Biodiversity refers to all the different kinds of living organisms within a given area, including plants, animals, fungi and other living things. It includes everything from towering redwood trees to tiny, single-cell algae that are impossible to see without a microscope. 

Kinds of Biodiversity

A common way to measure biodiversity is to count the total number of species living within a particular area. Tropical regions—areas that are warm year-round—have the most biodiversity. Temperate regions, which have warm summers and cool winters, have less biodiversity. Regions with cold or dry conditions, such as mountaintops and deserts, have even less biodiversity. 

Generally, the closer a region is to the Equator, the greater the biodiversity. At least 40,000 different plant species live in the Amazon Rainforest of South America, one of the most biologically diverse regions on the planet. By contrast, only around 600 plant species live on the Antarctic continent and in its lakes.

The warm waters of the western Pacific and Indian Oceans tend to have the most diverse marine environments. The Bird’s Head Seascape in Indonesia is home to more than 1,600 species of fish and more than 70 percent of the world’s coral species. Many of the corals build coral reefs, which are home to hundreds more species, from tiny seaweeds to large sharks.

Some regions in the world have a large number of endemic species, meaning species that exist only in that place. The Cape Floristic Region in South Africa is home to about 6,200 plant species found nowhere else in the world. Areas with high numbers of endemic species are called biodiversity hotspots. Scientists and communities are making a special effort to preserve biodiversity in these regions.

Biodiversity can also refer to the variety of ecosystems, or communities of living things and their environments. Ecosystems include deserts, grasslands and rainforests, among others. The African continent is home to tropical rain forests, alpine mountains and dry deserts. It enjoys a high level of biodiversity. Antarctica, covered almost entirely by an ice sheet, has low biodiversity.

Another way to measure biodiversity is through genetic diversity. Genes are the basic units of biological information that are passed on when living things reproduce. Human beings have about 25,000 genes. Some genes are the same for all individuals within a species—they are what make a daisy a daisy and a dog a dog. But some genes within members of the same species are different. This genetic variation is why some dogs are poodles and some are pit bulls, or why some people have brown eyes and some people have blue eyes. 

Greater genetic diversity within a species can make that species more resistant to diseases, and it allows a species to better adapt to a changing environment. 

Importance of Biodiversity

All species are interconnected; they depend on one another. Forests provide homes for animals. Animals eat plants, which need healthy soil to grow. Fungi help decompose organisms to fertilize the soil. Bees and other insects carry pollen from one plant to another, which enables the plants to reproduce. With less biodiversity, these connections weaken, and sometimes break, harming all the species in the ecosystem.

Ecosystems with a lot of biodiversity are generally stronger and more resistant to disease than those with fewer species. For instance, some diseases kill only one kind of tree. In the early 1900s, American chestnut blight killed most of the chestnut trees in the eastern forests of North America. The forest ecosystem was able to survived because other kinds of trees also grew there.

Biodiversity is important to people in many ways. Plants, for instance, help humans by giving off oxygen. They also provide food, shade, construction material, medicines and fiber for clothing and paper. The root system of plants helps prevent flooding. Plants, fungi and animals, such as worms, keep soil fertile and water clean. As biodiversity decreases, these systems break down. 

Hundreds of industries rely on plant biodiversity. Agriculture, construction, medical and pharmaceutical, and fashion industries all depend on plants for their success. When the biodiversity of an ecosystem is interrupted or destroyed, the economic impact on the local community can be enormous.

Biodiversity is especially important to the medical and pharmaceutical industries. Scientists have discovered many chemicals in rainforest plants that are now used in helpful medications. One of the most popular and safe pain relievers, aspirin, was originally made from the bark of willow trees.

Medicines that treat some forms of cancer have been made from rosy periwinkle (Catharanthus roseus), a flower that grows on the African island of Madagascar. Traditional medicine practitioners across Africa and Asia have used the flower for centuries to treat diabetes and stomach issues. This led scientists to investigate the chemistry of the plant in the 1950s, leading to the discovery that it could be used to treat cancer.

