In ecology, overexploitation describes one of the five main activities threatening global biodiversity. Ecologists use the term to describe populations that are harvested at
an unsustainable rate, given their natural rates of mortality and
capacities for reproduction. This can result in extinction at the
population level and even extinction of whole species. In conservation biology,
the term is usually used in the context of human economic activity that
involves the taking of biological resources, or organisms, in larger
numbers than their populations can withstand. The term is also used and defined somewhat differently in fisheries, hydrology and natural resource management.
Overexploitation can lead to resource destruction, including extinctions. However, it is also possible for overexploitation to be sustainable, as discussed below in the section on fisheries. In the context of fishing, the term overfishing can be used instead of overexploitation, as can overgrazing in stock management, overlogging in forest management, overdrafting in aquifer management, and endangered species
in species monitoring. Overexploitation is not an activity limited to
humans. Introduced predators and herbivores, for example, can
overexploit native flora and fauna.
History
When the giant flightless birds called moa were overexploited to the point of extinction, the giant Haast's eagle that preyed on them also became extinct.
The concern about overexploitation, while relatively recent in the
annals of modern environmental awareness, traces back to ancient
practices embedded in human history. Contrary to the notion that
overexploitation is an exclusively contemporary issue, the phenomenon
has been documented for millennia and is not limited to human activities
alone. Historical evidence reveals that various cultures and societies
have engaged in practices leading to the overuse of natural resources,
sometimes with drastic consequences.
One poignant example can be found in the ceremonial cloaks of Hawaiian kings, which were adorned with the feathers of the now-extinct mamo
bird. Crafting a single cloak required the feathers of approximately
70,000 adult mamo birds, illustrating a staggering scale of resource
extraction that ultimately contributed to its extinction. This instance
underscores how cultural traditions and their associated demands can
sometimes precipitate the overexploitation of a species to the brink of
extinction.
Similarly, the story of the dodo bird from Mauritius
provides another clear example of overexploitation. The dodo, a
flightless bird, exhibited a lack of fear toward predators, including
humans, making it exceptionally vulnerable to hunting. The dodo's
naivety and the absence of natural defenses against human hunters and
introduced species led to its rapid extinction. This case offers insight
into how certain species, particularly those isolated on islands, can
be disproportionately affected by human activities due to their
evolutionary adaptations.
Hunting
has long been a vital human activity for survival, providing food,
clothing, and tools. However, the history of hunting also includes
episodes of overexploitation, particularly in the form of overhunting.
The overkill hypothesis, which addresses the Quaternary extinction events, explains the relatively rapid extinction of megafauna.
This hypothesis suggests that these extinctions were closely linked to
human migration and population growth. One of the most compelling pieces
of evidence supporting this theory is that approximately 80% of North
American large mammal species disappeared within just approximately a
thousand years of humans arriving in the Western Hemisphere.
This rapid disappearance indicates a significant impact of human
activity on these species, underscoring the profound influence humans
have had on their environment throughout history.
The fastest-ever recorded extinction of megafauna occurred in New Zealand. By 1500 AD, a mere 200 years after the first human settlements, ten species of the giant moa birds were driven to extinction by the Māori.
This rapid extinction underscores the significant impact humans can
have on native wildlife, especially in isolated ecosystems like New
Zealand. The Māori, relying on the moa as a primary food source and for
resources such as feathers and bones, hunted these birds extensively.
The moa's inability to fly and their size, which made them easier
targets, contributed to their rapid decline. This event serves as a
cautionary tale about the delicate balance between human activity and
biodiversity and highlights the potential consequences of over-hunting
and habitat destruction. A second wave of extinctions occurred later with European settlement.
This period marked significant ecological disruption, largely due to the
introduction of new species and land-use changes. European settlers
brought with them animals such as rats, cats, and stoats, which preyed
upon native birds and other wildlife. Additionally, deforestation for
agriculture significantly altered the habitats of many endemic species.
These combined factors accelerated the decline of New Zealand's unique
biodiversity, leading to the extinction of several more species. The
European settlement period serves as a poignant example of how human
activities can drastically impact natural ecosystems.
Overexploitation does not necessarily lead to the destruction of the resource, nor is it necessarily unsustainable. However, depleting the numbers or amount of the resource can change its quality. For example, footstool palm
is a wild palm tree found in Southeast Asia. Its leaves are used for
thatching and food wrapping, and overharvesting has resulted in its leaf
size becoming smaller.
In 1968, the journal Science published an article by Garrett Hardin entitled "The Tragedy of the Commons". It was based on a parable that William Forster Lloyd
published in 1833 to explain how individuals innocently acting in their
own self-interest can overexploit, and destroy, a resource that they
all share. Lloyd described a simplified hypothetical situation based on medieval land tenure in Europe. Herders share common land on which they are each entitled to graze
their cows. In Hardin's article, it is in each herder's individual
interest to graze each new cow that the herder acquires on the common
land, even if the carrying capacity
of the common is exceeded, which damages the common for all the
herders. The self-interested herder receives all of the benefits of
having the additional cow, while all the herders share the damage to the
common. However, all herders reach the same rational decision to buy
additional cows and graze them on the common, which eventually destroys
the common. Hardin concludes:
Therein is the tragedy. Each man is locked into a system that compels
him to increase his herd without limit—in a world that is limited. Ruin
is the destination toward which all men rush, each pursuing his own
interest in a society that believes in the freedom of the commons.
Freedom in a commons brings ruin to all.
In the course of his essay, Hardin develops the theme, drawing in many examples of latter day commons, such as national parks, the atmosphere, oceans, rivers and fish stocks. The example of fish stocks had led some to call this the "tragedy of the fishers". A major theme running through the essay is the growth of human populations, with the Earth's finite resources being the general common.
The tragedy of the commons has intellectual roots tracing back to Aristotle, who noted that "what is common to the greatest number has the least care bestowed upon it", as well as to Hobbes and his Leviathan. The opposite situation to a tragedy of the commons is sometimes referred to as a tragedy of the anticommons: a situation in which rational individuals, acting separately, collectively waste a given resource by underutilizing it.
The tragedy of the commons can be avoided if it is appropriately
regulated. Hardin's use of "commons" has frequently been misunderstood,
leading Hardin to later remark that he should have titled his work "The
tragedy of the unregulated commons".
The Atlantic bluefin tuna
is currently overexploited. Scientists say 7,500 tons annually is the
sustainable limit, yet the fishing industry continue to harvest 60,000
tons.
In wild fisheries, overexploitation or overfishing occurs when a fish stock has been fished down "below the size that, on average, would support the long-term maximum sustainable yield of the fishery". However, overexploitation can be sustainable.
When a fishery starts harvesting fish from a previously unexploited stock, the biomass
of the fish stock will decrease, since harvesting means fish are being
removed. For sustainability, the rate at which the fish replenish
biomass through reproduction must balance the rate at which the fish are
being harvested. If the harvest rate is increased, then the stock
biomass will further decrease. At a certain point, the maximum harvest
yield that can be sustained will be reached, and further attempts to
increase the harvest rate will result in the collapse of the fishery.
