We Have Already Terraformed Earth
The best evidence we have that terraforming will succeed if you judge it by its definition, which includes changing the ecology, atmosphere, and terrain, is the fact that it has already succeeded. Despite the fact that life first appeared on Earth and that is how humans evolved, we have still dramatically altered the planet's environment.
Humankind has continuously changed the landscape throughout history. Today's islands are only there because humanity created them in the oceans. We remove hills and mountains or construct new ones as we see fit. From space, you can view the city and road system. Lakes and rivers are redirected by dams. It takes place everywhere.
There is sufficient data to demonstrate how pollution has contributed to the major change in climate that has resulted from human involvement. There is a lot of information that suggests that climate change is real and that civilization has worsened its impacts, but people still wish to dispute this. Not to mention the gap in the ozone layer that we created a few years ago.
Therefore, if the concept of terraforming seems too science fiction, keep in mind that we have already done it here without even intending to do so. It must be simpler on another planet if we put in the effort, don't you think?
