{{Short description|Increasing rate at which roads are being constructed worldwide}} {{multiple issues|{{essay-like|date=April 2019}} {{tone|date=April 2019}} {{unbalanced|date=February 2023}}}} {{Use dmy dates|date=September 2021}} [[File:Construction of Interstate 95, downtown Richmond (2899336022).jpg|upright=1.35|thumb|alt=Construction of Interstate 95, downtown Richmond|Construction of Interstate 95, downtown Richmond]] '''Road expansion''' refers to the increasing rate at which roads are constructed globally. Increases in population size and GDP, particularly in developing nations, are the primary drivers of road expansion<ref>Meijer, J. R.; Huijbregts, M. A. J.; Schotten, C. G. J. & Schipper, A. M. (2018). "Global patterns of current and future road infrastructure". ''Environmental Research Letters''. '''13''' (6), 064006. {{doi|10.1088/1748-9326/aabd42}}</ref> but transportation planning decisions also play an important role. The anticipated length of newly paved roads to be built between 2010 and 2050 would encircle the planet more than 600 times.<ref name=":0">Laurance, W.F., Clements, G.R., Sloan, S., O'Connell, C.S., Mueller, N.D., Goosem, M., Venter, O., Edwards, D.P., Phalan, B., Balmford, A., et al. (2014). A global strategy for road building. ''Nature'' 513, 229–232</ref> Approximately 90% of the new roads are being built in developing nations.<ref>Dulac, J. (2013). ''Global land transport infrastructure requirements: Estimating road and railway infrastructure capacity and costs to 2050'' (Paris, France: International Energy Agency), p. 50.</ref> Africa and Southeast Asia are predicted to experience a large amount of road expansion shortly.
Road expansion in Asian countries is a significant aspect of infrastructure development, driven by urbanization, economic growth, and connectivity needs. Countries like China, India, and Indonesia have ambitious plan for expanding their road networks to accommodate increasing traffic and trade demands. These projects often face challenges related to land acquisition, environmental impact, and funding, but they play a crucial role in fostering economic development and improving accessibility for remote regions.
Roads facilitate access to markets, health services and education but may adversely affect the natural environment, and impact communities and economies.<ref name=":0" /> There is also a disagreement on whether expanding and widening congested roadways truly relieves traffic congestion.<ref>{{Cite news|date=2021-09-28|title=The Unstoppable Appeal of Highway Expansion|language=en|work=Bloomberg.com|url=https://www.bloomberg.com/news/features/2021-09-28/why-widening-highways-doesn-t-bring-traffic-relief|access-date=2021-09-28}}</ref>
== Effects on the Environment == {{Main|Road ecology|l1=Road Ecology}}
The expansion of road infrastructure can have numerous impacts on environmental systems. Road construction and usage can serve as a significant source of mortality for wildlife.<ref name=":1">Laurance, W.F., Goosem, M., Laurance, S.G.W., 2009. Impacts of roads and linear clearings on tropical forests. Trends in Ecology & Evolution 24, 659–669.</ref><ref name=":2">Trombulak, S.C., Frissell, C.A., 2000. Review of ecological effects of roads on terrestrial and aquatic communities. Conservation Biology 14, 18–30.</ref> Roads can affect animal movements either by acting as a barrier or allowing easier movement.<ref name=":3">Forman, R.T.T., and Alexander, L.E. (1998). Roads and their major ecological effects. Annual Review of Ecology and Systematics ''29'', 207–231.</ref><ref name=":2" /><ref name=":17">Laurance, W.F., Croes, B.M., Tchignoumba, L., Lahm, S.A., Alonso, A., Lee, M.E., Campbell, P., Ondzeano, C., 2006a. Impacts of roads and hunting on Central African rainforest mammals. Conservation Biology 20, 1251–1261.</ref><ref name=":11">Blake, S., Deem, S.L., Strindberg, S., Maisels, F., Momont, L., Isia, I.-B., Douglas-Hamilton, I., Karesh, W.B., Kock, M.D., 2008. Roadless wilderness area determines forest elephant movements in the Congo Basin. PLoS ONE 3, e3546.</ref>
Habitat fragmentation caused by road expansion can impact the movement and migration of species, as well as breeding and genetic structure.<ref>Laurance, S.G.W., Stouffer, P.C., Laurance, W.F., 2004. Effects of road clearings on movement patterns of understory rainforest birds in Central Amazonia. Conservation Biology 18, 1099–1109.</ref><ref name=":16">Laurance, W.F., Croes, B.M., Guissouegou, N., Buij, R., Dethier, M., Alonso, A., 2008. Impacts of roads, hunting, and habitat alteration on nocturnal mammals in African rainforests. Conservation Biology 22, 721–732.</ref><ref>Shepard, D. B., Kuhns, A. R., Dreslik, M. J., & Phillips, C. A. (2008). Roads as barriers to animal movement in fragmented landscapes. Animal Conservation, 11(4), 288–296. doi:doi:10.1111/j.1469-1795.2008.00183.x</ref><ref name=":9">Clements, G.R., Lynam, A.J., Gaveau, D., Yap, W.L., Lhota, S., Goosem, M., Laurance, S., Laurance, W.F., 2014. Where and how are roads endangering mammals in Southeast Asia's Forests? PLoS ONE 9, e115376.