Wild horse sense

What could be more authentically Western than a herd of mustangs thundering across the range as windblown tumbleweeds roll across their path?

A lot of things, actually.

Both horses and tumbleweeds, or Russian thistle, were introduced from overseas, and both wreak environmental havoc. The thistle was imported accidentally on ships carrying grain; the horse's history goes back hundreds of years to the first Spanish explorers.

At least 67,000 feral horses and burros now live under the supervision of the U.S. Bureau of Land Management in 10 Western states from California to Montana, 31,000 of them corralled at a cost of $40 million a year. The rest roam freely and, wildlife advocates complain, damage range land by cropping grass too low to the ground and trampling natural watering holes.

A 1971 law protected the horses' ability to run free. As the heroes of such popular-culture favorites as "Spirit: Stallion of the Cimarron," they are rightly called majestic, but they also constitute a thorny wildlife issue.

They arouse impassioned arguments about what's natural in a world where nature has been thrown badly out of kilter. Some horse advocates contend that the equines should be considered legitimate wildlife, as opposed to a domesticated species that's gone feral, because they have been here for hundreds of years; others contend they are native to the region because horses originated in North America, with some migrating over the Bering land bridge to Asia. The North American horse became extinct about 10,000 years ago when the other large mammals of the Ice Age, such as the woolly mammoth, also died out. Their Asian cousins survived and eventually spread west, becoming the domesticated Iberian horses that were brought to North America by explorers starting in the 15th century, completing an evolutionary trip around the world.

The trouble is that during the 10,000 years without horses, North America evolved without them, and they no longer have a place in the natural environment. Arguing that mustangs have a right to open land because their remote ancestors lived here is like saying elephants should roam California because woolly mammoths used to frequent the La Brea tar pits.