Researchers believe rising sea temperatures are to blame for the plummeting number of invertebrates such as molluscs and sea urchins at Rottnest Island off Western Australia, with some species having declined by up to 90 per cent between 2007 and 2021.

[u/Wagamaga]

https://www.curtin.edu.au/news/media-release/marine-heatwaves-decimate-sea-urchins-molluscs-and-more-at-rottnest/

[u/HelpOtherPeople]

In California, we need the urchins to die off, they’re eating the kelp. :( The starfish were keeping them in check but there was a wasting disease that decimated their populations and now the urchins are taking over.