</ref> Fragmentation also produces edge effects that alter the microclimate and ecological succession of habitat patches.<ref>Ewers, R.M., Andrade, A., Laurance, S.G., Camargo, J.L., Lovejoy, T.E., Laurance, W.F. 2017. Predicted trajectories of tree community change in Amazonian rainforest fragments. Ecography 40, 26–35.</ref><ref name=":13">Laurance, W.F., Camargo, J.L.C., Luizão, R.C.C., Laurance, S.G., Pimm, S.L., Bruna, E.M., Stouffer, P.C., Williamson, G.B., Benítez-Malvido, J., Vasconcelos, H.L., Van Houtan, K.S., Zartman, C.E., Boyle, S.A., Didham, R.K., Andrade, A., Lovejoy, T.E., 2011. The fate of Amazonian forest fragments: a 32-year investigation. Biological Conservation 144, 56–67.</ref><ref name=":6">Laurance, W.F., Laurance, S.G., Ferreira, L.V., Rankin-de Merona, J.M., Gascon, C., Lovejoy, T.E., 1997. Biomass collapse in Amazonian forest fragments. Science 278, 1117–1118.</ref><ref name=":15">Laurance, W.F., Lovejoy, T.E., Vasconcelos, H.L., Bruna, E.M., Didham, R.K., Stouffer, P.C., Gascon, C., Bierregaard, R.O., Laurance, S.G., Sampaio, E., 2002b. Ecosystem decay of Amazonian forest fragments: a 22-year investigation. Conservation Biology 16, 605–618.</ref><ref>Laurance, W.F., Nascimento, H.E.M., Laurance, S.G., Andrade, A.C., Fearnside, P.M., Ribeiro, J.E.L., Capretz, R.L., 2006b. Rain forest fragmentation and the proliferation of successional trees. Ecology 87, 469–482.</ref> Exploitation. Expansion can increase accessibility to previously intact ecosystems, allowing for increased rates of (over-)exploitation of natural resources through hunting, logging, and mining.<ref name=":14">Gaveau, D.L.A., Sloan, S., Molidena, M., Husnayanem, Wijaya, A., Ancrenaz, M., Nasi, R., Wielaard, N., and Meijaard, E. (2014). Four decades of forest loss and degradation in Borneo. PLoS ONE ''9'', e101654.</ref><ref name=":34">Wilkie, D., Shaw, E., Rotberg, F., Morelli, G., and Auzel, P. (2000). Roads, Development, and Conservation in the Congo Basin. Conservation Biology ''14'', 1614–1622.</ref> These activities, along with fires and conversion of forest to other land uses are major causes of tropical forest loss across the globe.<ref name=":35">Laurance, W. F., Campbell, M. J., Alamgir, M., & Mahmoud, M. I. (2017c). Road expansion and the fate of africa's tropical forests. ''Frontiers in Ecology and Evolution, 5'' (75), 1–7. doi:10.3389/fevo.2017.00075</ref><ref>Laurance, W.F., Carolina Useche, D., Rendeiro, J., Kalka, M., Bradshaw, C.J.A., Sloan, S.P., Laurance, S.G., Campbell, M., Abernethy, K., Alvarez, P., Arroyo-Rodriguez, V., Ashton, P., Benitez-Malvido, J., Blom, A., Bobo, K.S., Cannon, C.H., Cao, M., Carroll, R., Chapman, C., Coates, R., Cords, M., Danielsen, F., De Dijn, B., Dinerstein, E., Donnelly, M.A., Edwards, D., Edwards, F., Farwig, N., Fashing, P., Forget, P.-M., Foster, M., Gale, G., Harris, D., Harrison, R., Hart, J., Karpanty, S., John Kress, W., Krishnaswamy, J., Logsdon, W., Lovett, J., Magnusson, W., Maisels, F., Marshall, A.R., McClearn, D., Mudappa, D., Nielsen, M.R., Pearson, R., Pitman, N., van der Ploeg, J., Plumptre, A., Poulsen, J., Quesada, M., Rainey, H., Robinson, D., Roetgers, C., Rovero, F., Scatena, F., Schulze, C., Sheil, D., Struhsaker, T., Terborgh, J., Thomas, D., Timm, R., Nicolas Urbina-Cardona, J., Vasudevan, K., Joseph Wright, S., Carlos Arias-G, J., Arroyo, L., Ashton, M., Auzel, P., Babaasa, D., Babweteera, F., Baker, P., Banki, O., Bass, M., Bila-Isia, I., Blake, S., Brockelman, W., Brokaw, N., Bruhl, C.A., Bunyavejchewin, S., Chao, J.-T., Chave, J., Chellam, R., Clark, C.J., Clavijo, J., Congdon, R., Corlett, R., Dattaraja, H.S., Dave, C., Davies, G., de Mello Beisiegel, B., de Nazare Paes da Silva, R., Di Fiore, A., Diesmos, A., Dirzo, R., Doran-Sheehy, D., Eaton, M., Emmons, L., Estrada, A., Ewango, C., Fedigan, L., Feer, F., Fruth, B., Giacalone Willis, J., Goodale, U., Goodman, S., Guix, J.C., Guthiga, P., Haber, W., Hamer, K., Herbinger, I., Hill, J., Huang, Z., Fang Sun, I., Ickes, K., Itoh, A., Ivanauskas, N., Jackes, B., Janovec, J., Janzen, D., Jiangming, M., Jin, C., Jones, T., Justiniano, H., Kalko, E., Kasangaki, A., Killeen, T., King, H.-b., Klop, E., Knott, C., Kone, I., Kudavidanage, E., Lahoz da Silva Ribeiro, J., Lattke, J., Laval, R., Lawton, R., Leal, M., Leighton, M., Lentino, M., Leonel, C., Lindsell, J., Ling-Ling, L., Eduard Linsenmair, K., Losos, E., Lugo, A., Lwanga, J., Mack, A.L., Martins, M., Scott McGraw, W., McNab, R., Montag, L., Myers Thompson, J., Nabe-Nielsen, J., Nakagawa, M., Nepal, S., Norconk, M., Novotny, V., O'Donnell, S., Opiang, M., Ouboter, P., Parker, K., Parthasarathy, N., Pisciotta, K., Prawiradilaga, D., Pringle, C., Rajathurai, S., Reichard, U., Reinartz, G., Renton, K., Reynolds, G., Reynolds, V., Riley, E., Rodel, M.