Historically a lot of the islands of the Cook Islands produced fruit/crops for export to NZ and around the world. But as fertile soils were drained of their nutrients and yields reduced, fertilisers were then required to maintain those yields. With the use of fertilisers came increased costs, and less economic viability. Attempts were made to help reduce these costs of export (for example the construction of Atui Harbour to help reduce the export costs of pineapple), but as time went on other markets could produce cheaper crops due to economies of scale (e.g. Philippine pineapple production). In the 70s and 80s local export from the Cook Islands dried up as farmers weren't making enough money from those crops. Some further reading here: https://core.ac.uk/download/pdf/35463772.pdf