Extinction risk from climate change

Source: Wikipedia, the free encyclopedia.
The Bramble Cay melomys, thought to be the first mammal species to go extinct due to the impacts of climate change.[1]

The extinction risk of climate change is the risk of

low-lying island habitats can also be rendered extinct by sea level rise; this has already happened with Bramble Cay melomys in Australia.[1] Finally, climate change has been linked with the increased prevalence and global spread of certain diseases affecting wildlife. This includes Batrachochytrium dendrobatidis, a fungus identified as one of the main drivers of the worldwide decline in amphibian populations.[7]

As of 2021, 19% of species on the

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.[9]

The

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 high risk of extinction. On the other hand, at 2 °C (3.6 °F), fewer than 3% of invertebrates, amphibians and flowering plants would be at a very high risk of extinction, while 18% of insects, 16% of plants, and 8% of vertebrates would be at a high risk. Fulfilling the Paris Agreement goal of 1.5 °C (2.7 °F) further reduces this to 6% of insects, 8% of plants, and 4% of vertebrates. These estimates do not include the other drivers of the Holocene extinction.[9]

Causes

Projections of extreme weather under different levels of global warming.

butterflies, birds and plants were moving towards the poles by 6.1 km per decade.[12]

When 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.[9]

The IPCC Sixth Assessment Report (2021) projects progressively large increases in both the frequency (horizontal bars) and intensity (vertical bars) of extreme weather events, for increasing degrees of global warming.[6]

Many of the species at risk are Arctic and Antarctic fauna such as polar bears[16] 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.[17] 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.[18][19] 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.[20]

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.[21] 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.[22] 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.[23]

Eagle River
in central Alaska, home to various indigenous freshwater species.

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.[24] 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.[24] Additionally, many fish species (such as salmon) utilize seasonal water levels of streams as a means of reproducing, typically breeding when water flow is high and migrating to the ocean after spawning.[24] 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.[24] 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.[24] 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.[24]

Furthermore, climate change may disrupt ecological partnerships among interacting species, via changes on behaviour and phenology, or via climate niche mismatch.[25] The disruption of species-species associations is a potential consequence of climate-driven movements of each individual species towards opposite directions.[26][27] 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.[25] Whole ecosystem disruptions will occur earlier under more intense climate change: under the high-emissions RCP 8.5 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 around the same time as the warming eventually reaches 4 °C (7.2 °F) under that scenario; in contrast, this would happen to fewer than 2% if the warming were to stay below 2 °C (3.6 °F).[28]

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.[29] 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)[29]
Higher taxon Species Hypothesized causes of extinction Possible link to climate change
Snail Graecoanatolica macedonica Loss of aquatic habitat due to drought Drought
Snail Pachnodus velutinus Habitat degradation, drought related to climate change, hybridization Drought
Snail Pseudamnicola desertorum Loss of aquatic habitat Possibly related to drought
Snail Rhachistia aldabrae Drought related to recent climate change Drought
Fish*[Note 1] Acanthobrama telavivensis Loss of aquatic habitat Drought
Fish Tristramella magdelainae Loss of aquatic habitat due to drought, pollution and water extraction Drought
Frog* Anaxyrus (Bufo) baxteri Chytrid fungus Chytrid
Frog Atelopus ignescens Synergistic effects of chytrid and climate change Chytrid
Frog Atelopus longirostris Chytrid, climate change, pollution, and habitat loss Chytrid
Frog Craugastor chrysozetetes Habitat modification and chytrid Chytrid
Frog Craugastor escoces Chytrid, possibly associated with climate change Chytrid
Frog Incilius (Bufo) holdridgei Chytrid, possibly associated with climate change Chytrid
Frog Incilius (Bufo) periglenes Global warming, chytrid, and pollution Chytrid
Bird Fregilupus varius Introduced disease, over-harvesting, forest fires, drought, deforestation Drought
Bird Gallirallus wakensis Overharvesting and occasional inundation of island due to storms Storms
Bird Moho braccatus Habitat destruction, introduced predators and diseases, and hurricanes Storms
Bird Myadestes myadestinus Habitat destruction, introduced predators and diseases, and hurricanes Storms
Bird Porzana palmeri Habitat destruction and predation by introduced species, storms Storms
Bird Psephotus pulcherrimus Drought and overgrazing reduced food supply, other factors include introduced species, disease, habitat destruction, and overharvesting Drought
Rodent Geocapromys thoracatus Introduced predators, storm Storm
  1. ^ Acanthobrama telavivensis and Anaxyrus (Bufo) baxteri are extinct in the wild rather than globally extinct.