-O., Rothman, J., Round, P., Sakai, S., Sanaiotti, T., Savini, T., Schaab, G., Seidensticker, J., Siaka, A., Silman, M.R., Smith, T.B., de Almeida, S.S., Sodhi, N., Stanford, C., Stewart, K., Stokes, E., Stoner, K.E., Sukumar, R., Surbeck, M., Tobler, M., Tscharntke, T., Turkalo, A., Umapathy, G., van Weerd, M., Vega Rivera, J., Venkataraman, M., Venn, L., Verea, C., Volkmer de Castilho, C., Waltert, M., Wang, B., Watts, D., Weber, W., West, P., Whitacre, D., Whitney, K., Wilkie, D., Williams, S., Wright, D.D., Wright, P., Xiankai, L., Yonzon, P., Zamzani, F., 2012. Averting biodiversity collapse in tropical forest protected areas. Nature 489, 290–294.</ref><ref name=":36">Laurance, W.F., Cochrane, M.A., Bergen, S., Fearnside, P.M., Delamônica, P., Barber, C., D'Angelo, S., Fernandes, T., 2001a. The future of the Brazilian Amazon. Science 291, 438–439.</ref><ref name=":5">Laurance, W.F., Sayer, J., Cassman, K.G., 2014b. Agricultural expansion and its impacts on tropical nature. Trends in Ecology & Evolution 29, 107–116.</ref> Road expansion increases deforestation through increased access to previously inaccessible forests, facilitating unofficial road building, legal and illegal logging, illegal colonization of previously undisturbed areas, land speculation, land grabbing, and forest conversion through illegal and legal means.<ref name=":36" /><ref name=":37">Kirby, K.R., Laurance, W.F., Albernaz, A.K., Schroth, G., Fearnside, P.M., Bergen, S., Venticinque, E.M., da Costa, C., 2006. The future of deforestation in the Brazilian Amazon. Futures 38, 432–453.</ref><ref name=":38">Laurance, W.F., Albernaz, A.K.M., Schroth, G., Fearnside, P.M., Bergen, S., Venticinque, E.M., Da Costa, C., 2002a. Predictors of deforestation in the Brazilian Amazon. Journal of Biogeography 29, 737–748.</ref><ref>Laurance, W.F., Balmford, A., 2013. A global map for road building. Nature 495, 308–309 </ref> A strong positive correlation has been observed between road building and deforestation in regions such as the United States,<ref name=":38" /> Europe,<ref>Bryan, J.E., Shearman, P.L., Asner, G.P., Knapp, D.E., Aoro, G., Lokes, B., 2013. Extreme differences in forest degradation in Borneo: comparing practices in Sarawak, Sabah, and Brunei. PLoS ONE 8, e69679. </ref> and China.<ref name=":35" /><ref name=":8">Laurance, W.F., Sloan, S., Weng, L., Sayer, J.A., 2015b. Estimating the environmental costs of Africa's massive "Development Corridors". Current Biology 25, 3202–3208.</ref> Around 95% of all deforestation in European countries has occurred within 5.5 km of legal or illegal roads,<ref>Barber, C.P., Cochrane, M.A., Souza Jr, C.M., Laurance, W.F., 2014. Roads, deforestation, and the mitigating effect of protected areas in the Amazon. Biological Conservation 177, 203–209.</ref> indicating a strong association of existing and planned roads as a proximate driver of forest loss and degradation.<ref name=":37" /><ref>Pfaff, A., Robalino, J., Walker, R., Aldrich, S., Caldas, M., Reis, E., Perz, S., Bohrer, C., Arima, E., Laurance, W., Kirby, K., 2007. Road investments, spatial spillovers, and deforestation in the Brazilian amazon. Journal of Regional Science 47, 109–123.</ref> Road expansion also facilitates increased access for hunters and poachers,<ref name=":17" /><ref name=":11" /><ref name=":9" /><ref name=":16" /><ref name=":19">Maisels, F., Strindberg, S., Blake, S., Wittemyer, G., Hart, J., Williamson, E.A., Aba'a, R., Abitsi, G., Ambahe, R.D., Amsini, F., Bakabana, P.C., Hicks, T.C., Bayogo, R.E., Bechem, M., Beyers, R.L., Bezangoye, A.N., Boundja, P., Bout, N., Akou, M.E., Bene, L.B., Fosso, B., Greengrass, E., Grossmann, F., Ikamba-Nkulu, C., Ilambu, O., Inogwabini, B.-I., Iyenguet, F., Kiminou, F., Kokangoye, M., Kujirakwinja, D., Latour, S., Liengola, I., Mackaya, Q., Madidi, J., Madzoke, B., Makoumbou, C., Malanda, G.-A., Malonga, R., Mbani, O., Mbendzo, V.A., Ambassa, E., Ekinde, A., Mihindou, Y., Morgan, B.J., Motsaba, P., Moukala, G., Mounguengui, A., Mowawa, B.S., Ndzai, C., Nixon, S., Nkumu, P., Nzolani, F., Pintea, L., Plumptre, A., Rainey, H., de Semboli, B.B., Serckx, A., Stokes, E., Turkalo, A., Vanleeuwe, H., Vosper, A., Warren, Y., 2013. Devastating decline of forest Elephants in Central Africa. PLoS ONE 8, e59469.</ref><ref name=":39">Blake, S., Strindberg, S., Boudjan, P., Makombo, C., Bila-Isia, I., Ilambu, O., Grossmann, F., Bene-Bene, L., de Semboli, B., Mbenzo, V., S'Hwa, D., Bayogo, R., Williamson, L., Fay, M., Hart, J., Maisels, F., 2007. Forest elephant crisis in the Congo Basin. PLOS Biology 5, e111. </ref> leading to an increase in both legal and illegal hunting. In Central Africa, the strongest predictors of decline in elephant populations were proximity to expanding infrastructure and the absence of law enforcement.<ref name=":19" /> A significant decline in African forest elephant populations between 2002 and 2011 was facilitated by increased road-building rates in Central Africa.<ref name=":11" /><ref name=":19" /><ref name=":39" /> In equatorial West Africa, the collapse of gorilla and chimpanzee populations was primarily caused by hunting that was spurred by a rapid expansion of road networks, which facilitated poaching as well as habitat conversion.<ref name=":10">Sloan, S., Supriatna, J., Campbell, M.J., Alamgir, M.., Laurance, W.F. (2018). Newly discovered orangutan species requires urgent habitat protection Current Biology. </ref><ref name=":40">Walsh, P.D., Abernethy, K.A., Bermejo, M., Beyers, R., De Wachter, P., Akou, M.E., Huijbregts, B., Mambounga, D.I., Toham, A.K., Kilbourn, A.M., et al. (2003). Catastrophic ape decline in western equatorial Africa. Nature ''422'', 611–614.</ref>
