Road expansion and persistence in forests of the Congo Basin

Abstract

Roads facilitate development in remote forest regions, often with detrimental consequences for ecosystems. In the Congo Basin, unpaved logging roads used by timber firms, as well as paved and unpaved public roads, have expanded greatly. Comparing old (before 2003) and new (2003–2018) road datasets derived from Landsat imagery, we show that the total length of road networks inside logging concessions in Central Africa has doubled since 2003, whereas the total length of roads outside concessions has increased by 40%. We estimate that 44% of roads in logging concessions were abandoned by 2018, as compared to just 12% of roads outside concessions. Annual deforestation rates between 2000 and 2017 near (within 1 km) roads increased markedly and were highest for old roads, lowest for abandoned roads and generally higher outside logging concessions. The impact of logging on deforestation is partially ameliorated by the nearly fourfold higher rate of road abandonment inside concessions, but the overall expansion of logging roads in the Congo Basin is of broad concern for forest ecosystems, carbon storage and wildlife vulnerable to hunting. Road decommissioning after logging could play a crucial role in reducing the negative impacts of timber extraction on forest ecosystems.

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Fig. 1: African road planning and construction from the continental to local levels.
Fig. 2: Congo Basin road networks.
Fig. 3: Forest loss around roads.

Data availability

The spatial datasets generated and analysed during the current study are publicly available in the ETH Zurich Research Collection with the DOI 10.3929/ethz-b-000342221 under the following link: https://www.research-collection.ethz.ch/handle/20.500.11850/342221.

Code availability

Google Earth Engine codes used during the current study are publicly available at https://code.earthengine.google.com/a4cc97c3cf4f0f0ce860aba4a3765a1d. R codes used during the current study are available from the corresponding author on reasonable request.

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Acknowledgements

F.K. is funded by the DAFNE project of the European Union H2020 programme (grant number 690268). W.F.L. is funded by the Arcus Foundation. S.J.G. acknowledges support of the NASA Applied Sciences Ecological Forecasting Program (grant NNX17AG51G). We thank B. Naimi for help with coding and I. Kornecki with road digitization. E. Forni, S. Gourlet-Fleury, J. Healey and A. Karsenty provided useful background discussions. We are grateful to all OpenStreetMap contributors who digitized road data, particularly the loggingroads.org initiative led by Moabi, the Joint Research Center of the European Commission and Global Forest Watch.

Author information

F.K. and W.F.L. conceived the ideas, F.K. and N.L. collected and analysed the data. J.G. and S.J.G. contributed to the interpretation of results and all authors contributed to the writing.

Correspondence to Fritz Kleinschroth.

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