Abstract
Roads are expanding at the fastest pace in human history. This is the case especially in biodiversity-rich tropical nations, where roads can result in forest loss and fragmentation, wildfires, illicit land invasions and negative societal effects1,2,3,4,5. Many roads are being constructed illegally or informally and do not appear on any existing road map6,7,8,9,10; the toll of such ‘ghost roads’ on ecosystems is poorly understood. Here we use around 7,000 h of effort by trained volunteers to map ghost roads across the tropical Asia-Pacific region, sampling 1.42 million plots, each 1 km2 in area. Our intensive sampling revealed a total of 1.37 million km of roads in our plots—from 3.0 to 6.6 times more roads than were found in leading datasets of roads globally. Across our study area, road building almost always preceded local forest loss, and road density was by far the strongest correlate11 of deforestation out of 38 potential biophysical and socioeconomic covariates. The relationship between road density and forest loss was nonlinear, with deforestation peaking soon after roads penetrate a landscape and then declining as roads multiply and remaining accessible forests largely disappear. Notably, after controlling for lower road density inside protected areas, we found that protected areas had only modest additional effects on preventing forest loss, implying that their most vital conservation function is limiting roads and road-related environmental disruption. Collectively, our findings suggest that burgeoning, poorly studied ghost roads are among the gravest of all direct threats to tropical forests.
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Data availability
The datasets used for this study (including comprehensive road maps as a raster of road density at 1-km2 resolution) are available in the Supplementary Information, on request to J.E.E. and W.F.L. or as follows. OpenStreetMap data are available from https://download.geofabrik.de/, and GRIP road data from https://www.globio.info/download-grip-dataset. National and subnational administrative-region data were obtained from GADM (https://gadm.org/). Population-density data were from WorldPop (https://www.worldpop.org/). GDP data were accessed at https://datadryad.org/stash/dataset/doi:10.5061/dryad.dk1j0. Protected-area data were from Protected Planet (https://www.protectedplanet.net/en). Waterways locations were obtained from the Global River Widths from Landsat Database (https://zenodo.org/records/1297434). Elevation data were accessed at http://srtm.csi.cgiar.org, and rainfall data at https://doi.org/10.16904/envidat.211. Data for all soil variables were obtained from Soil Grids (https://soilgrids.org/).
References
Dulac, J. Global Land Transport Infrastructure Requirements: Estimating Road and Railway Infrastructure Capacity and Costs to 2050 (International Energy Agency, Paris, 2013).
Laurance, W. F. et al. A global strategy for road building. Nature 513, 229–232 (2014).
Ascensão, F. et al. Environmental challenges for the Belt and Road Initiative. Nat. Sustain. 1, 206–209 (2018).
Kleinschroth, F. et al. Road expansion and persistence in forests of the Congo Basin. Nat. Sustain. 2, 628–634 (2019).
Ibisch, P. L. et al. A global map of roadless areas and their conservation status. Science 354, 1423–1427 (2016).
Barber, C. P., Cochrane, M. A., Souza, C. M. Jr & Laurance, W. F. Roads, deforestation, and the mitigating effect of protected areas in the Amazon. Biol. Conserv. 177, 203–209 (2014).
Laurance, W. F., Goosem, M. & Laurance, S. G. Impacts of roads and linear clearings on tropical forests. Trends Ecol. Evol. 24, 659–669 (2009).
Alamgir, M. et al. Economic, socio-political and environmental risks of road development in the tropics. Curr. Biol. 27, 1130–1140 (2017).
Fearnside, P. M. in Handbook of Road Ecology (eds van der Ree, R. et al.) 414–424 (John Wiley & Sons, 2015).
Hughes, A. C. Have Indo-Malaysian forests reached the end of the road? Biol. Conserv. 223, 129–137 (2018).
Schrieber-Gregory, D. Regulation Techniques for Multicollinearity: Lasso, Ridge, and Elastic Nets https://www.lexjansen.com/wuss/2018/131_Final_Paper_PDF.pdf (2018).
Hettige, H. When Do Rural Roads Benefit the Poor and How? An In-Depth Analysis (Asian Development Bank, 2006).
Laurance, W. F. et al. The future of the Brazilian Amazon. Science 291, 438–439 (2001).
Vilela, T. et al. A better Amazon road network for people and the environment. Proc. Natl Acad. Sci. USA 117, 7095–7102 (2020).
van der Ree, R., Smith, D. & Grilo, C. (eds) Handbook of Road Ecology (John Wiley & Sons, 2015).
Bebbington, A. et al. Priorities for governing large-scale infrastructure in the tropics. Proc. Natl Acad. Sci. USA 117, 21829–21833 (2020).
Meijer, J. R., Huijbregts, M. A. J., Schotten, K. C. G. J. & Schipper, A. M. Global patterns of current and future road infrastructure. Environ. Res. Lett. 13, 064006 (2018).
Ramm, F., Topf, J. & Chilton, S. OpenStreetMap: Using and Enhancing the Free Map of the World (UIT Cambridge, 2010).
Laurance, W. F. et al. Reducing the global environmental impacts of rapid infrastructure expansion. Curr. Biol. 25, 259–262 (2015).
Sloan, S. et al. Infrastructure development and contested forest governance threaten the Leuser Ecosystem, Indonesia. Land Use Policy 77, 298–309 (2018).