This point is called the maximum sustainable yield,
and in practice, usually occurs when the fishery has been fished down
to about 30% of the biomass it had before harvesting started.
It is possible to fish the stock down further to, say, 15% of the
pre-harvest biomass, and then adjust the harvest rate so the biomass
remains at that level. In this case, the fishery is sustainable, but is
now overexploited, because the stock has been run down to the point
where the sustainable yield is less than it could be.
Fish stocks are said to "collapse" if their biomass declines by more than 95 percent of their maximum historical biomass. Atlantic cod stocks were severely overexploited in the 1970s and 1980s, leading to their abrupt collapse in 1992. Even though fishing has ceased, the cod stocks have failed to recover. The absence of cod as the apex predator in many areas has led to trophic cascades.
About 25% of world fisheries are now overexploited to the point
where their current biomass is less than the level that maximizes their
sustainable yield. These depleted fisheries can often recover if fishing pressure is
reduced until the stock biomass returns to the optimal biomass. At this
point, harvesting can be resumed near the maximum sustainable yield.
The tragedy of the commons can be avoided within the context of fisheries if fishing effort and practices are regulated appropriately by fisheries management. One effective approach may be assigning some measure of ownership in the form of individual transferable quotas
(ITQs) to fishermen. In 2008, a large scale study of fisheries that
used ITQs, and ones that did not, provided strong evidence that ITQs
help prevent collapses and restore fisheries that appear to be in
decline.
Water resources, such as lakes and aquifers, are usually renewable resources which naturally recharge (the term fossil water is sometimes used to describe aquifers which do not recharge). Overexploitation occurs if a water resource, such as the Ogallala Aquifer,
is mined or extracted at a rate that exceeds the recharge rate, that
is, at a rate that exceeds the practical sustained yield. Recharge
usually comes from area streams, rivers and lakes. An aquifer which has
been overexploited is said to be overdrafted or depleted. Forests enhance the recharge of aquifers in some locales, although generally forests are a major source of aquifer depletion. Depleted aquifers can become polluted with contaminants such as nitrates, or permanently damaged through subsidence or through saline intrusion from the ocean.
This turns much of the world's underground water and lakes into finite resources with peak usage debates similar to oil. These debates usually centre around agriculture and suburban water
usage but generation of electricity from nuclear energy or coal and tar
sands mining is also water resource intensive. A modified Hubbert curve applies to any resource that can be harvested faster than it can be replaced. Though Hubbert's original analysis did not apply to renewable resources, their overexploitation can result in a Hubbert-like peak. This has led to the concept of peak water.
Forests are overexploited when they are logged at a rate faster than reforestation
takes place. Reforestation competes with other land uses such as food
production, livestock grazing, and living space for further economic
growth. Historically utilization of forest products, including timber
and fuel wood, have played a key role in human societies, comparable to
the roles of water and cultivable land. Today, developed countries
continue to utilize timber for building houses, and wood pulp for paper. In developing countries almost three billion people rely on wood for heating and cooking. Short-term economic gains made by conversion of forest
to agriculture, or overexploitation of wood products, typically leads
to loss of long-term income and long term biological productivity. West Africa, Madagascar, Southeast Asia and many other regions have experienced lower revenue because of overexploitation and the consequent declining timber harvests.
One of the key health issues associated with biodiversity is drug discovery and the availability of medicinal resources. A significant proportion of drugs are natural products derived, directly or indirectly, from biological sources. Marine ecosystems are of particular interest in this regard. However, unregulated and inappropriate bioprospecting could potentially lead to overexploitation, ecosystem degradation and loss of biodiversity.
It is not just humans that overexploit resources. Overgrazing
can be caused by native fauna, as shown in the upper right. However,
past human overexploitation (leading to elimination of some predators)
may be behind the situation.
Species from all groups of fauna and flora are affected by
overexploitation. This phenomenon is not bound by taxonomy; it spans
across mammals, birds, fish, insects, and plants alike. Animals are
hunted for their fur, tusks, or meat, while plants are harvested for
medicinal purposes, timber, or ornamental uses. This unsustainable
practice disrupts ecosystems, threatening biodiversity and leading to
the potential extinction of vulnerable species.
All living organisms require resources to survive.
Overexploitation of these resources for protracted periods can deplete
natural stocks to the point where they are unable to recover within a
short time frame. Humans have always harvested food and other resources
they need to survive. Human populations, historically, were small, and
methods of collection were limited to small quantities. With an
exponential increase in human population, expanding markets and increasing demand, combined with improved access and techniques for capture, are causing the exploitation of many species beyond sustainable levels. In practical terms, if continued, it reduces valuable resources to
such low levels that their exploitation is no longer sustainable and can
lead to the extinction of a species, in addition to having dramatic, unforeseen effects, on the ecosystem. Overexploitation often occurs rapidly as markets open, utilising previously untapped resources, or locally used species.
Today, overexploitation and misuse of natural resources is an ever-present threat for species richness. This is more prevalent when looking at island ecology and the species that inhabit them, as islands can be viewed as the world in miniature. Island endemic populations are more prone to extinction from overexploitation, as they often exist at low densities with reduced reproductive rates. A good example of this are island snails, such as the Hawaiian Achatinella and the French Polynesian Partula. Achatinelline snails have 15 species listed as extinct and 24 critically endangered while 60 species of partulidae are considered extinct with 14 listed as critically endangered. The WCMC have attributed over-collecting and very low lifetime fecundity for the extreme vulnerability exhibited among these species.
As another example, when the humble hedgehog was introduced to the Scottish island of Uist,
the population greatly expanded and took to consuming and
overexploiting shorebird eggs, with drastic consequences for their
breeding success. Twelve species of avifauna are affected, with some species numbers being reduced by 39%.
Where there is substantial human migration, civil unrest, or war,
controls may no longer exist. With civil unrest, for example in the Congo and Rwanda,
firearms have become common and the breakdown of food distribution
networks in such countries leaves the resources of the natural
environment vulnerable. Animals are even killed as target practice, or simply to spite the government. Populations of large primates, such as gorillas and chimpanzees, ungulates and other mammals, may be reduced by 80% or more by hunting, and certain species may be eliminated. This decline has been called the bushmeat crisis.
Vertebrates
Overexploitation threatens one-third of endangered vertebrates, as well as other groups. Excluding edible fish, the illegal trade in wildlife is valued at $10 billion per year. Industries responsible for this include the trade in bushmeat, the trade in Chinese medicine, and the fur trade. The Convention for International Trade in Endangered Species of Wild Fauna and Flora, or CITES
was set up in order to control and regulate the trade in endangered
animals. It currently protects, to a varying degree, some 33,000 species
of animals and plants. It is estimated that a quarter of the endangered
vertebrates in the United States of America and half of the endangered
mammals is attributed to overexploitation.
Overexploitation of species can result in knock-on or cascade effects. This can particularly apply if, through overexploitation, a habitat loses its apex predator. Because of the loss of the top predator, a dramatic increase in their prey
species can occur. In turn, the unchecked prey can then overexploit
their own food resources until population numbers dwindle, possibly to
the point of extinction.
