It's an ambitious project that, after 17 years, has reached the half-way mark.
The Maraetotara Tree Trust plans to fence, plant and protect nearly 90km of the Maraetotara riverbank in Hawke's Bay.
The project was first launched by local angler John Scott, who was appalled at the river's decline.
He set up the trust and moved on to become a major advocate for the region's waterways.
And while he's been battling, the Maraetotara River has started a remarkable transformation.
Its native plantings are providing a corridor for wildlife from Te Awanga on the coast, through Cape Sanctuary and towards Central Hawke's Bay.
Maraetotara Tree Trust secretary Alec Olsen said half of both sides of the 43km stream have been fenced and planted.
"We've perhaps picked the easier pieces, where we could get fences," he said.
"We used to chug along with two or three thousand trees a year, but recently through the generosity of the Department of Conservation's public funding, we've been able to lift that up to about 15,000 trees a year."
Hawke's Bay Regional Council has an important role to play, removing willow trees which slow the river flow and cause flooding.
The third partner is neighbouring landowners, who agree to covenant riparian margins – losing some grazing and stock access to water.
Maraetuna stock manager Paul Maher said the trust had helped make the process smooth.
"The cost side of things is really good, they've helped out a lot and we haven't had to put much into it," he said.
The farm lost 4ha of grazing but he wasn't concerned.
"You don't want to graze that close to the river anyway, there's the whole effluent-going-into-the-river side of things.
"It's going to build up the bird life which is going to trickle down the ecosystem to all the fish in the river. It's going to rejuvenate everything."
With tougher country yet to fence, it could take 20 more years to complete the project, depending on the generosity of donors.
Local resident, internationally acclaimed designer David Trubridge, has committed his company as a permanent sponsor.
"We are a clean company," Trubridge said.
"We do everything we can in the company to reduce our environmental impact.
"But there are some things we can't do anything about. We are responsible for a certain amount of carbon emissions so our idea is to offset those carbon emissions we can't do anything about, by planting trees. So our relationship with Maraetotara Tree Trust evolved out of that."
The lay of the land is not the only tough aspect of the second half of the project.
Both sides of a section of river need to be protected at the same time because cattle can wade across. Some landowners were reluctant to take part, but Olsen said there were shifting views.
"Public attitude now is a little bit more generous towards the rehabilitation of rivers and just the planting of native trees, for all the benefits that they have.
"We are absolutely dependant on the co-operation of the landowners and we are grateful for that."