Farmland preservation is a joint effort by non-governmental organizations and local governments to set aside and protect examples of a region's farmland for the use, education, and enjoyment of future generations. They are operated mostly at state and local levels by government agencies or private entities such as land trusts and are designed to limit conversion of agricultural land to other uses that otherwise might have been more financially attractive to the land owner. Through different government programs and policy enactments farmers are able to preserve their land for growing crops and raising livestock. Every state provides tax relief through differential (preferential) assessment. Easements are a popular approach and allow the farms to remain operational. Less common approaches include establishing agricultural districts, using zoning to protect agricultural land, purchasing development rights, and transferable development rights. It is often a part of regional planning and national historic preservation. Farmland preservation efforts have been taking place across the United States, such as in Virginia, Minnesota, Maryland, Florida, and Connecticut.