Protestors have lost their battle against a 1080 drop in the Hunua ranges - it's started.

Auckland Council said aerial application of bait containing the poison began this morning, with the first block of more than 21,000 hectares of forest covered by the operation.

It covers parklands, neighbouring Department of Conservation land, and some private land.

The Hunua Ranges, Waharau and Whakatiwai regional parks, and tracks within the neighbouring Mangatawhiri and Vining reserves are all closed, and will remain so for up to five days.