Where forest management is weak, road expansion proceeds unregulated and can be allowed to fragment crucial bioregions and protected areas. In Africa, upgraded and proposed road-development corridors intersected 345 protected areas, of which 69 were high-value protected areas (national parks, World Heritage Site, Ramsar site).<ref name=":32">{{Cite journal|last1=Sloan|first1=Sean|last2=Bertzky|first2=Bastian|last3=Laurance|first3=William F.|date=9 December 2016|title=African development corridors intersect key protected areas|journal=African Journal of Ecology|volume=55|issue=4|pages=731–737|doi=10.1111/aje.12377|issn=0141-6707}}</ref>
== Effects on the economy ==
=== Market access === Road infrastructure development lowers the cost of logistics, especially for remote communities. Increased consumer base allows producers, such as farmers, to increase the export of their goods, and thereby increase the flow of money into the industry. Improved road infrastructure has reduced poverty by facilitating higher production and exports in Peru,<ref>{{Cite journal|last1=Volpe Martincus|first1=Christian|last2=Carballo|first2=Jerónimo|last3=Cusolito|first3=Ana|date=March 2017|title=Roads, exports and employment: Evidence from a developing country|journal=Journal of Development Economics|volume=125|pages=21–39|doi=10.1016/j.jdeveco.2016.10.002|issn=0304-3878|url=https://digitalcommons.fiu.edu/srhreports/critical-infrastructure/critical-infrastructure/30 |url-access=subscription}}</ref> Bangladesh,<ref name=":30">Khandker, S., xa, R, Bakht, Z., Koolwal, G., xa, & B. (2009). The Poverty Impact of Rural Roads: Evidence from Bangladesh. ''Economic Development and Cultural Change, 57''(4), 685-722. doi:10.1086/598765</ref> and parts of Sub-Saharan Africa.<ref>{{Cite journal|last1=Dorosh|first1=Paul|last2=Wang|first2=Hyoung Gun|last3=You|first3=Liangzhi|last4=Schmidt|first4=Emily|date=6 December 2011|title=Road connectivity, population, and crop production in Sub-Saharan Africa|journal=Agricultural Economics|volume=43|issue=1|pages=89–103|doi=10.1111/j.1574-0862.2011.00567.x|issn=0169-5150}}</ref> Improved market access as a result of improved road infrastructure facilitates a shift from subsistence agriculture to increasingly specialized and commercialized agriculture.<ref name=":31">{{Cite journal|last1=N.|first1=Berg, Claudia|last2=Klaus|first2=Deichmann, Uwe|last3=Liu, Yishen|last4=Selod, Harris|date=14 July 2015|title=Transport policies and development|url=http://documents.worldbank.org/curated/en/893851468188672137/Transport-policies-and-development|pages=1–45}}</ref> Increased commercialization of agriculture results in economic gains for communities, however it can also increase dependence on external markets<ref name=":33">{{Cite journal|last=DeWalt|first=Kathleen M.|date=June 1993|title=Nutrition and the commercialization of agriculture: Ten years later|journal=Social Science & Medicine|volume=36|issue=11|pages=1407–1416|doi=10.1016/0277-9536(93)90383-f|pmid=8511629|issn=0277-9536}}</ref> and external sources of goods. This has been shown to either result in improved food security, as communities are not reliant on their own agricultural capacity,<ref>{{Cite journal|last1=Blimpo|first1=M. P.|last2=Harding|first2=R.|last3=Wantchekon|first3=L.|date=30 July 2013|title=Public Investment in Rural Infrastructure: Some Political Economy Considerations|journal=Journal of African Economies|volume=22|issue=suppl 2|pages=ii57–ii83|doi=10.1093/jae/ejt015|issn=0963-8024}}</ref> or be detrimental to nutritional status<ref name=":33" /><ref name=":41">{{Cite journal|last=Dewey|first=Kathryn G.|date=June 1981|title=Nutritional consequences of the transformation from subsistence to commercial agriculture in Tabasco, Mexico|journal=Human Ecology|volume=9|issue=2|pages=151–187|doi=10.1007/bf00889132|s2cid=154229177|issn=0300-7839}}</ref><ref name=":7">{{Cite journal|last1=Carletto|first1=Calogero|last2=Corral|first2=Paul|last3=Guelfi|first3=Anita|date=February 2017|title=Agricultural commercialization and nutrition revisited: Empirical evidence from three African countries|journal=Food Policy|volume=67|pages=106–118|doi=10.1016/j.foodpol.2016.09.020|issn=0306-9192|pmc=5384450|pmid=28413250}}</ref> as communities no longer produce a diverse range of crops.
