Currently I am a MBA student with concentration in finance. For my Ph.D.,my interests are leaning toward environmental economics, sustainability economics. I have a very hard time in selecting a specific program which will accommodate my broad interest, since I do not like to limit myself to one specific area. It is my goal to work in the field of economic development with a strong concern of environmental protection on a global base.
I would appreciate any advice towards my search of a program or a University.
Thank you

I don't know enough about this field to make specific recommendations, but I would start looking at who has recently published research on the subjects that interest you, which should give you an idea of potential supervisors, then you could approach them to discuss your ideas? Or maybe your current tutors could advise you about the best institutions for this sort of research?

With a PhD, it's your project, so you should be able to steer it in the direction you want (with advice from your supervisor). And there are plenty of people doing interdisciplinary PhD projects with two or more supervisors, which might be what you need.

Have a look at the School of International Development (or whatever it's called now - used to be Development Studies) at the University of East Anglia. I'm sure there are other universities that might be suitable, but this is the only one I have personal experience of. Good luck with finding something! :-)