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.

The concept of keystone species—organisms that have disproportionately large impacts on their ecosystems—was discovered through studies of purple starfish in Pacific tidepools.

Sea otters act as keystone predators by eating up to 15 pounds of seafood a day, including urchins, which feed on kelp forests that support over 800 species by providing them with habitats and food.

Contributing to one in every three bites of food consumed by humans, bees are a keystone species because of their essential role as pollinators of about 80% of all flowering plants worldwide.

As environmental engineers—a main type of keystone species—prairie dogs support over 150 other species through their grazing habits and burrowing of underground tunnels, which serve as habitats for owls, snakes, ferrets, insects, and other organisms.

During a tropic 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.

By targeting a diverse range of sick and injured marine life, sharks—a type of predatory keystone species—help keep ocean gene pools healthy and promote biodiversity by keeping prey species in check.

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.

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.

Research suggests ants are the most abundant insect on the planet, with an estimated 2.5 million of them for every human on Earth.

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.

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.

Possessing trunks that contain about 40,000 individual muscles, African elephants act as keystone species by trampling and clearing trees, making pathways in forests, digging water holes, and spreading seeds.

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.

Some mosquitoes are key pollinators—and eat disease-carrying mosquitoes.

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.

In Yellowstone National Park, grey wolves act as keystone predators by controlling elk and deer populations, which had previously overgrazed and disrupted river systems that supported many more mammal, fish, and avian species.

Able to hold their breath for up to 15 minutes, beavers are considered keystone species via their construction of dams and formation of wetlands, which serve as homes and food sources for fish, birds, insects, and other animals.

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.

Invasive species are the third biggest threat to Earth's biodiversity

According to the World Wildlife Fund's Living Planet Report 2020, changes in land and sea use account for about half of all recorded threats to the diversity of the planet's species. Species overexploitation is the second-largest proportional threat at 24%, while invasive species make up 13%.

Over 1 million fish, marine mammals, and invertebrate species depend on coral reefs for habitats, camouflage, and food.

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...

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.

Some animals, including certain tropical ants, have little or no microbial populations in their gut, upending the idea that all animals rely on this ecosystem to help maintain their health and proper functioning.

Bees are crucial for pollination and food security

When animals and insects pick up the pollen of flowers and spread it, they allow plants, including many food crops, to reproduce. The most common pollinator is the bee, but bees are at risk from pollution and pesticides.

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.

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

While invasive species typically harm ecosystems by outcompeting native organisms for resources, some provide unexpected benefits, including new shelters, nesting habitats, and reduced environmental heat stress.

Multiple species exhibit convergent evolution by developing crab-like features

Various organisms that appear to be different types of crabs, such as porcelain crabs and coconut crabs, have been shown to belong to distinct decapod lineages whose predecessors resemble shrimp or lobsters. Environmental pressures and other factors have caused these species to develop similar characteristics, which nature has shown are beneficial to survival.

T. rex needed the same amount of calories as 80 people every day

Tyrannosaurus rex is the most extensively studied fossil creature ever known. Every year, new research is added to the towering list of papers that try to draw …

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

There are lots of weird ideas about dinosaur extinction, like hungry, hungry caterpillars

One of the great historical puzzles is this: why did the dinosaurs go extinct? Whether an asteroid, poison plants, volcanos and climate change, or something else, it's still a mystery. Scientists have been debating this question for almost a hundred years. One insect scholar suggests that caterpillars are the culprits.

Biosphere 2 revealed limitations in maintaining wildlife in unfamiliar environments

Trees appeared to become weak and more prone to breaking because a lack of wind caused them to no longer need to develop stress wood. The extinction of pollinators—potentially due to an explosion in the population of longhorn crazy ants—was also unexpected.

The deep-sea fangtooth has the largest teeth of any marine species relative to body size

From transparent fish to the heaviest worms on the planet, these seven creepy creatures lurk in the deep sea. Learn all about them and the unique traits that help them survive and hunt.

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.