A classic example of cascade effects occurred with sea otters.
Starting before the 17th century and not phased out until 1911, sea
otters were hunted aggressively for their exceptionally warm and
valuable pelts, which could fetch up to $2500 US. This caused cascade
effects through the kelp forest ecosystems along the Pacific Coast of North America.
One of the sea otters’ primary food sources is the sea urchin. When hunters caused sea otter populations to decline, an ecological release of sea urchin populations occurred. The sea urchins then overexploited their main food source, kelp,
creating urchin barrens, areas of seabed denuded of kelp, but carpeted
with urchins. No longer having food to eat, the sea urchin became locally extinct
as well. Also, since kelp forest ecosystems are homes to many other
species, the loss of the kelp caused other cascade effects of secondary
extinctions.
In 1911, when only one small group of 32 sea otters survived in a
remote cove, an international treaty was signed to prevent further
exploitation of the sea otters. Under heavy protection, the otters
multiplied and repopulated the depleted areas, which slowly recovered.
More recently, with declining numbers of fish stocks, again due to
overexploitation, killer whales have experienced a food shortage and have been observed feeding on sea otters, again reducing their numbers.
The Pyrenean ibex,
also known as the bouquetin (French) and bucardo (Spanish), is the only
animal to have survived de-extinction past birth through cloning.
De-extinction (also known as resurrection biology, or species revivalism) is the process of generating an organism that either resembles or is an extinctorganism. There are several ways to carry out the process of de-extinction. Cloning is the most widely proposed method, although genome editing and selective breeding have also been considered. Similar techniques have been applied to certain endangered species, in hopes to boost their genetic diversity. The only method of the three that would provide an animal with the same genetic identity is cloning. There are benefits and drawbacks to the process of de-extinction ranging from technological advancements to ethical issues.
Methods
Cloning
Pictured above is the process used to clone the Pyrenean ibex. The tissue culture was taken from the last living, female Pyrenean ibex named Celia. The egg was taken from a goat (Capra hircus)
and the nucleus removed to ensure the offspring was purely Pyrenean
ibex. The egg was implanted into a surrogate goat mother for
development.
Cloning is a commonly suggested method for the potential restoration of an extinct species.
It can be done by extracting the nucleus from a preserved cell from the
extinct species and swapping it into an egg, without a nucleus, of that
species' nearest living relative. The egg can then be inserted into a host from the extinct species'
nearest living relative. This method can only be used when a preserved
cell is available, meaning it would be most feasible for recently
extinct species. Cloning has been used by scientists since the 1950s. One of the most well known clones is Dolly the sheep.
Dolly was born in the mid-1990s and lived normally until the abrupt
midlife onset of health complications resembling premature aging, that
led to her death. Other known cloned animal species include domestic cats, dogs, pigs, and horses.
Genome editing
Genome editing
has been rapidly advancing with the help of the CRISPR/Cas systems,
particularly CRISPR/Cas9. The CRISPR/Cas9 system was originally
discovered as part of the bacterial immune system. Viral DNA that was injected into the bacterium became incorporated into
the bacterial chromosome at specific regions. These regions are called
clustered regularly interspaced short palindromic repeats, otherwise
known as CRISPR. Since the viral DNA is within the chromosome, it gets
transcribed into RNA. Once this occurs, the Cas9 binds to the RNA. Cas9
can recognize the foreign insert and cleaves it. This discovery was very crucial because the Cas protein can now be viewed as a scissor in the genome editing process.
By using cells from a closely related species to the extinct
species, genome editing can play a role in the de-extinction process.
Germ cells may be edited directly, so that the egg and sperm produced by
the extant parent species will produce offspring of the extinct
species, or somatic cells may be edited and transferred via somatic cell
nuclear transfer. The result is an animal which is not completely the
extinct species, but rather a hybrid of the extinct species and the
closely related, non-extinct species. Because it is possible to sequence
and assemble the genome of extinct organisms from highly degraded
tissues, this technique enables scientists to pursue de-extinction in a
wider array of species, including those for which no well-preserved
remains exist. However, the more degraded and old the tissue from the extinct species
is, the more fragmented the resulting DNA will be, making genome
assembly more challenging.
Back breeding is a form of selective breeding. As opposed to breeding
animals for a trait to advance the species in selective breeding, back
breeding involves breeding animals for an ancestral characteristic that
may not be seen throughout the species as frequently. This method can recreate the traits of an extinct species, but the genome will differ from the original species. Back breeding, however, is contingent on the ancestral trait of the species still being in the population in any frequency. Back breeding is also a form of artificial selection by the deliberate
selective breeding of domestic animals, in an attempt to achieve an
animal breed with a phenotype that resembles a wild type ancestor,
usually one that has gone extinct.
A natural process of de-extinction is iterative evolution. This
occurs when a species becomes extinct, but then after some time a
different species evolves into an almost identical creature. For
example, the Aldabra rail was a flightless bird that lived on the island
of Aldabra. It had evolved some time in the past from the flighted white-throated rail,
but became extinct about 136,000 years ago due to an unknown event that
caused sea levels to rise. About 100,000 years ago, sea levels dropped
and the island reappeared, with no fauna. The white-throated rail
recolonized the island, but soon evolved into a flightless species
physically identical to the extinct species.
Not all extinct plants have herbarium specimens that contain seeds.
Of those that do, there is ongoing discussion on how to coax barely
alive embryos back to life. See Judean date palm and tsori.
In-vitro fertilisation and artificial insemination
In-vitro fertilisation and artificial insemination are assisted reproduction technology commonly used to treat infertility in humans. However, it has usage as a viable option for de-extinction in cases of functional extinction
where all remaining individuals are of the same sex, incapable of
naturally reproducing, or suffer from low genetic diversity such as the
northern white rhinoceros, Yangtze giant softshell turtle, Hyophorbe amaricaulis, baiji, and vaquita. For example, viable embryos are created from preserved sperm from deceased males and ova from living females are implemented into a surrogate species.
Advantages of de-extinction
The technologies being developed for de-extinction could lead to large advances in various fields:
An advance in genetic technologies that are used to improve the
cloning process for de-extinction could be used to prevent endangered
species from becoming extinct.
By studying revived previously extinct animals, cures to diseases could be discovered.
Revived species may support conservation initiatives by acting as "flagship species" to generate public enthusiasm and funds for conserving entire ecosystems.
Prioritising de-extinction could lead to the improvement of current
conservation strategies. Conservation measures would initially be
necessary in order to reintroduce a species into the ecosystem, until
the revived population can sustain itself in the wild. Reintroduction of an extinct species could also help improve ecosystems
that had been destroyed by human development. It may also be argued
that reviving species driven to extinction by humans is an ethical
obligation.
Disadvantages of de-extinction
The
reintroduction of extinct species could have a negative impact on
existing species and their ecosystem. The extinct species' ecological
niche may have been filled in its former habitat, thus making them an
invasive species. This could lead to the extinction of other species due
to competition for food or other competitive exclusion.
