The Seeds of Time

Clio Finn is a Dive pilot on a troubled Earth in 2019. Public paranoia about the AIDS virus and its successors has led to the imprisonment of the "subversives" of the society (namely, drug users and gays) in forced labor quarantine camps known as quarries. Meanwhile, Earth itself is dying from a progressive lack of greenery, as the UV irradiation from a successively depleted ozone layer is killing off all the plants, and therefore the planet's ability to sustain itself.
To counteract this problem, the powers of Earth have decided that new greenery must be found on alternate worlds, to supplement Earth's dying stock with heartier, alien strains. But since faster-than-light travel is still unavailable, a new method must be found to achieve this. Enter time travel, in which a quick jaunt down through time can bring ships into the position of planets which had rotated through Earth's present position in the distant past, due to the galaxy's extended period of...