However, there is abundant evidence for local extinctions from contractions at the warm edges of species' ranges.[29] 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.[29] Warm-edge populations tend to be the most logical place to search for causes of climate-related extinctions since these species may already be at the limits of their climatic tolerances.[29] This pattern of warm-edge contraction provides indications that many local extinctions have already occurred as a result of climate change.[29]

Extinction risk estimates

Early estimates

The first major attempt to estimate the impact of climate change on generalized species' extinction risks was published in the journal Nature in 2004. It suggested that between 15% and 37% of 1103 endemic or near-endemic known plant and animal species around the world would be "committed to extinction" by 2050, as their habitat will no longer be able to support their survival range by then.[30] However, there was limited knowledge at the time about the species' average ability to disperse or otherwise adapt in response to climate change, and about the minimum average area needed for their persistence, which limited the reliability of their estimate in the eyes of the scientific community.[31][32][33][34][35] In response, another 2004 paper found that different, yet still plausible assumptions about those factors could result in as few as 5.6% or as many as 78.6% of those 1103 species being committed to extinction,[36] although this was disputed by the original authors.[37]

Between 2005 and 2011, 74 studies analyzing the impact of climate change on various species' extinction risk were published. A 2011 review of those studies found that on average, they projected the loss of 11.2% of species by 2100. However, the average of predictions based on the extrapolation of observed responses was 14.7%, while the model-based estimates were at 6.7%. Further, when using

IUCN criteria, 7.6% of species would become threatened based on model predictions, yet 31.7% based on extrapolated observations.[38] The following year, this mismatch between models and observations was primarily attributed to the models failing to properly account for different rates of species relocation and for the emerging competition among species, thus causing them to underestimate extinction risk.[39]

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. It found that these areas could lose up to 25% and 50% of their species, respectively: they may or may not be able to survive outside of them. Madagascar alone would lose 60% of its species under 4.5 °C (8.1 °F), while Fynbos in Western Cape egion of South Africa would lose a third of its species.[40][41]

All species

In 2019, the

insects are threatened with extinction due to five main stressors. The land use change and sea use change was considered the most important stressor, followed by direct exploitation of organisms (i.e. overfishing). Climate change ranked third, followed by pollution and invasive species. The report concluded that global warming of 2 °C (3.6 °F) over the preindustrial levels would threaten an estimated 5% of all the Earth's species with extinction even in the absence of the other four factors, while if the warming reached 4.3 °C (7.7 °F), 16% of the Earth's species would be threatened with extinction. Finally, even the lower warming levels of 1.5–2 °C (2.7–3.6 °F) would "profoundly" reduce geographical ranges of the majority of the world's species, thus making them more vulnerable then they would have been otherwise.[42]

In 2020, a paper studied 538 plant and animal species from around the world and how they responded to rising temperatures. From that sample, they estimated that 16% of all species could go extinct by 2070 under the "moderate" climate change scenario RCP 4.5, but it could be one-third under RCP 8.5, the scenario of continually increasing emissions.[43][44] This finding was later cited in the IPCC Sixth Assessment Report.[45]

