Tarahumara Gentiles agriculture, Sierra Madres, northwest Mexico

The resource under consideration here is arable land. Arable land is a common pool resource in this case. On the dimensions of subtractability and excludability defined by Ostrom (2005), land is highly subtractble, but it is difficult to exclude resource users from land that is not continuously cultivated. In essence, cultivating a parcel of land means that there is less available land in the system; however, it is very difficult to exclude people from obtaining sufficient land for their subsistence needs. First, ethics demand that nuclear families have enough land to support themselves. Second, land fragmentation means that distance sharply increases the costs of continuously cultivating some fields. These fields become the subject of land claims from people who live nearer to the fields in question and can continuously cultivate the land. Though land rights are held by individuals, arable land is not a private resource because it is very difficult to exclude competing resource users from obtaining land sufficient for their needs