One of a family of five daughters, Mary Sutherland was born in London on 4 May 1893 to Nellie Miller Sutherland and her husband, David Sutherland, a medical wine manufacturer. Four of the sisters pursued careers: two in teaching, one in medicine, and Mary in forestry.
After attending the City of London School for Girls from 1908 to 1912, Mary took courses in agriculture and forestry at the University College of North Wales, Bangor, from 1912 to 1916, and became the first woman in the United Kingdom to complete a BSc in forestry. Subsequently, she served in the Women's Land Army and worked as a forester on estates in Renfrewshire and Inverness-shire. In 1917 she took up a position as assistant experimental officer with the Forestry Commission. However, in 1922 her career hopes were unexpectedly dashed when Sir Eric Geddes's Committee on National Expenditure made recommendations that led to retrenchment and the loss of her position.
A State Forest Service had been established in New Zealand in 1921, with Canadian-trained forester L. M. Ellis as director. Mary Sutherland was attracted to New Zealand because she felt it offered forestry conditions similar to those in the United Kingdom. She was made a forestry assistant in 1923, the first, and for many years the only, woman appointed to a professional grade in the newly established service. Her position became permanent in 1925. By this time, in order to overcome a predicted timber famine, the government had committed itself to establishing 300,000 acres of plantation forest within a decade.
Sutherland was the most junior of the few professionally qualified foresters, although two men were younger – one of whom was less qualified; in 1926 her salary was £320. Her botanical knowledge and professionalism were acknowledged, but under-used during this dramatic period of forestry development. Unable to share a tent with male staff, she was seldom sent on field work as other accommodation had to be paid for. As a consequence, she was mostly employed on technical calculations for volume tables and in time-consuming microscope work. In 1924 she had spent time in Rotorua compiling information on plantations and nurseries in the area. In 1929 she began a detailed investigation for a paper entitled 'A microscopical study of the structure of the leaves of the genus pinus', which was published in the Transactions and Proceedings of the New Zealand Institute in 1933.
Although her skills were not fully utilised, Mary Sutherland did important technical and planning work during the 1920s afforestation boom and her professional commitment to forestry did not waver. In 1924 she had become a member of the Empire Forestry Association; in 1928 she was a charter-member of the New Zealand Institute of Foresters, and in the same year she was elected a fellow of the Society of Foresters of Great Britain. She served on the Council of the New Zealand Institute of Foresters in 1935 and was vice president from 1940 to 1941. Her drawing of a sprig of fruiting rimu was adopted as the emblem for the institute's official seal. She also served on the Council of the New Zealand Forestry League in 1936.
The National Expenditure Commission in 1932 recommended a sizeable reduction in State Forest Service expenditure and Mary Sutherland again found herself unemployed. However, in 1933 she secured a position at the Dominion Museum, Wellington, and remained there until 1946. Initially working as a clerk, she was eventually reclassified as a botanist. She presented a paper at the Pacific Science Congress in 1933.
Mary Sutherland maintained a wide range of interests through her involvement with the Society for the Oversea Settlement of British Women and the New Zealand Federation of University Women, of which she was Wellington branch secretary from 1935 to 1937. During the Second World War she served as assistant superintendent of the YWCA hostel at Woburn, which catered for 300 young women.
The most important part of her professional career still lay ahead. This began in 1946 when Sutherland transferred to the Department of Agriculture as the sole farm forestry officer, on a salary of £460. She was charged with extensive work on farm-shelter plantations and woodlots, a role particularly suited to her early training in agriculture as well as forestry. She was also responsible for the layout of plantations at the Winchmore Irrigation and Invermay Agricultural Research Stations. Vigorous and forthright, wearing knee boots and jacket, she cut a distinctive figure in the field. Between 1947 and 1949 she wrote an important series of articles for the New Zealand Journal of Agriculture on the potential benefits of planting trees on farms, which formed the basis of a 1951 Department of Agriculture bulletin on homestead shelter planting. In 1950 she contributed a chapter, 'Native vegetation', to the department's publication Farming in New Zealand.
In 1952 Mary Sutherland visited forests in Britain, Denmark, Norway, Canada and the United States. Her job required considerable travel, but was rewarding in allowing her the opportunity to encourage farmers to rethink old attitudes, especially about forests as a land use in direct conflict with pastoral agriculture. It was on one such field excursion to Central Otago in March 1954 that Sutherland became ill with a kidney condition, which abruptly ended her working career and directly contributed to her death a year later on 11 March 1955 in Wellington. She had never married.
Mary Sutherland's early career had parallels with the first women foresters in the United States Forest Service. Had she not encountered prejudice within the State Forest Service, her career could have been much more significant. Ultimately, the farm forestry work was probably her most important contribution because of the way it helped reshape attitudes towards land use and break down barriers between farmers and foresters.