An August 2021 paper found that the

genera was correlated to a >7 °C (13 °F) global cooling and a 7–9 °C (13–16 °F) global warming, while for the terrestrial tetrapods, the same losses would be seen under ~7 °C (13 °F) of global cooling or warming.[47]

Kaiho's follow-up paper estimated that under what he considered the most likely scenario of climate change, with 3 °C (5.4 °F) of warming by 2100 and 3.8 °C (6.8 °F) by 2500 (based on the average of

nuclear war (defined as a nuclear exchange between India and Pakistan or an event of equivalent magnitude) would cause extinctions of 10–20% of species on its own, while a major nuclear war (defined as a nuclear exchange between United States and Russia) would cause the extinctions of 40-50% species.[48]

In July 2022, a survey of 3331 biodiversity experts estimated that since the year 1500, around 30% (between 16% and 50%) of all species have been threatened with extinction - including the species which had already gone extinct. With regards to climate change, the experts estimated that 2 °C (3.6 °F) threatens or drives to extinction about 25% of the species, although their estimates ranged from 15% to 40%. When asked about 5 °C (9.0 °F) warming, they believed it would threaten or drive into extinction 50% of the species, with the range between 32 and 70%.[49]

February 2022 IPCC Sixth Assessment Report included median and maximum estimates of the percentage of species at high risk of extinction for every level of warming, with the maximum estimates increasing much more than the medians. For instance, for 1.5 °C (2.7 °F), the median was 9% and the maximum 14%, for 2 °C (3.6 °F) the median was 10% and the maximum 18%, for 3 °C (5.4 °F) the median was 12% and the maximum 29%, for 4 °C (7.2 °F) the median was 13% and the maximum 39%, and for 5 °C (9.0 °F) the median was 15% but the maximum 48%) at 5°C.[9]

Vertebrates

A 2013 paper looked at 12 900 islands in the

low-lying islands in the Pacific Ocean would be threatened by high waves at the end of the century, with the risk substantially reduced under the more moderate RCP 4.5 scenario.[51]

A 2018

Science Magazine paper estimated that 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 4%, 8% and 26% of vertebrate species.[52] This estimate was later directly cited in the IPCC Sixth Assessment Report. 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.[9]

In 2022, a

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. By 2100, those would increase to ~13% and ~27%, respectively. These estimates included local extinctions from all causes, not just climate change: however, it was estimated to account for the majority (~62%) of extinctions, followed by secondary extinctions or coextinctions (~20%), with land use change and invasive species combined accounting for less than 20%.[53]

In 2023, a study estimated the proportion of vertebrates which would exposed to extreme heat beyond what they were known to have experienced historically in at least half their distribution by the end of the century. Under the highest-emission pathway SSP5–8.5 (a warming of 4.4 °C (7.9 °F) by 2100, according to the paper), this would include ~41% of all land vertebrates (31.1% mammals, 25.8% birds, 55.5% amphibians and 51% reptiles). On the other hand, SSP1–2.6 (1.8 °C (3.2 °F) by 2100) would only see 6.1% of vertebrate species exposed to unprecendented heat in at least of their area, while SSP2–4.5 (2.7 °C (4.9 °F) by 2100) and SSP3–7.0 ((3.6 °C (6.5 °F) by 2100) would see 15.1% and 28.8%, respectively.[54]

Amphibians

See also: Decline in amphibian populations

A 2013 study estimated that 670–933 amphibian species (11–15%) are both highly vulnerable to climate change while already being on the

Red List of threatened species. A further 698–1,807 (11–29%) amphibian species are not currently threatened, but could become threatened in the future due to their high vulnerability to climate change.[55]

The

amphibians and 24% of salamanders would be at a very high risk of extinction. [9]

