Environmental science cheat sheet

Energy and matter

Energy flows through food webs, while matter cycles between organisms and the physical environment.

Carbon can move between air, plants, animals and soil.

Population change

Population size changes through births, deaths, immigration and emigration. Resource limits affect growth.

Net change = births + immigration − deaths − emigration.

Climate and weather

Weather describes short-term atmospheric conditions. Climate describes patterns over longer periods.

A cold day alone cannot establish a long-term climate trend.

Impact assessment

Identify a pressure, the system it affects, a measurable outcome and the uncertainty in the evidence.

Compare water measurements upstream and downstream, with suitable sampling controls.

Biodiversity at different scales

Genetic, species and ecosystem diversity describe different features of biological variety. Species richness counts species; evenness describes how individuals are distributed among them.

Two habitats may each contain five species but have very different abundance patterns.

Positive and negative feedback

Positive feedback amplifies an initial change; negative feedback counteracts it. These labels describe direction, not whether an outcome is desirable.

Reduced ice cover can reduce reflection and increase warming: an amplifying feedback.

Concentration and load

Concentration is substance per unit volume; load is total substance transported over time. Compare both when flow rates differ.

Load rate = concentration × flow rate, with consistent units.

Sampling and controls

Replicate measurements across space or time, define a comparison and keep methods consistent. A change after an intervention is not automatically caused by that intervention.

A before–after comparison is stronger when a comparable untreated site is also measured.

Worked example: pollutant transport

Water containing 3 mg/L of a substance flows at 20 L/s. The transport rate is 3 × 20 = 60 mg/s, assuming the concentration and flow values represent the same interval.

Doubling flow at the same concentration doubles the mass transported per second.

Common mistake: concentration alone

A lower measured concentration may reflect dilution rather than a smaller total discharge. Check flow, sampling conditions and measurement uncertainty before comparing impacts.

Use a consistent system boundary when accounting for inputs, storage and outputs.

Check your understanding

Is “positive feedback” necessarily beneficial?

No. It means that a process amplifies a change; benefit or harm depends on the outcome.

Curriculum connections

Sources