I remember walking up the slope of tall grass waving in the breeze of a cool South Dakota morning. I was a young graduate student on my first archaeological project, and we were conducting site surveys along the east shore of Lake Oahe in the summer of 1979.It was also my introduction to the wanton destruction of our archaeological heritage by looters.It was the Mobridge site, a prehistoric American Indian village established centuries ago along the Missouri River. The people had been drawn there by the arable and soft floodplain soils, where they grew maize, beans and squash and hunted bison on the prairies that seemed to extend forever outward from the river.As we walked among the large depressions left from the ancient lodges the ancestors of the Arikara tribe had constructed, we saw depressions of another kind.These were the large holes, carelessly dug with shovels, into the lodge depressions and burials. Piles of old back dirt nearby attested to the careless digging of artifact hunters seeking "treasures": pottery, arrowheads or other artifacts that could be bought, sold, displayed and savored, while the unwanted detritus of the collectors -- human remains, broken stone tools and destroyed house floors and storage pits -- were left behind as testaments to human greed.I still recall the words of one of my crewmates: "It looks like they threw hand grenades in here."It takes centuries or longer for archaeological sites to form and be trapped by natural forces that preserve them. They are finite resources, and once they are gone, they are lost forever. It only takes a few hours to destroy them.I cringe when I hear the word "treasure" applied to archaeological things. Treasure implies hunters, and treasure hunting is a mindset that says it's OK to take a shovel, or a back hoe or bulldozer, and gouge out a portion of an archaeological site to find buried artifacts like pots and grave goods. This is what archaeologists call time crime.Looting is profitable. Prehistoric pots can go for thousands of dollars at artifact shows, antiquities shops and art galleries. Many of those involved are commercial looters who will risk jail time because the payoff can be hefty. Others are methamphetamine addicts who provide local art dealers and collectors with illegally obtained artifacts. For others, particularly out west, it's a family tradition to go out to public lands and dig up prehistoric sites and collect the artifacts.While there may be a world of difference between a person who pockets an arrowhead for a vacation keepsake and the commercial looters who gutted the Mobridge site, it's a slippery slope.In Texas, the situation is serious because recent years of drought have dropped lake levels and exposed archaeological sites. In 2011, for example, Lake Whitney was hit hard. More than 30 people were arrested and fined for looting American Indian sites.A random study of 401 sites in 15 counties found that 7 percent of the sites had been looted/or collected from, and 2 percent had been vandalized. A survey of Texas archaeologists that I helped conduct in spring 2012 indicated that 98 percent considered looting and vandalism significant threats.We need to double down on our efforts at public education, from grade school to universities, and in civic organizations and local government, to instill in people a heritage ethic that sees value in the past and importance in preserving and protecting these resources.It's not just about protecting archaeological resources. It's also about changing an attitude about public lands that says, "I found it, it's mine."It's not "mine," it's ours. Every rationalization for looting robs the rest of us of our collective heritage.Jeffery Hanson of Keller teaches forensic archaeology at Texas Christian University and chairs the anti-looting committee of the Council of Texas Archaeologists.