Extinction risk from climate change

Due to this rapid change, for example cold-blooded animals (a category which includes amphibians, reptiles and all invertebrates) may struggle to find a suitable habitat within 50 km of their current location at the end of this century (for a mid-range scenario of future global warming).

[14] Out of 4000 species analyzed by the IPCC Sixth Assessment Report, half were found to have shifted their distribution to higher latitudes or elevations in response to climate change.

In contrast, even the more modest Paris Agreement goal of limiting warming to 2 °C (3.6 °F) reduces the fraction of invertebrates, amphibians and flowering plants at a very high risk of extinction to below 3%.

Ocean krill, a cornerstone species, prefer cold water and are the primary food source for aquatic mammals such as the blue whale.

[28] Warmer-than-ideal conditions result in higher metabolism and consequent reductions in body size despite increased foraging, which in turn elevates the risk of predation.

[29] Species of fish living in cold or cool water can see a reduction in population of up to 50% in the majority of U.S. freshwater streams, according to most climate change models.

[30] The increase in metabolic demands due to higher water temperatures, in combination with decreasing amounts of food will be the main contributors to their decline.

[30] To add to this, rising seas will begin to flood coastal river systems, converting them from fresh water habitats to saline environments where indigenous species will likely perish.

As a consequence of the spatial decoupling of species-species associations, ecosystem services derived from biotic interactions are also at risk from climate niche mismatch.

[12] Hundreds of animal species have been documented to shift their range (usually polewards and upwards) as a signal of biotic change due to climate warming.

The paper estimated that this level of warming over the preindustrial occurring today would also result in a mass extinction event of the same magnitude (~75% of marine animals wiped out).

According to the IUCN Red List criteria, such a range loss is sufficient to classify as species as "endangered", and it is considered equivalent to >20% likelihood of extinction over the 10–100 years.

[15] In 2022, a Science Advances paper estimated that local extinctions of 6% of vertebrates alone would occur by 2050 under the "intermediate" SSP2-4.5 scenario, and 10.8% under the pathway of continually increasing emissions SSP5-8.5.

[56] A 2022 paper found that 45% of all marine species at risk of extinction are affected by climate change, but it's currently less damaging to their survival than overfishing, transportation, urban development and water pollution.

[63] According to the IUCN Red List criteria, such a range loss is sufficient to classify as species as "endangered", and it is considered equivalent to >20% likelihood of extinction over the 10–100 years.

Updated 2022 estimates show that even at a global average increase of 1.5 °C (2.7 °F) over pre-industrial temperatures, only 0.2% of the world's coral reefs would still be able to withstand marine heatwaves, as opposed to 84% being able to do so now, with the figure dropping to 0% by 2 °C (3.6 °F) and beyond.

A 2018 Science Magazine paper estimated that at 1.5 °C (2.7 °F), 2 °C (3.6 °F) and 3.2 °C (5.8 °F), over half of climatically determined geographic range would be lost by 6%, 18% and ~49% of insect species, with this loss corresponding to >20% likelihood of extinction over the next 10–100 years according to the IUCN criteria.

The strongest effects were seen in the southern regions, where rapid increases in frequency of extreme warm years had exceeded the species’ historical temperature ranges.

[46] A 2018 study from the University of East Anglia team analyzed the impacts of 2 °C (3.6 °F) and 4.5 °C (8.1 °F) of warming on 80,000 plant and animal species in 35 of the world's biodiversity hotspots.

The apes could potentially disperse to new habitats, but those would lie almost completely outside of their current protected areas, meaning that conservation planning needs to be "urgently" updated to account for this.

One population of these possums in the mountain forests of North Queensland is severely threatened by climate change as the animals cannot survive extended temperatures over 30 °C (86 °F).

[97] It's been estimated that by 2050, climate change alone could reduce species richness of trees in the Amazon Rainforest by 31–37%, while deforestation alone could be responsible for 19–36%, and the combined effect might reach 58%.

The paper's worst-case scenario for both stressors had only 53% of the original rainforest area surviving as a continuous ecosystem by 2050, with the rest reduced to a severely fragmented block.

It found that if their water temperature increases by 4 °C (7.2 °F) in July (said to occur under approximately the same amount of global warming), then cold-water fish species like cisco would disappear from 167 lakes, which represents 61% of their habitat in Minnesota.

Under high greenhouse gas emissions, at most a few high-Arctic populations will remain by 2100: under more moderate scenario, the species will survive this century, but several major subpopulations will still be wiped out.

[108] Under the worst-case warming trajectory, king penguins will permanently lose at least two out of their current eight breeding sites, and 70% of the species (1.1 million pairs) will have to relocate to avoid disappearance.

[116] Climate change conditions such as increase in atmospheric temperature and carbon dioxide concentration directly affect availability of biomass energy, food, fiber and other ecosystem services.

[119] The effects that climate change has on both plant and animal species within certain ecosystems has the ability to directly affect the human inhabitants who rely on natural resources.

[123] Rising temperatures are beginning to have a noticeable impact on birds,[124] and butterflies nearly 160 species from 10 different zones[125] have shifted their ranges northward by 200 km in Europe and North America.

[127] Birds are a group of warm-blooded vertebrates constituting the class Aves, characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.