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D4.3.6—Range shifts

Climate-driven range shifts occur when species move poleward, upslope, or into new habitats as temperature, water, and resources change over time.

Syllabus
First assessment 2025
Objective
D4.3.6
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper3
Typical marks1

Common command terms

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Recent exam appearances

May 2024Paper3 ["HL"] · TZ116(b)[ 1 ]D4.3.6—Range shifts

Coverage 2024–2024 · Updated 16 Jul 2026

Species Track Moving Climate Zones Poleward and Upslope

Range boundary Response to warming
warm or equatorward/low-elevation edge local populations decline or disappear as tolerance is exceeded
cool or poleward/upper edge colonization can extend the range if habitat and dispersal allow
mountaintop or coastline barrier available climate space contracts because no farther suitable area exists

A range shift is a population-distribution change, not an individual animal choosing to evolve. Movement, establishment and local extinction together redraw the range.

A map and mountain cross-section show a temperate species shifting poleward and a montane bird shifting upslope as its modern climate envelope moves.

Climate Space Can Move Faster Than Species Can Track It

Tracking requirement Possible barrier
dispersal seeds, juveniles or adults move too slowly
connected habitat farms, cities or fragmented forest block movement
suitable soil and partners climate arrives without pollinators, hosts or substrate
population growth colonists fail to establish at the new edge

Repeated surveys can compare historical and modern upper and lower limits. Consistent upslope or poleward shifts across many species strengthen the climate interpretation, while species-specific exceptions reveal other controls.

Tree saplings may shift faster than mature-tree distributions because adult trees persist long after recruitment conditions change. Range contraction can occur even while old individuals remain.

Climate Effects Follow Forcing, Feedback, Exposure and Biological Response

human greenhouse-gas source → enhanced infrared retention → climate variable changes → feedback may amplify the change → habitat or physiological mechanism alters survival, production or distribution → population and ecosystem consequences

Impact Mechanism that must appear
boreal sink becomes source carbon release exceeds uptake through drought, mortality, fire and thaw
ice-dependent species decline required resting or breeding platform is lost at the critical time
marine productivity falls stratification reduces nutrient upwelling to phytoplankton
range contracts or shifts climate space moves but dispersal and habitat constrain tracking
reef degrades bleaching removes symbiont energy and acidification suppresses calcification

Do not jump directly from “warming” to “species decline.” The biological mechanism and the relevant time or place make the explanation causal.

Range shifts

[ 1 ]

The data shows how the hardiness zones in part of North America are predicted to change over the next 25 years. A hardiness zone is an area that has a certain average annual minimum temperature, a factor relevant to the survival of many plants. The lower the number, the more cold

resistant the plants must be.

What is a likely consequence of this change for tree species?

Concept essentials

  • Warming can move suitable climate zones and food supplies northward or upslope.
  • Range shifts can change predation, competition, biodiversity, and food-web structure.
  • Species that cannot track suitable conditions may decline or disappear from parts of their range.