Critical natural capital is the one that accomplishes environmental functions that are not functionally replaceable by other environmental elements or by other capitals. The criticality degree can be related to ecological and socio-cultural criteria, and also to the threat degree brought to anthropic pressures. This approach implies the acknowledgement of biodiversity. The article introduces the Critical natural capital and complexity concepts, associated to the habitat functions (related to the provision of natural ecosystems, shelter places and wild organisms’ reproduction) as components of the environmental management for a sustainable development.