Dendrology--The Scientific Study of Trees A rich variety of trees can be found in this area due to its micro-climates. However the non-native trees are becoming more invasive and are crowding out local trees. Additionally the fresh water shortage in this area has caused many trees to be cut down, including the avocado trees which in the past had made Fallbrook, CA the Avocado Capital of the World. That distinction is no longer applicable as groves are being cutback due to high water costs.