Mr Howard said the message had hit home, and a large number of people had indicated they would attend on Sunday.
Mr Howard would not be drawn on what form any action might take.
He said it was important to send Evolution Mining and its backers the message that the company and mining is not welcome in Northland.
"Evolution is committed to leading environmental practices and if we are unable to identify a way to conduct our activities safely and without harm to the environment, we will not proceed," the Evolution spokesman said.
Evolution had completed and capped four drillholes at Puhipuhi to find if there are gold and silver deposits that can be safely and economically mined by underground methods, the project's chief geologist Jackie Hobbins said.
The collapse of an iron ore tailings dam in Bento Rodrigues, Brazil, in November last year - the event pictured on the poster - caused downstream flooding, 19 deaths and many injuries.
About 60 million cubic metres of waste-bearing sludge flowed into the Doce River, ruining water supplies to several cities and pouring toxic mud into the Atlantic Ocean.