It depends on the type of trees and the designation of the land. You can find out on the Cadastral what the designation of the land is and the type of trees 'supposed' to be planted there. Next go to the adjuntament with the details and ask, they may refer you to the 'Forestals' who may come and inspect. In most cases permission is given or may not be needed. Having said that, we bought a property where the previous owners had cut down a hectare of olives and were find '000s of euros and told to replant. Best to be sure... Your estate agent should help. Ask Maxine in Perello Properties if you are in that area.