Facilitating access of remote communities to urban markets can also have the effect of allowing urban market influences to affect rural economies. In the Democratic Republic of the Congo, urban markets are subject to greater control by soldiers than are rural markets, resulting in hunters and farmers paying more protection money and getting less of a share of profits made.<ref name=":42">{{Cite journal|last1=De MERODE|first1=EMMANUEL|last2=COWLISHAW|first2=GUY|date=10 March 2006|title=Species Protection, the Changing Informal Economy, and the Politics of Access to the Bushmeat Trade in the Democratic Republic of Congo|journal=Conservation Biology|volume=20|issue=4|pages=1262–1271|doi=10.1111/j.1523-1739.2006.00425.x|pmid=16922242|s2cid=25757273 |issn=0888-8892}}</ref> Greater market intensity is in some instances environmentally detrimental. In the Democratic Republic of the Congo, more large-bodied and endangered animals are hunted for sale in urban markets than in rural markets.<ref name=":42" />
=== Road construction === Roads must be well designed and constructed to reduce impacts on regional geomorphology and hydrology. In undulating terrain, road construction typically proceeds via cut-and-fill activities, in which high parts of the landscape are cut down and the fill (soil and mineral earth) is bulldozed into lower areas, in order to flatten-out the topography along the road route. Concurrently, vegetation is usually cleared along and adjacent to a road footprint. These practices dramatically increase surface erosion and sediment inputs to water courses, altering hydrological patterns, reducing water quality for humans and livestock and elevating water turbidity and temperature.<ref>Sidle, R.C., Sasaki, S., Otsuki, M., Noguchi, S., Rahim Nik, A., 2004. Sediment pathways in a tropical forest: effects of logging roads and skid trails. Hydrological Processes 18, 703–720.</ref><ref name=":4">Sidle, R.C., Ziegler, A.D., 2012. The dilemma of mountain roads. Nature Geosci 5, 437–438.</ref><ref>Sidle, R.C., Ziegler, A.D., Negishi, J.N., Nik, A.R., Siew, R., Turkelboom, F., 2006. Erosion processes in steep terrain—truths, myths, and uncertainties related to forest management in Southeast Asia. Forest Ecology and Management 224, 199–225.</ref> The altered existing hydrological dynamics resulting from cut and fill activities, inadequate drainage, culverts, and bridges associated with road construction can also obstruct surface-water flow, leading to impeded drainage and localized flooding, particularly during high-rainfall episodes.<ref>Beevers, L., Douven, W., Lazuardi, H., Verheij, H., 2012. Cumulative impacts of road developments in floodplains. Transportation Research Part D: Transport and Environment 17, 398–404.</ref><ref>Douven, W., Buurman, J., 2013. Planning practice in support of economically and environmentally sustainable roads in floodplains: the case of the Mekong delta floodplains. Journal of Environmental Management 128, 161–168.</ref>
Road construction in mountainous areas or steep terrain increases the risks of landslides,<ref>Leshchinsky, B., Olsen, M.J., Mohney, C., Glover-Cutter, K., Crook, G., Allan, J., Bunn, M., O'Banion, M., Mathews, N., 2017. Mitigating coastal Iandslide damage. Science 357, 981–982.</ref> particularly in wet environments.<ref name=":4" /> Site disturbances, vegetation clearing, unstable terrain caused by cut-and-fill activities, and road drainage all contribute to the elevated rates of landslides in mountainous or steep terrain areas with roads[48]{{Unreliable source?|date=February 2023}}, with the likelihood of landslides in close proximity to roads being up to five times higher.<ref>Larsen, M.C., Parks, J.E., 1997. How wide is a road? The association of roads and mass-wasting in a forested montane environment. Earth Surface Processes and Landforms 22, 835–848.</ref> In the Brazilian Amazon, ~90% of fires occurred within ≤10 km of roads.<ref>Adeney, J.M., Christensen, N.L., Jr., Pimm, S.L., 2009. Reserves protect against deforestation fires in the Amazon. PLoS ONE 4, e5014.</ref>
Road construction in forests leads to an increased frequency of fires.<ref name=":1" /><ref name=":5" /> This happens via numerous mechanisms, including intentionally lit fires (leading to deforestation), leaked fires from land management practices adjacent to fragmented forests or roads, and accidental fires due to increased human-ignition sources.<ref>Alencar, A., Nepstad, D., Diaz, M.C.V., 2006. Forest understory fire in the Brazilian Amazon in ENSO and Non-ENSO years: Area burned and committed carbon emissions. Earth Interactions 10, 1–17.</ref><ref>Laurance, W.F., Williamson, G.B., 2001. Positive feedbacks among forest fragmentation, drought, and climate change in the Amazon. Conservation Biology 15, 1529–1535.</ref> Increased fire frequency results directly in biomass loss and carbon emissions, and elevated fire regimes alter the species composition and ecological dynamics of susceptible forests.
