Alastair Fitter is a plant ecologist with wide-ranging research interests, including soil ecology and how plants behave in a changing world. He has contributed to our understanding of the structure and function of plant root systems and their symbiotic fungi.

He demonstrated that the architecture or three-dimensional structure of a root system is central to its ability to acquire nutrients in natural soil. He also showed that sunshine — rather than soil temperature — controls root development in grassland, and that soils may therefore be less good at retaining carbon dioxide in a warming world. His work on mycorrhizas, the symbiotic relationship between plant roots and fungi, revealed their central role in ecosystems.

Alastair is the son of naturalist Richard Fitter, with whom he collaborated on several popular natural history books and a paper in the journal Nature about the effects of a warming climate on the timing of flowering in plants. He was awarded a CBE in 2010 for his services to environmental science.