In The Beginning

One of the problems with introducing magic into real world ecology is maintaining the balance. For every new species, the competition for resources gets more heated. Of course, nature would compensate by making food more plentiful, but you cannot have your cake and eat it too. Adding dragons alone to a world of say 400 AD earth would cause many issues. First of which is how many humans or cows or deer does a dragon eat per month? How many dragons per hundred square miles of land are required to maintain the species? Myths aside, you could not just insert 20 dragons in all of Europe and expect them to survive unless they hatched prodigious amounts of young every year.

Also, magic is a technology. Given a standard very old age category D&D dragon with maximum spells and bonuses, how long would it last today against modern weapons? Not long. How primitive does weaponry have to be for dragons to just stay ahead of the extinction curve, but not really flourish? Would the same dragon survive Agincourt if the English brought their bows? How about Caesar's Legions? Dragons good against ground troops with limited missile defense? What if a spellcaster was there? Multiple spellcasters? Dragons are the type of threat that smart rulers eliminate. To extinction.

So, if the civilization is capable of supporting a standard D&D group, then the population base is huge. For a population base to become huge, the territory must be tamed with no credible threats or hindrances to food production. Again, how many cows or sheep does a dragon eat? Kings would not tolerate wolves or any other predator. At what point in your timeline do dragons start to dwindle?

Ok, so maybe the dragons all live in the wild, outside the kingdoms of men, elves, dwarves, orcs, hobgoblins, centaurs, etc. Dragons were killed by heroes of the first kings of whatever country we are speaking of. That also goes for all other big baddies and evil races.

Of course, all these creatures of myth have to have their own homelands and ecologies to survive and flourish (just to fall to our adventurers later). That means less space for man. Elves, dwarves and even halflings need their own hard-won space.

Clearly, as these various homelands grow, these races will meet and conflict. How does this turn out? Do elves have superior magic and enslave the humans? Do dwarves have superior weapons and slay the others?

Sustainable balance is our quest.