You must have some plan for job or some profession after doing this particular PhD. This has been not seen clearly in your question. Anyway regarding doing PhD from a recognized institute is a good proposition and the discipline is also very contemporary. Only thing is if you get a good subject for your thesis and of course a good and reputed guide you can complete it with flying colours.
After completing the thesis and its award you can look forward to teaching line in general and joining an organisation which requires that type of specialization in particular.
There are particular type of job opportunities for this type of qualification and some of them are -
Environmental manager, Environmental consultant, Nature conservation officer, Water quality scientist, Recycling executive, Sustainability consultant, Nature conservation officer, Waste management executive and Environmental education officer.
Those are some areas of interest and if you have plans to start your own consulting or join some existing entrepreneurship entity then that is fine.
Knowledge is power.