Vast acreage was planted in sugarcane until the mid 90's when the industry completely left Hawaii. That land was sold off cheaply and many new owners bought it to hold and have not put it back into agriculture. Just sitting there growing weeds. Also many parcels are 20 acres and people build one little house on it and ignore the rest of the land. There is a tax break given to any residential land used for agriculture which in practice means people lease their land to contract farmers who grow sweet potatoes or ginger for one year then leave it fallow for years after that due to pests. All in all a huge waste.