https://en.wikipedia.org/wiki/Nauru
"Nauru had 12,511 residents as of July 2021.[6][7] The population was previously larger, but in 2006 the island saw 1,500 people leave during a repatriation of immigrant workers from Kiribati and Tuvalu. The repatriation was motivated by significant layoffs in phosphate mining.[116]
Nauru is one of the most densely populated Westernized countries in the South Pacific.[136] "
They mined a lot of phosphate (Bird guano) at one time.