Biological consequences of global warming

Global warming changes the conditions in habitats. As temperatures rise, a habitat may become less suitable for some organisms to survive and reproduce, while other areas may become suitable. The effects depend on whether organisms can find suitable conditions and respond to the changes.

Changes in geographical range

A species’ geographical range is the area where it lives. As its habitat warms, a species may shift its range towards cooler areas, such as towards the poles or to higher altitudes. However, if a species cannot reach or establish itself in a suitable area, its population may decline.

Changes in seasonal timing

Seasonal temperatures help determine when events such as migration, breeding and the appearance of food occur. As temperatures change, these events may happen earlier or later.

Species that depend on one another do not necessarily respond at the same rate. For example, if a bird breeds after the peak availability of the food its chicks need, fewer chicks may survive. Such mismatches can disrupt relationships between species and alter food webs.

Population decline and biodiversity

When suitable habitat is lost, or when a species cannot move or respond quickly enough to changing conditions, fewer individuals may survive and reproduce. Its population can decline, increasing its risk of extinction. If species are lost, biodiversity—the variety of living organisms in an area—decreases.

Greenhouse gases and global warming

Earth’s surface absorbs energy from the Sun and emits some of this energy as infrared radiation. Carbon dioxide and methane are greenhouse gases in the atmosphere. They absorb some of the outgoing infrared radiation and re-emit it in different directions, including towards Earth’s surface.

When the atmospheric concentrations of these gases increase, more outgoing infrared radiation is absorbed and re-emitted. This strengthens the greenhouse effect and reduces the rate at which energy escapes to space. As a result, Earth’s surface and lower atmosphere warm over time.

Global warming is a long-term rise in average global temperature. It does not mean that the temperature increases at every place or at every time: individual places can still experience cold periods while the global average rises.