Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [236]
A final reason for my choosing Australia for this chapter is that it’s a country that I love, of which I have long experience, and which I can describe both from firsthand knowledge and sympathetically. I first visited Australia in 1964, en route to New Guinea. Since then I have returned dozens of times, including for a sabbatical at Australian National University in Australia’s capital city of Canberra. During that sabbatical I bonded to and imprinted on Australia’s beautiful eucalyptus woodlands, which continue to fill me with a sense of peace and wonder as do just two other of the world’s habitats, Montana coniferous forest and New Guinea rainforest. Australia and Britain are the only countries to which I have seriously considered emigrating. Thus, after beginning this book’s series of case studies with the Montana environment that I learned to love as a teenager, I wanted to close the series with another that I came to love later in my life.
For purposes of understanding modern human impacts on the Australian environment, three features of that environment are particularly important: Australian soils, especially their nutrient and salt levels; availability of freshwater; and distances, both within Australia and also between Australia and its overseas trading partners and potential enemies.
When one starts to think of Australian environmental problems, the first thing that comes to mind is water shortage and deserts. In fact, Australia’s soils have caused even bigger problems than has its water availability. Australia is the most unproductive continent: the one whose soils have on the average the lowest nutrient levels, the lowest plant growth rates, and the lowest productivity. That’s because Australian soils are mostly so old that they have become leached of their nutrients by rain over the course of billions of years. The oldest surviving rocks in the Earth’s crust, nearly four billion years old, are in the Murchison Range of Western Australia.
Soils that have been leached of nutrients can have their nutrient levels renewed by three major processes, all of which have been deficient in Australia compared to other continents. First, nutrients can be renewed by volcanic eruptions spewing fresh material from within the Earth onto the Earth’s surface. While this has been a major factor in creating fertile soils in many countries, such as Java, Japan, and Hawaii, only a few small areas of eastern Australia have had volcanic activity within the last hundred million years. Second, advances and retreats of glaciers strip, dig up, grind up, and redeposit the Earth’s crust, and those soils redeposited by glaciers (or else blown by the wind from glacial redeposits) tend to be fertile. Almost half of North America’s area, about 7 million square miles, has been glaciated within the last million years, but less than 1% of the Australian mainland: just about 20 square miles in the southeastern Alps, plus a thousand square miles of the Australian offshore island of Tasmania. Finally, slow uplift of crust also brings up new soils and has contributed to the fertility of large parts of North America, India, and Europe. However, again only a few small areas of Australia have been uplifted within the last hundred million years, mainly in the Great Dividing Range of southeastern Australia and in the area of South Australia around Adelaide (map, p. 386). As we shall see, those small fractions of the Australian landscape that have recently had their soils renewed by volcanism, glaciation, or uplift are exceptions to Australia’s otherwise prevalent pattern of unproductive soils, and contribute disproportionately today to modern Australia’s agricultural productivity.
The low average productivity of Australian soils has had major economic consequences for Australian agriculture,