Natural assets with significant economic value differ from developed natural assets in that they are generally used as raw inputs into production in their natural state, either as intermediate products or as investments. For example, uncultivated biological resources, such as tuna harvested from the ocean, are included as environmental assets, whereas cultivated biological resources, such as rockfish raised on a fish farm, are included in developed assets. Other categories in environmental assets are uncultivated land, unproved subsoil assets, water, and air.
Cultivated land such as agricultural land, parkland, and land underlying buildings is included in developed natural assets, whereas uncultivated land such as wetlands and forestland (not included as timberland) are considered natural environmental assets. The agricultural land must be developed before it can be used as farmland, whereas wetlands are used, for example, for their disposal services in their natural state by the economy. Water, which is subdivided by type, and air also provide services to the economy in the form of recreational and waste disposal services.