What are the "physical" parts in my topic?

It is not easy to do a real interdisciplinary research, especially when you are all along and have less than 3 years' time.  However, I do not think a purely human geographic study would be suitable for my study, or worth a PhD.  I need to attempt an approach to integration of physical geography study in social-economic studies.

A precondition to this is to find out what are the physical part in the study.  For me it is something about ecology, maybe animal behaviour as well.  However, it is still too wide and too vague.  If I want to determine the resilience of the system, what environmental information do I need?  To answer this question, I think, is to determine the physical part of my research.

Such environmental information may include environmental impacts in terms of vegetation and land cover change, hydrology, soil and nutrient; environmental responses in terms of livestock population dynamics, recovery from disasters, and so on.  Rebuilding environmental history will also involve physical geography methods such as laminate and glacial sediment analysis.

How I get this physical information is another problem.  It would be impractical to try to obtain detailed ecological information for every aspect of the grassland.  Thus a study of which factors to consider and a scoping process are necessary before I go to the field.