Indigenous people around the world, particularly those who live in tropical rainforests, have long used plants for medicinal purposes. Scientists have studied only a small percentage of rainforest species in their search for cures. Many important drugs have evolved from field observations of how Indigenous people use certain plants for healing. This kind of research is called ethnobotany. But thousands of species are at risk of becoming extinct before scientists can determine whether they might be useful in medicines.

Decreasing Biodiversity

In the past hundred years, biodiversity around the world has decreased dramatically. Thousands of species are in danger of extinction. Extinction is a natural process; some species naturally die out while new species evolve. But human activity has changed the natural processes of extinction and evolution. Scientists estimate that species are dying out at hundreds of times the natural rate.

Human activity altering and destroying natural habitats is a major reason for the loss of biodiversity. As habitats shrink, fewer species can live there. Those that survive have fewer breeding partners, leading to a decline in genetic diversity.

People and corporations clear and pollute land to plant crops, keep livestock, further develop cities, mine precious metals or build housing and factories. Human-driven climate change and development have destroyed about 35% of the world’s wetlands since 1970, a habitat that 40% of plant and animal species depend on. People cut down forests for lumber and to make space for cattle ranching, which accounts for 80% of deforestation in Amazon countries. Companies have cleared large areas of rainforest in Indonesia and Malaysia to create vast plantations of palm oil trees. Companies use the fruit of the tree to create palm oil for commercial use. This large-scale deforestation is destroying habitats for critically endangered wildlife.

Pollution, overfishing and overhunting have also caused a drop in biodiversity. Global climate change—the latest rise in the average temperature around the globe, linked to human activity—is also a factor. Warmer ocean temperatures damage fragile ecosystems, such as coral reefs. A single coral reef can shelter thousands of fish species and other sea creatures, such as clams and sea stars. Scientific research has linked climate change to human activities, like burning fossil fuels and clearing forests for agriculture.

Biodiversity can also be harmed by non-native species. When people introduce species from one part of the world to another, they typically have no natural predators. These non-native species thrive in their new habitat, often destroying native species in the process. Brown tree snakes, for instance, were accidentally brought into Guam, an island in the South Pacific, in the 1950s. Because brown tree snakes have no natural predators on Guam, they quickly multiplied. The snakes, which prey on birds, have hunted at least 10 of the island’s native forest-dwelling bird species to extinction.

People all over the world are working to protect the planet’s biodiversity. In the United States, the Endangered Species Act protects over 2,000 organisms that are in danger of extinction. In a historic move in 2021, African Parks relocated 30 white rhinos from South Africa to Rwanda’s Akagera National Park to establish a protected breeding population of white rhinos. Some organizations are working to create sustainably grown mushrooms to satisfy consumers as well as the local ecosystem. The National Geographic Photo Ark is a multi-year effort, led by National Geographic Explorer and photographer Joel Sartore, that aims to document every species living in the world’s zoos, aquariums and wildlife sanctuaries, inspire action through education, and help protect wildlife by supporting on-the-ground conservation efforts.

Around the globe, thousands of wilderness areas have been set up to conserve plants, animals and ecosystems. Local, national and international organizations are cooperating to preserve the biodiversity of regions threatened by development or natural disasters. The United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site program recognizes areas of global importance, such as the enormous wetland region of the Pantanal in South America. Many national parks, such as Glacier National Park in the U.S. state of Montana, protect biodiversity within the park by restricting extractive activities, such as mining and drilling. In Ecuador, the Jocotoco Foundation has purchased land across the country to protect the habitats of threatened wildlife. More than 16 biological reserves have been established, including areas in the Amazon rainforest and the Galapagos Islands. 

Marine protected areas (MPAs) have been established to preserve sea life. In the MPA around Australia’s Great Barrier Reef, no-fishing zones have helped fish populations thrive. People are also working to limit pollution and restore coral reef ecosystems in the area. As ecosystems become healthier, their biodiversity increases.