A million species could vanish, and people are to blame | Science News for Students

A million species could vanish, and people are to blame

Here are five ways humans are speeding up the rate of extinctions
Jun 19, 2019 — 6:45 am EST
a photo of an orange toad, Incilius periglenes, on a green leaf

The golden toad Incilius periglenes was once abundant in the cloud forests of Central America. Its last recorded sighting was May 15, 1989.

Papa Lima Whiskey/Wikimedia Commons

Everyone’s heard stories about certain species on the brink of extinction. A new tally reveals just how many plants and animals are at risk. One million species could vanish, it finds. Some might disappear within a few decades.

That number is equal to 1 in every 8 animal or plant species known. It comes from a sweeping new analysis of about 15,000 scientific studies published within the past 50 years. Those studies covered topics ranging from biodiversity and climate to the health of ecosystems. During that half-century, the human population has doubled in size — from 3.7 billion in 1970 to 7.6 billion today. And all those people are what threaten wildlife, concludes an international group of scientists.

Worldwide, species are disappearing tens to hundreds of times faster than what had been the average rate throughout the past 10 million years. That acceleration is thanks to human activities, says IPBES. That stands for the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. This group published a summary of its new findings on May 6. IPBES has 132 member countries, including the United States. It plans to release its full 1,500-page report by year’s end.

The report contains many alarming numbers. More than four in every 10 amphibian species, it finds, are endangered with extinction or likely to become extinct. So are one in every three sharks, marine mammals and coral-reef-building animals. One in every 10 insect species also may vanish. And if people don’t change their activities, the report says, the rate of wildlife extinctions will only speed up.

Here are the top five ways people are speeding the loss of species:

1. Leaving species fewer places to live on land

The top human-linked threat comes from habitat loss, the report says. People have “severely altered” about three-fourths of all land on Earth. Since 1992, urban areas more than doubled. Farms have taken over many habitats that used to be diverse. By diverse, the reports means they might once have been forests, wetlands or wild grasslands.

The report says that 85 percent of the wetlands that existed in 1700 were gone by 2000. And, it notes, forests now cover just about two-thirds (68 percent) of the area they had before about 1850.

Much land has been diverted to farming. Growing food crops now covers three times as much land as it did in 1970. In the world’s tropics, farmlands grew between 1980 and 2000 by 1 million square kilometers (386,000 square miles). In Southeast Asia, plantations of oil palms have edged out wild forests. And in Central America, cattle ranches have expanded into what had been forests.

a palm oil plantation
Millions of hectares of once-lush, intact forest in Southeast Asia have given way to farms. More than 80 percent of the region’s agricultural expansion comes from plantations, like this one, of palm oil trees.
Yusnizam/iStock/Getty Images Plus

2. Overfishing the oceans

Even sea life has been suffering from habitat loss. Human actions have altered about two-thirds of the ocean’s surface, the report finds. Here, the top human threat to ocean life is fishing. Industrial boats fish more than 55 percent of the ocean’s surface. People are now harvesting about one-third of the ocean’s fish populations too quickly. These fish no longer reproduce fast enough to keep their populations from shrinking.

Atlantic halibut and bluefin tuna are among the world’s most overfished species. So are all types of sharks. Non-fished species — such as dolphins and loggerhead sea turtles — have also been dying after being accidentally trapped by nets and other fishing gear.

3. Not tackling climate change fast enough

The world has already warmed by an average of about 1 degree Celsius (1.8 degrees Fahrenheit) since before 1850. That warming is linked to more frequent and intense extreme-weather events (such as floods, fires and droughts). Earth’s fever not only has made seas rise but also shifted where species have been migrating to become more comfortable. Warmer oceans also are placing stress on many fish species. That means people can catch fewer fish without doing long-term damage to the health of their populations.

Changes in how people use land also is tied to climate change. About one-quarter of the world’s emissions of greenhouse gases currently come from land clearing, crop production and the use of fertilizers. (Fertilizers boost the activity of soil microbes that then give off greenhouse gases.) Three-quarters of these farm-related emissions come from raising livestock for food.

And because of decreasing biodiversity, some tropical forests are releasing more carbon (as carbon dioxide) to the atmosphere than they’re soaking up. When there are more types of plants in a forest, they can capture sunlight at different heights, soaking up and storing more carbon from the air. Diverse forest plants also attract different types of animals, some of which help pollinate more types of plants. Those, in turn, can boost forest growth.

