Laukosargas Svarog has created the island of Svarga in Second Life. This is a fully-functional ecosystem, with rain, plants, and animals – all relying on each other for survival. If Laukosargas was to turn off the clouds, “the whole system would die in about six hours.” Laukosargas is a veteran game programmer, and has worked on Black & White, a classic “god game”. New World Notes has a great article on this.