EzraS wrote:
If they turn Australia into one big forest that should take care of things.
As Magz mentioned Australia is quite arid.
We have a thin coastal northern plain that is sub-tropical and a thin southern coastal plain that is Mediterranean climate (the latter is where 80% of the population live) and the bulk of inland is arid/dry with little rainfall.
There has been various attempts to introduce farming and stock inland but that has just made things worse for the topsoil.
The other issue is the dry soils lack water so even if you introduce fast growing colonising species the lack of water means you can't establish lower plants that lock in nitrogen (mosses/lichen/fungi) so there will be little nutrition.
Arid plant species are low biomass and slow growing.