Biodiversity

Definition of biodiversity

The term "biodiversity" emerged in the second half of the 80s. It comes from a contraction of "biological diversity".

A definition of biodiversity was given during Rio's 1992 Earth Summit:

"The variability among living organisms from all sources, including, 'inter alia', 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." ⁽¹⁾

Thus, biodiversity is a comprehensive concept comprised of three levels:

• the diversity of living species, or specific (or inter-specific) diversity,
• the genetic variability within a species, or genetic (or intra-specific) diversity,
• the different organisations between species within the environment where they coexist, or ecosystem diversity.

Birth and death of species

Life appeared on Earth more than 3.5 billion years ago. Since then, the number of species has steadily increased. How? Through the phenomena of genetic mutations, rare and random, but regular. Usually, such mutations are useless or unnecessary, and can handicap individual beings. However, sometimes the opposite occurs; some mutations can provide an advantage (speed, more developed senses...). The theory of natural selection states that those creatures who are best adapted to their living conditions have better chances of survival and they transmit their genetic composition to their descendants. Thus, genes showing an advantage for a species spread within the population, while harmful genes tend to disappear. This natural selection is one of the foundations of the theory of evolution.

A species is a group of interbreeding individuals that are isolated from other living beings, from a reproductive standpoint. When two groups of individuals from the same species are separated (whether isolation is geographic or otherwise, and leads to a reproductive barrier), their distinct genetic evolution can make them inter-sterile. This leads to two species that grow apart from each other as a result of the accumulation of specific adaptations to their respective living conditions.

The extinction of species is inseparable from evolution: the adaptation of a species to its living conditions is very slow. Thus, when the environment changes quickly or extensively (temperature, appearance of a new predator...), this causes a major disruption within the living communities. We now estimate that, on average, a species lives between 1 and 4 million years: approximately 99% of all species that have lived on earth are now extinct ⁽²⁾!

Genetic Heritage

Numerous successive or parallel genetic mutations within a species as well as genetic mixing associated with reproduction lead to a set of unique individuals. Some adapt better to cold weather, others are more resistant to certain diseases or strong enough to protect their community from external threats. This multitude of characteristics within a single species, due to its genetic diversity, is one of the huge assets of biodiversity.

Although Noah might disagree, we understand that protecting biodiversity doesn't just mean preserving a few individuals from each species. Some even believe that the only "useful" biodiversity is genetic diversity ⁽³⁾.

Ecosystems: a fragile balance

An ecosystem is a group formed by a natural or artificial environment, a biotope, and the living organisms that live there, the biotic community. The elements that make up this ecosystem develop a network of interdependencies for the maintenance and development of life. Ecosystems vary widely in terms of size and lifetimes (puddle, forest...) and can be "nested" (puddle in the middle of the forest).

These interdependent links are a force for life because they can adapt to many different living conditions. But they also explain its fragility: the slightest change in the environment or one of its inhabitants can disrupt the entire ecosystem. Thus, in the early 20^th century, the disappearance of wolves, chased out of Yellowstone Park (USA), has resulted in rapid growth of the elk (large deer) population. These elk caused the decline of several tree species, starving the beavers which deserted the park. The artificial lakes created by the beaver dams and where the trout thrived then disappeared. This process could only be reversed by the reintroduction of wolves, which took place in 1995… ⁽⁴⁾

The services provided by biodiversity

Biological diversity doesn't just provide us with a pleasant and unique living environment. It provides mankind with a range of services that are key for its survival: climate and water cycle regulation, pollination, a supply of raw materials and food, disease prevention... In order to promote biodiversity, people have even been tried to quantify these ecological services: they were estimated at about 33 trillion dollars per year ⁽⁵⁾, more than twice the wealth produced by mankind!

However, even if it is important to find biodiversity indicators to guide major decisions, monetising nature is a real headache that is a source of much controversy. Can we really assign a value to a unique heritage that exists as a result of billions of years of gradual evolution?

Written by Florent Planas for "One year for the Planet" (translated by Anyword).

Find out more…

1. Article 2 from the Convention on Biological Diversity (1992)
2. Yves Sciama, Petit atlas des espèces menacées (Larousse, 2008)
3. Edward Wilson, La diversité de la vie (Odile Jacob, 1993)
4. Hélène et Robert Pince, La biodiversité et moi (Plume de carotte pour Nature et Découvertes, 2009)
5. R. Constanza, The value of the world’s ecosystem services and natural capital (1997)