Exiles of ColSec by Douglas Hill, 1984.
This is the first book in a sci-fi series, the ColSec Trilogy.
In the future, Earth is controlled by a repressive government that sends criminals and dissidents (especially strong youths) into exile on other planets. These exiles are assigned to different planets to form colonies by ColSec (short for Colonization Section). The government then reaps the benefits of whatever resources the colonists find or produce, all while keeping them at a safe distance to prevent them from starting rebellions.
The system works very well as far as the government is concerned, but this time, things don’t go according to plan. The ship of dissident colonists destined for the planet Klydor crashes, killing most of the people on board. There are only six survivors, all teenagers:
Cord — A boy from the Scottish Highlands, an area more wild and uncontrolled than most areas of Earth.
Samella — From the area once known as Minnesota (or possibly Manitoba, even the people who live there aren’t sure of the old name). She lived as part of a commune until a harsh winter brought them to the brink of starvation, and her own family sold her into slavery. On Klydor, she begins to discover that she has ESP.
Heleth — From the Bunkers, the old Underground tunnels under Old London. She belonged to a gang called the Vampires, who purposely dye their skin jet black to blend into the darkness of their hidden homes.
Jeko and Rontal — a pair of Free Streeters, gang members from Limbo, in the area of what was once Chicago.
Lamprey — The most dangerous of all, a homicidal maniac who quickly forces the others to do his bidding for fear that he will kill them.
These few survivors are alone on a strange world, where they will have to figure out how to continue to survive and somehow create a life for themselves . . . if Lamprey doesn’t kill them all first. The other rebels from Earth decide that they will have to stage a rebellion within their own group to get rid of Lamprey, and Cord finds himself appointed to be their leader.
But, it turns out that they aren’t quite as alone on Klydor as they thought, and possibly the most formidable creatures on the planet might be . . . the trees.
This is largely a story of survival as the colonists work together to protect themselves from Lamprey and uncover the secrets of their new world that will allow them to survive. Samella’s ESP is what allows them to realize the truth about the forest where they have crashed.