There are several plausible pathways that could lead to plant and animal species extinction from climate change. Every species has evolved to exist within a certain ecological niche, but climate change leads to changes of temperature and average weather patterns. These changes can push climatic conditions outside of the species' niche, and ultimately render it extinct. Normally, species faced with changing conditions can either adapt in place through microevolution or move to another habitat with suitable conditions. However, the speed of recent climate change is very fast. 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).

Climate change also increases both the frequency and intensity of extreme weather events, which can directly wipe out regional populations of species. Those species occupying coastal and low-lying island habitats can also become extinct by sea level rise. This has already happened with Bramble Cay melomys in Australia, which was the first mammal to go extinct due to human-induced sea level rise, with the Australian government officially confirming its extinction in 2019.

Climate change has been linked with the increased prevalence and global spread of infectious diseases affecting wildlife. This includes Batrachochytrium dendrobatidis, a fungus that is one of the main drivers of the worldwide decline in amphibian populations.

So far, climate change has not yet been a major contributor to the ongoing holocene extinction. In fact, nearly all of the irreversible biodiversity loss to date has been caused by other anthropogenic pressures such as habitat destruction. Yet, its effects are certain to become more prevalent in the future. As of 2021, 19% of species on the IUCN Red List of Threatened Species are already being impacted by climate change. 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. According to IUCN, once a species has lost over half of its geographic range, it is classified as "endangered", which is considered equivalent to a >20% likelihood of extinction over the next 10–100 years. If it loses 80% or more of its range, it is considered "critically endangered", and has a very high (over 50%) likelihood of going extinct over the next 10–100 years.

The IPCC Sixth Assessment Report projected that in the future, 9%-14% of the species assessed would be at a very high risk of extinction under of global warming over the preindustrial levels, and more warming means more widespread risk, with placing 12%-29% at very high risk, and 15%-48%. In particular, at , 15% of invertebrates (including 12% of pollinators), 11% of amphibians and 10% of flowering plants would be at a very high risk of extinction, while ~49% of insects, 44% of plants, and 26% of vertebrates would be at a high risk of extinction. In contrast, even the more modest Paris Agreement goal of limiting warming to reduces the fraction of invertebrates, amphibians and flowering plants at a very high risk of extinction to below 3%. However, while the more ambitious goal dramatically cuts the proportion of insects, plants, and vertebrates at high risk of extinction to 6%, 4% and 8%, the less ambitious target triples (to 18%) and doubles (8% and 16%) the proportion of respective species at risk.

Causes

Climate change has already adversely affected marine and terrestrial ecoregions, including tundras, mangroves, coral reefs, and caves. Consequently, increasing global temperatures have already been pushing some species out of their habitats for decades.

When the IPCC Fourth Assessment Report was published in 2007, expert assessments concluded that over the last three decades, human-induced warming had likely had a discernible influence on many physical and biological systems, and that regional temperature trends had already affected species and ecosystems around the world. By the time of the Sixth Assessment Report, it was found that for all species for which long-term records are available, half have shifted their ranges poleward (and/or upward for mountain species), while two-thirds have had their spring events occur earlier.

Many of the species at risk are Arctic and Antarctic fauna such as polar bears In the Arctic, the waters of Hudson Bay are ice-free for three weeks longer than they were thirty years ago, affecting polar bears, which prefer to hunt on sea ice.On Thinning Ice Michael Byers London Review of Books January 2005 Species that rely on cold weather conditions such as gyrfalcons, and snowy owls that prey on lemmings that use the cold winter to their advantage may be negatively affected. Climate change is also leading to a mismatch between the snow camouflage of arctic animals such as snowshoe hares with the increasingly snow-free landscape.

Then, many species of freshwater and saltwater plants and animals are dependent on glacier-fed waters to ensure a cold water habitat that they have adapted to. Some species of freshwater fish need cold water to survive and to reproduce, and this is especially true with salmon and cutthroat trout. Reduced glacier runoff can lead to insufficient stream flow to allow these species to thrive. Ocean krill, a cornerstone species, prefer cold water and are the primary food source for aquatic mammals such as the blue whale. Marine invertebrates achieve peak growth at the temperatures they have adapted to, and cold-blooded animals found at high latitudes and altitudes generally grow faster to compensate for the short growing season. 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. Indeed, even a slight increase in temperature during development impairs growth efficiency and survival rate in rainbow trout.

