Some billions of years ago, life evolved the chemistry of photosynthesis. The planet was transformed in profound ways. For example, oxygen is a byproduct of photosynthesis. As plants extracted energy from sunlight, oxygen in the atmosphere began to rise, from zero to the present level. I suspect we would all call the oxygenated atmosphere natural, not artificial.
Within the last millions of years, one species of animal evolved sufficient neuronal complexity to give rise to an unprecedented level of intelligence, technology, and speech. A long-established predator-prey equilibrium was disrupted and human population soared. Anthropogenic carbon dioxide in the atmosphere increases. The Earth warms. Ice melts. Oceans rise. Natural or artificial?
I would say that it is both "natural" and inevitable that the planet will become- for better or ill- a human artifact. It already is a human artifact. It would be difficult to find any place on Earth that has not been transformed by human activity. It is too late to talk about a natural/artificial dichotomy. A human engineered Earth is no more artificial or less natural than an oxygenated atmosphere.
So let's dump the notion of humans versus the environment. Let's start thinking about what sort of Earth we want our descendants to inherit. Do we want an Earth with wild rivers? Mountain gorillas? Pristine seas? Healthy babies? We will not get the Earth we want by backing off and leaving "nature" alone, as if that were possible. We will only get it by making it, the way we might make a magnificent painting, a cathedral, or a symphony.
This is our destiny, like it or not, our Great Work. To contrive a planet that is a human work of art, that nourishes what is best and good in the human spirit, that is generous and caring of our fellow creatures. A planet that is a natural artifact.
Utopian? It is the only choice we have short of killing off six billion humans, surely an unnatural solution if ever there was one. Maybe nature will do the killing for us, through pandemic disease. In the meantime, we can stop wasting energy on a futile natural/artificial debate- humans vs.nature- and focus our creativity on planetary transformation that will involve science, technology, architecture, art and ethics.”