A 2022 study estimated that while right now, 14.8% of the global range of all

anurans (frogs) is in an extinction risk area, this will increase to 30.7% by 2100 under Shared Socioeconomic Pathway SSP1-2.6 (low emission pathway), 49.9% under SSP2-4.5, 59.4% under SSP3-7.0 and 64.4% under the highest-emitting SSP5-8.5. Extreme-sized anuran species are disproportionately affected: while currently only 0.3% of these species have >70% of their range in a risk area, this number will increase to 3.9% under SSP1-2.6, 14.2% under SSP2-4.5, 21.5% under SSP3-7 and 26% under SSP5-8.5[56]

A 2018 paper estimated that both Miombo Woodlands of South Africa and southwestern Australia would lose around 90% of their amphibians if the warming were to reach 4.5 °C (8.1 °F).[40]

Birds

See also: Climate change and birds

In 2012, it was estimated that on average, every degree of warming results in between 100 to 500 land bird extinctions. For a warming of 3.5 °C (6.3 °F) by 2100, the same research estimated between 600 and 900 land bird extinctions, with 89% occurring in the tropical environments.

Red List of threatened species, and 1,715–4,039 (17–41%) bird species are not currently threatened but could become threatened due to climate change in the future.[55]

In Australia, it was predicted that while emus would survive as a species, some local populations may be wiped out by fires, with the coastal emus of New South Wales considered at high risk.[58]

A 2012 study connected climate change with the observed decline in numbers and range reduction of the rusty blackbird, a formerly common yet currently vulnerable North American species.[59] In 2015, it was projected that native forest birds in Hawaii would be threatened with extinction due to the spread of avian malaria under the high-warming RCP 8.5 scenario or a similar scenario from earlier modelling, but would persist under the less extreme RCP 4.5[60]

A Southern Yellow-billed Hornbill female.

The

Ethiopian Bush-crow, would lose 68-84% and >90% of their range by 2070. As their existing geographical range is already very limited, this means that it would likely end up too small to support a viable population even under the scenario of limited climate change, rendering these species extinct in the wild.[64]

Climate change is particularly threatening to penguins. As early as in 2008, it was estimated that every time Southern Ocean temperatures increase by 0.26 °C (0.47 °F), this reduces king penguin populations by 9%.[65] A 27-year study of the largest colony of Magellanic penguins in the world, published in 2014, found that extreme weather caused by climate change kills 7% of penguin chicks in an average year, accounting for up to 50% of all chick deaths in some years.[66][67] Since 1987, the number of breeding pairs in the colony has reduced by 24%.[67] It was also estimated that while Adélie penguins will retain some of its habitat past 2099, one-third of colonies along the West Antarctic Peninsula (WAP) will be in decline by 2060. Those colonies are believed to represent about 20% of the entire species.[68]

Fish

See also: Effects of climate change on oceans

It has been projected in 2015 that many fish species will migrate towards the North and South poles as a result of climate change. Under the highest emission scenario RCP 8.5, 2 new species would enter (invade) per 0.5° of latitude in the Arctic Ocean and 1.5 in the Southern Ocean. It woul also result in an average of 6.5 local extinctions per 0.5° of latitude outside of the poles.[69]

In 2019,

net primary production would decline by 3% to 10% by the end of the century, while fish biomass would decline by 3% to 25%.[42]

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

Permian-Triassic extinction event, or "The Great Dying". On the other hand, staying at low emissions would reduce future climate-driven extinctions in the oceans by over 70%.[70][71]

A 2021 study which analyzed around 11,500

freshwater fish species concluded that 1-4% of those species would be likely to lose over half of their current geographic range at 1.5 °C (2.7 °F) and 1-9% at 2 °C (3.6 °F). A warming of 3.2 °C (5.8 °F) would threaten 8-36% of freshwater fish species with such range loss and 4.5 °C (8.1 °F) would threaten 24-63%. The different percentages represent different assumptions about how well freshwater fishes could disperse to new areas and thus offset past range losses, with the highest percentages assuming no dispersal is possible.[72] 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.[9]

Mammals

Polar bear hopping from melting sea ice.

