Koalas contributes the diversity of life because if there were no more koalas, the dingo would become endangered because, it would have nothing to eat. also, there would be much more empty eucalyptus trees, without koala living and eating in them. Humans impact the natural environment of koalas by,Taking koalas from there natural environment. Human also take the essential oil for the eucalyptus trees that they live in and koalas need the oil.