Venter, O. et al. Sixteen years of change in the global terrestrial human footprint and implications for biodiversity conservation. Nat. Commun. 7, 12558 (2016).
Williams, B. A. et al. Change in terrestrial human footprint drives continued loss of intact ecosystems. One Earth 3, 371–383 (2020).
Watson, J. E. M. et al. Catastrophic declines in wilderness areas undermine global environment targets. Curr. Biol. 26, 2929–2934 (2016).
Curtis, P. G., Slay, C., Harris, N., Tyukavina, A. & Hansen, M. C. Classifying drivers of global forest loss. Science 361, 1108–1111 (2018).
Pendrill, F. et al. Agricultural and forestry trade drives large share of tropical deforestation emissions. Glob. Environ. Change 56, 1–10 (2019).
Pendrill, F. et al. Disentangling the numbers behind agriculture-driven tropical deforestation. Science 377, eabm9267 (2022).
Geist, H. J. & Lambin, E. F. Proximate causes and underlying driving forces of tropical deforestation. BioScience 52, 143–150 (2002).
Thünen, J. H. V. The Isolated State in its Relation to Agriculture and National Economy (Pergamon Press, 1966).
Meyfroidt, P. et al. Middle-range theories of land system change. Glob. Environ. Change 53, 52–67 (2018).
Rodrigues, A., Ewers, R., Souza, C., Verissimo, A. & Balmford, A. Boom-and-bust development patterns across the Amazon deforestation frontier. Science 324, 1435–1437 (2009).
Geldmann, J., Manica, A., Burgess, N. D., Coad, L. & Balmford, A. A global-level assessment of the effectiveness of protected areas at resisting anthropogenic pressures. Proc. Natl Acad. Sci. USA 116, 23209–23215 (2019).
Vancutsem, C. et al. Long-term (1990–2019) monitoring of forest cover changes in the humid tropics. Sci. Adv. 7, eabe1603 (2021).
Botelho, J., Costa, S., Ribeiro, J. & Souza, C. M. Mapping roads in the Brazilian Amazon with artificial intelligence and Sentinel‐2. Remote Sens. 14, 3625 (2022).
das Neves, P. et al. Amazon rainforest deforestation influenced by clandestine and regular roadway network. Land Use Policy 108, 105510 (2021).
Cameroon Road Network (World Food Programme, Logistics Cluster, accessed 1 July 2022); https://dlca.logcluster.org/23-cameroon-road-network
Katovai, E., Sirikolo, M., Srinivasan, U., Edwards, W. & Laurance, W. F. Post-logging recovery dynamics and their effects on tree diversity in tropical forests of the Solomon Islands. For. Ecol. Manag. 373, 53–63 (2016).
Qin, S. et al. Protected area downgrading, downsizing, and degazettement as a threat to iconic protected areas. Conserv. Biol. 33, 1275–1285 (2019).
Laurance, W. F. et al. Averting biodiversity collapse in tropical forest protected areas. Nature 489, 290–294 (2012).
Sloan, S., Bertzky, B. & Laurance, W. F. African development corridors intersect key protected areas. Afr. J. Ecol. 55, 731–737 (2017).
Haddad, N. M. et al. Habitat fragmentation and its lasting impact on Earth’s ecosystems. Sci. Adv. 1, e1500052 (2015).
Herfort, B., Lautenbach, S., Albuquerque, J., Anderson, J. & Zipf, A. The evolution of humanitarian mapping within the OpenStreetMap community. Sci. Rep. 11, 3037 (2021).
Laurance, W. F. Wanted: AI experts to map road-building boom. Nature 558, 30 (2018).
Sloan, S., Talkhani, R. R., Huang, T., Engert J. & Laurance, W. F. Mapping remote roads using artificial intelligence and satellite imagery. Remote Sens. 16, 839 (2024).
Wang, W. et al. A review of road extraction from remote sensing images. J. Traffic Transp. Eng. 3, 271–282 (2016).
De Clerk, E. Facebook uses AI technology to map roads of Thailand. Intelligent Transport https://www.intelligenttransport.com/transport-news/85277/facebook-ai-map-roads-thailand/ (2019).
Acknowledgements
We thank J. Barlow, R. Chazdon, M. Cochrane, S. Das, M. Goosem, J. Jaeger, P. Negret, C. Souza Jr, R. Talkhani and H. Tao for many helpful comments, and our volunteer road-mappers, including Wild Green Memes for Ecological Fiends, for their efforts. The Australian Research Council, James Cook University and an anonymous philanthropic donor provided support.
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W.F.L., J.E.E., M.J.C., M.A. and S.S. conceived the study; J.E.E., J.E.C. and W.F.L. coordinated data analysis. W.F.L., J.E.E., J.E.C. and M.J.C. wrote the manuscript. J.E.E., Y.I., J.C. and S.S. generated key road datasets. M.J.C., J.E.C., M.A., S.S. and J.S. provided ideas and critical feedback.
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Nature thanks Robin Chazdon, Jochen Jaeger, Pablo Negret and Carlos Souza Jr for their contribution to the peer review of this work.
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Engert, J.E., Campbell, M.J., Cinner, J.E. et al. Ghost roads and the destruction of Asia-Pacific tropical forests. Nature 629, 370–375 (2024). https://doi.org/10.1038/s41586-024-07303-5
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DOI: https://doi.org/10.1038/s41586-024-07303-5
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