Plant life is an important part of terraforming – it releases oxygen via photosynthesis, and it grows the ecosystem.
But Mars is an arid place and plants need water, so conditions have to be changed. Even releasing some water is not enough. It needs to be made available in vast areas by introducing a water cycle. But we can’t wait for a natural water cycle, can we? Let’s create one by chemically initiating cloud formation and precipitation in the desired areas.
This will need to be continually supported, and the clouds will reflect some of the sunlight, but this loss of heat will be more than compensated by the great increase in plant growth!
When there is enough water, Cloud Seeding is a great way to get your ecosystem going. Especially your city-dwellers will enjoy the greenery growing in the nearby countryside (a city gets 1 VP for each greenery tile adjacent to it). It does decrease your MegaCredit production, but on the other hand it allows you to decrease an opponent’s heat production. A nice little way to interfere with their plans.