2.2.7 [HL] Ecological Yields & Efficiency

Learning Objectives

For a given natural resource such as a crop,

= annual gain in biomass or energy through growth and recruitment.

Maximum sustainable yield (MSY) is the maximum flow of a given resource such that the stock does not decline over time.
That is, the highest rate of harvesting that does not lead to a reduction in the original natural capital.
MSYs can be estimated for natural ecosystems and agricultural or silvicultural systems.
Silviculture involves the treatment of forests to conserve and improve their productivity

An energy-flow diagram showing the flow of energy through an ecosystem. Storages (boxes) and flows (arrows) vary in width and are proportional to the amount of energy being transferred.

Entropy = Disorder.
The second law of thermodynamics shows how the entropy of a system increases as biomass passes through ecosystems.
An increase in entropy arising from energy transformations reduces the energy available to do work.
Therefore, as less energy becomes available, disorder (entropy) increases.
In any isolated system, where there is no new input of energy, entropy tends to increase spontaneously.
The universe can be seen as an isolated system in which entropy is steadily increasing so eventually, in billions of years’ time, no available energy will be present.
Living systems can maintain a high degree of organization and low entropy through the net increase in entropy resulting largely from cellular respiration.

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