It could also lead to the extinction of prey species if they have more
predators in an environment that had few predators before the
reintroduction of an extinct species. If a species has been extinct for a long period of time the environment
they are introduced to could be wildly different from the one that they
can survive in. The changes in the environment due to human development
could mean that the species may not survive if reintroduced into that
ecosystem. A species could also become extinct again after de-extinction if the
reasons for its extinction are still a threat. The woolly mammoth might
be hunted by poachers just like elephants for their ivory
and could go extinct again if this were to happen. Or, if a species is
reintroduced into an environment with disease for which it has no
immunity, the reintroduced species could be wiped out by a disease that
current species can survive.
De-extinction is a very expensive process. Bringing back one
species can cost millions of dollars. The money for de-extinction would
most likely come from current conservation efforts. These efforts could
be weakened if funding is taken from conservation and put into
de-extinction. This would mean that critically endangered species would start to go extinct faster because there are no longer resources that are needed to maintain their populations. Also, since cloning techniques cannot perfectly replicate a species as
it existed in the wild, the reintroduction of the species may not bring
about positive environmental benefits. They may not have the same role
in the food chain that they did before and therefore cannot restore
damaged ecosystems.
Current candidate species for de-extinction
The woolly mammoth is a current prime candidate for de-extinction through cloning or genome editing.
The existence of preserved soft tissue remains and DNA from woolly mammoths (Mammuthus primigenius) has led to the idea that the species could be recreated by scientific means. Two methods have been proposed to achieve this:
The first would be to use the cloning process; however, even the most intact mammoth samples have had little usable
DNA because of their conditions of preservation. There is not enough DNA
intact to guide the production of an embryo. The second method would involve artificially inseminating an elephant egg cell with preserved sperm of the mammoth. The resulting offspring would be a hybrid of the mammoth and its closest living relative the Asian elephant.
After several generations of cross-breeding these hybrids, an almost
pure woolly mammoth could be produced. However, sperm cells of modern
mammals are typically potent for up to 15 years after deep-freezing,
which could hinder this method. Whether the hybrid embryo would be carried through the two-year
gestation is unknown; in one case, an Asian elephant and an African
elephant produced a live calf named Motty, but it died of defects at less than two weeks old.
In 2008, a Japanese team found usable DNA in the brains of mice
that had been frozen for 16 years. They hope to use similar methods to
find usable mammoth DNA. In 2011, Japanese scientists announced plans to clone mammoths within six years.
In March 2014, the Russian Association of Medical Anthropologists
reported that blood recovered from a frozen mammoth carcass in 2013
would now provide a good opportunity for cloning the woolly mammoth. Another way to create a living woolly mammoth would be to migrate genes
from the mammoth genome into the genes of its closest living relative,
the Asian elephant, to create hybridized animals with the notable
adaptations that it had for living in a much colder environment than
modern day elephants. This is currently being done by a team led by Harvard geneticist George Church. The team has made changes in the elephant genome with the genes that
gave the woolly mammoth its cold-resistant blood, longer hair, and an
extra layer of fat. According to geneticist Hendrik Poinar, a revived woolly mammoth or
mammoth-elephant hybrid may find suitable habitat in the tundra and
taiga forest ecozones.
George Church has hypothesized the positive effects of bringing
back the extinct woolly mammoth would have on the environment, such as
the potential for reversing some of the damage caused by global warming. He and his fellow researchers predict that mammoths would eat the dead
grass allowing the sun to reach the spring grass; their weight would
allow them to break through dense, insulating snow in order to let cold
air reach the soil; and their characteristic of felling trees would
increase the absorption of sunlight. In an editorial condemning de-extinction, Scientific American
pointed out that the technologies involved could have secondary
applications, specifically to help species on the verge of extinction
regain their genetic diversity.
In March 2025, Colossal Biosciences, a startup founded by George Church with funding from Ben Lamm announced the birth of woolly mice.
These mice, while they do not contain almost any mammoth genetic
information – most of the edited genes are known mice fur genetic
variants, and not woolly mammoth variants –, exhibit some of the key traits of the woolly mammoth, such as cold
tolerance and long, shaggy, tawnt-toned fur, giving further credence to
the feasibility of reviving the woolly mammoth through genome editing of
the Asian elephant.
Aurochs
A bull from the Taurus Project, a project aiming to de-extinct the aurochs through back breeding modern domesticated cattle.
The aurochs (Bos primigenius) was widespread across Eurasia, North Africa, and the Indian subcontinent during the Pleistocene, but only the European aurochs (B. p. primigenius) survived into historical times. This species is heavily featured in European cave paintings, such as Lascaux and Chauvet cave in France and was still widespread during the Roman era. Following the fall of the Roman Empire, overhunting of the aurochs by nobility caused its population to dwindle to a single population in the Jaktorów forest in Poland, where the last wild one died in 1627.
However, because the aurochs is ancestral to most modern cattle breeds, it is possible for it to be brought back through selective or back breeding. The first attempt at this was by Heinz and Lutz Heck using modern cattle breeds, which resulted in the creation of Heck cattle.
This breed has been introduced to nature preserves across Europe;
however, it differs strongly from the aurochs in physical
characteristics, and some modern attempts claim to try to create an
animal that is nearly identical to the aurochs in morphology, behavior,
and even genetics. There are several projects that aim to create a cattle breed similar to
the aurochs through selectively breeding primitive cattle breeds over a
course of twenty years to create a self-sufficient bovine grazer in
herds of at least 150 animals in rewilded nature areas across Europe,
for example the Tauros Programme and the separate Taurus Project. This organization is partnered with the organization Rewilding Europe to help revert some European natural ecosystems to their prehistoric form.
A competing project to recreate the aurochs is the Uruz Project by the True Nature Foundation, which aims to recreate the aurochs by a more efficient breeding strategy using genome editing,
in order to decrease the number of generations of breeding needed and
the ability to quickly eliminate undesired traits from the population of
aurochs-like cattle. It is hoped that aurochs-like cattle will reinvigorate European nature
by restoring its ecological role as a keystone species and bring back
biodiversity that disappeared following the decline of European megafauna, as well as helping to bring new economic opportunities related to European wildlife viewing.
Sometime in 2025, Tauros Programme and Rewilding Europe plan to
release their aurochs into the wild in select areas of Europe and to
have the species recognised as a protected wildlife species again. In 2026, these animals will be reintroduced to parts of the Scottish Highlands.
Quagga
Living quagga, 1870
The quagga (Equus quagga quagga) is a subspecies of the plains zebra that was distinct in that it was striped on its face and upper torso, but its rear abdomen was a solid brown. It was native to South Africa, but was wiped out in the wild due to overhunting for sport, and the last individual died in 1883 in the Amsterdam Zoo. However, since it is technically the same species as the surviving
plains zebra, it has been argued that the quagga could be revived
through artificial selection. The Quagga Project aims to breed a similar form of zebra by selective breeding of plains zebras. This process is also known as back breeding. It also aims to release
these animals onto the western Cape once an animal that fully resembles
the quagga is achieved, which could have the benefit of eradicating introduced species of trees such as the Brazilian pepper tree, Tipuana tipu, Acacia saligna, bugweed, camphor tree, stone pine, cluster pine, weeping willow and Acacia mearnsii.
