The biodiversity of New Zealand is one of the most varied and unique on earth due to its long isolation from other continental landmasses. Due to its long geological isolation since breaking away from the supercontinent Gondwana about 80 million years ago, New Zealand’s plant and animal life has developed down a unique evolutionary path.
Many of native plants and animals are endemic, that is, found nowhere else in the world. The level of endemism among New Zealand plants and animals is one of the highest in the world.
This isolation in the absence of mammalian predators for millions of years also meant that many of native species were virtually defenseless against attack.
When humans arrived in New Zealand, introduced mammals came with them: rats, possums, stoats, ferrets, weasels, deer, pigs, mice, cats, dogs and others. These introduced species quickly took a heavy toll as they prayed and browsed on New Zealand’s largely defenseless native species, or competed with them.