Sentience is central to the philosophy of animal rights, because sentience is necessary for the ability to suffer, and thus is held to confer certain rights.

That said, in my opinion, as it relates to optimal ecosystems, sentience at best might be a consideration.

Impact, contribution, etc. to an ecosystem would be a more natural measure.

Humans have a pretty horrible impact on, and contribution to, the ecosystem. Can I kill them? /s

Does that actually matter in and of itself beyond how it affects sentient individuals?

Yes, a health ecosystem requires non-sentient live for a number of reasons including that non-sentient is the source of genetically different sentient live. Diversity is critical for ecosystems.

How you determine something is sentient or not? That's a tough one.

The two can be combined:

https://en.wikipedia.org/wiki/Sentience_quotient

That's not the sentience we're talking about. From the article: >This is a non-standard usage of the word "sentience"...