In 2020, a study in Nature Climate Change estimated the effects of Arctic sea ice decline on polar bear populations (which rely on the sea ice to hunt seals) under two climate change scenarios. 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.[73][74]

In 2019, it was estimated that the current

great ape range in Africa will decline massively under both the severe RCP 8.5 scenario and the more moderate RCP 4.5. 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.[75]

In the wake of

World Wildlife Fund concluded that the jaguar is already "near threatened" and the loss of food supplies and habitat due to the fires make the situation more critical.[76] The fires affect water chemistry (such as decreasing the amount of dissolved oxygen in the water), temperature, and erosion rates, which in turn affects fish and mammals that depend on fish, such as the giant otter (Pteronura brasiliensis).[76]

A 2017 analysis found that the mountain goat populations of coastal Alaska would go extinct sometime between 2015 and 2085 in half of the considered scenarios of climate change.[77] Another analysis found that the Miombo Woodlands of South Africa are predicted to lose about 80% of their mammal species if the warming reached 4.5 °C (8.1 °F).[40]

In 2008, the

white lemuroid possum was reported to be the first known mammal species to be driven extinct by climate change. However, these reports were based on a misunderstanding. 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. However, another population 100 kilometres south remains in good health.[78] On the other hand, the Bramble Cay melomys, which lived on a Great Barrier Reef island, was reported as the first mammal to go extinct due to human-induced sea level rise,[1] with the Australian government officially confirming its extinction in 2019. Another Australian species, the greater stick-nest rat (Leporillus conditor) may be next. Similarly, the 2019–20 Australian bushfire season caused a near-complete extirpatin of Kangaroo Island dunnarts, as only one individual may have survived out of the population of 500.[58] Those bushfires have also caused the loss of 8,000 koalas in New South Wales alone, further endangering the species.[79][80]

Reptiles

In a 2010 study led by

Sceloporus lizards since 1975. Using a model developed from these observed extinctions the researchers surveyed other extinctions around the world and found that the model predicted those observed extirpations, thus attributing the extirpations around the world to climate warming. These models predict that extinctions of the lizard species around the world will reach 20% by 2080, but up to 40% extinctions in tropical ecosystems where the lizards are closer to their ecophysiological limits than lizards in the temperate zone.[81][82]

A 2015 study looked at the persistence of

common lizard populations in Europe under future climate change. It found that under 2 °C (3.6 °F), 11% of the lizard population would be threatened with local extinction around 2050 and 14% by 2100. At 3 °C (5.4 °F) by 2100, 21% of the population are threatened, and at 4 °C (7.2 °F), 30% of the populations are.[83]

Green sea turtle grazing grass.

Sex ratios for sea turtles in the Caribbean are being affected because of climate change. Environmental data were collected from the annual rainfall and tide temperatures over the course of 200 years and showed an increase in air temperature (mean of 31.0 degree Celsius). These data were used to relate the decline of the sex ratios of sea turtles in the North East Caribbean and climate change. The species of sea turtles include Dermochelys coriacea, Chelonia myads, and Eretmochelys imbricata. Extinction is a risk for these species as the sex ratio is being afflicted causing a higher female to male ratio. Projections estimate the declining rate of male Chelonia myads as 2.4% hatchlings being male by 2030 and 0.4% by 2090.[84]

Invertebrates

The IPCC Sixth Assessment Report estimates that while at 2 °C (3.6 °F), fewer than 3% of invertebrates would be at a very high risk of extinction, 15% would be at a very high risk at 3.2 °C (5.8 °F). This includes 12% of pollinator species.[9]

Arachnids

A 2018 study examined the impact of climate change on

the Alps and found that even the low-emission scenario RCP 2.6 would reduce their habitat by ~45% by 2050, while the high emission scenario would reduce it by ~55% by 2050 and ~70% by 2070. The authors suggested that this may be sufficient to drive the most restricted species to extinction.[85]

Corals

See also: Environmental issues with coral reefs
Coral reefs off Raja Ampat Islands in New Guinea
.

