Some people worry about the match between an extinct clone or novel chimera and the modern natural habitat. Firstly, there are worries that introducing these new species could disrupt natural ecosystems, or the so-called "balance of nature".This was one of the many ethical themes in the novel and film Jurassic Park. Perhaps extinct animals are dead for a good ecological reason, so to speak, and "unnaturally" re-introducing them, particularly those that vanished long ago, would be futile or even pose serious global risks to life on the planet.