Schedule 4 land is in short, our most ecologically-prized land, including all 14 national parks.
On Saturday, tens of thousands of people marched up Auckland's Queen St in opposition to the mining of that land.
Estimates of the actual numbers vary, from 20,000 up to 50,000 people.
In any case, it was a huge turnout and one of the largest protests seen in New Zealand in recent years – around 10 times larger than the well-funded ‘March for Democracy’, for example.
Tonight we ask why were all these people there?
To help us answer that, two key players in the debate are in the studio - Lucy Lawless, the high-profile face of the Greenpeace campaign against Schedule 4 mining; and Gerry Brownlee, Minister of Energy.
Watch the video.