The dog fence in Australia has been erected to keep out hostile invaders, in this case hordes of yellow dogs called dingoes. The empire it preserves is that of wool growers. Yet the fence casts a much broader ecological shadow. For the early explorers, a kangaroo or a wallaby sighting marked a noteworthy event. Now try not to see one. Without a native predator there is no check on the marsupial population. The kangaroos are now cursed more than the dingoes. They have become rivals of sheep, competing for water and grass. The State Governments now cull more than three million kangaroos a year to keep Australia’s natural symbol from over running the pastoral lands. The marsupial population is up in Australia because :

The dog fence in Australia has been erected to keep out hostile invaders, in this case hordes of yellow dogs called dingoes. The empire it preserves is that of wool growers. Yet the fence casts a much broader ecological shadow. For the early explorers, a kangaroo or a wallaby sighting marked a noteworthy event. Now try not to see one. Without a native predator there is no check on the marsupial population. The kangaroos are now cursed more than the dingoes. They have become rivals of sheep, competing for water and grass. The State Governments now cull more than three million kangaroos a year to keep Australia’s natural symbol from over running the pastoral lands. The marsupial population is up in Australia because :