Earths Life Support systems

What is the water cycle?

The flow of water between the atmosphere, land and oceans.

What is a closed system?

No matter can be transferred to surroundings, but energy can.

What is an open system?

One in which matter and energy can be transferred to and from its surroundings, as well as between stores.

What is a system?

Elements that work cohesively to complete a cycle.

The global water and carbon cycles are…

Closed systems - however, on a local scale they become open.

How much water is stored in our oceans, and how long does it stay there?

1,370,000 Gigatones & 3000 years

Why is water important to life on earth?

1. The ocean regulates global temperatures by absorbing and gradually releasing thermal energy

2. Clouds reflect 20% of incoming solar radiation & cool the planet

3. Mammals are made up of 65-95% water, require it for metabolic functions

4. Water is used for economic activity

   1. Plants require water for photosynthesis, respiration & transpiration.

Why is carbon important to life on earth?

1. All life on earth is built on large molecules of carbon atoms

2. Economic resources

3. Stored in carbonate rocks, seawater, the atmosphere and biosphere.

What is photosynthesis?

The process by which plants use CO2 and water and sunlight to create 02 and energy - vital to all plant life.

How much water is in the atmosphere, and how long does it stay there?

13 GT, 10 days

How much water is in the land store, and why is it variable?

39,000 GT. If surface run off occurs, water will be in land for less than a day VS. percolation or infiltration.

How much carbon is in the atmopsheric store, and why might this not be 100% accurate?

600Gt - though, emissions enlarge this.

What is the carbon cycle

The carbon cycle is the flow of carbon between the stores of atmospheres, oceans, biomass and rocks. 

How much carbon is stored in rocks, and how long does it stay there?

60 to 100 million GT, and 150 million years.

What is the smallest store of carbon?

Biomass

How much carbon is stored in terrestrial biomass globally?

560 GT

Respiration

The proccess in which living organisms take in oxygen, and emit CO2. They require this to sustain themselves

Evaporation

The change of state as water is heated to 100 degrees, and becomes vapourTR

Transpiration

When plants release water vapour through their leaves. 10% of atmospheric moisture

Evapotranspiration

The combined process occurring in most plants releasing water vapour

Anthropogenic

Originating from human activity

Interception

precipitation captured by vegetation, preventing it from instantly reaching the ground.

Decomposition

The breakdown of organic matter by bacteria and fungi, releasing CO2 and nutrients into the soil and atmosphere

Weathering

The in situ breakdown of rock. Chemical weathering caused by chemical reactions

Carbonation

Water combining with CO2 to create carbonic acid - reacting with mineral rocks.

Combustion

The burning of organic material, releasing Carbon Dioxide into the atmopshere.

Annual flux rate of photosynthesis and respiration

120 GT

Why is the annual flux rate of decomposition variable?

As its dependant on temperature, Oxygen availability, and water availability

Combustion

The burning of organic material, rapidly releasing CO2 into the atmopshere. A

Annual flux rate of combustion?

10 GT per year

Precipitation

Water particles that have condensed, and grown to a critical size release. This can be either snow, hail or rain.

Ablation

Loss of mass from glaciers due to sublimation and melting

Infiltration

The downward movement of water into soil

Percolation

The downward movement of water through soil and into porous rocks underground.

Throughflow

The lateral (sideways) movement of water through the upper layers of soil

Groundwater flow

The horizontal movement of water through saturated bedrock or deep soil - very slow

Overland flow

The flow of water over land when precipitation intensity is greater than infiltration capacity of soil

Saturated overland flow

Surface run off of water when the soil is already saturated (no space to absorb more water) - common in floods.

What is dynamic equillibrium

When a system with continuous inputs, outputs and throughputs that can adapt to change through feedback, achieving balance.

Feedback

An automatic response to changes in a system which disturb balance/equillibrium

Positive feedback

When something is added to a system, that causes further change away from equilibrium/balance

Negative feedback

When something is added to the system, restoring equilibrium - a ‘controlling effect’

What is an aquifer?

A layer of permeable rock and soil that stores and allows the movement of groundwater

What are the main land use changes that affect the cycles

• Urbanisation

• Forestry

• Farming

How can urbanisation affect the water cycle

• Replacing soil with concrete & so more impermeable surfaces, decreased infiltration and groundwater storage and increased overland flow - affects volume of rivers and rate of flow

• Urban drainage systems deliver water to rivers faster - increasing flood risk and rising water levels

• Development on flood plains reduces water storage capacity - increased river flow and flood risk.

