| Abbreviation | Definition |
|---|---|
| CLRA | Canadian Land Reclamation Association |
| CLS | Conservation Leadership School |
| CLUD | Compatible Land Use Development |
| CLUT | Cycle Last Used Tabs |
| CLW | Council for a Livable World |
| CM | Carbon Monoxide |
| CMA | Catchment Management Authority |
| CMAS | Conservation and Management of Archaeological Sites |
| CMC | IUCN Conservation Monitoring Centre |
| CMEC | COX McLain Environmental Consulting |
| CMEP | Centre for Marine Environmental Prediction |
| CMER | Center for Marine and Environmental Radioactivity |
| CMER | Centre for Minerals Environmental Research |
| CMRA | Construction Materials Recycling Association |
| CMRI | Central Mining Research Institute (India) |
| CMWS | CGE Monitoring and Warning System |
| CNLM | Center for Natural Lands Management |
| C-NLOPB | Canada-Newfoundland and Labrador Offshore Petroleum Board |
| CNS | Catchment Nature Reserve |
| COBWEB | Complexity and Organized Behaviour Within Environmental Bounds |