Alexander is an environmental specialist, with vast work experience in the water, natural resources, environmental policy and risk analysis and management, and biosecurity.

Alexander has worked as a senior policy advisor and analyst, scientist, project manger and senior executive for the New Zealand government, as well as private sector.

Alexander has contributed to the development of New Zealand environmental regulation. He is co-author of Guidelines for Drinking-water Quality Management for New Zealand, Drinking-water Standards for New Zealand 2000 and 2005 (revised 2008), and several other environmental and water policy documents.

Alexander has written a number of publications on water, environment, and biosecurity issues.