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. Finally, climate change has been linked with the increased prevalence and global spread of certain 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 1.5 °C (2.7 °F) of global warming over the preindustrial levels, and more warming means more widespread risk, with 3 °C (5.4 °F) placing 12%-29% at very high risk, and 5 °C (9.0 °F) 15%-48%. In particular, at 3.2 °C (5.8 °F), 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 2 °C (3.6 °F) reduces the fraction of invertebrates, amphibians and flowering plants at a very high risk of extinction to below 3%. However, while the more ambitious 1.5 °C (2.7 °F) 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.

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. 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.