Having no natural predators increases population size.
Any population has the potential to produce more offspring than the environment can support.
Having no natural predators increases potential to produce more offspring than the environment can support.
having what increases the potential to produce more offspring than the environment can support?

no natural habitat
no natural prey
competing for resources
peachleaf willow
no natural owners
members of their own species
animals with backbones
no natural predators