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Biodiversity

9.2 Biodiversity (ESGBR)

Biodiversity is the term we use to refer to the variation in life forms in an ecosystem, biome or the entire planet. The term also describes the genetic wealth within each species, the inter-relationships between them and the natural areas in which they occur.

In this chapter we will focus on understanding the existing biodiversity and how scientists attempt to describe it. Biodiversity varies widely across the Earth, depending on temperature, rainfall, soils, geography and the presence of other species.

Biodiversity varies greatly across different regions of the Earth. In addition, biodiversity has also varied greatly across time. You will learn more about how biodiversity has changed over Earth's history in the following chapter: 'The History of Life on Earth'.

Scientists have described over \(\text{1,7}\) million of the world's species of animals, plants and algae. A rich species diversity is found in South Africa. With a land surface of approximately \(\text{148 000}\) square kilometres, representing approximately \(\text{1}\%\) of the Earth's total surface, South Africa contains\(\text{10}\%\) of the world's total known bird, fish and plant species, and \(\text{6}\%\) of the world's mammal and reptile species.

This natural wealth is threatened by the expansion of the human population and the increasing demand this places on the environment. South Africa as a country is a 'hotspot' of biodiversity, a term given to an area with a large biodiversity of plants and animals. The Karoo and the Cape are biodiversity hotspots in South Africa. South Africa has a wide range of climatic conditions and many variations in landscape as you learnt in the previous chapter. These various landscapes give rise to the biomes which allow a wide variety of life to survive. In the table below are listed some of the major plant, mammal, bird, reptile and amphibian, fish and insect species found in South Africa. You are not expected to know any of the numbers but they are given to you in order to illustrate the extent of biodiversity that exists in South Africa.

Life formDiversity and threatened species

Plants

More than \(\text{20 300}\) species of flowering plants occur in South Africa. One of the six most important areas of plant growth in the world is in the Western Cape. Most of the \(\text{2 000}\) threatened species of plants are found in the fynbos in South-West Cape.

Mammals

\(\text{243}\) mammals found in the region. Among the \(\text{17}\) threatened species in South Africa are the black rhino, pangolin, giant golden mole. The blue antelope and quagga have become extinct.

Birds

Of more than \(\text{800}\) bird species, \(\text{26}\) are threatened, including the penguin, Cape vulture, martial eagle and Cape parrot.

Reptiles and Amphibians

In total \(\text{370}\) reptiles and amphibians occur in the region of which \(\text{21}\) are threatened. Six of these are endangered.

Fish

\(\text{220}\) freshwater fishes occur of which \(\text{21}\) are threatened. There are more than \(\text{2 000}\) marine fish species.

Insects

\(\text{80 000}\) insects are known to occur. There are many insect species that are unidentified.

Most of the diverse species found in South Africa are endemic or indigenous to the country.

  • Indigenous means that these species originate or occur naturally in South Africa.

  • Endemic means that these species occur only in South Africa and nowhere else.