Rick Allen and Dirk Spennemann, researchers from the Charles Sturt University , have warned that, if left to their own devices, olives can turn into huge woody weeds that could prove to be a stranglehold on the nation's farmers. Rick Allen believes that "strategies to prevent the escape [of feral olives] into the surrounding environment should be part of planning for new and existing commercial olive groves," although this is a little easier said then done. Attractive because of the energy source in the oil, many birds and mammals will pick up and carry olives, spreading the seed for many miles.