=== Traffic and road maintenance === Funding for new road infrastructure in developing nations is focused on initial road construction, with less money being earmarked for ongoing maintenance.<ref name=":23">Alamgir, M., Campbell, M.J., Sloan, S., Goosem, M., Clements, G.R., Mahmoud, M.I., Laurance, W.F., 2017. Economic, socio-political and environmental risks of road development in the tropics. Current Biology 27, R1130-R1140.</ref> With many new roads being constructed in high-rainfall tropical environments, degradation leading to slumping and pot-holing is rendering expensive paved roads impassable in just a few years. Road degradation increases the cost of using the road, by lengthening travel time or causing damage to vehicles.<ref name=":43">{{Cite journal|last=Kerali|first=Henry|date=January 2003|title=Economic appraisal of road projects in countries with developing and transition economies|journal=Transport Reviews|volume=23|issue=3|pages=249–262|doi=10.1080/0144164032000068920|s2cid=153362304|issn=0144-1647}}</ref> Poor quality paved roads may cost less on initial construction, but are more costly to maintain and produce greater costs of use over the life of the road.<ref name=":43" />
Maintaining roads involves long-term and major investments which are subjected to corrupt practices of those responsible for maintenance. Moreover, budgeting high construction costs, but building substandard roads which require higher levels of maintenance are both common practice and a major drain on public expenditure and private investment.<ref name=":23" /> Such activities escalate costs and reduce the usable lifetime of roads, and are particularly evident in many developing countries where corruption is more pervasive and implicitly tolerated.<ref name=":8" /><ref name=":24">Mahmoud, M. I., Sloan, S., Campbell, M. J., Alamgir, M., Imong, I., Odigha, O., . . . Laurance, W. F. (2017). Alternative routes for a proposed nigerian superhighway to limit damage to rare ecosystems and wildlife. ''Tropical Conservation Science, 10'', 1940082917709274.</ref><ref name=":46">World Bank. (2010). ''Cost-benefit analysis in world bank projects''. Retrieved from Washington, DC </ref>
Increased road expansion incentivizes people to purchase cars and use roads to a greater extent. This results in further degradation of the roads, leading to higher maintenance costs. Increased use of vehicles and roads leads to more accidents, particularly in regions where roads are of poor quality and motor vehicle use is relatively novel.<ref name=":31" /><ref>{{Cite news|url=https://www.worldatlas.com/articles/the-countries-with-the-most-car-accidents.html|title=Countries With the Most Car Accidents|work=WorldAtlas|access-date=17 September 2018}}</ref> More roads result in more traffic, due to induced demand, further increasing the rate of road degradation. As such, economic appraisals of road projects in developing countries often find that improving existing road infrastructure is more beneficial than construction of new road infrastructure.<ref name=":43" />
== Effects on societies ==
=== Access to services === In developing countries especially, goods and services such as health facilities and educational facilities are often concentrated in urban regions, with little to no availability in remote and rural areas. Road expansion provides greater accessibility to urban centers, and hence improves educational attainment.<ref name=":7" /> In both Bangladesh<ref name=":30" /> and Madagascar<ref>{{Cite journal|last1=Jacoby|first1=Hanan G.|last2=Minten|first2=Bart|date=May 2009|title=On measuring the benefits of lower transport costs|journal=Journal of Development Economics|volume=89|issue=1|pages=28–38|doi=10.1016/j.jdeveco.2008.06.004|issn=0304-3878|hdl=10986/6489|s2cid=1697016|url=http://www-wds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2008/01/22/000158349_20080122155649/Rendered/PDF/wps4484.pdf |hdl-access=free}}</ref> investments in improving rural roads have led to greater education attainment. Similarly, greater access to urban areas gives remote communities better access to health facilities, including medical supplies and medical information,<ref>{{Cite news|url=http://theconversation.com/bridges-and-roads-as-important-to-your-health-as-whats-in-your-medicine-cabinet-78979|title=Bridges and roads as important to your health as what's in your medicine cabinet|last=Smith|first=Korydon|work=The Conversation|access-date=17 September 2018}}</ref> and has been associated with better health outcomes.<ref name=":44">{{Cite journal|last1=Weiss|first1=D. J.|last2=Nelson|first2=A.|last3=Gibson|first3=H. S.|last4=Temperley|first4=W.|last5=Peedell|first5=S.|last6=Lieber|first6=A.|last7=Hancher|first7=M.|last8=Poyart|first8=E.|last9=Belchior|first9=S.|date=10 January 2018|title=A global map of travel time to cities to assess inequalities in accessibility in 2015|journal=Nature|volume=553|issue=7688|pages=333–336|doi=10.1038/nature25181|issn=0028-0836|pmid=29320477|bibcode=2018Natur.553..333W |s2cid=205263338|url=https://researchonline.lshtm.ac.uk/id/eprint/4657237/1/weiss_et_al_2017_accepted.pdf}}</ref>
Access to urban centers facilitated by road expansion improves employment opportunities. In Indonesia, improved roads allowed job creation in manufacturing industries and an occupational shift amongst workers away from agriculture.<ref>Gertler, P. J., M. Gonzalez-Navarro, T. Gracner, and A. D. Rothenberg (2014) [http://sites.bu.edu/neudc/files/2014/10/paper_250.pdf "The Role of Road Quality Investments on Economic Activity and Welfare: Evidence from Indonesia's Highways"].</ref> Conversely, a greater supply of people seeking employment can drive down the wages in an area, producing a negative effect on livelihoods.<ref name=":45">Grant, U. (2008) Opportunity and exploitation in urban labour markets London: Overseas Development Institute</ref>
While access to goods and services associated with urban centers is beneficial, increased relocation to already densely populated centers increases the strain on cities already struggling to cope with growing populations, particularly in developing regions.<ref>Economic Intelligence Unit. 2013. The Socio-economic Costs of Traffic Congestion in Lagos. Ministry of Economic Planning & Budget.</ref> Increasing urbanization presents problems including increased crime, increasing inequality, and public health concerns.<ref name=":45" /><ref>Malik, A. A. (2016). Urbanization and Crime: A Relational Analysis. J. HUMAN. & Soc. Scl., 21, 68–69 </ref><ref>{{Cite journal|last1=Eckert|first1=Sophie|last2=Kohler|first2=Stefan|date=30 January 2014|title=Urbanization and Health in Developing Countries: A Systematic Review|journal=World Health & Population|volume=15|issue=1|pages=7–20|doi=10.12927/whp.2014.23722|pmid=24702762|issn=1929-6541|doi-access=free}}</ref>
