Our biodiversity hotspot
What's so special about the Gondwana Link area?
To help make decisions about where conservation work can be most effective, various organisations like Conservation International and individuals like the British ecologist Norman Myers, have identified the areas of the world in which there is the most diversity and the most endemism (species that are found nowhere else). Australia is one of these areas!
Further studies identified the world’s biodiversity hotspots: the world’s most biologically rich but most threatened places (see map below). Southwestern Australia is one of these. The 34 hotspots account for a staggering 90% of the species on earth, with a high proportion of the world’s endemic species – over 50% of the world’s plant species and 42% of the terrestrial vertebrate species. Yet the combined area of remaining habitat in all the hotspots covers only 2.3% of the earth’s surface. It should be noted that the figures don’t reflect what has been described as “the other 99%” of the biodiversity – the fungi, insects and microscopic organisms that are so poorly studied and understood. (STOP PRESS: the north eastern Australia rainforests have recently been added to this list - welcome aboard folks!)
Within the southwestern Australia biodiversity hotspot, areas of particularly high plant species richness and endemism have been identified by Professor Stephen Hopper and Dr Paul Gioia by mapping ‘isoflors’, or areas of similar species numbers.
Species richness in 0.25° latitude by 0.25° longitude grids in the South West Botanical Provinces and Districts. Species distribution was determined from specimen labels at the Western Australian Herbarium and adjusted for collection intensity. From: SD Hopper & P Gioia (2004) The Southwest Australian Floristic Region: Evolution and Conservation of a Global Hot Spot of Biodiversity Annu. Rev. Ecol. Evol. Syst. 2004. 35:623–50.
So, in a nutshell, Gondwana Link is taking place in
one of the world’s 17 Megadiverse countries,
in one of the world’s 34 global biodiversity hotspots,
linking across several of the main centres of plant richness end endemism,
AND it’s doing that by connecting the largest areas of intact natural habitats remaining in that global biodiversity hotspot.
And according to Conservation International’s assessment, southwestern Australia is one of the biodiversity hotspots with the most opportunities to save species and habitats because of our relatively low population pressures. So it makes perfect sense to concentrate a large conservation effort here to protect those habitats and restore what we can of the losses.
It makes even more sense when you consider that Gondwana Link is also taking place along an important climate gradient from the wetter, cooler southwestern corner to the drier interior – a direction of major evolutionary shifts in the past and quite likely to be repeated again under more rapid climate shifts.
But why is Australia, and this part of Australia in particular, home to so many species, and why are they so different from those found anywhere else in the world?
There are several reasons for the differences from other places: one is that Australia has been isolated from the rest of the world for about 45 million years since it finally separated from Antarctica and began its northward drift. This drift eventually took Australia to latitudes where the rainfall is much lower for the majority of the country and can be very variable. This is compounded by the influence of the oceans and currents on climate, particularly through the influence of the El Niño-Southern Oscillation (ENSO) effect. Species had to evolve to deal with this, and a lot of the diversity and endemism is seen is those organisms that coped best with the conditions, animals like the reptiles, and plants like the eucalypts and acacias.
Then there are the low nutrient soils: much of Australia’s surface - and this is especially true for the southwest – is comprised of flat surfaces and very low nutrient soils. This is due to the surface being one that has resulted from stability and weathering, rather than the upheavals and rejuvenation of the land’s surface that comes from events such as volcanic eruptions, the major faulting and folding that lead to mountain building, or glacial activity. So it is thought that plant species here have evolved on ancient surfaces and have therefore had far longer to evolve into diverse forms that are highly specialised – and still evolving.
The different conditions under which species evolved here means that there are also many differences between the ecological processes operating compared to those that dominate the landscapes in other parts of the world. For example, with nutrients being so limiting, both plant and animal species have evolved mechanisms to make the most efficient use of their environments. A good example is one of the Fitzgerald River National Park’s iconic species, the Royal Hakea (Hakea victoriae) which recycles nutrients within its leaves resulting in spectacular colour changes during the life of the plant and its individual leaves. Naturally, the low nutrient status of the plants means that the browsers and grazers amongst the fauna must also adapt, and one of the common means is to have very low metabolic rates.
Australia’s plants and animals have evolved many mechanisms to cope with the variable and often extreme climatic events, the most frequent being drought. For example, there are several freshwater crayfish with very restricted ranges in the far southwest living in burrows that can be several metres deep and reach to fresh groundwater. The Gondwanan relic, the salamanderfish (Lepidogalaxias salamandroides) also practices aestivation (or burying itself in the mud), as do some of the frogs. They can survive for some time until there is enough water available to resume their life above ground. Drought adaptations will often equip a plant or animal to deal with another of the major disturbances that is experienced in Australia – fire.
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