Based on a species' population size, distribution, and habitat, it may be designated as a threatened species—vulnerable, endangered, or critically endangered—if it is at high risk of extinction.

According to the International Union for Conservation of Nature, as of 2025, there are over 18,000 endangered animal species worldwide, with the share of fish, insects, mollusks, and reptiles increasing since 2007.

Although ecologists have struggled to identify a species as a keystone—one of outsized importance to its ecosystem—an analysis of 50 years of data and 157 studies identified 230 such species.

Desert wildlife: diverse, threatened, and misunderstood

This article sheds light on the surprisingly diverse wildlife that thrive in deserts, while also highlighting the gaps in human understanding of these ecosystems. Deserts are home to one-quarter of terrestrial vertebrate species—three percent of...

Benign species can become invasive if introduced into predator-free habitats

Most ecosystems contain organisms that, over many generations, have evolved into a stable balance with one another and their surroundings. In a new environment, a species may no longer be restricted by the limiting factors it is used to, and the native organisms in the area may not adapt quickly enough to the invader to establish a new balance.

View a breakdown of the identified species on Earth, led by about one million insect species, while mammals such as humans make up one of the smallest groups.

Native, wild bees are at much greater risk of extinction than honey bees

It is estimated that there are more honey bees, which often compete with native bees for resources, on the planet than at any point in human history. Meanwhile, 40% of invertebrate pollinator species, including wild bees and butterflies, face extinction in the coming decades.

View the biggest threats to biodiversity, according to the World Wildlife Fund, led by changes to species' environments, species overexploitation, and invasive species.

Learn about the plant and animal species in every US county that are federally protected under the US Endangered Species Act with this interactive map.

What's happening to the snowy owl?

This article explores the alarming decline of snowy owls in the Arctic. Once abundant in these northern regions, the snowy owl is now classified as "vulnerable" by the International Union for Conservation of Nature (IUCN). The adult population...

Even in nature reserves, climate change is driving rapid ecological collapse

Studies show a dramatic decline in insect populations, resulting in cascading global biodiversity losses across non-insect species. The balances in tropical ecosystems are the most affected by climate change.

There have been five mass extinction events in Earth’s history

Each extinction event has resulted in the loss of at least 70% of Earth’s species at the time of the event, often due to significant changes in global temperatures. The most recent event occurred 66 million years ago and wiped out all non-avian dinosaurs.

At any given time, there are an estimated 10 quintillion individual insects alive on Earth.

Rapid environmental changes are exacerbating natural extinction processes

Human activities behind climate change, habitat destruction, pollution, and overhunting have resulted in extinction rates up to 1,000 times greater than normal, triggering massive biodiversity loss. This has led scientists to refer to the current geological age as the Anthropocene era, in which humans are the dominant force shaping nature.

Butterfly populations have declined by 22% from 2000 to 2020

Research suggests that one in every five butterflies is lost due to pesticide use, habitat loss, and climate change. Playing a vital role in pollination, their declining populations threaten plant reproduction and the health of ecosystems.

Visual deep dive into the collapse of insects

The most diverse group of organisms on the planet are in trouble, with recent research suggesting insect populations are declining at an unprecedented rate. Explore this visual interactive on the issue from Reuters Graphics.

Increasing contact between humans and wild animals is driving zoonotic threats

Zoonotic diseases, which spread from animals to humans, present one of the most significant emerging threats worldwide. Scientists have identified around 200 viruses capable of infecting humans, and unfortunately, the number of such diseases are on the rise—at least 60% of all emerging infectious diseases are zoonotic in origin.

Nearly all species introduced into a new environment are not invasive

Introduced by zoologist Charles Elton in 1958, the term "invasive species" refers to organisms that are not native to an environment but cause harm after their introduction. Some ecologists argue that terminology such as "native" and "non-native" may only serve to assist in extinction when legislation is limited to protecting "native" organisms.

