Biodiversity


Edley island - Iceland © Yann Arthus-Bertrand

18/07/2008 5:25 pm

Figures change regularly, but the Earth is home to 1.75 million known species and 3.6 - 15 million others yet to be discovered. According to the latest report by The International Union for Conservation of Nature (IUCN), 12% of the world’s 10 000 known bird species are endangered or face immediate extinction, along with 23% of its 4 776 mammals, 46% of its fish, a third of all reptiles and 70% of all known plants. Among mammals, the 240 non-human primate species in existence are endangered and nearly half are threatened with extinction. Humankind is the cause of 99% of these threats. The IUCN estimates there were 24 endangered species in 1975, 1000 in 1985 and 16 306 in 2007, a year during which 785 of those species became extinct. A rich biodiversity makes it easier for life on Earth to adapt to environmental change. The study of biodiversity leads to many questions that are currently unanswered: How many species can be lost before the equilibrium of ecosystems becomes threatened? How resistant are ecosystems on human interference ? How will climate change affect biodiversity ?

Signed in Rio de Janeiro in 1992, the Convention on Biological Diversity defines biodiversity as « the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems, the ecological complexes and diversity within species, between species and of ecosystems».

Interdependance

In every ecosystem, living creatures including humans interact with one another as well as with the air, water and earth. Due to global warming – which leads to the displacement of species in both space and time (annual blooming seasons, for example) – and the disappearance of certain species, 60% of inter-species interaction has been eliminated (IUCN estimates, 2006). The more species there are in a functional group, the less vulnerable that group; a change in one of its components can affect the entire system. Inversely, saving one particular species requires ensuring that the entire ecosystem in which it lives functions correctly.

Convention on Biological Diversity

The Convention on Biological Diversity (Rio, 1992), adopted by the governments of 187 countries, sets three goals: the conservation of biological diversity, the sustainable use of constituent elements, the fair distribution of the advantages that come from the use of genetic resources for commercial and other purposes. By 2010, a significant reduction of the rate of loss of biodiversity should be obtained, contributing “to poverty alleviation and to the benefit of all life on Earth”. In Göteborg in 2001, the European Union States announced their strategy to “halt the loss of biodiversity by 2010” through prioritized actions.

At the end of 2008, a new global structure of scientific expertise on biodiversity should have been launched, based upon the model of the intergovernmental group of experts on climate evolution. Its aims will be to “provide independent and credible expertise”, to reinforce scientific activity, to raise international public awareness and to guide global and regional policies.

Is a sixth wave of extinctions on the way?

Scientists believe that five waves of extinctions have occurred since life first appeared on Earth. The most recent one took place 65 million years ago and is considered to have caused the disappearance of dinosaurs as well as a fifth of all other species. According to Lester R. Brown, "we are witnessing the preliminary stages of a sixth wave of extinctions. Unlike the other five, which were caused by natural phenomena, this one is attributable to humans. For the first time in history, […] a species has evolved to a point where it is capable of eradicating other forms of life. […] The number of species with which we share the planet decreases as the human population increases".

Factors like habitat fragmentation (by roads for example), heavy extraction in the environment, pollution and climate warming jointly contribute to today’s high rate of extinction, estimated to be between 1000 and 10 000 times higher than it has been over the last 60 million years. Humankind leaves an imprint on 83% of the Earth’s surface, a pressure that animals, plant species and microorganisms are less and less able to withstand.

A Vast Natural Capital

From a utilitarian viewpoint, ecosystems provide humankind with numerous goods and services – for what we eat (farming and fishing require a rich ecosystem), what we make (wood, rubber, wool, wicker fibre, combustibles etc.) and for our medicine: over half of all pharmaceutical substances are plant-based (only 5 000 of the world’s 250 000 flowering plants have been studied for potential therapeutic properties), or mushroom-based (penicillin and other antibiotics for example). Pollination, the spreading of seeds, insect population control and nutrient recycling all occur as a result of interactions between living organisms. When species disappear and biodiversity is reduced, nature cannot provide these services. When humans burn down the Amazon jungle, they are burning one of the biggest reserves on Earth of genetic information that could be used to multiple purposes, nutritional and medical in particular. The intrinsic value of many species – known and unknown – make the creation of a large-scale strategy to prevent their extinction essential.

The annual contributions of biological diversity to humankind are estimated to be between $29 trillion and $380 trillion. In the world’s poorest countries, natural capital is said to represent on average 25% of an individual’s wealth. This figure falls to 1% in rich, urbanized countries.

Birds

Of 9,775 known bird species, 70% are endangered and 1 212 face immediate extinction. Habitat destruction is a frequent cause, as is the case in Singapore where 61 species became extinct with the destruction of the country’s tropical forests. In England over the last thirty years, between 50 and 80% of all willow warblers, song thrushes and spotted flycatchers have disappeared, likely due to the destruction of hedges and thickets and the use of pesticides. In India and Southern Asia, three types of vultures – the long-billed, slender-billed and oriental white-backed varieties – were placed on the IUCN’s red list of threatened species in 2004; since the 1990s, populations have dropped by 97% due to an anti-inflammatory drug given to cows that the birds eat.

Mammals

The surface over which 173 emblematic mammal species have been traditionally distributed has been reduced by 50% over six continents. This stems from the cutting down of one-third of the Earth’s forest since the first agrarian societies appeared. All primate species are endangered and half of them face extinction due to habitat destruction and poaching. Bonobo populations have fallen 97%, from 100 000 animals in the 1980s to 3 000 today.

Fish and Coral

37% of the freshwater fish in North America’s lakes and rivers are either extinct or face extinction; since 1995, 10 species have disappeared. In Europe, nearly 80% of the region’s 193 known freshwater fish species are endangered. Climate warming could lead to the disappearance by 2100 of all the world’s coral and the ecosystem which it supports.

34 Biodiversity Hotspots

Scientists have drawn up a list of 34 biodiversity hotspots. These are regions that are particularly rich biologically speaking, which contain over 1 500 endemic varieties of vascular plants and which have lost at least 70% of their original habitat. While they only cover 2.3% of the Earth’s surface, these areas are home to 50% of all vascular plant varieties and 42% of land invertebrates. Nearly 38% of hotspots are located in protected areas such as parks and reserves, while 68% are in non-protected areas. Notable hotspots include the Mediterranean basin, the Cerrado in South America (which holds at least 10 000 plant varieties, 4 000 of which are endemic ), Madagascar, South-East Asia, the mountains of Central Asia, New Zealand and the islands of the Indian Ocean.

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