I used to work with a young-looking Korean woman (who I later discovered was quite a bit older than me, although she looked my age!), who once commented to me how her generation was much taller than her parents and those before them. I asked her why she thought that was, and she answered without hesitation that it was because of the introduction of cow's milk to their culture via USA influence.
Definitely something to think about.
There has to be a way to do it vegan. If cows get their calcium from grass, perhaps we need to start eating grass. Where do deer get their calcium? Where do elk get theirs?
Mis-management of farmland is probably a major culprit these days. What farmer routinely fortifies his land with genuine minerals? Seems like collecting tons of volcanic ash from Mt. St. Helens' last eruption and using it to re-mineralize good farmland might be in order.
Let me add here that I (am pretty sure that I) read in The Cure For All Diseases that the vegetables which provide calcium (spinach, for example) don't do it well UNLESS JUICED. Something else to look into, I think.