Old-growth forests remove carbon dioxide from the atmosphere1,2 at rates that vary with climate and nitrogen deposition3. The sequestered carbon dioxide is stored in live woody tissues and slowly decomposing organic matter in litter and soil4. Old-growth forests therefore serve as a global carbon dioxide sink, but they are not protected by international treaties, because it is generally thought that ageing forests cease to accumulate carbon5,6. Here we report a search of literature and databases for forest carbon-flux estimates. We find that in forests between 15 and 800 years of age, net ecosystem productivity (the net carbon balance of the forest including soils) is usually positive. Our results demonstrate that old-growth forests can continue to accumulate carbon, contrary to the long-standing view that they are carbon neutral. Over 30 per cent of the global forest area is unmanaged primary forest, and this area contains the remaining old-growth forests7. Half of the primary forests (6 × 108 hectares) are located in the boreal and temperate regions of the Northern Hemisphere. On the basis of our analysis, these forests alone sequester about 1.3 ± 0.5 gigatonnes of carbon per year. Thus, our findings suggest that 15 per cent of the global forest area, which is currently not considered when offsetting increasing atmospheric carbon dioxide concentrations, provides at least 10 per cent of the global net ecosystem productivity8. Old-growth forests accumulate carbon for centuries and contain large quantities of it. We expect, however, that much of this carbon, even soil carbon9, will move back to the atmosphere if these forests are disturbed.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
We thank all site investigators, their funding agencies and the various regional flux networks (Afriflux, AmeriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, ChinaFlux, Fluxnet-Canada, KoFlux, LBA, NECC, OzFlux, TCOS-Siberia and USCCC), and the Fluxnet project, whose support was essential for obtaining our measurements. S.L. was supported by CoE ECO UA-Methusalem and the Research Foundation - Flanders (FWO-Vlaanderen) with a post-doctoral fellowship and a research grant. A.K. was supported by the European Union with a Marie Curie fellowship, and B.E.L. was supported by the regional North American Carbon Program project ORCA (US Department of Energy, Terrestrial Carbon Program, award number DE-FG02-04ER63917). E.-D.S. was supported by DFG-Exploratories. Additional funding for this study was received from CarboEuropeIP (project number GOCE-CT-2003-505572) and Ameriflux.
Author Contributions S.L., B.E.L., A.K. and P.C. compiled the data set. S.L., A.B. and D.H wrote code and analysed the data. S.L., E.-D.S., A.K., B.E.L., P.C. and J.G. designed the analyses and wrote the manuscript.
This file contains Supplementary Methods, Supplementary References and Supplementary Figures S1-S5
About this article
Soil organic carbon variation in relation to land use changes: the case of Birr watershed, upper Blue Nile River Basin, Ethiopia
Journal of Ecology and Environment (2018)