nauru was one of three great phosphate rock islands in the pacific ocean (the others were banaba (ocean island) in kiribati and makatea in french polynesia). the phosphate reserves on nauru are now almost entirely used up. phosphate mining in the central plateau has left a barren terrain of jagged limestone pinnacles up to high. mining has stripped and devastated about 80 per cent of nauru's land area, and has also affected the surrounding exclusive economic zone; 40 per cent of marine life is estimated to have been killed by silt and phosphate runoff.