Thylacine
The last known thylacine died from neglect in the Hobart Zoo in 1936.
The thylacine (Thylacinus cynocephalus), commonly known as the Tasmanian tiger, was native to the Australian mainland, Tasmania and New Guinea. It is believed to have become extinct in the 20th century. The thylacine had become extremely rare or extinct on the Australian mainland before British settlement of the continent. The last known thylacine died at the Hobart Zoo,
on September 7, 1936. It is believed to have died as the result of
neglect—locked out of its sheltered sleeping quarters, it was exposed to
a rare occurrence of extreme Tasmanian weather: extreme heat during the day and freezing temperatures at night. Official protection of the species by the Tasmanian government was
introduced on July 10, 1936, roughly 59 days before the last known
specimen died in captivity.
In December 2017, it was announced in the journal Nature Ecology and Evolution
that the full nuclear genome of the thylacine had been successfully
sequenced, marking the completion of the critical first step toward
de-extinction that began in 2008, with the extraction of the DNA samples
from the preserved pouch specimen. The thylacine genome was reconstructed by using the genome editing method. The Tasmanian devil was used as a reference for the assembly of the full nuclear genome. Andrew J. Pask from the University of Melbourne
has stated that the next step toward de-extinction will be to create a
functional genome, which will require extensive research and
development, estimating that a full attempt to resurrect the species may
be possible as early as 2027.
In August 2022, the University of Melbourne and Colossal Biosciences
announced a partnership to accelerate de-extinction of the thylacine
via genetic modification of one of its closest living relatives, the fat-tailed dunnart. In October 2024, Colossal claimed to have reconstructed a 99.9%
complete genome of the thylacine from a well-preserved skull estimated
to be 110 years old; however, the data has not yet been published. In January 2025, Colossal Biosciences and University of Melbourne claimed to have developed an artificial marsupial womb to further accelerate the de-extinction of thylacine and conservation for endangered marsupials.
The passenger pigeon (Ectopistes migratorius)
numbered in the billions before being wiped out due to unsustainable
commercial hunting and habitat loss during the early 20th century. The
non-profit Revive & Restore
obtained DNA from the passenger pigeon from museum specimens and skins;
however, this DNA is degraded because it is so old. For this reason,
simple cloning would not be an effective way to perform de-extinction
for this species because parts of the genome would be missing. Instead,
Revive & Restore focuses on identifying mutations in the DNA that
would cause a phenotypic difference between the extinct passenger pigeon
and its closest living relative, the band-tailed pigeon.
In doing this, they can determine how to modify the DNA of the
band-tailed pigeon to change the traits to mimic the traits of the
passenger pigeon. In this sense, the de-extinct passenger pigeon would
not be genetically identical to the extinct passenger pigeon, but it
would have the same traits. In 2015, the de-extinct passenger pigeon
hybrid was forecast ready for captive breeding by 2025 and released into
the wild by 2030. In October 2024, Revive & Restore collaborated with Applied
Ecological Institute to simulate forest disturbances in the American
state of Wisconsin
to see how trees would react to the reintroduced passenger pigeons. The
original 2025 goal was not met, with the new goal for reviving the
species for captive breeding set for between 2029 and 2032. However, it
could take decades for the species to be reintroduced to the wild.
Bush moa
Skeleton of the bush moa
The bush moa, also known as the little bush moa or lesser moa (Anomalopteryx didiformis) is a slender species of moa slightly larger than a turkey that abruptly went extinct around 500–600 years ago following the arrival and proliferation of the Māori people in New Zealand, as well as the introduction of Polynesian dogs. Scientists at Harvard University
assembled the first nearly complete genome of the species from toe
bones, thus bringing the species a step closer to de-extinction. Trevor Mallard, a New Zealander politician, has also previously suggested bringing back a medium-sized species of moa. The proxy of the species will likely be the emu.
Maclear's rat
Maclear's rat, naturalist's painting
The Maclear's rat (Rattus macleari),
also known as the Christmas Island rat, was a large rat endemic to
Christmas Island in the Indian Ocean. It is believed Maclear's rat might
have been responsible for keeping the population of Christmas Island red crab in check. It is thought that the accidental introduction of black rats by the Challenger expedition infected the Maclear's rats with a disease (possibly a trypanosome), which resulted in the species' decline. The last recorded sighting was in 1903. In March 2022, researchers discovered the Maclear's rat shared about 95% of its genes with the living brown rat,
thus sparking hopes in bringing the species back to life. Although
scientists were mostly successful in using CRISPR technology to edit the
DNA of the living species to match that of the extinct one, a few key
genes were missing, which would mean resurrected rats would not be
genetically pure replicas.
The dodo (Raphus cucullatus) was a flightless bird endemic to the island of Mauritius in the Indian Ocean. Due to various factors such as the inability to feel fear
caused by isolation from significant predators, predation from humans
and introduced invasive species such as pigs, dogs, cats, rats, and crab-eating macaques,
competition for food with invasive species, habitat loss, and the birds
naturally slow reproduction, the species' numbers declined rapidly. The last widely accepted recorded sighting was in 1662. Since then, the
bird has become a symbol for extinction and is often cited as the
primary example of man-made extinction. In January 2023, Colossal Biosciences
announced their project to revive the dodo alongside their previously
announced projects for reviving the woolly mammoth and thylacine in
hopes of restoring biodiversity to Mauritius and changing the dodo's
status as a symbol of extinction to de-extinction.
Steller's sea cow
Model of Steller's sea cow
The Steller's sea cow was a sirenian endemic to Bering Sea between Russia and the United States but had a much larger range during the Pleistocene. First described by Georg Wilhelm Steller in 1741, it was hunted to extinction 27 years later due to its buoyancy
making it an easy target for humans hunting it for its meat and fur in
addition to an already low population caused by climate change. In 2021,
the nuclear genome of the species was sequenced. In late 2022, a group of Russian scientists funded by Sergei Bachin
began their project to revive and reintroduce the giant sirenian to its
former range in the 18th century to restore its kelp forest ecosystem.
Arctic Sirenia plans to revive the species through genome editing of the
dugong, but they need an artificial womb to conceive a live animal due to lack of an adequate surrogate species. Ben Lamm of Colossal Biosciences has also expressed desire to revive the species once his company develops an artificial womb.
Northern white rhinoceros
Sudan, the final male northern white rhinoceros was euthanised due to age-related illnesses on the Ol Pejeta Conservancy in 2018
The northern white rhinoceros or northern white rhino (Ceratotherium simum cottoni) is a subspecies of the white rhinoceros endemic to East and Central Africa south of the Sahara.
Due to widespread and uncontrollable poaching and civil warfare in
their former range, the subspecies' numbers dropped quickly over the
course of the late 1900s and early 2000s. Unlike the majority of the potential candidates for de-extinction, the northern white rhinoceros is not extinct, but functionally extinct and is believed to be extinct in the wild with only two known female members left, Najin and Fatu who reside on the Ol Pejeta Conservancy in Kenya. The BioRescue Team in collaboration with Colossal Biosciences
plan to implement 30 northern white rhinoceros embryos made from egg
cells collected from Najin and Fatu and preserved sperm from dead male
individuals into female southern white rhinoceros by the end of 2024.
