John Rentoul, beekeeper, amateur botanist and Cheviot domain board chairman from 1909–24, started planting the 20-hectare reserve and bird sanctuary, set aside in 1897.
By the early 20th century, the lagoon had become popular for picnicking and boating. In recent years mostly native species have been planted, by volunteers from the Cheviot Reserves sub-committee of the Hurunui District Council (who own the lagoon) and farmers on adjoining private land.
James and Joanna Paterson bought 356-hectare Ridgeway Farm bordering St Anne’s Lagoon in 1993. A major selling point was the view from the homestead across the lagoon to rolling farmland backed by the Seaward Kaikoura Range and Mt Tapuae-o-Uenuku. They began planting natives to help return the lagoon to a more natural state and in 2014 the Hurunui-Waiau Water Management Zone Committee granted the couple $21,900 of Immediate Steps funding to fence the lake edge and gullies to keep out cattle then plant natives such as Carex secta, raupo, flax, cabbage trees and toi toi.
Ngāi Tahu have a strong connection to Mata Kopae. Their ancestors built the banks at its entrance to retain tuna (eel) breeding stock, later shifted to build populations in other areas. Connected to the Waiau River through Caroline Stream, it was an important mahinga kai (food gathering) place for tuna, other native fish and waterfowl.