4. Continuing to pollute the environment

Plastic pollution has become a growing threat to sea life. People make 10 times as much of this plastic pollution as they did 40 years ago. This affects at least 267 species, the report finds. These include 86 percent of marine turtles, 44 percent of seabirds and 43 percent of marine mammals.

Plastics can find their way into soils, too. That’s especially true of tiny pieces called microplastics. Other forms of pollution also pose big risks. Those include oil spills, mining wastes, untreated urban sewage and wastes running off in rainwater from farms and ranches.

a macro photo of an emerald ash borer
The emerald ash borer (Agrilus planipennis) is a wood-boring beetle native to forests in Russia, Japan and China. It was first spotted in Michigan in 2002. Since then, these beetles have killed millions of North American ash trees.
USGS Bee Inventory And Monitoring Lab/Flickr

5. Paving the way for invaders

Invasive species are organisms that take hold in parts of the globe where they don’t belong. As humans travel and move products all around the world, they sometimes accidentally carry species to new places. These resettled species can become “weeds” that bully the native species they encounter. The report looked at the 21 countries with the most detailed records about this. It found that the number of invasive species per country has increased by about 70 percent since 1970.

Those invaders compete with native species for water and other resources. They also can wipe out vast numbers of native plants or animals. Among such invasive species are the frog-killing chytrid (KIH-trid) fungus and tree-munching emerald ash borer. 

But there’s hope …

As bad as these trends sound, there remains reason for hope, the report’s authors say. People can slow the loss of species. Between 1996 and 2008, conservation efforts lowered the extinction risk by almost one-third for mammals and birds in 109 countries. Saving more species, however, will take “transformative changes” in human behavior, the report says. That includes changing how people consume energy, food and water — and how they limit pollution and other threats to Earth’s ecosystems.

a family of golden lion tamarin sitting on a tree branch
The golden lion tamarin is still endangered, but it’s also somewhat of a success story. Due to the loss of its habitat in Brazil, the species nearly went extinct by the 1960s. Since then, a captive-breeding and reintroduction program has helped these wild monkeys rebound. There are now some 1,500 individuals.
sherseydc/Flickr (CC BY-SA 2.0)

Power Words

(more about Power Words)

acceleration     A change in the speed or direction of some object.

ash     (in biology) A group of deciduous trees in the olive family that are popular in landscaping and for timber.

Atlantic     One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.

atmosphere     The envelope of gases surrounding Earth or another planet.

average     (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

behavior     The way something, often a person or other organism, acts towards others, or conducts itself.

biodiversity     (short for biological diversity) The number and variety of species found within a localized geographic region.

carbon     The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

carbon dioxide (or CO2)     A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.

chytrid fungus     A common shortened name for fungi — Batrachochytrium dendrobatidis and B. salamandrivorans —  that can create a lethal infection in amphibians, especially frogs. The formal name of the infection is chytridiomycosis.    

climate change     Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

conservation     The act of preserving or protecting something. The focus of this work can range from art objects to endangered species and other aspects of the natural environment.

coral     Marine animals that often produce a hard and stony exoskeleton and tend to live on reefs (the exoskeletons of dead ancestor corals).

crop     (in agriculture) A type of plant grown intentionally grown and nurtured by farmers, such as corn, coffee or tomatoes. Or the term could apply to the part of the plant harvested and sold by farmers. 

dolphins     A highly intelligent group of marine mammals that belong to the toothed-whale family. Members of this group include orcas (killer whales), pilot whales and bottlenose dolphins.

drought     An extended period of abnormally low rainfall; a shortage of water resulting from this.

ecosystem     A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra. The term can also be applied to elements that make up some an artificial environment, such as a company, classroom or the internet.

endangered     An adjective used to describe species at risk of going extinct.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

extinction     (adj. extinct) The permanent loss of a species, family or larger group of organisms.

fertilizer     Nitrogen, phosphorus and other plant nutrients added to soil, water or foliage to boost crop growth or to replenish nutrients that were lost earlier as they were used by plant roots or leaves.

forest     An area of land covered mostly with trees and other woody plants.