The ivory-billed woodpecker(Campephilus principalis) is the largest woodpecker native to the United States, with an endemic subspecies in Cuba. The species numbers have declined since the late 1800s due to logging and hunting. Similarly to the northern white rhinoceros, the ivory-billed woodpecker
may not be completely extinct, but rather functionally extinct, though
the evidence suggests that the species is 'very likely extinct'. In October 2024, Colossal Biosciences announced their non-profit
Colossal Foundation, a foundation dedicated to conservation of extant
species with their first projects being the Sumatran rhinoceros, vaquita, red wolf, pink pigeon, northern quoll,
and ivory-billed woodpecker. Colossal plans to revive or rediscover the
species through genome editing of its closest living relatives, such as
the pileated woodpecker and using drones and AI to identify any potential remaining individuals in the wild.
Heath hen
Ornithologist, professor Alfred Otto Gross holding Booming Ben, the last known heath hen
The heath hen(Tympanuchus cupido cupido) was a subspecies of greater prairie chicken endemic to the heathland barrens of coastal North America. It is even speculated that the pilgrims' first Thanksgiving featured this bird as the main course instead of wild turkey. Due to overhunting caused by its perceived abundancy, the population became extinct in mainland North America by 1870, leaving a population of 300 individuals left on Martha's Vineyard.
Despite conservation efforts, the subspecies became extinct in 1932
following the disappearance and presumed death of Booming Ben, the final known member of the subspecies. In the summer of 2014, non-profit organisation, Revive & Restore
held a meeting with the community of Martha's Vineyard to announce
their project to revive the heath hen in hopes of restoring and
maintaining the sandplain grasslands. On April 8, 2020, germs cells were collected from greater prairie chicken eggs at Texas A&M.
Yangtze giant softshell turtle
One of the final two remaining wild turtles at Dong Mo Lake in Son Tay, Vietnam
The Yangtze giant softshell turtle (Rafetus swinhoei) is a softshell turtle
endemic to China and Vietnam and is possibly the largest living
freshwater turtle. Due to various factors such as habitat loss, wildlife
trafficking, trophy hunting, and the Vietnam War,
the species population has been reduced to only three male individuals,
rendering it functionally extinct similar to the northern white
rhinoceros and ivory-billed woodpecker. There is one captive individual in Suzhou Zoo
in China, and two wild individuals at Dong Mo Lake in Vietnam. Efforts
to save the species from extinction through various means of assisted reproduction in captivity have been ongoing since 2009 by the Suzhou Zoo and Turtle Survival Alliance.
Despite efforts to breed the turtles naturally, the eggs laid by the final known female were all infertile and unviable. In May 2015, artificial insemination was performed for the first time in the species. In July of the same year, the female laid 89 eggs, but like all previous natural attempts, they were all unviable. In April 2019, the female individual at the zoo died after another failed artificial insemination attempt. In 2020, a female was discovered in the wild, reigniting hope for the survival of the species. However, this individual was found dead in early 2023. Several searches across China and Vietnam are currently underway to
locate female individuals to breed with the final known males, or to
undergo artificial insemination.
There have been attempts to recreate the dire wolf (Aenocyon dirus)
in modern times. The first is a project called the Dire Wolf Project, a
project begun in 1988 that aims to revive the species through backbreeding of domestic dogs, similar to the Quagga project. However, this project is not based in scientific method.
In April 2025, it was announced that Colossal Biosciences used cloning and gene-editing to birth three genetically modified wolf pups
with the characteristics of the dire wolf, six-month-old males Romulus
and Remus and two-month-old female Khaleesi. In-house scientists at
Colossal analyzed the dire wolf genome, extracted from two ancient
samples – a 13,000-year-old tooth and a 72,000-year-old ear bone. After
comparing the genomes of gray wolves
and dire wolves to identify the genetic differences responsible for the
dire wolf's distinctive features, Colossal made edits to the genetic
code of the gray wolf to replicate those traits. Domestic dogs were used
as surrogate mothers for the pups.Colossal claims that these minor genetic modifications effectively
revive dire wolves as a species, though "no ancient dire wolf DNA was
actually spliced into the gray wolf's genome".
Indian cheetah
Ramanuj Pratap shot three of the final Indian cheetahs in 1948, leaving a lone female who was last spotted in 1951.
The Indian cheetah was a population of the Asiatic cheetah (Acinonyx jubatus venaticus) that was endemic to India. The Asiatic cheetah was extirpated from the region due to trapping by Indian royalty to aid in coursing since the 16th century, and later poaching, habitat loss, and loss of prey in the 20th century, leading to being declared extinct by the Indian government in 1952. In 2022 and 2023, African cheetahs have been imported to India to act as an ecological proxy for the locally extinct subspecies. In April 2025, Birbal Sahni Institute of Palaeosciences in collaboration with Zoological Survey of India
announced plans to revive and rewild the Indian cheetah through the
same methods as Colossal Biosciences' dire wolf project, editing the
genome of the African cheetah to reflect that of the Indian cheetah with
an African cheetah acting as a surrogate.
Further species considered for de-extinction
A "De-extinction Task Force" was established in April 2014 under the auspices of the Species Survival Commission
(SSC) and charged with drafting a set of Guiding Principles on Creating
Proxies of Extinct Species for Conservation Benefit to position the
IUCN SSC on the rapidly emerging technological feasibility of creating a
proxy of an extinct species.
Avians
Giant moa – The tallest birds to have ever lived. Both the northern and southern species became extinct by 1500 due to overhunting by the Māori in New Zealand.
Elephant bird – The heaviest birds to have ever lived, the elephant birds were driven to extinction by the early colonization of Madagascar. Ancient DNA has been obtained from the eggshells but may be too degraded for use in de-extinction.
The Carolina parakeet is a prime candidate for de-extinction due to the genome already being sequenced
Carolina parakeet - One of the few native parrots
to the United States, it was driven to extinction by destruction of its
habitat, overhunting, competition from introduced honeybees, and
persecution for crop damages and declared extinct following the death of
its final known member, Incas
in 1918. Hundreds of specimens with viable DNA still exist in museums
around the world, making it a prime candidate for revival. In 2019, the
full genome of the Carolina parakeet was sequenced.
Great auk - A flightless bird native to the North Atlantic
physically similar to penguins. The great auk went extinct in the 1800s
due to overhunting by humans for food. The last two known great auks
lived on an island near Iceland and were clubbed to death by sailors.
There have been no known sightings since. The great auk has been identified as a good candidate for de-extinction
by Revive and Restore, a non-profit organization. Because the great auk
is extinct it cannot be cloned, but its DNA can be used to alter the
genome of its closest relative, the razorbill,
and breed the hybrids to create a species that will be very similar to
the original great auks. The plan is to introduce them back into their
original habitat, which they would then share with razorbills and puffins,
who are also at risk for extinction. This would help restore the
biodiversity and restore that part of the ecosystem. Colossal
Biosciences has also expressed interest in reviving the species.
