Don is currently the Key Relationships Manager for Mercury, a role he has held since 2003. Don’s career has focused on caring for the rivers, wetlands and catchments of the Waikato while serving organisations as diverse as Mercury/Mighty River Power, the former Electricity Corporation of New Zealand, Waikato Regional Council, Hauraki Catchment Board and the Ministry of Energy. Don has also worked internationally as a geologist in the United States, Asia, Australia, South America and in the Caribbean.

Don is the co-Chair of the Maungatautari Ecological Island Trust, the largest conservation project on mainland New Zealand, a founding member of the Waikato Ecological Enhancement Trust since 2003, and an Advisory Trustee of Waikato River Care. His efforts have seen many hundreds of environmental projects be initiated, funded and delivered. He was elected Chair of the National Wetland Trust in October 2019. His broader contribution has been in enabling local iwi to develop social and economic enterprises that are founded in community-based environmental initiatives. His work has led to job creation, improved consultation with Māori, and improvement to public places and reserves, such as Lake Rotopiko reserve. Mr Scarlet is also a Trustee of the National Wetland Trust and he has assisted in gaining full public access to the site and creating a pest-free area around part of the site. The wider benefits of this project to the community, iwi and the environment include community education, increased visitor numbers, and restoration of the wetland site.

Don was awarded the New Zealand Order of Merit in 2020 for his significant contributions to environmental restoration and conservation within the Waikato Region. Don has a BSc (Hons) from the University of Canterbury.