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 water 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.