Carbon (C) density (carbon mass per hectare) is a critical variable in determining the extent of the effect of human activity on ecosystems and our environment, because many ecological processes depend on the C cycle. Quantifying the human impact on C density of forest ecosystems is very important for reducing the uncertainties pertaining to C emission from terrestrial ecosystems. Using the volume-derived method, we have estimated the total vegetative C pool and density in the forest ecosystems for every province in China, and then analyzed the relationship between the C density and population density. In China, forest C storage was 3255.71 Tg, of which 59% was located in remote regions including Helongjiang, Sichuan, Yunnan, and Inner Mongolia Provinces. The area-weighed vegetative C density is 32 Mg/ha with a range of 5–75 Mg/ha on a provincial scale. A good negative correlation was found between the C densities and population densities at a significant level (carbon density=−9.84. In (population density)+75.13, r 2=0.64). It can be concluded that, apart from changes in land use, forest degradation also causes significant carbon release to the atmosphere, and that existing forest ecosystems can sequester a considerable amount of carbon if effective management systems are applied.