Even if only one rabbit lived in each warren, the population would be enough to prevent the regeneration of native seedlings. There is a whole suite of plant species and dependent animals threatened with severe range-contraction or extinction. Rabbits make this problem worse. This doesn't take into account environmental damage and the effects on the sustainability of future landuse. Rabbits pressure native wildlife by competing for food, particularly under drought conditions.
Rabbits hinder the regeneration of native plant species.
Rabbits eat more seedlings per year in Australia than could be planted in a decade of tree-planting. They also select the most nutritious parts of plants. Rabbits can graze plants to ground level and eat roots, which sheep and cattle can't do because of their different grazing abilities. Areas heavily grazed by rabbits can lose all perennial plant species like bluebush and salt-bush which can lead to woody weed invasion, pasture instability and reduced carrying capacity of the land. Rabbits are implicated in the decline of many species of native animals.