Sustainable agriculture advocate John Hart is visiting Whanganui next week to speak about the future of farming.

Ranked 12 on the Green Party's initial candidate list for the 2017 election, Mr Hart is an organic sheep and beef farmer in the Wairarapa. He spends his time between his farm, a young family, and a trust he co-founded to empower rural students through technology.

Whanganui's Green Party branch will be hosting the visit.

Mr Hart said a discussion needed to be had about the future of farming in New Zealand.

"We face some real threats as an industry from climate change, new sources of protein, and our own success as producers - showing up primarily in the intensification of dairying but also short-term focused practices like this 'spray and pray'," he said.

"Agriculture accounts for almost half of New Zealand's greenhouse gas emissions. There are ways to tackle this and changing some of the ways we farm is necessary - bare land isn't just vulnerable to erosion and increased nitrate loss, it can accelerate carbon emissions."

Local Greens candidate Nicola Patrick described Mr Hart was a "smart, caring farmer".

"[He] understands the constraints because he faces them daily. He's got solid ideas, that he's already implementing, about how New Zealand can have a strong rural economy that doesn't cost the earth."

"One of John's strengths is the strong networks he has built up across the country and the credibility he has with farmers," Ms Patrick said.

Mr Hart will be speaking at the Davis lecture theatre on Thursday, May 4 at 7.30pm. No charge for entry - koha towards venue hire.