fungus     (plural: fungi) One of a group of single- or multiple-celled organisms that reproduce via spores and feed on living or decaying organic matter. Examples include mold, yeasts and mushrooms.

greenhouse gas     A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.

habitat     The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

invasive     An adjective that refers to something that can invade some environment (such as an invasive species) or alter some environment (such as invasive medical procedures).

invasive species     (also known as aliens) A species that is found living, and often thriving, in an ecosystem other than the one in which it evolved. Some invasive species were deliberately introduced to an environment, such as a prized flower, tree or shrub. Some entered an environment unintentionally, such as a fungus whose spores traveled between continents on the winds. Still others may have escaped from a controlled environment, such as an aquarium or laboratory, and begun growing in the wild. What all of these so-called invasives have in common is that their populations are becoming established in a new environment, often in the absence of natural factors that would control their spread. Invasive species can be plants, animals or disease-causing pathogens. Many have the potential to cause harm to wildlife, people or to a region’s economy.

livestock     Animals raised for meat or dairy products, including cattle, sheep, goats, pigs, chickens and geese.

mammal     A warm-blooded animal distinguished by the possession of hair or fur, the secretion of milk by females for feeding their young, and (typically) the bearing of live young.

marine     Having to do with the ocean world or environment.

marine mammal     Any of many types of mammals that spend most of its life in the ocean environment. These include whales and dolphins, walruses and sea lions, seals and sea otters, manatees and dugongs — even polar bears.

microbe     Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

microplastic     A small piece of plastic, 5 millimeters (0.2 inch) or smaller in size. Microplastics may have been produced at that small size, or their size may be the result of the breakdown of water bottles, plastic bags or other things that started out larger.

native     Associated with a particular location; native plants and animals have been found in a particular location since recorded history began. These species also tend to have developed within a region, occurring there naturally (not because they were planted or moved there by people). Most are particularly well adapted to their environment.

organism     Any living thing, from elephants and plants to bacteria and other types of single-celled life.

palm     A type of evergreen tree that sprouts a crown of large fan-shaped leaves. Most of the roughly 2,600 different species of palms are tropical or semitropical.

plantation     A site where some species of tree or other valuable, wild-like plant (such as coffee, banana or tobacco) has been planted as a crop.

plastic     Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.

policy     A plan, stated guidelines or agreed-upon rules of action to apply in certain specific circumstances. For instance, a school could have a policy on when to permit snow days or how many excused absences it would allow a student in a given year.

pollinate     To transport male reproductive cells — pollen — to female parts of a flower. This allows fertilization, the first step in plant reproduction.

population     (in biology) A group of individuals from the same species that lives in the same area.

reef     A ridge of rock, coral or sand. It rises up from the seafloor and may come to just above or just under the water’s surface.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

sea     An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

sewage     Wastes — primarily urine and feces — that are mixed with water and flushed away from homes through a system of pipes for disposal in the environment (sometimes after being treated in a big water-treatment plant).

sharks     A family of primitive fishes that rely on skeletons formed of cartilage, not bone. Like skates and rays, they belong to a group known as elasmobranchs. Then tend to grow and mature slowly and have few young. Some lay eggs, others give birth to live young.

species     A group of similar organisms capable of producing offspring that can survive and reproduce.

stress     (in biology) A factor — such as unusual temperatures, movements, moisture or pollution — that affects the health of a species or ecosystem.

tropics     The region near Earth’s equator. Temperatures here are generally warm to hot, year-round.

urban     Of or related to cities, especially densely populated ones or regions where lots of traffic and industrial activity occurs. The development or buildup of urban areas is a phenomenon known as urbanization.

waste     Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.

weed     (in botany) A plant growing wild in, around — and sometimes smothering over — valued plants, such as crops or landscape species (including lawn grasses, flowers and shrubs). Often a plant becomes such a botanical bully when it enters a new environment with no natural predators or controlling conditions, such as hard frosts. (in biology, generally) Any organism may be referred to as a “weed” if it enters an environment and begins to overwhelm the local ecosystem.

wetland     As the name implies, this is a low-lying area of land either soaked or covered with water much of the year. It hosts plants and animals adapted to live in, on or near water.


Report:​ ​​Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Media release: Nature’s dangerous decline ‘unprecedented;’ species extinction rates ‘accelerating.’