=== Migration and culture === Road expansion leads to forced migration of local peoples, with indigenous groups often being highly vulnerable. This happens via the influx of non-indigenous settlers who migrate into the region for employment or to exploit local resources. Non-indigenous settlers can attain or claim the land title through land grabbing, land speculation, and illegal colonization.<ref name=":12">Koji, T., Hoban, C., 1997 Roads and the environment: a handbook, p. 252. The World Bank, Washington, DC.</ref><ref>Porter, G., 1997. Mobility and inequality in rural Nigeria: the case of off-road communities. Tijdschrift voor Economische en Sociale Geografie 88, 65–76.</ref><ref>Singleton, I., Wich, S., Husson, S., Stephens, S., Atmoko, S.U., Leighton, M., Rosen, N., Traylor-Holzer, K., Lacy, R., Byers, O., 2004. Orangutan population and habitat viability assessment: final report, p. 65. IUCN/SSC Conservation Breeding Specialist Group, Apple Valley, MN, USA.</ref><ref>Wind, J., 1996. Gunung Leuser National Park: history, threats and options, In Leuser a Sumatran Sanctuary. eds C.P. van Shaik, J. Supratna, pp. 4–27. Perdana Ciptamandiri, Jakarta. </ref> While migration increases urbanization, potentially leading to increased development, this is at the expense of indigenous populations.{{Citation needed|date=February 2023}}
Road expansion is particularly threatening for vulnerable remote communities. Large road projects generate an influx of temporary migrant workers, which increases the demand for services such as prostitution and black-market products.<ref name=":26">Carswell, J.W., 1987. HIV infection in healthy persons in Uganda. AIDS 1, 223–227.</ref><ref name=":9" /><ref name=":1" /> Beyond this, road expansion in remote areas also promotes activities such as illegal logging, illegal mining, poaching, smuggling and illicit drug production.<ref>Asner, G.P., Llactayo, W., Tupayachi, R., Luna, E.R., 2013. Elevated rates of gold mining in the Amazon revealed through high-resolution monitoring. Proceedings of the National Academy of Sciences 110, 18454-18459.</ref><ref name=":1" /><ref>Laurance, W.F., Peletier-Jellema, A., Geenen, B., Koster, H., Verweij, P., Van Dijck, P., Lovejoy, T.E., Schleicher, J., Van Kuijk, M., 2015a. Reducing the global environmental impacts of rapid infrastructure expansion. Current Biology 25, R259-R262.</ref><ref>McSweeney, K., Nielsen, E.A., Taylor, M.J., Wrathall, D.J., Pearson, Z., Wang, O., Plumb, S.T., 2014. Drug policy as conservation policy: narco-deforestation. Science 343, 489–490.</ref><ref>Suárez, E., Morales, M., Cueva, R., Bucheli, V.U., Zapata-Ríos, G., Toral, E., Torres, J., Prado, W., Olalla, J.V., 2009. Oil industry, wild meat trade and roads: indirect effects of oil extraction activities in a protected area in north-eastern Ecuador. Animal Conservation 12, 364–373.</ref><ref name=":34" /> Such activities can have chain-reaction-like impacts on the traditional culture and social structure of local communities. The scale and pace of these impacts are most severe in indigenous communities.{{Citation needed|date=February 2023}}
The traditional culture and lifestyles of indigenous groups that have lived in remote areas for many generations are substantially altered by new roads. Unprecedented road penetration into their natural landscapes can damage the aesthetic of the landscape and traditional cultural practices, the influx of non-indigenous land settlers violates traditional land rights, and increased commercial poaching alters traditional hunting practices. All such consequences degrade the cultural heritage of indigenous communities, increasing loss of their traditional identity and culture.<ref name=":23" /><ref>Colombijn, F., 2002. Introduction: on the road. Journal of the Humanities and Social Sciences of Southeast Asia 158, 595 – 617.</ref><ref name=":12" />
===Diseases=== Temporary workers for road building and the influx of settlers resulting from road building bring new pests and diseases into communities. This mechanism is particularly dangerous for indigenous communities that have limited tolerance and immunity to new pathogens. For instance, the construction of the Route 8 in Bolivia in the 1970s resulted in the death of 45% of one indigenous community within a single year.<ref>Hecht, S.B., Cockburn, A., 2010. The Fate of the Forest: Developers, Destroyers and Defenders of the Amazon, Updated edn. The University of Chicago Press, Chicago, USA. </ref>
Road expansion increases the incursion of common diseases into communities such as malaria and also increase the vulnerability of communities to previously uncommon diseases such as HIV. This occurs as pests and pathogens use roads as a pathway to spread from one place to another place. Human enteric pathogen levels, for instance, were 2–8-times higher in Ecuadorian villages near roads than in more remote areas<ref name=":43" /> and incursions of dengue fever, malaria, and HIV were higher among people living near roads than in remote communities.<ref name=":26" /><ref>Dutta, P., Khan, S. A., Sharma, C. K., Doloi, P., Hazarika, N. C. and Mahanta, J., 1998. Distribution of potential dengue vectors in major townships along the national highways and trunk roads of Northeast India. Southeast Asian Journal of Tropical Medicine and Public Health 29, 173–176.</ref>
=== Conflict === The influx of non-indigenous migrants through road building, and the associated intensification of contact, create inter-group conflicts, such as seen between indigenous Amazonian tribes and loggers or gold miners.<ref>{{Cite news|url=https://news.nationalgeographic.com/2018/03/peruvian-amazon-road-forests-uncontacted-tribes-indigenous-rights/|archive-url=https://web.archive.org/web/20180428184505/https://news.nationalgeographic.com/2018/03/peruvian-amazon-road-forests-uncontacted-tribes-indigenous-rights/|url-status=dead|archive-date=28 April 2018|title=Isolated Tribes and Forests Threatened by New Amazon Road|date=23 March 2018|access-date=17 September 2018}}</ref> Additionally, increased road access increases the spread of conflicting forces in war-torn regions, and the pace at which conflicts escalate. In the Democratic Republic of Congo, more accessible regions were exposed to more violent events than less accessible regions resulting in a decrease of population welfare.<ref>{{Cite journal|last1=Ali, Rubaba|last2=Federico|first2=Barra, Alvaro|last3=N.|first3=Berg, Claudia|last4=Damania, Richard|last5=D.|first5=Nash, John|last6=Daniel|first6=Russ, Jason|date=18 May 2015|title=Infrastructure in conflict-prone and fragile environments : evidence from the Democratic Republic of Congo|url=http://documents.worldbank.org/curated/en/810421468000299138/Infrastructure-in-conflict-prone-and-fragile-environments-evidence-from-the-Democratic-Republic-of-Congo|pages=1–58}}</ref>
== Reducing the impacts of road expansion == There are a few ways of reducing its impacts.
