Undeveloped real estate always has been a prized commodity. The great land rushes of the 1870s and 1880s displaced entire tribes of Native Americans and sent hundreds of thousands of settlers, prospectors, and land speculators spreading across the American frontier. That massive influx of people led to the settlement of towns like Guthrie, Okla., in a single day.

Problems with unbridled expansion would not become evident until much later, when easily accessible land suitable for commercial development began to vanish and builders set their sights on family farms. Today, like Guthrie 125 years ago, housing developments and sprawling shopping malls seem to spring up overnight.

The driving force is money. While it might be tempting to criticize land owners who "sell out" to developers, such complaints fly in the face of economic reality. Land almost always is worth far more as a development site than as rural agricultural property, and maximum realization of a farm’s economic potential usually requires a sale to developers. This equation becomes particularly important for future generations who might have less interest in holding onto a marginally profitable family farm.

Preserving farmland is frequently difficult, but not always impossible. One of the most successful tools for that purpose is a conservation easement, a legal procedure that allows a land owner to surrender development rights to land