Vector-borne diseases kill more than 700,000 people globally each year—and are growing

The diseases with the greatest potential to spread widely aren't the ones that quickly kill human hosts. Instead, the best hosts or reservoirs for vector-borne diseases would be chronically ill over the long term, increasing the likelihood that the pathogen could be transmitted to others.

Feral and free-ranging cats rank among the most harmful invasive species

Transported across the planet by humans, cats can now be found in many environments and are estimated to kill about 2 billion birds each year in the US. Studies suggest cats have contributed to the extinction of at least 63 species worldwide.

The jaguar is the largest feline in the Americas and serves as a keystone species by acting as an apex predator with a diverse diet across multiple environments, thereby regulating the populations of dozens of species.

During a trophic cascade, the disappearance of a keystone species, which plays an indispensable role in ecosystems, triggers a domino effect within food webs that disrupts the populations of many more species.

South Asia and sub-Saharan Africa are most at risk from falling pollinator numbers

Researchers at the Harvard T.H. Chan School of Public Health found that declines in pollinator populations would lead to higher rates of nutritional deficiencies, particularly in developing nations. Nations with large populations, such as China and India, would also be significantly impacted.

What is the rarest color in nature?

Plants, animals, or minerals found in nature bear almost every color imaginable. There are two factors that influence what hues you see in the wild: physics and evolution. So, which colors are you least likely to see in the natural world? Victoria Hwang explores one of nature's rarest spectacles.

Synthetic biology can prevent extinction by creating create disease-resilient plants and animals

Through gene editing and the deployment of artificial cells, scientists can leverage learnings from the genetic sequencing of animals with known resistances to protect endangered species. Gene editing of certain species, such as mosquitoes, can also reduce their ability to spread diseases like malaria between humans.

Microbial research suggests shifts in diverse populations may help an invasive species establish itself

In 1958, English ecologist Charles Elton suggested that diverse ecosystems should be more resistant to invasive species because gaining a foothold would be more challenging when resources are more thinly spread. However, in lab-grown microbial ecosystems with greater biodiversity, population volatility opened more ecological roles that invasive species could easily fill.

Why genetic similarities between humans suggest a past near-extinction event

Researchers have found that low genetic diversity among humans—even those on opposite sides of the planet—may result from a breeding population of as few as 1,280 adults, estimated to have existed 930,000 years ago. This genetic bottleneck may have resulted from a near-extinction or from a small population of human ancestors, from which we all descend, that broke off from a larger population.

Invasive species may harm new ecosystems via the spread of disease

Besides damaging native species through direct interactions such as competition for resources and predation, invasive species may come from environments with greater biodiversity than the new environment. This makes them more likely to carry pathogens unfamiliar to native species, increasing the risk of biodiversity loss.

Humans may be the ultimate invasive species

Originating in East Africa, Homo sapiens migrated across the world beginning about 60,000 years ago and directly harmed countless species by consuming resources and modifying ecosystems to serve our needs. While meeting the definition of an invasive species, some ecologists argue the opposite, claiming that humans have helped preserve numerous species.

How sea ice decline threatens polar bears

This two-minute video discusses a recent study warning that arctic polar bears are at risk of near-extinction by the end of the century due to the rapid melting of the sea ice they rely on for survival. The study used models based on satellite data...

There are five key mechanisms—small population size, nonrandom mating, mutation, gene flow, and natural selection—that drive evolution, or the change in the abundance of specific genetic traits found within a population.

California is one of the world’s 35 biodiversity hotspots

The state comprises the hotspot known as the California Floristic Province, where roughly 3,000 species of vascular plants grow—roughly three-fifths of which are found nowhere else in the world (also known as endemic).

Environment and genetics explain why animals have widely different lifespans

Both environmental conditions and genetic factors shape how long various animals live. For some creatures, colder conditions allow for less energy use and slower aging. Larger animals have fewer predators. While humans don't live the longest, we are a rare species that successfully lengthened its average lifespan over time.

Nearly 99% of the Smithsonian's specimens are hidden in high-security

At the National Museum of Natural History, nearly 99% of its 147 million specimens are stored in secure research collections rather than on display, where they are actively used for scientific work ranging from tracking invasive species to improving aviation safety.

