Isabel Noeline Baker was born at Opawa, Christchurch, on 25 December 1878, the second and only surviving child of John Holland Baker, chief surveyor of Canterbury, and his wife, Isabel Strachey. Noeline, as she was known, was educated at home. When only 11 she accompanied her father on an inspection trip around Banks Peninsula. After his appointment as commissioner of Crown lands for the Wellington land district in 1891, they explored the wilderness areas of his North Island territory. One of Baker's surveyors, T. N. Brodrick, named a Mt Cook glacier the Noeline after his chief's adventurous daughter.
When John Baker retired in 1896 the family went to live in England. Noeline had shown an early talent for art and in 1899 at the age of 20 she became a student at the Slade School of Fine Art, London. After the family moved to Guildford, Surrey, around 1905, she also became involved in the women's suffrage campaign. She joined the National Union Of Women's Suffrage Societies, and was a founder member of its Guildford branch in 1910. As a member of the London Society for Women's Suffrage she took charge of the society's register of voluntary women workers at the outbreak of the First World War. Appointed honorary secretary and treasurer of a Surrey women's farm labour committee in May 1916, she organised training and found work for women on farms. In 1917, as a food crisis deepened, the British government's Board of Agriculture and Fisheries founded a Women's Land Army: Noeline Baker became organising secretary for Surrey. She was appointed an MBE in 1920 for her war work.
Noeline Baker remained unmarried, and from her mother's death in 1920 was a companion to her elderly father. After his death in 1930 she returned to New Zealand to edit his memoirs, published as A surveyor in New Zealand in 1932. While engaged on this task she stayed at Stewart Island, which she found a perfect haven. She leased her Guildford home, purchased about 34½ acres of bush-clad land at Halfmoon Bay, and in 1934–35 built a distinctive house, similar to the Dutch colonial homesteads of South Africa, which she named Moturau Moana.
Influenced by garden designer Gertrude Jekyll, with whom she was acquainted, and inspired by her appreciation of New Zealand flora, Noeline Baker created a unique garden. Her aim was to grow all plants indigenous to Stewart Island as listed by the botanist Leonard Cockayne. Over the next 15 years her garden became a place of botanical significance and in 1949 she was awarded the Loder Cup. The citation noted that she had 'long been an ardent student of Stewart Island botany, and through her collection and personal enthusiasm…stimulated many others'.
When war seemed imminent in 1939 Noeline Baker returned to England. Her offer of service to the Ministry of Agriculture and Fisheries was accepted and she resumed her former position with the Women's Land Army in Surrey. The work proved too demanding: she soon resigned and returned to New Zealand. Influenced by the writings of Sir Norman Angell, she began to promote the study of post-war reconstruction. 'To wait until peace is in sight', she wrote, 'is dangerous because the building of an enduring peace is a task that demands careful and prolonged study.' In 1941 she helped to found Wellington's Post-War Reconstruction Study Group, and in 1943 the Canterbury Post-War Reconstruction Society. She also helped set up the Christchurch Women's Active Service Club in 1942, to provide a recreational facility for women serving in the armed forces, and was its first honorary secretary.
During 1940 Baker gave Moturau Moana to the New Zealand government after the University of Otago and Canterbury University College had declined to accept it for financial reasons. On 21 December 1940, 32 acres of bush were designated a scenic reserve and, at Noeline's request, named in memory of her father. She continued to live in the house and tend the garden. On 7 December 1948, at an official ceremony attended by the minister of lands, C. F. Skinner, she handed over the keys to the house so that it and the garden could be used as a centre for botanical study and research. Although this was described by the eminent botanist G. T. S. Baylis as a 'unique gift to learning in New Zealand', to her disappointment government officials did not share her vision for Moturau Moana. The house, a tourist attraction for many years, was destroyed by fire in 1967. The garden became an arboretum and picnic area, administered first by the Department of Internal Affairs, then the New Zealand Forest Service and later the Department of Conservation.
Noeline Baker built a quaint cottage for herself on Stewart Island and created another beautiful garden there, then purchased a house in Nelson, where she began to spend the winter months. She died at Stewart Island on 25 August 1958. Moturau Moana, New Zealand's southernmost public garden, is her memorial.