Fonds documents Craig Campbell’s interest and involvement in the conservation of Canada’s natural heritage. Textual records consist of correspondence related to his research and conservation efforts; correspondence related to his work for CARCS; correspondence with conservation agencies, academics and scientists from various institutions across North America; published and unpublished manuscripts written by Campbell, research materials, field notes, reports, newspaper clippings and photocopies of publications with annotations. Graphic records include photographs, slides, x-rays, and drawings of amphibians, reptiles and observation sites. Cartographic records include diagrams and maps. The fonds is arranged in 5 series as follows: Timber Rattlesnake Records, Hybrid Salamander Records, Salamander Habitat and Breeding Records, Turtle Records, and Natural Heritage Conservation Records.

The fonds consists of Stuart L. Thompson’s personal diaries in which he documents his daily life in the City of Toronto along with noting bird and mammal sightings. There are a number of special diaries documenting Thompson's various travels. The fonds also consists of bird sighting charts and of two items of Thompson’s correspondence. The fonds does not include two diaries documenting Thompson's overseas service during World War I.

Where specimens were collected, Thompson made a notation in his diary with a collection number. Several of the diaries have indexes of his collection at the back.