The eco-terrorists' plan to save the world in Godzilla: King of the Monsters was actually inspired by a real-life event. The efforts of the movie's humans villains is what drove the plot of the third MonsterVerse installment, and all the fighting that took place between the movie's four central Titans: Godzilla, Mothra, Rodan, and King Ghidorah.
In Godzilla: King of the Monsters, Emma and Madison were kidnapped by Jonah's eco-terrorists immediately after the emergence of Mothra. Monarch chased them all the way to Antarctica, where they awakened Godzilla's ancient nemesis, Ghidorah. Eventually, they discovered that this whole scheme was secretly orchestrated by Emma herself, who acquired Jonah's help after telling him of her intentions. Apparently, the plan from the beginning was to gradually wake up the Titans so that they could act as a "reset button" for the Earth. She believed that the destruction caused by unleashing the Titans would lead to the planet being healed of the damage that had been done it to by humanity.
During a Godzilla: King of the Monsters watch party hosted by Legendary, director Mike Dougherty mentioned in a tweet that Emma's plan was inspired by the reintroduction of wolves at Yellowstone National Park [via Twitter]. In 1995, gray wolves from Canada were brought into Yellowstone to help deal with the overpopulation of elk. This idea had been floated to Congress all the way back in 1966, but it was met with so much controversy and push-back from government officials and environmental activists that it was held up for years. When it finally did happen, the elk population was lowered and overgrazing was prevented.
Today, there is still concern about the danger posed to the region by the gray wolves, but most scientists feel that the plan worked out well for Yellowstone. As Dougherty pointed out, the elk population is still "thriving", but their numbers aren't the problem they once were. The controversy surrounding it and what resulted from it is not unlike the conflict that played out in King of the Monsters. The Godzilla: King of the Monsters credits revealed that, despite all the pain and destruction the eco-terrorists caused, Emma's plan did indeed work. Ethical issues aside, the MonsterVerse's Titans brought life back to several parts of the planet, just as Emma and Jonah hoped they would.
Essentially, what Godzilla: King of the Monsters did was take this real-life controversy and magnify the scale of it by replacing wolves and elk with humans and Titans. What may have sounded like a insane idea - especially to Monarch - turned out to be a sound plan. The Titans revived vegetation in multiple regions, took several animals off the endangered species list, provided a new energy source, and more. The idea that the villains of the movie were right about being able to save the planet is a fascinating concept, and one that the MonsterVerse was able to utilize in an interesting and effective way.