http://www.northwestweeds.nsw.gov.au/prickly_pear_history.htm -
May be a bit of a read, I'll cut to the relevant bit I was thinking about "By 1920, prickly pear was completely out of control, infesting some 60 million acres of land in New South Wales and Queensland. It was estimated at the time that the pear was spreading at the rate of one millions acres a year. "
They did fix it.
"The answer to the main prickly pear problem came in the form of biological control. As the amazing spread of prickly pear in eastern Australia was considered to be one of the botanical wonders of the world, its virtual destruction by cactoblastis caterpillars (Cactoblastis cactorum) is still regarded as the world's most spectacular example of successful weed biological control."
I am however talking more about growing tough succulent type species of plants for this purpose. Many succulent species of plants are just sooo amazing in times of drought, not only in just holding out for times of rain, but in still giving something back to the species around them in the form of nectar from flowers, or from offering biomass to be eaten or consumed by the species hanging on. Euphorbia is another potentially awesome plant for this purpose, the idea of the desert "hedgerow". Anyone else have some ideas as to species for such an approach? Imagine a hedge that is grown for this purpose and as it progresses over the land gradually changes the soil, improving it for the next "guild" of species behind it. A rolling, "terraforming" guild of species that could regreen deserts and provide shelter and food for the previously struggling species.
Cheers.