Northern Territory does not require a specific structural landscaping licence, but structural work falls under home improvement, which means that you will require a home improvement licence to carry out any structural landscaping work.
The Australian building and construction industry is highly regulated, which results in the highest quality of international standards. The above processes outline how you can obtain your builder's licence by state.
It's good to remember that other options do exist. Experienced individuals need not be required to spend any unnecessary time in the classroom.