There was a segment in Blue Planet II where they showed an infestation of sea urchins devastating a kelp forest. It turned out that because the predators that kept sea urchins in check--the sea otter--was over-hunted. I somehow suspect that the starfish infestation here might stem from a similar issue.
Every kid in Australia learns about these things. They seem to be linked to disintegrating conditions for the reefs. There is little hope for reefs, even if they are well managed, due to climate change. It is estimated that by 2050 there will be more plastic in the ocean by volume than fish. Truly we have trashed this planet.
It is incredibly sad indeed.
And it is mind-boggling how wide-spread ignorance and/or denial of these issues is.