Leng has several roles, her most current is Chief Scientist for Environmental Change Adaptation and Resilience at the British Geological Survey. She is also Director of the Centre for Environmental Geochemistry, a collaboration between the British Geological Survey and the University of Nottingham, Leng leads research around environmental change, human impact, food security, and resource management. Leng has been involved in deep drilling as part of the International Continental Scientific Drilling Program, and worked in Lake Ohrid in Macedonia and Lake Chala in East Africa. She also heads the Stable Isotope Facility at the British Geological Survey, which is part of the National Environmental Isotope Facility. Stable isotopes can be used to better understand climate change and human-landscape interactions, with increasing importance on the Anthropocene and the modern calibration period; tracers of modern pollution; and understanding the hydrological cycle especially in areas suffering human impact. Leng takes part in expeditions, most recently the Natural Environment Research Council (NERC) mission called Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA). She actively blogs about her research.
Leng serves on the editorial board of the journals Quaternary Research, Quaternary Science Reviews, Scientific Reports and the Journal of Paleolimnology.
She has written several articles about successfully undertaking a PhD.