Abiotic factors: wind intensity and direction

The idea

Wind is a non-living (abiotic) factor that varies in intensity (how strong it blows) and direction (where it blows from). Intensity affects organisms physically and physiologically: strong wind increases transpiration and evaporation, can uproot shallow-rooted trees, and damages leaves, while gentle air movement supplies carbon dioxide and cools leaves. Direction determines which organisms are exposed and which are sheltered, and carries seeds, spores, insects and pollutants.

For example: On an exposed hillside, windward trees grow shorter and more stunted than leeward ones, and lichens tolerant of drying dominate.

What earns the marks

• Wind is an abiotic (non-living) factor, so it is studied alongside temperature, light, moisture and soil pH when investigating an ecosystem.
• Wind intensity is the strength or speed of moving air; it is measured with an anemometer, often in metres per second (m/s).
• Wind direction is the compass bearing from which the wind blows; it is measured with a wind vane and recorded as a compass direction such as north-west.
• High wind intensity increases the rate of transpiration and evaporation from leaves and soil, which can cause water loss and wilting in plants.
• Strong winds can physically damage or uproot plants, break branches and disperse seeds, spores and small invertebrates.
• Wind direction controls exposure: windward slopes and coasts receive the strongest, most drying winds, while leeward sides are sheltered and often support taller, broader-leaved vegetation.
• Wind also affects animals by increasing heat loss by convection, influencing where insects shelter and how far airborne spores and pollutants travel.
• When comparing sites, wind intensity and direction should be recorded at the same time and in the same way so that differences in species distribution can be linked to the wind factor.

Common mistakes and how to put them right

• Treating wind as a biotic factor.

  Put it right: Wind is non-living, so it is abiotic; biotic factors are the living organisms such as predators, competitors and disease.

• Confusing intensity with direction.

  Put it right: Intensity is how strong the wind is (speed), while direction is where the wind blows from; a wind vane shows direction, not strength.

• Assuming wind always harms plants.

  Put it right: Moderate air movement aids gas exchange and cooling, and wind disperses seeds and spores, so its effect depends on intensity and species.

• Recording wind direction as the direction the wind blows towards.

  Put it right: Meteorological convention records the direction the wind blows from, so a north wind comes from the north.

Exam tips

• Link each wind observation to a named organism or plant feature, for example 'exposed site: stunted hawthorn, few aphids', rather than writing only that it was windy.
• Use the correct instrument names: anemometer for wind speed and wind vane for wind direction; state the unit m/s for speed.
• When describing an investigation, say you would sample both a windward and a leeward area and compare species abundance using quadrats or transects.
• Explain the mechanism, not just the pattern: strong wind increases transpiration, so plants lose water faster and may wilt or grow more slowly.