There have actually been many times when changes in geography and climate have occurred over the timescales of human civilization. Rivers change course, little ice ages happen, fertile soils are depleted, coastlines recede and put coastal cities inland or underwater and so on. Plus now we’re hitting the whole climate change era in earnest, which will have plenty of impact.
What he’s saying is definitely not wrong though on the whole, geographical variability and changes are at most one of many factors that shape the material conditions of societies.