Return to Nature: Spread Forests when expending missionaries and diplomatic units, and passively based on influence. Forests created this way grant Culture and Faith to Fauna and the tile owner when worked.

When a missionary or diplomatic unit (Vox Populi) is expended, a forest is placed on a random tile in the target city's working radius, replacing any existing features. Tiles with resources, Natural Wonders, Great People Improvements, or Nature's Grace (see below) will not be selected.

A tile converted to Forest also gets a special improvement, Nature's Grace, replacing any existing improvements on the tile. This improvement gives +1 Culture and Faith, increasing to +2 with Philosophy and +3 with Fertilizer. In addition, on her turn, Fauna gets +1 Culture and Faith for each Nature's Grace worked by other civs and city-states.

In addition to being spread by missionaries and diplomatic units, each turn each city has a chance of a tile being converted to forest and receiving Nature's Grace. The percent chance is (Influence factor + trade route bonus - distance)

- Influence factor: The base percent chance for a forest conversion each turn. It is calculated differently depending on whether the city belongs to Fauna, another civ, or a city-state.
	For Fauna's cities, the influence factor is 10 * number of eras that have passed (0 for Ancient, 10 for Classical, 20 for Medieval, etc)
	For cities belong to other major civs, the influence factor is 10 * Fauna's influence level toward the city owner (0 for Unknown, 10 for Exotic, 20 for Familiar, 30 for Popular, 40 for Influential, 50 for Dominant)
	For city-states, the influence factor is 1/2 of Fauna's influence score on that city-state, capped at 25 (increased to 50 if allied).
- Trade route bonus: The percent chance is increased by 20% if Fauna has at least one trade route targeting the city.
- Distance: The number of tiles between the target city and Fauna's capital is subtracted from the final percent probability.

For example, given a city 12 tiles away from Fauna's capital, if Fauna has a trade route toward the city and is Popular with the city owner, the percent chance of a forest appearing around that city each turn is
	30 + 20 - 12 = 38%