I believe some of this is due to changes in what types of olives were considered desirable. I'm not an expert, but some of the green stuffing olives have been

I believe some of this is due to changes in what types of olives were considered desirable. I'm not an expert, but some of the green stuffing olives have been replaced with different varieties. Also there are pests and diseases that are taking over, so newer resistant varieties are valuable replacements. Three years is also not a terrible time period compared to other nut trees that are grown in the area, specially if harvesting can be improved to be less manual. Some of the trees that are being replaced are 80-100 years old, so the wood can be a valuable resource that will cover the costs.