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. 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. Additionally, many fish species (such as salmon) use seasonal water levels of streams as a means of reproducing, typically breeding when water flow is high and migrating to the ocean after spawning. Because snowfall is expected to be reduced due to climate change, water runoff is expected to decrease which leads to lower flowing streams, affecting the spawning of millions of salmon. 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. In southeast Alaska, the sea rises by 3.96 cm/year, redepositing sediment in various river channels and bringing salt water inland. This rise in sea level not only contaminates streams and rivers with saline water, but also the reservoirs they are connected to, where species such as sockeye salmon live. Although this species of Salmon can survive in both salt and fresh water, the loss of a body of fresh water stops them from reproducing in the spring, as the spawning process requires fresh water.

Furthermore, climate change may disrupt ecological partnerships among interacting species, via changes on behaviour and phenology, or via climate niche mismatch. The disruption of species-species associations is a potential consequence of climate-driven movements of each individual species towards opposite directions. Climate change may, thus, lead to another extinction, more silent and mostly overlooked: the extinction of species' interactions. 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. Whole ecosystem disruptions will occur earlier under more intense climate change: under the high-emissions RCP8.5 scenario, ecosystems in the tropical oceans would be the first to experience abrupt disruption before 2030, with tropical forests and polar environments following by 2050. In total, 15% of ecological assemblages would have over 20% of their species abruptly disrupted if as warming eventually reaches ; in contrast, this would happen to fewer than 2% if the warming were to stay below .

Extinctions attributed to climate change Besides Bramble Cay melomys (see below), few recorded species extinctions are thought to have been caused by climate change, as opposed to the other drivers of the Holocene extinction. For example, only 20 of 864 species extinctions are considered by the IUCN to potentially be the result of climate change, either wholly or in part, and the evidence linking them to climate change is typically considered as weak or insubstantial. These species' extinctions are listed in the table below. +Causes of global extinction for 20 species whose declines were possibly linked to climate change (data from IUCN)Higher taxonSpeciesPossible link to climate changeHypothesized causes of extinctionSnailGraecoanatolica macedonicaDroughtLoss of aquatic habitat due to droughtSnailPachnodus velutinusDroughtHabitat degradation, drought related to climate change, hybridizationSnailPseudamnicola desertorumPossibly related to droughtLoss of aquatic habitatSnailRhachistia aldabraeDroughtDrought related to recent climate changeFish*Acanthobrama telavivensis and Anaxyrus (Bufo) baxteri are extinct in the wild rather than globally extinct.Acanthobrama telavivensisDroughtLoss of aquatic habitatFishTristramella magdelainaeDroughtLoss of aquatic habitat due to drought, pollution and water extractionFrog*Anaxyrus (Bufo) baxteriChytridChytrid fungusFrogAtelopus ignescensChytridSynergistic effects of chytrid and climate changeFrogAtelopus longirostrisChytridChytrid, climate change, pollution, and habitat lossFrogCraugastor chrysozetetesChytridHabitat modification and chytridFrogCraugastor escocesChytridChytrid, possibly associated with climate changeFrogIncilius (Bufo) holdridgeiChytridChytrid, possibly associated with climate changeFrogIncilius (Bufo) periglenesChytridGlobal warming, chytrid, and pollutionBirdFregilupus variusDroughtIntroduced disease, over-harvesting, forest fires, drought, deforestationBirdGallirallus wakensisStormsOverharvesting and occasional inundation of island due to stormsBirdMoho braccatusStormsHabitat destruction, introduced predators and diseases, and hurricanesBirdMyadestes myadestinusStormsHabitat destruction, introduced predators and diseases, and hurricanesBirdPorzana palmeriStormsHabitat destruction and predation by introduced species, stormsBirdPsephotus pulcherrimusDroughtDrought and overgrazing reduced food supply, other factors include introduced species, disease, habitat destruction, and overharvestingRodentGeocapromys thoracatusStormIntroduced predators, storm