It's primary shitty third-worlders -- largely African and Arab -- that are spewing out children at an unsustainable rate. It's not until you get to number 43 that you get outside Africa and the Middle East. The world average is 2.55, just between spots 89 and 90. The first Western country on the list is the United States at number 126, with a birth rate of 2.05; and that's only because we have a shit-load of Mexicans here. Plus the US is the Western country with the most non-whites.
Number one is Niger with 7.19.
So if sustainability is an issue that you'd like to champion, take it up with the shitty third-worlders.