changing fields - Post physics PhD, how could I go about working in ecology, environmental science or earth sciences?

I am approaching the end of a PhD in experimental physics. My work involves building and operating experimental equipment, primarily optics, with some electronics. I also have a significant data analysis and theoretical component. I majored in physics at the same school (a pretty well known one) and graduated near the top of my class.

However, despite what might look like a solid set of credentials proving that I really want to build a quantum computer and the obvious next step being a post doc or industry position researching the same field, I have realized that my reasons for pursuing this line of research for so long were primarily to earn prestige and respect and not because I personally care about what I am doing (although it is wonderful that others do!). In doing this I have always enjoyed the process of science and the combination of thought and creativity with the practicality of lab work, however due to my lack of enthusiasm or motivation for the actual topic of research I have often been unhappy.

I am trying to remember what exactly it was that motivated me to be a scientist and what I used to enjoy. My undergraduate degree combined a broad span of sciences and I worked on lab biology projects during vacation. However, I am quite sure that my real lifelong passion lies somewhere in the direction of ecology, earth science or environmental science, with maybe a preference towards plant sciences or broader scale ecology.

I am really aware of how vague and naive that might sound. I grew up outdoors but I never took seriously the things I care about as a possible option I would be allowed to consider in my adult life. Following a few personal revelations I now know that this is the way to madness, and you are never going to be a successful researcher in a field you don't care about anyway!

There are many things I don't know right now, but I do know that I remain a scientist and I am very much not afraid of a great deal of hard work.

Given all this my questions are:

1. 
   

   How likely is it that I could make such a large career shift?

   
   


2. 
   

   How do I go about finding out more about what research is out there and what I might like specifically, given the very large quantity of research that exists??

   
   



3. 
   

   Does anyone know of any examples of people who have made similar shifts? (Partly just because right now I need the inspiration and belief I am not trapped!)

   
   


4. 
   

   What sort of things might I do directly after my PhD to build experience/learn more? Is trying to get field experience a good idea? Should I start to consider Master's programs?

   
   


5. 
   

   Am I completely as doomed as I think I could be?? :)