72,000 wild horses and burros. According to who, exactly?
So many holes in this argument, it's difficult to know where to begin.
You're aware, aren't you, that wild horses and burros are biological entities, subject to the same frailties as deer, moose, elk, etc? 
For example - a severe, five year long drought? During which time, apparently, even with a lack of water and forage, they still managed to triple their populations, subsisting on sand and sagebrush.
Of the thousands of infants born in a season, 50% will not survive to their first birthday. Not a BLM declaration, of course. This is the result of several independent reports. But as hard as it is for the Bureau, et al, to accept, wild horses and burros absolutely DO die. To the tune of at least 10- and in years of environmental catastrophe - 25% mortality.
The higher the population, the more animals die. 
Maybe before stringing them up, en masse, a little verification outside the BLM box might be in order?