Imperial woodpecker
– The largest woodpecker to have ever lived. Endemic to Mexico and
possibly extinct, it has not been seen since 1956 due to habitat
destruction and hunting. The Federal government of Mexico
has considered the species extinct since 2001, 47 years after the last
widely accepted sighting. However, they have conservation plans if the
species is rediscovered or attempts at de-extinction are made.
Cuban macaw – A colourful macaw that was endemic to Cuba and Isla de la Juventud, it was the only macaw species of the Antilles. It became extinct in the late 19th century due to overhunting, pet trade, and habitat loss.
Labrador duck
– A duck native to North America. it became extinct in the late 19th
century due to colonisation in their former range combined with an
already naturally low population. It is also the first known endemic
North American bird species to become extinct following the Columbian Exchange.
The huia was one of the very first proposed candidates for de-extinction through cloning
Huia – A species of Callaeidae native to New Zealand. It became extinct in 1907 due to overhunting from both the Māori and European settlers, habitat loss, and predation from introduced invasive species. In 1999, students of Hastings Boys' High School proposed the idea of de-extinction of the huia, the school's emblem through cloning. The Ngāti Huia tribe approved of the idea and the de-extinction process would have been performed by the University of Otago with $100,000 funding from a Californian-based internet startup. However, due to the poor state of DNA in the specimens at Museum of New Zealand Te Papa Tongarewa, a complete huia genome could not be created, making this method of de-extinction improbable to succeed.
Moho – An entire family and genus of songbirds
that were endemic to the islands of Hawaii. The genus and family became
extinct in 1987 following the extinction of its final living member,
the Kauaʻi ʻōʻō. The reasons for the genus' decline were overhunting for their plumage, habitat loss caused by colonization of Hawaii, naturaldisasters, mosquito-borne diseases, and predation from introduced invasive species.
Mammals
Caribbean monk seal – A species of monk seal that was native to the Caribbean. It became extinct in 1952 due to poaching and starvation caused by overfishing of its natural prey.
Bluebuck – A species of antelope that was native to Africa.
The species was hunted to extinction by 1799 or 1800 by Europeans, and
the species had a naturally low population similar to the Labrador duck.
In 2024, the nuclear genome of the species was sequenced by University of Potsdam and Colossal Biosciences. Colossal Biosciences has also expressed interest in reviving the species in the future.
Pyrenean ibex – A subspecies of ibex that was native to the Pyrenees,
the subspecies was declared extinct in the early 2000 following the
death of Celia, the endling of the subspecies after two centuries of
overhunting and competition with livestock and introduced species. Celia
was successfully cloned by Spanish scientists in 2003, but the clone
died shortly after its birth due to a lung defect. 10 years later, The
Aragon Hunting Federation in collaboration with CITA (Centre for Research and Food Technology of Aragon)
began a second attempt to potentially revive the subspecies by
verifying if Celia's frozen cells were still viable for future cloning
attempts. As of April 2025, no further statements have come out from
this project.
Vaquita – The smallest cetacean to have ever lived; endemic to the upper Gulf of California in Mexico. The vaquita is not completely extinct, but functionally extinct with an estimate of 8 or less members left due to entanglement in gillnets meant to poach totoabas, a fish with a highly valued swim bladder on Asian black markets due to its perceived medicinal values.In October 2024, Colossal Biosciences launched their Colossal
Foundation, a non-profit foundation dedicated to conservation of extant
species with one of their first projects being the vaquita. In addition
to using technology to monitor the final remaining individuals, they aim
to collect tissue samples from vaquitas in order to revive it if it
does become extinct in the near future.
Irish elk – The largest deer to have ever lived, formerly inhabiting Eurasia from present day Ireland to present day Siberia during the Pleistocene. It became extinct 5–10 thousand years ago due to suspected overhunting from humans.
Cave lion – A species of Panthera related to the modern lion found throughout the Holarctic
during the Pleistocene. It is estimated that the species died out 14-15
thousand years ago due to climate change and low genetic diversity. The
discovery of well-preserved cubs in the Sakha Republic, Russia ignited a project to clone the animal.
Cave hyena
– A species or subspecies of hyena that was endemic to Eurasia during
the Pleistocene. It is estimated that the species died out 31 thousand
years ago due to competition with early humans and other carnivores and
decreased availability of prey.
Castoroides
– An entire genus of giant beavers endemic to North America during the
Pleistocene. It is unknown how the species died out, but some suggest
that climate change and competition are factors. Beth Shapiro of Colossal Biosciences has expressed interest in reviving a species from this genus.
Steppe bison – The ancestor species of all modern American bison, formerly endemic to Western Europe to eastern Beringia in North America during the Late Pleistocene.
The discovery of the mummified steppe bison of 9,000 years ago could
help people clone the ancient bison species back, even though the steppe
bison would not be the first to be "resurrected". Russian and South Korean scientists are collaborating to clone steppe bison in the future using DNA preserved from an 8,000-year-old tail and wood bison as a surrogate species, which themselves have been introduced to Yakutia to fulfil a similar niche.
Longhorn bison
– Also known as the giant bison, a species of bison native to North
America from Southern Canada to Mexico during the Late Pleistocene. It
is estimated that the species died out 13,000 years ago, possibly due to
pressure from early humans and overhunting.
Ground sloths – An extremely diverse group of sloths
native to the Americas during the Pleistocene with some growing to the
size of modern elephants. Ground sloths died out on the mainland 11
thousand years ago, but relict populations in the Caribbean survived until about 4 thousand years ago like the final populations of woolly mammoths on Wrangel island.
Ground sloths died out primarily due to climate change and some suspect
that their size and slowness made them easy targets for early humans.
The insular Caribbean populations were likely driven to extinction
through overhunting.
Woolly rhinoceros – A species of rhinoceros that was endemic to Northern Eurasia during the Pleistocene.
It is believed to have become extinct as a result of both climate
change and overhunting by early humans. In November 2023, scientists
managed to sequence the woolly rhinoceros's genome from faeces of cave
hyenas in addition to the existence of mummified specimens.
Miracinonyx – Also known as American cheetahs, an entire genus of felines
that were native to North America during the Pleistocene. It is unknown
how the genus went extinct, but some suggest that they died out for the
same reasons as other North American megafauna; climate change, loss of
prey, and competition with early humans and other carnivores.
Head of a mummified Homotheirum latidens cub, the only mummified specimen of the entire Machairodontinae subfamily
Machairodontinae – Commonly referred to as sabre-tooth cats or sabre-tooth tigers, an entire subfamily of feline apex predators that were widespread globally with the exceptions of Oceania and Antarctica from the middle Miocene to early Holocene. The final two genera of this subfamily, Smilodon and Homotherium,
are estimated to have become extinct during the Quaternary extinction
event 10–13 thousand years ago for the same reasons as other carnivorous
megafauna. Despite one of their common names, the biggest challenge in
the restoration of any species belonging to this subfamily is that they
are too genetically distinct from modern big cats, such as tigers. In 2020, a mummified Homotherium latidens cub was discovered in Yakutia, Russia.
Columbian mammoth – A species of mammoth that was endemic to North America across what are now the United States and northern Mexico.