===Expanding existing roads=== Following the 'first-cut-is-the-deepest' dictum, the expansion or upgrading of roads in previously settled areas is believed to cause less environmental impact per kilometer of road development than where new roads penetrate intact forest landscapes. Beyond this rule of thumb, however, road expansion threatens remnant habitats of endangered species and leads to the loss of remnant areas of rare ecosystems (e.g., lowland tropical forest). This is increasingly common as new major road developments seek to consolidate earlier, rudimentary road networks (often characterized by penetration roads, improvised roads, and rough tracks) to expand agricultural and industrial activities in partially deforested landscapes. Many economic appraisals of road projects in developing countries have found that improving existing road infrastructure is more beneficial than construction of new road infrastructure.<ref name=":43" />
Examples of such consolidative road-expansion projects include the various 'development corridors' of Africa,<ref name=":32" /><ref name=":8" /> meant to facilitate trans-national economic activities; Indonesia's development corridors as per its Master Development Plan,<ref>CMEA (2011). Master Plan: Acceleration and Expansion of Indonesia Economic Development, 2011–2025, Jakarta.</ref> meant to accelerate agro-industrial development, mining and timber extraction; and China's Belt and Road initiative.<ref>Lechner, A.M., Chan, F.K.S., and Campos-Arceiz, A. (2018). Biodiversity conservation should be a core value of China's Belt and Road Initiative. Nature Ecology & Evolution ''2'', 408–409.</ref> In northern Sumatra, Indonesia, proposed road developments extending the Trans-Sumatran Highway if they were to occur will affect six of the eight local conservation priority areas of the Leuser Ecosystem,<ref>Sloan, S., Campbell, M.J., Alamgir, M., Collier-Baker, E., Nowak, M., Usher, G., and Laurance, W.F. (In Press). Infrastructure development and contested forest governance threatened the Leuser Ecosystem, Indonesia. Land Use Policy.</ref> comprising 89% of the remaining Sumatran orangutan'<nowiki/>s habitat.<ref>Wich, S.A., Riswan, J., Refisch, J., and Nellemann, C. (2011). Orangutans and the economics of sustainable forest management in Sumatra. Birkeland Trykkeri, Norway.</ref> In fact, Forest conversion due to road development in this region has been projected as a major factor influencing the decline in orangutan populations.<ref>Gaveau, D.L.A., Wich, S., Epting, J., Juhn, D., Kanninen, M., and Leader-Williams, N. (2009). The future of forests and orangutans (Pongo abelii) in Sumatra: Predicting impacts of oil palm plantations, road construction, and mechanisms for reducing carbon emissions from deforestation. Environmental Research Letters ''4'', 034013.</ref><ref>Wich, S.A., Singleton, I., Nowak, M.G., Atmoko, S.S.U., Nisam, G., Arif, S.M., Putra, R.H., Ardi, R., Fredriksson, G., and Usher, G. (2016). Land-cover changes predict steep declines for the Sumatran orangutan (Pongo abelii). Science Advances ''2'', e1500789.</ref>
===Limiting road expansion=== Road planning to limit the extension of existing roads in ecologically vulnerable areas or mitigation measures such as restriction of road width and the inclusion of faunal overpasses is an emerging field of conservation science. Aside from the environmental benefits, limiting road expansion is beneficial for social and economic factors in developing regions. Many roads in remote areas have uncertain socio-economic benefits and surprisingly high economic, social, and environmental risks, and a cost-benefit analysis of 33 planned 'development corridors' in sub-Saharan Africa concluded that less than one-fifth of the projects were clearly justified.<ref name=":8" /> Many road developments will be characterized by upgrades to rudimentary road networks, rather than entirely new roads.<ref name=":32" /> The Trans-Borneo Highway in Sabah, Malaysia is one example, as virtually all road developments on this route planned for 2033 will coincide with existing logging roads or two-lane access roadways.<ref>Campbell, M.J., Sloan, S., Alamgir, M., and Laurance, W.F. (In preparation). Trans-Borneo Highway Development in Sabah Undermines Heart of Borneo Transnational Conservervation Pledge.</ref><ref>Ministry of Local Government and Housing (2016). Sabah Structure Plan 2033, (Kota Kinabalu, Sabah, Malaysia: Town and Region Planning Department of Malaysian Ministry of Local Government and Housing).</ref>
=== Project assessment === The use of more rigorous approaches to project assessment and planning, such as cost-benefit analyses, proactive land-use planning,<ref name=":0" /> and strategic environmental-impact assessments, is important for the improvement of road developments.<ref name=":8" /><ref name=":24" /><ref name=":46" />
== See also == *Agricultural expansion *Automotive city * Braess's paradox *Freeway removal *Highway revolt *Road diet *{{Annotated link|Sustainable Development Goal 11}}
==External links== * James Cook University – Centre for Tropical Environmental and Sustainability Science: [https://www.jcu.edu.au/tess/research/reducing-the-global-impacts-of-rapid-infrastructure-expansion Reducing the global impacts of rapid infrastructure expansion] * [http://www.global-roadmap.org/ Global Road Maps]: A strategic approach for advancing nature and sustainability. * [https://www.laurancelab.org/ Laurance Lab]: James Cook University laboratory website with information about the team and current projects. * [http://roadfree.org/ Road Free]: A key website for those concerned about road impacts on wilderness and biodiversity * [http://alert-conservation.org/ Alert Conservation:] A scientific organization that focuses on tropical forests, wilderness, and environmental conservation issues. Provides links to many topical articles, conservation news, and research. * [http://conservationbytes.com/ Conservation Bytes:] A lively website for news and opinion about nature conservation.
== References == <!-- Inline citations added to your article will automatically display here. See https://en.wikipedia.org/wiki/WP:REFB for instructions on how to add citations. --> {{Reflist}}
Category:Roads Category:Environmentalism Category:Transportation planning Category:Road transport