1.2 - Systems

System

Made of individual parts working together to perform a particular function

Systems Approach

is a holistic approach to visualise a complex set of interactions

Emergent Properties

The properties of a complex system that arise from the simple interactions of its component parts.
(the whole is greater than the parts)

What is a system made out of

A system is comprised of storages and flows
The flows provide inputs and outputs of energy and matter.

Types of flows?

Transfer - change in location
Transformation - change in state/chemical composition/energy type

Open system

Energy + matter freely exchanged with environment
(All ecosystems come under this)

closed system

Exchange only energy with the environment
Very rare and usually only exist experimentally

Isolated System

Exchanges neither matter nor energy
Hypothetical
The entire Universe as a system can be considered an isolated system

Model

• Simplified representation of a complex matter

How would you answer: Evaluate the use of models as a tool in a given situation

-State what the model is
-State advantages
-State disadvantages
-Give own judgement

Biosphere

(all living organisms and their interactions)

Hydrosphere

Earth's water bodies

Cryosphere

Ice/snow covered areas

Geosphere

Solid rock and minerals part of the Earth

Atmosphere

the layers of gases immediately surrounding the earth

Anthroposphere

Parts of the Earth that are affected by and interact with humans.

The Gaia Hypothesis

• The world acts like a single biological being made up of many individual and interconnected units (A SYSTEM ).

• introduced to explain how atmospheric composition and temperatures are interrelated through feedback control mechanisms

Negative Feedback

Return a system to its original state
Stabilise systems as they reduce change by counteracting it

Positive Feedback

Change a system to a new state
Destabilise systems as they increase change

Resilience

is the tendency of a system to return to its original state after a disturbance

Steady state equilibrium

• Continuous inputs and outputs of energy and matter, but the system as a whole remains in a constant state

• Maintained by stabilising negative feedback loops

Static Equilibrium

• No inputs or output of matter or energy (isolated systems)

• No changes in the system over time

• If there is a disturbance the system will adopt a new equilibrium

A stable equilibrium

Tends to return to the same equilibrium after a disturbance

Unstable Equilibrium

The system returns to a new equilibrium after a disturbance

What increases resilience of a system?

• More complex systems (more interactions)

• Higher biodiversity (species and genetic)

• Larger storages within systems

• Higher productivity (and hence a larger storage)

• Species with faster reproductive rates and wider geographical ranges

How does complexity increase stability of a system?

Many flows between storages and feedback loops, a change is less likely to affect it.

Example of system with low resilience

• Irish potato famine - monoculture of potatoes all were affected by potato blight, people died from lack of food as they were extremely dependent on the food.

Tipping point

Tipping point is minimum amount of change needed to cause destabilisation within a system; system then changes to new equilibrium.

Issues with monitoring tipping points

• Change in ecosystem is too far to stabilise it

• Cannot be precisely predicted using models

• Changes are long lasting and hard to reverse

• The effects of processes can often take a long time to see (time lag)

Benefits of a model

• Easier to understand and communicate to public,

• can make predictions on how system will change in future

• can inform policy making better...

Negatives of a model

• Simplification = loss of accuracy

• up to interpretation

• complex environmental systems may not translate well to a model.