A plan to eradicate gorse in the Lake Rotorua catchment as a way of stopping nitrogen runoff into the lake has been launched by the Bay of Plenty Regional Council.
Council general manager of natural resources Warwick Murray says gorse can contribute as much nitrogen as a dairy farm but because it's so widely spread, the control of it rests with landowners.
He says it's a very difficult task to accomplish because the gorse is often on steep, difficult country and comes back quickly after being cleared unless some alternative vegetation cover is established.
Mr Murray says most of the options will involve getting forestry of some sorts on those sites so they eventually grow and crowd out the gorse.
He says each landowner will be treated on a case-by-case basis and funding for the gorse conversion project will be available until 2016.
Mr Murray says the amount of nitrogen lost to the lake needs to be reduced by 320 tonnes a year.