Poleward and Upslope Range Shifts of Temperate Species
- As the planet warms, species are forced to adapt by shifting their ranges to cooler areas.
- This often means moving toward the poles or upslope in mountainous regions.
Definition
Range shift
A range shift refers to the movement of a species’ habitat in response to environmental changes, such as climate warming.
Why Do Species Move?
- Temperature Sensitivity: Many species have narrow temperature tolerances. As temperatures rise, their current habitats become unsuitable.
- Habitat Availability: Cooler areas at higher latitudes or elevations provide refuge.
- Resource Dependency: Changes in temperature affect food availability, breeding sites, and other critical resources.
- It’s a common misconception that all species can simply move higher or farther to escape warming.
- Many species, like those at the top of mountains, have nowhere else to go, making them highly vulnerable to extinction.
Tropical Montane Bird Species in New Guinea
- Tropical montane birds in New Guinea are shifting their ranges upslope as temperatures rise in their current lowland habitats.
- These birds, which once thrived in lower-elevation tropical forests, are now migrating to cooler, higher elevations, where the temperature is more favorable.
- Upslope shifts may cause crowding at higher elevations and limit available habitats, leading to competition among species and potential extinction risks for those unable to adapt or migrate.
Birds like the New Guinea robin and the black-capped mannikin have been observed moving to higher altitudes in the central mountain ranges of New Guinea, in response to temperature increases in their native lowlands.
Range Shifts in North American Trees
- In North America, warming temperatures have caused certain temperate tree species to shift northward and contract in the south.
- Trees like the red maple (Acer rubrum) and American beech (Fagus grandifolia), traditionally found in the southern parts of the continent, are now expanding their ranges northward as they adapt to warmer temperatures.
- As trees shift northward, forest composition may change, potentially affecting the ecological balance, including the species that depend on these trees for food and shelter.
- Additionally, warmer conditions in the south may lead to drier conditions, threatening tree survival in the areas they once inhabited.
The red spruce (Picea rubens) has been found to be migrating northward in the northeastern U.S. and Canada, while its southern range is retreating.
Evidence of Range Shifts
- Northward Expansion: As temperatures rise, trees are colonizing areas farther north where conditions are now suitable.
- Southern Range Contraction: Warmer temperatures and drought stress are making southern parts of their range uninhabitable.
- When studying range shifts, focus on both the expansion into new areas and the contraction in original habitats.
- This dual process is key to understanding how climate change affects species distributions.
Implications of Range Shifts
1. Ecosystem Disruption
- Competition: New species entering an area can outcompete native species for resources.
- Predator-Prey Dynamics: Changes in species distributions can disrupt food webs.
2. Biodiversity Loss
Species with nowhere to move, such as those at the tops of mountains, face a high risk of extinction.
3. Human Impacts
Changes in tree distributions affect forestry, agriculture, and ecosystem services like carbon storage.
Theory of Knowledge- How do range shifts challenge our understanding of conservation?
- Should efforts focus on preserving current habitats or facilitating species movement to new areas?
- What causes species to shift their ranges?
- Give examples of species that have experienced upslope or poleward range shifts.