Mammals gradually expanded in size and diversity after the dinosaur extinction

After an asteroid impact caused a mass extinction event 66 million years ago, small mammals were among the few surviving species. With fewer predators, mammals steadily grew larger as new habitats emerged.

De-extinction techniques create new species from existing organisms

Rather than recovering a genetic sample of a lost species and editing it with that of living creature—as has been depicted in science fiction—scientists begin with living cells from close genetic relatives and use tools like CRISPR to swap in extinct versions of specific traits to create new hybrid species.

Stress affects different animals in different, but useful, ways

Animals feel stress when they experience actual dangers—such as a zebra chased by a lion. Humans often feel stress from worries, memories, or even thoughts about problems that may occur in the future. For this reason, animals tend to experience stress in short, intense bursts. Conversely, people can feel stressed for long periods, which can eventually be harmful to their health.

How the California wildfires are impacting wildlife

The deadly 2025 Eaton and Palisades Fires in California have devastated neighborhoods, forested canyons and chaparral—a type of shrubland. In addition to taking dozens of human lives and displacing thousands, the fires destroyed countless habitats and displaced many species. See the unfortunate effects of the flames on wildlife populations, including birds, snakes, wildcats, and fish.

About one-third of the world's food supply depends on pollinators like bees, butterflies, and bats to transfer pollen between flowers, which use bright colors, scents, and nectar to attract them.

Why are there as many males as females?

Pretty much every species breaks down with an equal sex-ratio, with roughly the same number of males as females. But on the surface, it appears that most species wouldn't need many males to keep the population growing, with their energy-efficient, abundant sex cell production. So why is it equal? Scientists argue an equal ratio is the most evolutionarily stable. Learn about this quirk of biology here.

The highly contaminated Chernobyl region suffers from reduced biodiversity

Although isolation and radiation have driven adaptations in some organisms, decades of radiation have caused ongoing harm to wildlife and vegetation, including population declines in birds and insects. Higher rates of deformities and tumors have also been seen compared with animals in surrounding regions.

As of 2023, there are about 1.1 billion objects stored in 73 of the world's largest natural history museums, but only about 16% of specimens are available in digital archives.

Three examples of how humans are still evolving

For much of nature, natural selection and "survival of the fittest" still play a dominant role; only the strongest can survive in the wild. As little as a few hundred years ago, the same was true for humans, but what about now?

A collection of fascinating facts about the planet and its creatures

You may have already heard that cheetahs are the fastest animals on land, but did you know that Savannah elephants are the strongest? This page on the World Wildlife Fund's UK website features a diverse range of articles on mammals, underwater creatures, birds, reptiles, insects, and landscapes. Discover captivating information about Earth and the creatures you share it with.

Fig trees are considered keystone species because they provide year-round habitat and fruit, which are eaten by an estimated 1,300 species of birds and mammals worldwide.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

See which countries have already reached their peak population, and when others will eventually reach theirs.

The last Pinta Island tortoise died in 2012 at over 100 years old

Unfortunately, different animal species continue to go extinct. See a list of these recent extinctions, and learn the story of Lonesome George, who died without finding a mate in the Galapagos Islands.

From 1970 to 2017, invasive species have caused $1.28T in damage globally

The costliest species were the Asian tiger and yellow fever mosquitoes ($149B), which arrived in the US from Asia and sub-Saharan Africa, respectively. The bulk of their damage came from their transmission of diseases such as Zika, chikungunya, and dengue. (Some readers may experience a paywall.)

Extremophiles were likely to have been Earth's first, and are expected to be its last, organisms

Their ability to survive in an enormous range of environmental conditions, including some resembling what has been modeled to have existed relatively shortly after Earth's formation, makes them the leading candidates for enduring the increasing solar intensity and the subsequent effects (e.g., zero-oxygen atmosphere, evaporated oceans) expected in the coming billions of years.

Mosquitoes top the ranking of the world's deadliest animals.