During the Holocene, a great amount of carbon has been stored in the peaty soils beneath the wet coastal tundra at Barrow, Alaska, and in the wet peatlands of the bottomland taiga near Fairbanks, Alaska. On the basis of fossil pollen, plant macrofossil spectra, and present vegetation, an attempt is made to estimate rough carbon budgets for the present and during the last 5000 years at these sites. Carbon capture and carbon accumulation rates have varied cyclically in the past at both sites. However, both tundra and taiga have remained sinks for atmospheric CO 2 through this time. In view of the probable warming of these climates due to increasing atmospheric CO 2 concentrations, future fates of this carbon, now stored in permafrost, are in doubt. Future carbon balances may be quite different from those that have prevailed during the Holocene and at present. These ecosystems may well become carbon sources rather than remain carbon sinks. The use of field and phytotron simulation experiments is suggested as well as the use of mathematical models in attempting to predict the future of these carbon-rich ecosystems in the 21st and 22nd centuries.