[ericffr]

Not every weed moves as fast as a virus. It might take decades before we realize that some species have disappeared, and in their wake, others are going too, and we are left with a homogeneous ecosystem where a new virus will come and be even worse (like the wheat rust which decimated the single species of wheat growing in North America). Obviously, Nature, being random, might cause destruction on its own (like when plants appeared and the high level of oxygen they produced killed earlier species), but this happens on millions of years. And sure, nothing prevents "Nature" from killing humans too. We are not more precious than any other species, from the Nature point of view.

[hutzlibu]

"we realize that some species have disappeared, and in their wake, others are going too, and we are left with a homogeneous ecosystem "

Species come and go all the time. Globalisation just made it a lot faster. So there will be imbalances and local system collapsing and temporary a dominating species etc., but alltogether the diversity of species will be increased, with fast global exchange. Because there are more candidates to fill a niche.

Local established ones still have a home bonus. Their DNA is adopted to the local climate and soil, unlike the invaders. They won't vanish anytime soon.

The thing really threatening diversity are monoculture fields with pesticides.