The large-scale production and spread applications of carbon nanomaterials in the past few years have led to a very high proportion of carbon store in these materials worldwide, which may be imported into the carbon cycle. Carbon nanomaterials can enter living organisms, the atmosphere, soil, water and sediments, without being unchanged or degraded during their transfer. Here, we show that there is a scientific basis for researchers and policy-makers to be concerned about the potential impact of carbon nanomaterials on the carbon cycle and integrate them into the map of carbon cycle. (C) 2018 Elsevier Ltd. All rights reserved.