The species became extinct 12 thousand years ago during the Quaternary
extinction event due to climate change, overhunting from early humans,
and habitat loss.
Mastodon – An entire genus of proboscideans that were native to North America from the Miocene
to the early Holocene. Like the Columbian mammoth, the species became
extinct about 11,795 to 11,345 years ago due to climate change,
overhunting from early humans, and habitat loss.
Arctodus – An entire genus of short-faced bears
endemic to North America during the Pleistocene. It is estimated that
they became extinct 12 thousand years ago following the death of its
final member, Arctodus simus due to climate change and low
genetic diversity. Beth Shapiro of Colossal Biosciences has expressed
interest in reviving one of the two species from the genus.
Amphibians
Gastric-brooding frog – A genus of ground frogs that were native to Queensland, Australia. They became extinct in the mid-1980s primarily due to chytridiomycosis.
In 2013, scientists in Australia successfully created a living embryo
from non-living preserved genetic material, and hope that by using
somatic-cell nuclear transfer methods, they can produce an embryo that
can survive to the tadpole stage.
Insects
Museum specimens of the Xerces blue, an extinct butterfly
Xerces blue – A species of butterfly that was native to the Sunset District of San Francisco in the American state of California. It is estimated that the species became extinct in the early 1940s due to urbanization of their former habitat. Similar species to the Xerces blue, such as Glaucopsyche lygdamus and the Palos Verdes blue,
have been released into the Xerces blue's former range to substitute
its ecological role. On April 15, 2024, non-profit organisation Revive & Restore announced the early stages of their plans to potentially revive the species.
Plants
Glyphs of Paschalococos, an extinct genus of palm trees native to Easter Island
Paschalococos – A genus of coccoid palm trees that were native to Easter Island,
Chile. It is believed to have become extinct around 1650 due to
overharvesting for its edible nuts and its subsequent disappearance from
the pollen records.
Hyophorbe amaricaulis – A species of palm tree from the Arecales
family that is native to the island of Mauritius. Unlike the majority
of potential candidates, this palm is not completely extinct, but functionally extinct and is believed to be extinct in the wild with only one known specimen left in the Curepipe Botanic Gardens.
In 2010, there was an attempt to revive the species through germination
in vitro in which Isolated and growing embryos were extracted from
seeds in tissue culture, but these seedlings only lived for three months.
Methuselah, the first resurrected Judean date palm through germination of 2000 year old seeds found in the Masada excavations in the 1960s
Judean date palm
The Judean date palm is a species of date palm native to Judea
that is estimated to have originally become extinct around the 15th
century due to climate change and human activity in the region. In 2005, preserved seeds found in the 1960s excavations of Herod the Great's palace were given to Sarah Sallon by Bar-Ilan University after she came up with the initiative to germinate some ancient seeds. Sallon later challenged her friend, Elaine Solowey of the Center for Sustainable Agriculture at the Arava Institute for Environmental Studies
with the task of germinating the seeds. Solowey managed to revive
several of the provided seeds after hydrating them with a common
household baby bottle warmer along with average fertiliser and growth
hormones. The first plant grown was named after Lamech's father, Methuselah, the oldest living man in the Bible. In 2012, there were plans to crossbreed the male palm with what was considered its closest living relative, the Hayani date of Egypt to generate fruit by 2022. However, two female Judean date palms have been sprouted since then. By 2015 Methuselah had produced pollen that has been used successfully
to pollinate female date palms. In June 2021, one of the female plants,
Hannah, produced dates. The harvested fruits are currently being studied
to determine their properties and nutritional values. The de-extinct Judean date palms are currently at a Kibbutz located in Ketura, Israel.
Rastreador Brasileiro
Gaya, a female member of the Rastreador Brasileiro breed that was revived through preservation breeding
The Rastreador Brasileiro (Brazilian Tracker) is a large scent hound from Brazil that was bred in the 1950s to hunt jaguars and wild pigs. It was originally declared extinct and delisted by the Fédération Cynologique Internationale and Confederação Brasileira de Cinofilia in 1973 due to tick-borne diseases and subsequent poisoning from insecticides in attempt to get rid of the ectoparasites. In the early 2000s, a group named Grupo de Apoio ao Resgate do
Rastreador Brasileiro (Brazilian Tracker Rescue Support Group) dedicated
to reviving the breed and having it relisted by Confederação Brasileira
de Cinofilia began work to locate dogs in Brazil that had genetics of
the extinct breed to breed a purebred Rastreador Brasileiro. In 2013, the breed was de-extinct through preservation breeding from descendants of the final original members and was relisted by the FCI.
Floreana giant tortoise
The Floreana giant tortoise (Chelonoidis niger niger) is a subspecies of the Galápagos tortoise endemic to Floreana Island, Ecuador that is believed to have become extinct by 1850 due to overexploitation, predation, and habitat degradation by sailors and invasive species such as ferallivestock, rodents, and stray dogs and cats. A deliberate wildfire started by Thomas Chappel, a crew member of the Essex in 1820 is also cited as a reason for the subspecies initial decline. In 2012, Floreana and Volcán Wolf tortoise hybrids were discovered Isabela Island. Allegedly, these tortoises were imported or abandoned on the island in
the early 19th century, allowing them to hybridise with the native
subspecies. In 2017, a breeding programme was established to revive the
subspecies through back breeding the hybrids to regain their genetic
purity. As of 2025, 400 Floreana giant tortoises have been hatched on Santa Cruz Island with plans to release them into the wild on Floreana Island after the successful extirpation of invasive species. However, IUCN
has yet to update the status of the subspecies due to lack of a
genetically pure specimen at the time of the 2017 evaluation and the
de-extinct subspecies has yet to reproduce naturally in the wild.
Unknown Commiphora
In 2010, Sarah Sallon of Arava Institute for Environmental Studies grew a seed found in excavations of a cave in the northern Judean desert in 1986. The specimen, Sheba reached maturity in 2024 and is believed to be an entirely new species of Commiphora with many believing that Sheba may be the tsori or Judean balsam, plants that are said to have healing properties in the Bible.
York groundsel
The York groundsel is a species of Senecio that was first discovered in York, England in 1979 and last seen in the wild in 1991. A survey by UK government advisory body Natural England found it was
driven to extinction by 2000, partly due to the use of weedkiller. Seeds of the plant were stored at the Millennium Seed Bank,
successfully germinated, and reintroduced to York in 2023, marking the
first time an extinct species has been revived and successfully
reintroduced into its native range.
Montreal melon
Drawing of the Montreal melon, a de-extinct cultiver of melon
The Montreal melon, also known as the Montreal market muskmelon, Montreal nutmeg melon, and in French as melon de Montréal (Melon of/from Montreal) is a cultivar of melon native to Canada and traditionally grown around the Montreal
area. Despite its status as a delicacy on the east coast of North
America, the Montreal melon disappeared from farms and was presumed
extinct by the 1920s due to urbanisation in the region and being
ill-suited for agribusiness. In 1996, seeds of the lost melon were discovered in a seed bank in the American state of Iowa. Since then, the plant has been reintroduced to its former range by local gardeners.
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