Much of El Salvador's crop production is in mountainous areas with gradients over 15%. The main crops are shade-grown coffee, sugar cane, citrus and other fruit trees, and staples for local consumption, including maize, beans, rice, and sorghum. The latter are produced on small-scale subsistence farms in mountainous zones (0.3–2 ha per farmer) characterised by intensive use of the soil and a lack of conservation practices. Until now, most rural development projects have used incentives to mitigate the effects of the resulting environmental degradation. Records for Central America show that approximately 86% of soil and water conservation projects use incentives. Nevertheless, it is rare to observe spontaneous diffusion and medium- or long-term adoption of the technologies promoted through incentives on a significant number of farms or larger areas. Most technologies are implemented locally by a few farmers and are abandoned as soon as the project terminates. Therefore, efforts are now being made in Central American countries to institute payment for environmental services (PES).