Almost no other ecosystem is as vulnerable to climate change as coral reefs. Updated 2022 estimates show that even at 1.5 °C (2.7 °F), 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.[86][87] However, it was found in 2021 that each square meter of coral reef area contains about 30 invididual corals, and their total number is estimated at half a trillion - equivalent to all the trees in the Amazon, or all the birds in the world. As such, most individual coral reef species are predicted to avoid extinction even as coral reefs would cease to function as the ecosystems we know.[88][89] A 2013 study found that 47–73 coral species (6–9%) are vulnerable to climate change while already threatened with extinction according to the IUCN Red List, and 74–174 (9–22%) coral species were not vulnerable to extinction at the time of publication, but could be threatened under continued climate change, making them a future conservation priority.[55] The authors of the recent coral number estimates suggest that those older projections were too high, although this has been disputed.[88][90][91]

Insects

See also: Decline in insect populations
Bumblebee collecting pollen.

Insects account for the vast majority of invertebrate species. One of the earliest studies to link insect extinctions to recent

precipitation.[92]

A 2014 long-term study of more than 60 bee species published in the journal Science found that climate change causes drastic declines in the population and diversity of bumblebees across North America and Europe, at rates "consistent with a mass extinction." North America's bumblebee populations fell by 46% during the two time periods the study used, which were from 1901 to 1974 and from 2000 to 2014. North America's bumblebee populations fell by 46% because bee populations were hardest hit in warming southern regions such as Mexico. According to the study, there have been more frequent extreme warm years, which exceeded the species’ historical temperature ranges.[93]

A 2018

IUCN criteria.[52][9]

Plants

The 2018

Science Magazine estimate found 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 8%, 16%, and 44% of plant species, corresponding to >20% likelihood of extinction over the next 10–100 years under the IUCN criteria.[52][9]

The 2022 IPCC Sixth Assessment Report estimates that while at 2 °C (3.6 °F), fewer than 3% of flowering plants would be at a very high risk of extinction, this increases to 10% at 3.2 °C (5.8 °F).[9]

A 2020 meta-analysis found that while 39% of

fungi, it estimated that 9.4% are threatened due to climate change, while 62% are threatened by other forms of habitat loss.[94]

Viola Calcarata or mountain violet, which only grows on mountainsides in southeastern Europe, and is projected to go extinct around 2050.

Alpine and mountain plant species are known to be some of the most vulnerable to climate change. In 2010, a study looking at 2,632 species located in and around European

European Alps, their range would, on average, decline by 44%-50% by the end of the century - moreover, lags in their shifts would mean that around 40% of their remaining range would soon become unsuitable as well, often leading to an extinction debt.[96] In 2022, it was found that those earlier studies simulated abrupt, "stepwise" climate shifts, while more realistic gradual warming would see a rebound in alpine plant diversity after mid-century under the "intermediate" and most intense global warming scenarios RCP 4.5 and RCP 8.5. However, for RCP 8.5, that rebound would be deceptive, followed by the same collapse in biodiversity at the end of the century as simulated in the earlier papers.[97] This is because on average, every degree of warming reduces total species population growth by 7%,[98] and the rebound was driven by colonization of niches left behind by most vulnerable species like Androsace chamaejasme and Viola calcarata going extinct by mid-century or earlier.[97]

It's been estimated that by 2050, climate change alone could reduce

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.[99] Another study estimated that the rainforest would lose 69% of its plant species under the warming of 4.5 °C (8.1 °F).[40]

Another estimate suggests that two prominent species of seagrasses in the Mediterranean Sea would be substantially affected under the worst-case greenhouse gas emission scenario, with Posidonia oceanica losing 75% of its habitat by 2050 and potentially becoming functionally extinct by 2100, while Cymodocea nodosa would lose ~46% of its habitat and then stabilize due to expansion into previously unsuitable areas.[100]

