Early this century biologists recognised that some regions of the Earth were unusually rich in the number of unique species living there but also threatened by human activity. They called these regions ‘biodiversity hotspots’. Thirty-four are currently recognised, including the South-west Botanical Province in Western Australia. This area of about 360000 km2 is characterised by low soil fertility and a Mediterranean climate, with most rainfall during winter and dry summers. It is bounded to the south and west by ocean and by desert to the north and east. The climate, low soil fertility and isolation are the driving forces in the evolution of a diverse and unique biota. The province contains nearly 6000 described plant species (including about 4500 unique to the region) and 456 vertebrates (including 100 unique to the region). Although the invertebrate diversity is poorly described, it is likely to be extremely rich as well.

In this third theme of Environmental Biology we apply your understanding of the scientific method to the problems of classifying the diversity of life in biodiversity hotspots and elsewhere on Earth. You will also learn how the abundance and distribution of species is determined by interactions within and between species and between species and their environment.