[nroets]

Let's say the tree lobster on Lord Howe is replaced by rats and cats. Then Lord Howe lost one specie and gained 2, for a net gain of one specie. So local biodiversity increased. The planet lost one specie, so global biodiversity decreased.

[xanthopan]

I'm sure Lord Howe lost much more than just one species of tree lobster.

[hampizza]

You're right. go down to page 26 of this pdf: http://www.environment.nsw.gov.au/resources/threatenedspecie...

Makes for scary reading!

[yareally]

That assumes nothing else in the ecosystem was dependent on the lost species.

[xenihn]

You think the rats won't continue to displace other species? And what happens to the rats when there's nothing left to displace? And then what happens to the cats?