7.2.4 Impact of environmental change

Environmental change and distribution

1. The distribution of a species means where its members are found across a habitat or region.
2. When the environment changes, a species may spread into new areas or disappear from places that no longer suit it.
3. In the exam you are often given data and asked to evaluate how a change affects where a species lives.

Factors that change distribution

1. Temperature: a change in temperature can shift a species towards cooler or warmer areas, so some birds now nest further north as the climate warms.
2. Availability of water: if an area becomes drier, species that need moist conditions retreat, while drought-tolerant species spread in.
3. Composition of atmospheric gases: changes such as more air pollution can make some areas unsuitable for sensitive species, so they are found in fewer places.

Causes of environmental change

1. Seasonal changes repeat through the year, so many birds migrate to warmer places in winter and return in spring.
2. Geographic changes, such as a new river or the clearing of land, can separate areas or open up new ones, changing where species can live.
3. Human interaction, such as deforestation, farming and pollution, changes habitats and shifts where species are found.

Evaluating the impact from data

1. Read the data to see how the distribution has changed, quoting figures where you can.
2. Link the change to the environmental factor that caused it, such as temperature or water.
3. Give a balanced conclusion, noting that other factors might also be affecting the species.