How can urbanisation impact the carbon cycle

• Reduction in surface vegetation - however this is more impactful in tropical areas than temperate (TRF)

• Increased CO2 emissions from energy consumption in urban areas - increased transport and industry infrastructure (building)

What percentage of fossil fuel emissions do urban areas account for

over 70%

Impacts on the water cycle in forestry areas

• Plantations of natural forest intercept rainfall - increased evaporation, and increased precipitation

• Runoff and stream discharge decreased

• Lagtimes are longer, and total discharge is low

• Localised deforestation causes a sharp dip in evapotrans..; interception, Inverse occurs after trees are felled for profit

Impacts on the carbon cycle from forestry

• Increase in carbon stores

• Trees extract CO2 from the atmosphere, and sequest it for 100 year

However, forest trees are only active carbon sinks for the first 100 years of their lives

Impacts on the water cycle from farming

• Irrigation averts water from rivers and groundwater supplies to cultivated land. Some evapotranspiration

• Interception, evaporation and transpiration are all lower in agroecosystems versus forest or grassland

• Ploughing increases soil moisture loss - runoff and erosion

• Heavy machienery compacts soil and runoff

How does farming affect the carbon cycle

• Clearance of forest for farmland decreases above and below ground carbon stores

• Ploughing decreases soil carbon stores, and exposes soil organic matter to oxidation

• After harvesting, small amounts of organic matter are returned to soil

• Rice paddies generate methane

• Increased CO2 emissions from machienary.

Example of a positive feedback loop for the water cycle

• Increased global temperatures due to the GHG effect

• Atmosphere can hold more moisture

• Higher temperatures increase evaporation rates

• More water is stored in clouds/more cloud cover & increased precipitation

• Increased water vapour in the atmosphere increases global temp. (GHG)

• Loop - higher global temperatures

Equation for photosynthesis

6CO2 + H20 —> C6 H12 O6 + 6O2

Example of a negative feedback loop for the water cycle (global scale)

• Increased water vapour creates greater cloud cover - which reflects solar radiation back into space

• Smaller amounts of solar radiation mean decreasing temperatures, and so falling water vapour as less evaporation

Example of a negative feedback loop for the water cycle (drainage basin scale)

• above average precipitation in a year

• increased river flow and evaporation

• excess water from precipitation recharges aquifers, increasing water store in permeable rocks.

Positive feedback loop for the water cycle (glaciation)

• Increased atmospheric temperatures

• increased sea surface temperatures

• melts polar sea ice

• decreases albedo effect from snow and ice cover

• Increases seasurface temperature

Positive feedback loop for the carbon cycle

• Enhanced GHG effect increases global temperatures

• Permafrost able to melt faster

• releasing CH4 and CO2 from decomposed matter within the permafrost

• contributing more GHG and increasing global temperatures

Negative feedback loop for the carbon cycle

• Increased atmospheric CO2 emissions

• increases amount of CO2 in atmosphere

• CO2 available to plants increases

• Carbon fertilisation occurs - plants able to absorb more carbon from the atmosphere

• Atmospheric carbon falls

What is urbanisation

Converting land from a rural use (farmland/woodland), to urban use

What is forestry

The art/science of managing forests to yield constant crops (for logging/lumber)Wh

What is farming

the practise of cultivating plants and animals for human use

How does population impact water stores

Population growth & increased living standards (affordability of water, leading to sanitation/daily bathing/washing machines/dishwashers) put pressure on water stores (ground and terrestrial)

How does extraction impact water stores

increased urban population & demand for water in industry has led to the use of water extraction from rivers/groundwater supplies

How has livestock impacted water stores

Increasing population means a higher demand for food/produce. The livestock being reared require food and water, putting pressure on water stores

How has irrigation impacted water stores

to provide food security, irrigation is used to ensure water supply for crops/farming. Removes water from rivers/groundwater & puts additional pressure on supply

How has industry impacted water stores

EDC’s = rapid industrialisation. Often require large amounts of water, putting pressure on supplies

How has fossil fuel impacted carbon stores

billions of GT of carbon are being removed from terrestrial stores to keep up w energy demand

What percent of global primary energy consumption is fossil fuels

87%

How has deforestation impacted carbon stores

Removing trees (carbon sinks) increases atmospheric carbon stores & decreases carbon in biosphere

How has human activity in wetlands impacted carbon stores

Many wetlands have been drained so land can be used for cultivation/development. Reduced amount of carbon stored in wetlands

How have livestock impacted carbon stores

Livestock release CO2 and CH4 into the atmosphere (increased atmospheric store).

