I have hired Environmental people back in the day and I would say timing is key. If you do a Master's straight away, then no it is a waste of time. You need to build your career up first before doing the Masters. It probably is good for people looking to make the jump from junior roles into management/leadership or maybe if you are focused on a hyper-technical niche environmental field.
More broadly, you need to be very intentional with education pathways. Given how expensive degrees are and the impact of HECS on your ability to get a mortgage, I would not be doing any degree (Masters or otherwise) unless it is directly linked to career progression and earning more money. Once you are working in environmental science, you will be able to gauge whether it is necessary.
Take me and my partner. Im in HR, she is in nursing. For her, a Masters is highly valuable for career progression especially because the Masters is quite technical and gives you skills beyond a regular nurse. Furthermore, a Nursing Masters is heavily subsidised (less than $5k). In contrast, a Masters in HR is not really very beneficial in terms of content and it will do little for your career progression (this is dictated mainly by experience in HR). Also a HR Masters is $60k - for that I could get a sports car which would probably be a better use of the money.