Class L: Marginal planets are typically rocky planets with a
nominal ecosystem consisting almost entirely of plants. It is
extremely uncommon for higher forms of life, such as animals and
humanoid life, to evolve naturally on marginal worlds. A
contributing factor in this lack of fauna is a limited supply of
surface water (generally more than 20% of the surface is covered in
water, otherwise the planet is Class H: Desert).

While the limited water supply prevents widescale colonization,
marginal planets can easily support modest humanoid populations,
and a small amount of terraforming can easily transform them into
robust and completely habitable worlds.