Species Distribution & Change
Explain how environmental change (climate change, habitat loss, pollution) affects the distribution of species, including range shifts, local extinction, and invasive species
What a learner can do afterwards
- Describes at least two ways environmental change can affect species distribution
- Gives a real example of a species whose range has shifted due to climate change
- Explains what an invasive species is and how environmental change can enable invasions
- Discusses why some species are more vulnerable to environmental change than others
1 · Read
A species' distribution is where it lives. Climate change, habitat loss and pollution can make places unsuitable. A range may expand into suitable new areas or shrink as populations disappear. Local extinction means a species disappears from one area but survives elsewhere. Global extinction means no individuals remain anywhere. Losing one habitat does not always mean losing the whole species.
The comma butterfly has expanded its range northwards in Britain as the climate has warmed. Warmer conditions have helped it survive and breed in northern areas. A population's range changes as individuals spread and reproduce. This does not mean that every butterfly makes a single long journey from the old range to the new one.
To measure a boundary shift, compare positions measured from the same reference point. Subtract the earlier position from the later one. In the invented survey, 80 minus 0 is 80 km. The northern boundary has shifted 80 km north. A boundary shift measures a change in distribution, not how far one animal travelled.
An invasive species is introduced outside its native range and causes, or can cause, harm there. It may compete with native species, eat them or spread disease. A native species expanding its range is not automatically invasive. Environmental change can help an introduced species survive: milder winters may remove a cold barrier. Transport explains how it arrives; suitable conditions help it establish.
A specialist depends on a narrow set of foods or conditions. If its only food plant disappears, it has fewer feeding options than a generalist that can use several remaining foods. This can make it more vulnerable to that change. A varied diet can help, but it does not guarantee survival if other needs are not met.
Suitable habitat is useful only if a species can reach it. A road may block a small land animal even when food and shelter remain on both sides. A usable wildlife crossing can reconnect those areas. Movement also depends on distance and the species' abilities. Connecting habitats can help some species move, but the destination must still meet their needs.
Environmental change can expand or shrink ranges and cause local extinction. It can help introduced species establish. Food needs and access to suitable habitat affect survival.
Lesson revisions, questions and flashcard revisions written for this dataset. Survey numbers are invented teaching examples, not measurements of the comma butterfly.
The three readings were written for this dataset. Video credits: Human impacts on ecosystems, Khan Academy; How does climate change affect biodiversity?, California Academy of Sciences; Biogeography: where life lives, NOVA PBS Official. Video references were imported through the academy collection. Rights remain with their respective creators.
More to read
Reading a changing range
A distribution map shows where a species lives. Compare maps from different times to find places where populations appeared or disappeared. A new population can expand the range. Losing populations from an area can shrink it.
A local extinction removes a species from one area. Other populations may still exist elsewhere. Global extinction means the species has no living individuals anywhere.
Habitat can become unsuitable without disappearing from a map. Polluted water may no longer support a population even though the pond remains. Habitat loss can also divide a once-connected area into separate patches. To understand a range change, ask both whether suitable places remain and whether organisms can reach them.
How an introduction can become an invasion
People sometimes carry organisms outside their native ranges. Seeds may travel with goods, or an animal may escape after being transported. Arrival does not guarantee that a population will establish. The organisms must survive and reproduce in the new conditions.
Consider an invented example. A transported plant once died during northern winters. After winters become milder, it survives and spreads into space used by native plants. The transport explains its arrival, and the warmer conditions explain its changed chance of survival.
An introduced species is invasive when it causes, or can cause, harm in its new area. Competition, predation and disease are possible routes of harm. An introduction is not automatically an invasion, and a native species expanding into newly suitable habitat is not automatically invasive.
Needs and access
Two species can respond differently to the same change. If a plant disappears, an animal that eats only that plant loses its food source. An animal with several remaining foods has more feeding options. This comparison depends on which resources remain available.
Movement creates another difference. Suitable woodland across a road may be reachable for one species but cut off from another. A wildlife crossing can help only if the species can use it and the habitat beyond still meets its needs.
To explain vulnerability, name the need that is threatened and the options that remain. Avoid assuming that every specialist will disappear or that every mobile animal can find a safe new home.
Explore more
2 · Watch
En anglaisTake it off screen
Where it sits
Learn first
Optional connections
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.