To help his students understand biodiversity in its natural habitats, he organised field courses for many of his classes, including to Tenerife (Canary Islands), Romania, Rwanda, and various locations in France (Vosges, Alsace, and Brittany).

Its work and research focuses on taking ecology into account in the fields of safeguarding and managing natural resources, biodiversity, and landscapes.

Other administrative positions that Sérusiaux held relating to environmental organisations include: president of Aquapole, a research centre within the Liège University campus dedicated to water science, from 2002 to 2019; member of the Research Council of the University of Liège from 2005 to 2009; and member of the Administrative Board of LEPUR (Centre de recherche sur la ville, le territoireet le milieu rural) from 2004 to 2019.

[2] He has also served administratively for Natagora, a non-governmental organisation dedicated to biodiversity and conservation in Wallonia, from 2012 to 2017, and as the president of the Société wallonne des eaux [fr] from 2001 to 2007.

[6] Sérusiaux helped to develop a molecular biology facility at the University of Liège where DNA was extracted and prepared from thousands of lichen specimens.

This has enabled him and his colleagues to publish phylogenies for several lichen genera, including Nephroma, Peltigera, Niebla, Sticta, and the family Pannariaceae.

In addition to circumscribing a new family (Lepidostromataceae) and twenty new genera (Aplanocalenia, Bapalmuia, Brasilicia, Bryogomphus, Eugeniella, Fellhaneropsis, Ferraroa, Gallaicolichen, Hippocrepidea, Isalonactis, Jamesiella, Kantvilasia, Lambinonia, Lilliputeana, Lithogyalideopsis, Nyungwea, Phyllocratera, Rubrotricha, Savoronala, Sporopodiopsis), he has also formally described 206 new species.

He defined the term goniocystangium—a concave, hollow, cup-like structure producing goniocysts that are found in the genera Catillaria and Opegrapha.

His first scientific publication, in 1975, was about the water birds of the upper Meuse, a river in Belgium; this was followed a year later by a study of the foliicolous lichen specimens held at the Farlow Herbarium of Cryptogamic Botany.