Mads Thomsen is a senior lecturer at the University of Canterbury. Mads has been a quantitative seaweed enthusiast since he, as an undergraduate in 1994, did his first diving-seaweed-mapping project in the Baltic Sea. Mads has since studied seaweed ecology in Scandinavia, North America, Australia and more recently New Zealand. Today, Mads has collated a large photo library showing himself (and a few with his children) holding up seaweed of contrasting colours, sizes, and shapes. Mads has been (un)lucky to experience first-hand cataclysmic ecological changes to the systems he has studied, including native-turn-invasive in North America, new surprise-invasions in Scandinavia, destructive earthquakes in New Zealand and unprecedented heatwaves in both Australia and New Zealand. These dramatic changes have fuelled Mads’ passion for long-term field monitoring and experimental approaches to better understand and predict why different seaweeds are where they are.