Most of the "need" concepts come back to "what does Nature actually use?" and "is this behavior/change/process persistent over generational/geologic time periods?" Then, the questions about humans become, "what allowed humans persist?", "what is different about humans?", "What are humans capable of contributing to their places, the greater nature of Nature, and each other?"
Everything else in Nature came about by taking advantage of available resources and contributing to the whole (extra offspring, beaver dams, nutrient cycling, etc), and because of random risks, a little extra has to be either hoarded (fat stores, nuts, etc) or saved 'just in case'. Harrari calls this "anti-fragility", but I call it "net future usefulness".
Earth as it is needs nothing because "life finds a way". Humans do, however, present one function that Nature didn't have before: the ability to model a future environment and also model versions of ourselves as part of the change (intentional participation in the future).
This may or may not be needed, but it is obviously useful. The test of Intentionality as necessary will be whether it transfers across time and species or to other planets that don't have it.
Humans, as we know ourselves in the here and now, mostly waste our ability to be intentional animals. Our systems are actually designed to poke, prod, blind and stimulate our primitive responses and prevent intentional, thoughtful behaviors. Marketers know this ("Coercion: Why we do what They say" by Douglas Rushkoff), and whenever they talk about "free choice", it probably isn't.
Humans are being murdered by our own systems of systems.
Can we change these circumstances to be truly intelligent participants? That really is where the complexity has to be forced back and cut down like the rabid dog that is the evil around us: unquestioned behaviors and sacred cows.