About biodiversity

What is biodiversity?

Biological diversity - or biodiversity - is a term we use to describe the variety of life on Earth. It refers to the wide variety of ecosystems and living organisms: animals, plants, their habitats and their genes.

Biodiversity is the foundation of life on Earth. It is crucial for the functioning of ecosystems which provide us with products and services without which we couldn’t live. Oxygen, food, fresh water, fertile soil, medicines, shelter, protection from storms and floods, stable climate and recreation - all have their source in nature and healthy ecosystems. But biodiversity gives us much more than this. We depend on it for our security and health; it strongly affects our social relations and gives us freedom and choice.

Biodiversity is extremely complex, dynamic and varied like no other feature of the Earth. Its innumerable plants, animals and microbes physically and chemically unite the atmosphere (the mixture of gases around the Earth), geosphere (the solid part of the Earth), and hydrosphere (the Earth's water, ice and water vapour) into one environmental system which makes it possible for millions of species, including people, to exist.

At the same time, no other feature of the Earth has been so dramatically influenced by man’s activities. By changing biodiversity, we strongly affect human well-being and the well-being of every other living creature.

Biodiversity glossary
  • Biodiversity: the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part; this includes diversity within species, between species, and of ecosystems.
  • An ecosystem: a community of plants, animals and smaller organisms that live, feed, reproduce and interact in the same area or environment.
  • An ecosystem service: a service people obtain from the environment. Ecosystem services are the transformation of natural assets (soil, plants and animals, air and water) into things that we value. They can be viewed as provisioning such as food and water; regulating, for example, flood and disease control; cultural such as spiritual, recreational, and cultural benefits; or supporting like nutrient cycling that maintain the conditions for life on Earth. Ecosystem ‘goods’ include food, medicinal plants, construction materials, tourism and recreation, and wild genes for domestic plants and animals.


Where is biodiversity and how can we measure it?

Biodiversity is everywhere. It occurs both on land and in water, from high altitudes to deep ocean trenches and it includes all organisms, from microscopic bacteria to more complex plants. Although many tools and data sources have been developed, biodiversity remains difficult to measure precisely. According to the Millenium Ecosystem Assessment, the total number of species on Earth ranges from five to 30 million and only 1.7–2 million species have been formally identified.

But we do not need precise figures and answers to devise an effective understanding of where biodiversity is, how it is changing over space and time, what are the drivers responsible for this change, its consequences for ecosystem services and human well-being, and the available response options.

There are many measures of biodiversity. Species richness (the number of species in a given area) represents a single but important metric that is valuable as the common currency of the diversity of life—but to fully capture biodiversity, it must be integrated with other metrics.

IUCN has access to many different kinds of information on species. The Red List of Threatened Species™ provides global assessments of the conservation status of species. The IUCN Species Survival Commission, together with the Species Programme and their partners have developed a number of approaches to build up a comprehensive picture of the status and trends in species and biodiversity at global, regional and national levels.

How much is it worth?

Unlike foods and other products that we buy in supermarkets, many ecosystem services have no price tag attached to them. This means that the importance of biodiversity and natural processes in providing benefits to people is ignored by financial markets. If the full economic value of these services was taken into account in decision-making, the degradation of ecosystem services could be significantly slowed down or even reversed.

This is what the Economics of Ecosystems and Biodiversity (TEEB) study is working towards. The study aims at developing mechanisms to assess the value of nature, drawing attention to the global economic benefits of biodiversity and highlighting the growing costs of its loss. IUCN plays a central role in this work.

The results of the study have demonstrated clearly that the economic value of biodiversity and ecosystems is significant but still poorly recognized and inadequately reflected in public and private decisions. In order to build support for and guide efforts to reduce ecosystem degradation and halt biodiversity loss, more information and wider understanding is needed of the local and global benefits of ecosystem services, and of the full costs of restoration and conservation.

Click here to learn more about IUCN's work on greening business and the world economy.

  • The appliance of science

    The appliance of science

    Photo: GBRMPA/Paul Marshall

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  • Biodiversity


    Photo: © John Mendelsohn & © Rafael Rojas

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  • Biodiversity quiz

    Biodiversity quiz

    Photo: GBRMPA/Paul Marshall

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    Ogaswara Islands, Japan


Want to learn more?

Read IUCN's World Conservation magazine on biodiversity:

A world without biodiversity?