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10.3: Biogeography in Australia and the Pacific

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    21111
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    The relative isolation of Oceania defines it as a region but has also contributed to perhaps its quirkiest characteristic: its distinctive wildlife. Biogeography is a branch of geography that explores the spatial distribution of the world’s flora (plant life) and fauna (animal life). While every world region has its own, unique plants and animals, some of the creatures found in Australia and the Pacific are found nowhere else on Earth. A number of world regions have an impressive degree of biodiversity, meaning there are a wide variety of species present. These regions are generally located in the tropics. British biogeographer Alfred Russel Wallace was one of the first to try and determine the boundary of Australia and Southeast Asia’s unique plants and animals in the 19th century.

    Geography is more than the where, however, but is also a discipline that asks “Why?” Why does Australia have such unique, and frankly a bit frightening at times, flora and fauna? Why are monotremes, mammals that lay eggs rather than give birth to live young, only found in the isolated region of Australia and New Guinea? It is the isolation of this region that’s key. 200 million years ago, Australia was situated on the far-reaches of Pangaea, the last supercontinent (Figure \(\PageIndex{1}\)). Around 175 million years ago, Pangaea began to break apart. During the same time period, the earliest mammals were evolving, diverging first from egg-laying reptiles and then continuing to adapt and change. Early egg-laying monotremes were found throughout Pangaea but eventually went extinct in the other world regions, out-competed by more evolutionarily advanced mammals. Australia and New Guinea, however, broke away before more advanced mammals arrived, and thus monotremes remained. The only modern monotremes are the platypus and the echidna.

    clipboard_e08d7e5fd916dfca725454c8b7ae6dad1.png
    Figure \(\PageIndex{1}\): Map of Pangaea with Modern Continental Outlines (© User:Kieff, Wikimedia Commons, CC BY-SA 3.0)

    In addition to monotremes, Australia is home to the world’s largest and most diverse array of marsupials, mammals who carry their young in a pouch. A number of marsupials are also found in Central and South America and just one species lives in North America: the Virginia opossum, more typically referred to as a “possum.” In Oceania, well-known marsupials include the kangaroo, koala, wombat, and the Tasmanian devil. The Kangaroo in particular is a widely used symbol of Australia and kangaroo meat, though controversial, can be found throughout Australia.

    Australia is not just home to cuddly marsupials like koalas, wallabies, and quokkas, though. It is also home to some of the world’s deadliest creatures. There are more deadly snakes in Australia than in any other country in the world including the taipan, considered by some to be the world’s most venomous. An episode of the children’s television show “Peppa Pig” was actually banned in Australia because it featured a “friendly spider” and local officials believed it would send the wrong message to Australian children in a country where spiders can be deadly. Offshore, Australia’s box jellyfish can kill simply by the pain inflicted by its sting which can send the body into shock.

    Another key area of biodiversity is New Zealand, particularly in terms of its flora. Its isolation allowed for species of trees that have remained relatively unchanged for the past 190 million years. Several species of birds in New Zealand, such as the moas, went extinct due to hunting shortly after humans first arrived in the region. Few mammals existed in New Zealand before human settlement and the arrival of the first mammals here, such as rats and weasels, led to widespread extinctions of native species that had never had to evolve to compete with these predators. Rabbits in particular proved to be a particularly troublesome invasive species, which refers to a species of plant, animal, or fungus that is not native to an area but spreads rapidly. Early settlers to New Zealand brought rabbits for fur and meat, but the high reproductive capacity of rabbits quickly proved troublesome and by the 1880s, rabbits were having a considerable negative effect on agriculture. The solution in the late 19th century was to introduce stoats, ferrets, and weasels, natural predators of rabbits. Unfortunately, these species proved devastating to local bird species and had only minimal impact on the increasing rabbit population. Cats were similarly introduced, but they too caused the extinction of several bird species and a native bat. (The children’s story about the old lady who swallowed the fly comes to mind.) These species are still seen as some of the biggest threats to New Zealand’s wildlife.

    Biogeography:

    a branch of geography that explores the spatial distribution of the world’s flora and fauna

    Biodiversity:

    having a wide variety of species present in an are

    Monotremes:

    an egg-laying mammal

    Invasive species:

    a species of plant, animal, or fungus that is not native to an area but spreads rapidly


    10.3: Biogeography in Australia and the Pacific is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by Caitlin Finlayson.