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Biodiversity and climate change
Diversity is a fundamental characteristic of life itself.
Biological diversity or biodiversity is an expression used to describe the richness or variety of living organisms found in an area or type of environment, including both the number and frequency of genes, species and ecosystems.
Biodiversity is usually divided into three fundamental categories:
  • genetic diversity; the genetic variation within each species
  • diversity of species: the different species in a given area or habitat
  • diversity of ecosystems. The natural environment comprises many different types of habitats.
  1. The problem:
    There are limits to how much any biological resource can be exploited, and in many cases mankind is exceeding those limits.
    The elimination or change of habitats is the leading cause of loss of biodiversity.

    The introduction of non-native or alien species to the habitat also causes severe problems, like diseases and harder competition.
    (Example: Rabbits in Australia, Nile perch in Lake Victoria)
    Invasive or opportunistic species also mean harder competition.
    Invasive species often have no natural enemies or competitors in the new habitat.
    (Example: Water hyacinth in many shallow lakes in the tropics)

    Overhunting and overharvesting in addition to the factors already mentioned may also cause extinction of some species.
    Others become rare or disappear from the habitats locally.

    Human encroachments, like urban settlements, roads, clearcutting of forests, dams and mass tourism tend to fragment the habitats, making it difficult for species needing large, continuous areas of habitat to survive.

  1. Why conserve biological diversity?
    Species extinction is a natural part of the evolutionary process. Due to human activities, however, species and ecosystems are more threatened today than ever before in recorded history. The losses are taking place in tropical forests -- where 50 - 90 per cent of identified species live -- as well as in rivers and lakes, deserts and temperate forests, and on mountains and islands. The most recent estimates predict that, at current rates of deforestation, some two to eight per cent of the Earth's species will disappear over the next 25 years.

    While these extinctions are an environmental tragedy, they also have profound implications for economic and social development. At least 40 per cent of the world's economy and 80 per cent of the needs of the poor are derived from biological resources. In addition, the richer the diversity of life, the greater the opportunity for medical discoveries, economic development, and adaptive responses to such new challenges as climate change.
    Furthermore, it is well known to ecologists that the more species there are living in an
    ecosystem, the more stable the ecosystem is. Increasing the number of species, increases the productivity and the ability to withstand e.g.drought.

    To date, an estimated 1.7 million species have been identified. The exact number of the Earth's existing species, however, is still unknown. Estimates vary from a low of 5 million to a high of 100 million. Zoos and botanical gardens are unable to cater for more than a small fraction of the species already known. As the majority of species are still unknown, it is obvious that preserving a few species in a human made habitat is rather futile. - The only way to preserve the present biodiversity is by preserving the species in their original habitats. It is crucial to establish a sufficient number of large enough areas to sustain at least the more important habitats.



    The variety of life is our insurance policy. Our own lives and livelihood depend on it.

    Penguins in Boulder bay, SA. Photo: Å. Bjørke




  1. Climate change and biodiversity
    Many plant and animal species are adapted to a certain environment - their habitat.
    When climate changes quickly, many species are unable to adapt at the same speed.
    They either have to move and find a new habitat where they can survive, or die.

    When it gets warmer, they either can move towards the poles, to colder regions, or they can seek higher altitudes in the mountains. However, with human settlements, roads and various activities, there are several impediments to migration.
    Sooner or later, there are no places to go for some species.

    The extermination of species is now over one thousand times quicker than natural. The current rate of extermination is so severe that it can be compared to the extermination rates 55-65 million years ago, under the Paleo-Eocene termic maximum (PETM) and when dinosaurs died out.
    Receding tundra will change the North

    Sea turtle. Cape Town aquarium. Photo: Å. Bjørke

  1. Some studies conclude that increases in nitrogen deposition and CO2 content in the atmosphere will favor species that often are seen as invasive.
    Climate change is one of the pressures which is expected to result in the extinction of many species.
    Africa occupies about one-fifth of the global land surface and contains about one-fifth of all known species of plants, mammals, and birds in the world, as well as one-sixth of amphibians and reptiles (Siegfried, 1989).

    About one-fifth of southern African bird species migrate on a seasonal basis within Africa, and a further one-tenth migrate annually between Africa and the rest of the world (Hockey, 2000).

    One of the main intra-Africa migratory patterns involves waterfowl, which spend the austral summer in southern Africa and winter in central Africa .

    Palearctic migrants spend the austral summer in locations such as the Langebaan Lagoon, near Cape Town , and the boreal summer in the wetlands of Siberia .

    If climatic conditions or very specific habitat conditions at either terminus of these migratory routes change beyond the tolerance of the species involved, significant losses of biodiversity could result.

    Although the species involved have some capacity to alter their destinations, in an increasingly intensively used world the probability of finding sufficient areas of suitable habitat in the new areas is small.

    The current system of protected habitats under the Ramsar Convention is based on the present distribution of climate, raising the possibility of vastly changed habitat type and quality under climate change.


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