Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [248]
There have been more or less similar histories in most other food-producing areas of Australia. What made so many initially profitable food-producing properties become less profitable? The reason is Australia’s number-one environmental problem, land degradation, resulting from a set of nine types of damaging environmental impacts: clearance of native vegetation, overgrazing by sheep, rabbits, soil nutrient exhaustion, soil erosion, man-made droughts, weeds, misguided government policies, and salinization. All of these damaging phenomena operate elsewhere in the world, in some cases with even greater individual impact than in Australia. Briefly, these impacts are as follows:
I mentioned above that the Australian government formerly required tenants leasing government land to clear native vegetation. While that requirement has now been dropped, Australia still clears more native vegetation per year than any other First World country, and its clearance rates are exceeded in the world only by Brazil, Indonesia, the Congo, and Bolivia. Most of Australia’s current land clearance is going on in the state of Queensland for the purpose of creating pasture land for beef cattle. The Queensland government has announced that it will phase out large-scale clearing—but not until 2006. The resulting damage to Australia includes land degradation through dryland salinization and soil erosion, impairment of water quality by runoff of salt and sediment, loss of agricultural productivity and land values, and damage to the Great Barrier Reef (see below). Rotting and burning of the bulldozed vegetation contribute to Australia’s annual greenhouse gas emissions a gas quantity approximately equal to the country’s total motor vehicle emissions.
A second major cause of land degradation is overstocking of sheep in numbers that graze down the vegetation faster than it can regrow. In some areas such as in parts of the Murchison District of Western Australia, overgrazing was ruinous and irreversible because it led to loss of the soil. Today, now that overgrazing’s effects are recognized, the Australian government imposes maximum stocking rates for sheep: i.e., farmers are forbidden to stock more than a certain number of sheep per acre on leased land. Formerly, however, the government imposed minimum stocking rates: farmers were obliged to stock a certain minimum number of sheep per acre as a condition of holding the lease. When sheep stocking rates first became well documented in the late 19th century, they were three times higher than the rates considered sustainable today, and before documentation began in the 1890s sheep stocking rates were apparently up to 10 times higher than sustainable rates. That is, the first settlers mined the standing crop of grass, rather than treating it as a potentially renewable resource. Just as was true for land clearance, the government thus required farmers to damage the land and cancelled leases of farmers who failed to damage the land.
Three other causes of land degradation have already been mentioned. Rabbits remove vegetation as do sheep, cost farmers by reducing the pasturage available to sheep and cattle, and also cost farmers through the expense of the bulldozers, dynamite, fences, and virus release measures that farms adopt to control rabbit populations. Nutrient exhaustion of soils often develops within the first few years of agriculture, because of the low initial nutrient content of Australian soils. Erosion of topsoil by water and wind increases after its cover of vegetation has been thinned or