Professor Johnston is a leading authority in marine ecology, is a sustainability and diversity champion and a Chief Author of the Australian State of Environment Report 2021. She has led major research projects for industry, government, the Australian Research Council and the Australian Antarctic Science Program and contributed to the development of international and national research strategies, priorities and plans. As the past President of Science & Technology Australia (STA), an elected position, she is a highly influential figure in the Australian higher education and research sector.

Professor Johnston was made an Officer of the Order of Australia (AO) in the 2018 Queen’s Birthday honours for distinguished service to higher education, particularly to marine ecology and ecotoxicology, as an academic, researcher and administrator, and to scientific institutes.