Geography adds a spatial context to disciplines such as history, economics, population dynamics, botany, and so forth. History adds a temporal context to disciplines such as geography, economics, population dynamics, literature, and so forth.
Historical geography adds both a spatial and temporal context to studies.
In Australia most of the historical geography research tends towards 'human' geography related topics, but my work involves 'physical' geography. It could also be referred to as environmental or landscape history. For example, it is no good assuming that a particular land surface is part of the natural environment when it fact it is mining debris.