They bought land, made a wetland and now Whanganui's Sisters of St Joseph of the Sacred Heart want to plant the steep hillside below their Mount St Joseph.
The hill is "what's holding it all up", Sister Noelene Landrigan said. It suffered slips in the June 2015 heavy rain and sheep can no longer be grazed on it.
The sisters applied to Trees That Count's Matariki competition for a donation of up to 300 native trees to help hold on to the soil. There were more than 1000 applications and theirs was one of seven lucky ones.
The Sisters used to own a little farm on the edge of St John's Hill. They kept the land at the top, and their Mount St Joseph base and Nazareth Rest Home and Hospital are built on it.
They bought a 1ha swampy area back from a neighbour, and turned it into the Te Punanga Ripo wetland in 2004. It's now a nursery for eels, Sr Noelene said, and the eels have to leave it to get to sea and breed.
"Some of the staff have seen old female eels heading across our drive down to the river."
Some of the Sisters' hillside is already taken up with one of the City Mission's gardens, and about 80 fruit trees. Much of the rest is very steep.
Sr Noelene has had Whanganui plant ecologist Colin Ogle there, to make a list of suitable trees. She wants some for bird and bee forage, and all will store carbon, slow the pace of rainwater and hold on to the hillside soil.
Species are likely to include ngaio, pittosporums and matai. She's hoping they will shade out the kikuyu grass growing there, and stop it spreading.
Much of the work will be done by part-time employee Shane Dean, who helps with the planning. The Corrections Department's community workers will do any heavy jobs.
The project is in line with Pope Francis' views on "integral ecology", and Sr Noelene is part of a group of sisters investigating the true meaning of kaitiakitanga with tangata whenua.
"It's the local understanding of love of the Earth and relationship with the Earth," she said.