SEEK Volunteer (volunteer.com.au/) and GoVolunteer (govolunteer.com.au/) list Australian volunteer roles by category and location; GoVolunteer showed more than 10,000 roles including 383 in Environment and Conservation and 543 in Education and Training when we checked. Small plastics non-governmental organisations (NGOs) often list bookkeeping, grant-writing, design and web roles here.
Honest caveat: GoodCompany (goodcompany.com.au/au) is a commercial platform whose listings we could not read; use it as a second search.
How to start: volunteer.com.au/