Impacts of species degradation due to climate change on livelihoods

The livelihoods of nature dependent communities depend on abundance and availability of certain species.[101] 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.[102] Degradation of species supplying such products directly affect the livelihoods of people relying on them more so in Africa.[103] The situation is likely to be exacerbated by changes in rainfall variability which is likely to give dominance to invasive species especially those that are spread across large latitudinal gradients.[104] 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. Frequently, the extinction of plant and animal species create a cyclic relationship of species endangerment in ecosystems which are directly affected by climate change.[105]

Species adaptation

A young red deer in the wild in Scotland.

Rising temperatures are beginning to have a noticeable impact on birds,[106] and butterflies nearly 160 species from 10 different zones[107] have shifted their ranges northward by 200 km in Europe and North America. The migration range of larger animals may be constrained by human development.[108] In Britain, spring butterflies are appearing an average of 6 days earlier than two decades ago.[109]

Scientists have observed that

Antarctic hair grass is colonizing areas of Antarctica where previously their survival range was limited.[110][111]ue to the ever hotter weather, birds are forced to move to foreign lands. Other effects of global warming include less snow fall, rising sea levels, Ozone depleting and weather changes. These may influence human activities and the ecosystem.[111]

Climate change has affected the gene pool of the red deer population on Rùm, one of the Inner Hebrides islands, Scotland. Warmer temperatures resulted in deer giving birth on average three days earlier for each decade of the study. The gene which selects for earlier birth has increased in the population because those with the gene have more calves over their lifetime.[112]

A study in Chicago showed that the length of birds' lower leg bones (an indicator of body sizes) shortened by an average of 2.4% and their wings lengthened by 1.3%. A study from central Amazon showed that birds have decreased in mass (an indicator of size) by up to 2% per decade, and increased in wing length by up to 1% per decade, with links to temperature and precipitation shifts. The findings of these studies suggest the morphological changes are the result of climate change, and may demonstrate an example of evolutionary change following Bergmann's rule.[113][114][115][116]

The Jutfelt Fish Ecophysiology lab[117] at the Norwegian University of Science and Technology (NTNU), under their director professor Fredrik Jutfelt, investigates how evolution can lead to physiological adaptation to the temperature environment where the fish live. They recently performed a large artificial selection experiment, published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), showing that evolution of tolerance to warming can occur in fish. The rate of evolution, however, was suggested to be too slow for evolutionary rescue to protect fish from the impacts of climate change.[118]

Prevention

In addition to reducing future warming to the lowest possible levels, preserving the current and likely near-future habitat of endangered species in

30x30 is a crucial aspect of helping species survive. A more radical approach is the assisted migration of species endangered by climate change to new habitats, whether passively (through measures like the creation of wildlife corridors to allow them to move to a new area unimpeded), or their active transport to new areas. This is approach is more controversial, since some of the rescued species may end up invasive in their new locations. I.e. while it would be relatively easy to move polar bears, which are currently threatened by Arctic sea ice decline, to Antarctica, the damage to Antarctica's ecosystem is considered too great to allow this. Finally, species which are extinct in the wild may be kept alive in artificial surroundings until a suitable natural habitat may be restored. In cases where captive breeding fails, embryo cryopreservation has been proposed as an option of last resort.[9]

Apiculture initiatives to prevent human-wildlife conflict in Zimbabwe

Women in rural communities in Hurungwe rural district Zimbabwe have resorted to placing beehives at the border of fields and villages (bio fencing) to protect themselves and their crops from elephants.[119]

Assisted migration

Assisted migration is the act of moving plants or animals to a different habitat. It has been proposed as a way to rescue species which may not be able to disperse easily, have long generation times or have small populations.[120] This strategy has already been implemented to save multiple tree species in North America. For instance, the Torreya Guardians have coordinated an assisted migration program to save the Torreya taxifolia from extinction.[121]

See also

Notes

References

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External links

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