The ones that remain are tremendously compromised. Our benchmarks tend to be recent: personal experience within a lifetime especially.

For the oceans, little data predates the 1950s, after much damage was done. The degradation since is still staggering.

Over the past few centuries, let alone millennia, impacts have been massive. Few are evident directly, most require geological orother scientific inference ... buried traces of past ecosystems.

Don't worry, you wouldn't be not impressed for long.