Infrastructure Development
Peer-Reviewed Publications
Roads and other infrastructure development projects are expanding globally at the fastest rate in human history, especially in biodiversity-rich developing tropical regions. Infrastructure expansion often promotes forest loss and land-cover conversion, fires, poaching, and other environmental and societal impacts. Understanding where and how these development projects will impact tropical forests is crucial to their survival. My work focuses on modelling the impacts of roads on land use change in tropical forests, in order to identify methods of minimizing the environmental impacts of future development.
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Road Ecology has experienced rapid growth as a field, yet significant knowledge and research gaps remain, particularly regarding underexplored impacts of roads on fauna and flora, ecosystems and landscapes, as mitigation methods and management solutions to avoid or reduce negative impacts. Here, we synthesize the key research needs identified throughout the book and emphasize topics that have received limited attention, highlighting the growing need for interdisciplinary and technologically advanced studies, and innovative statistical methodologies to assess infrastructure impacts and the combined effects of different types of infrastructures (such as roads and powerlines) on biodiversity. We highlight the need for more comprehensive studies on ecosystem functioning, evolutionary effects, and the role of roadside habitats, while calling for improvements in the cost-effectiveness of mitigation measures and large-scale assessments of road impacts. Emerging research priorities for Road Ecology include a growing emphasis on interdisciplinary and technologically advanced studies, and innovative statistical methodologies to assess infrastructure impacts and the combined effects of multiple infrastructures (such as roads and powerlines) on biodiversity. The impact of new infrastructure in areas supporting multiple migratory species is also becoming a priority issue, especially in regions where there is significant growth in infrastructure projects. Interdisciplinary efforts should prioritize strategies that balance infrastructure development with biodiversity conservation, especially in rapidly developing regions.
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Road networks have been expanding at a dramatic pace in recent decades, driven by growing demand for resources, energy, and access to markets. However, roads can also open a Pandora’s box of environmental ills, the most significant of which may be habitat loss and fragmentation. The scale of habitat loss driven by roads is dependent on their capacity to promote travel, and hence outcomes differ for paved and unpaved roads and for different habitat types. Where habitat fragments remain intact, spiderweb-like road networks create edge effects and act as barriers to movement for disturbance-sensitive species of plants and animals. This fragmentation means large expanses of remaining habitats are highly degraded and have altered species composition and ecological function. A substantial proportion of all roads today are not recorded in existing roadmaps. With millions of kilometers of new roads expected worldwide in the near future, it will be vital to develop new methods to detect roads in order to document the effects of road-related habitat disruption, and develop strategic road plans to minimize these disruptions.
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Roads act as conduits for human incursions and hence underlie many of humanity’s impacts on nature, including deforestation, wildfires, and natural-resource overexploitation. Unfortunately, existing roadmaps often drastically underestimate the true extent of road networks and future predictions of road-related impacts rely on incomplete and outdated data, undermining development planning and conservation decision-making. Here, we develop a multivariate “road expansion risk” index to identify areas prone to road building and therefore vulnerable to road-related environmental impacts. Using a massive road dataset—137 million 1-ha raster cells drawn from three different sources arrayed across the Amazon and Congo basins and insular Asia-Pacific region—we predict road-prone locations via a statistical model that integrates a range of biophysical, socioeconomic, and administrative data. This highly integrative, large-scale approach allowed us to identify areas likely to experience future road building and regions that may contain unmapped roads. Importantly, our road expansion risk index is a strong predictor of forest loss and degradation and can hence identify future road building and deforestation hotspots, even for the many tropical forest locales with grossly deficient road data.
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In the tropics and beyond, roads are key proximate drivers of environmental impacts, including forest fragmentation, fires, mining, and land clearing. Such impacts may be amplified for the initial roads constructed in intact forests—which we term “first-cut roads”—which often promote a rash of associated secondary roads branching off the new infrastructure. These secondary roads in turn can dramatically elevate forest and biodiversity losses. Although widely seen as a conservation concern, the magnitude and effects of secondary road development have not been previously quantified. Without such information, impact assessment procedures for road projects risk misjudging the level of expected forest loss, hampering decision-making. Here, we quantify the environmental impacts of both first-cut and secondary roads in three of the world’s major tropical regions where high-quality road maps have recently become available: the Brazilian Amazon, the Congo Basin, and New Guinea. We identified 92 first-cut roads across our study region for which we quantified the length of adjoining secondary roads and the area of related forest loss and degradation. On average, we found 4.8, 9.8, and 49.1 km of secondary road for every kilometer of first-cut road in the Congo Basin, New Guinea, and Brazilian Amazon regions, respectively. Forest loss and degradation associated with these secondary roads was remarkably heavy, being 31.5, 22.2, and 305.2 times greater, respectively, than that directly linked with first-cut roads. Our findings provide key insights into the potential scale and extent of forest loss and degradation that will emerge with proposed roads and development corridors in tropical forests.