Feeding, rearing and transporting of livestock require burning of fossil fuels (increased emissions)

In 2006, according to the UN, what percentage of the world’s anthropogenic GG emissions were from domesticated livestock

18%

How does ocean acidification impact carbon stores

it leads to a decline in phytoplankton population. They currently absorb over half of CO2 emitted by burning fossil fuels (and so eventual increase in atmospheric carbon)

How many tonnes of carbon per year are transferred from fossil fuels to the atmosphere

8 billion

Why are phytoplankton so integral for equilibrium in the carbon cycle

They absorb more Co2 than tropical rainforests

Strategies to protect the carbon cycle:

• afforestation

• wetland restoration

• improving agricultural practices and reducing emissions

• Carbon trading

• International agreements

What was the first international agreement signed to work on global emissions

The Kyoto protocol

Key facts about Kyoto

• Acknowledged different countries had diff. capabilites to manage their emissions and so set different goals for everyone

• 193 countries signed it

• adopted in 1997, implemented in 2005

Strengths of the Kyoto protocol

• 36 countries complied with the protocol

What is the water balance equation

Precipitation = Runoff + evapotranspiration + change in stores

What is carbon sequestration

the process by which carbon dioxide is removed from the atmosphere (either naturally or anthropogenically), and held in solid or liquid form.

What is the technology used for carbon sequestration called

CCS (or carbon capture and storage)

How does CCS work

1. Capture - CO2 is seperated from the power station using chemical solvents that bind to CO2 and are heated to release pure CO2.

2. Transport/Compression. CO2 is compressed into liquid form and transported in pipelines

3. Storage - liquid CO2 is injected into porous rocks underground, protected by a layer of impermeable rock.

What percentage of emissions can CCS capture

90%

By what percentage could CCS cut global emissions by

19%

What is water extraction

the process of taking water from the surface or ground either temporarily or permenantly (often for agricultural, industrial or domestic use)

Whats the water table

The border between saturated and dry rock. This fluctuates according to the season and the amount of water abstraction

whats an artesian basin

where groundwater is confined between impermeable layers of sedimentary rock

Impacts of water extraction on the water cycle: surface water

• Reduces channel flow - increased sedimentation

• Dissolved oxygen falls, water temperature increases - threatens living organisms

• pollutants are more concentrated

• fewer floods mean a decreased supply of alluvium to plants (loose, fertile soil and sediment)

Impacts of water extraction on the water cycle: ground water

• In coastal areas, saltwater intrusion degrades groundwater stores

• Fossilised water can be used sooner

• levels of water in aquifers and basins decrease - streams and springs dry up

Example of surface water extraction The river Kennet

• South east england

• drains roughly 1200km2 in wiltshire/berkshire

• most of the river’s flow is from groundwater (as upper catchment is chalk)

• Several areas (Swindon) rely on Kennet for public water supply

Impacts of the Kennet water extraction on the water cycle

• groundwater extraction rates exceed recharge

• Falling water table decreases flows by 10 to 14%

• 2003 drought - flows decreased by 20% (up to 40% early 90’s)

• Lower flows have decreased flooding, creating temporary areas of wetland

• decreased groundwater levels - springs are dried up

Why do artesian basins occur… & leading on to water extraction

• Sedimentary rocks form a basin shape (or syncline)

• an aquifer forms that is trapped between impermeable layers. This means water is stored under pressure

• Allows for water to rise to the surface through a well under its own pressure. this is an artesian aquifer

• When drills are made at the bottom of the U-shaped basin, water is able to rise to the surface, as a hole has been made in the impermeable rock.

How much did the water table fall by due to industry in london

90m

How are we managing against water table levels falling/maintaining equillibrium in groundwater stores

Less industry occurring in the CBD and so no demand for water.. however now water table levels are rising & so to prevent flooding, Thames water have an abstraction license to maintain equilibrium.

Advantages of CCS

• Cuts global emissions

• CO2 can be pumped into mature oil fields that are otherwise uneconomic to recover

• Drax project can capture 2 million tonnes of Co2/year

Disadvantages of CCS

• 2 UK based projects will cost atleast £1 billion

• 20% of a power plants output is used up by compression (loss of energy)

• Requires storage reservoirs with porous rock overlain with impermeable rock (not common)

• No awareness of long-term consequences