Ice cores: Provide evidence of past atmospheric carbon dioxide and temperature changes.

Tree rings: Provide information about past climate conditions.

Climate stations: Measure temperature and precipitation.

River gauges: Measure river discharge and changes in water levels.

Ocean buoys: Monitor ocean temperatures and conditions.

Soil sampling: Measures soil moisture and carbon storage.

Why monitoring is important

Identifies changes in stores and flows.

Helps scientists understand climate change.

Allows future trends to be modelled.

Supports environmental management and policy decisions.

To what extent are the water and carbon cycles linked?

Vegetation

Plants absorb water through their roots.

Plants absorb carbon dioxide through photosynthesis.

Transpiration transfers water vapour into the atmosphere.

Photosynthesis transfers carbon from the atmosphere into vegetation.

Therefore, vegetation is important to both cycles.

Oceans

Oceans store large quantities of water and carbon.

Carbon dioxide dissolves into seawater.

Ocean temperatures affect how much carbon dioxide can be absorbed.

Warmer oceans generally absorb less carbon dioxide.

Ocean currents move heat and dissolved carbon around the planet.

Atmosphere

Water vapour is a greenhouse gas that influences global temperatures.

Carbon dioxide and methane also contribute to the greenhouse effect.

Changes in atmospheric temperatures influence evaporation, precipitation and plant growth.

Cryosphere

Ice sheets and glaciers store large amounts of water.

Permafrost stores large amounts of carbon.

Rising temperatures melt ice and thaw permafrost.

Thawing permafrost can release carbon dioxide and methane, increasing atmospheric greenhouse gases.

How human activities change the availability of water and carbon

Deforestation reduces vegetation carbon stores and alters interception and transpiration.

Fossil fuel combustion increases atmospheric carbon dioxide.

Water extraction reduces water availability in rivers and groundwater stores.

Agriculture alters soil carbon stores and water flows.

Climate change affects precipitation, evaporation, ice stores and ocean carbon absorption.

Long-term climate change impacts

• Higher temperatures increase evaporation.

• Changes in atmospheric circulation alter rainfall patterns.

• More intense rainfall can increase surface runoff and flooding.

• Drought can reduce soil moisture and plant growth.

• Melting glaciers and ice sheets increase sea levels.

• Permafrost thaw releases stored carbon.

• Warmer oceans absorb less carbon dioxide, potentially increasing atmospheric carbon dioxide.

Protecting the carbon cycle

Protecting the carbon cycle

Afforestation and reforestation

Planting trees increases carbon sequestration.

Trees absorb atmospheric carbon dioxide through photosynthesis.

Increases carbon stores in vegetation and soils.

Helps regulate the global climate.

Wetland restoration

Wetlands store large amounts of carbon in waterlogged soils.

Low oxygen conditions slow decomposition.

Restoring wetlands increases carbon storage.

Also improves biodiversity and water quality.

Improving agricultural practices

Reduced tillage helps protect soil carbon stores.

Cover crops reduce soil erosion.

Agroforestry increases vegetation carbon storage.

Sustainable farming can reduce greenhouse gas emissions.

Reducing emissions

Renewable energy reduces reliance on fossil fuels.

Energy efficiency reduces fuel consumption.

Carbon capture and storage prevents some carbon dioxide from entering the atmosphere.

Carbon trading places a financial value on emissions and allows organisations to trade emissions allowances or credits.

International agreements encourage countries to reduce greenhouse gas emissions.

Protecting water cycles

Improving forestry techniques

Afforestation increases interception.

Tree roots improve soil structure and infiltration.

Reduces soil erosion and surface runoff.

Helps maintain water quality.

Water allocation

Water is distributed between domestic, industrial and agricultural users.

Helps prevent over-extraction.

Supports sustainable water supplies.

Water allocation plans can prioritise essential needs during shortages.

Drainage basin planning

Manages water across an entire drainage basin.

Includes management of rivers, reservoirs, groundwater and surface runoff.

Helps reduce flood risk and manage water resources.

Sustainable drainage systems (SuDS) can increase infiltration and reduce rapid surface runoff.