The naturalist Walter Buller later managed to purchase Papaitonga and its environs for his country home, which led to its forest being preserved and it eventually becoming a scenic reserve.

The lake was once a sandy coastal lagoon at the mouth of the Ohau River, and the forested terraces on its landward side were once sea cliffs.

[3] The bottom of the lake now consists of 15 m of accumulated silt and mud over the original sand, and preserves layers of volcanic ash from eruptions 8,000 and 5,900 years ago.

The lake was the home of the Māori Muaūpoko iwi, who lived in several villages around it and harvested longfin and shortfin eels, waterfowl, and kākahi from its wetlands.

[1] The forest was preserved for its groves of kiekie, which produced a sweet fruit and much-prized succulent flower bracts (called tāwhara).

[5] He and his warriors vowed revenge, and eventually returned and massacred 600 Muaūpoko on Papaitonga Island; the tribe was defeated and lost their territory, influence, and prestige.

[3][1] Buller had long coveted Papaitonga: when he first saw the lake he was "struck by its singular loveliness", and called it "one of the prettiest bits of scenery in New Zealand".

[3] Buller intended to build a wildlife sanctuary and country estate around the lake, and carefully preserved the forest and wetland, while introducing species of birds both native and exotic; five white swans from the Royal flock in Kew Gardens were released in 1893.

Lake Papaitonga has long been a waterfowl sanctuary; when Buller lived there, up to 200 brown teal (today an endangered species) could be seen at a time.

[3] Black swan, shoveler, mallards, and dabchicks live on the lake, and kingfishers, pūkeko, harriers, kererū, and welcome swallows are also present.

[4] These native snails are threatened by rats, which take up to 25% of adults annually, by introduced blackbirds and song thrushes,[10] and by the gradual drying out of Papaitonga from construction of drainage ditches, artesian bores, and farm irrigation.

[11] The reserve is administered by the Department of Conservation (DOC), who undertake possum and rat control, and have banned dogs, hunting, and mountain biking.