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The island of New Guinea harbors some of the world's most biologically diverse and highly endemic tropical ecosystems. Nevertheless, progressing land-use change in the region threatens their integrity, which will adversely affect their biodiversity as well as carbon stocks and fluxes. Our objectives were to (1) compare deforestation drivers between Indonesian New Guinea and Papua New Guinea, (2) identify areas with a high risk of future deforestation under different development scenarios, and (3) evaluate the effects of potential deforestation scenarios on carbon pools. We integrated machine learning and cellular automata to model and forecast deforestation across New Guinea. We assessed the potential loss of irrecoverable carbon stocks for four deforestation scenarios ranging from 4.8 % (business-as-usual) to 28 % (high development scenario) forest loss between 2020 and 2040. Areas of high deforestation risk were consistently forecasted in lowland regions across the four deforestation scenarios. In Indonesian New Guinea, 75 % of deforestation was forecasted below ~380 m a.s.l., but ranged higher in Papua New Guinea (<750 m a.s.l.). Land change-induced carbon loss varied largely across the four scenarios and ranged between 156 and 918 Mt in Indonesian New Guinea and between 223 and 1082 Mt in Papua New Guinea, respectively. Our analysis reveals promising potential for integrating random forests and cellular automata models to forecast high-resolution deforestation over large spatial extents. Our models reveal the vulnerability of New Guinea's lowlands to future deforestation, emphasizing the need to protect key areas where deforestation conflicts with the conservation of carbon stocks, ecosystem functions, and biodiversity.
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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 effects. Many roads are being constructed illegally or informally and do not appear on any existing road map; 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 correlate 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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Road building has long been under-mapped globally, arguably more than any other human activity threatening environmental integrity. Millions of kilometers of unmapped roads have challenged environmental governance and conservation in remote frontiers. Prior attempts to map roads at large scales have proven inefficient, incomplete, and unamenable to continuous road monitoring. Recent developments in automated road detection using artificial intelligence have been promising but have neglected the relatively irregular, sparse, rustic roadways characteristic of remote semi-natural areas. In response, we tested the accuracy of automated approaches to large-scale road mapping across remote rural and semi-forested areas of equatorial Asia-Pacific. Three machine learning models based on convolutional neural networks (UNet and two ResNet variants) were trained on road data derived from visual interpretations of freely available high-resolution satellite imagery. The models mapped roads with appreciable accuracies, with F1 scores of 72–81% and intersection over union scores of 43–58%. These results, as well as the purposeful simplicity and availability of our input data, support the possibility of concerted program of exhaustive, automated road mapping and monitoring across large, remote, tropical areas threatened by human encroachment.
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In October of 2019, the Indonesian Ministry of Environment and Forestry gave approval for construction of an 88 km-long mining road through the Harapan Forest, an area with outstanding biodiversity values on the island of Sumatra, Indonesia (Diana, 2020). The road approval, granted to Indonesian mining firm PT Marga Bara Jaya, immediately prompted protests from scientists and conservation groups in Indonesia and internationally, as well as from indigenous communities residing within the forest (Diana, 2020; Engert et al., 2021). Construction of the road, which is yet to penetrate the Harapan Forest, is likely to cause significant loss of Sumatran lowland rainforest, a critically endangered ecoregion currently represented by only around 3 % of its original extent (Fig. 1) (Laumonier, 1997; Olson et al., 2001).
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Road-infrastructure projects are expanding rapidly worldwide while penetrating into previously undisturbed forests. In Sumatra, Indonesia, a planned 88-km-long mining road for transporting coal would imperil the Harapan Forest, the island's largest surviving tract of lowland rainforest. Such roads often lead to increased forest encroachment and illegal logging, fires, poaching, and mining. To evaluate the potential impact of the proposed road, we first manually mapped all existing roads inside and around the Harapan Forest using remote-sensing imagery. We then calculated the expected increase in forest loss from three proposed mining-road routes using a metric based on travel-time mapping. Finally, we used least-cost-path analyses to identify new routes for the road that would minimize forest disruption and road-construction costs. We found that road density inside and nearby the Harapan Forest is already 3–4 times higher than official data sources indicate. Based on our analyses, each of the three proposed mining-road routes would lead to 3,000–4,300 ha of additional forest loss from human encroachment plus another 424 ha lost from road construction itself. We propose new routes for the mining road that would result in up to 3,321 ha less forest loss with markedly lower construction costs than any other planned route. We recommend approaches such as ours, using least-cost-path analysis, to minimize the environmental and financial costs of major development projects.
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The forests of Borneo—the third largest island on the planet—sustain some of the highest biodiversity and carbon storage in the world. The forests also provide vital ecosystem services and livelihood support for millions of people in the region, including many indigenous communities. The Pan-Borneo Highway and several hydroelectric dams are planned or already under construction in Sarawak, a Malaysian state comprising part of the Borneo. This development seeks to enhance economic growth and regional connectivity, support community access to services, and promote industrial development. However, the implications of the development of highway and dams for forest integrity, biodiversity and ecosystem services remained largely unreported. We assessed these development projects using fine-scale biophysical and environmental data and found several environmental and socioeconomic risks associated with the projects. The highway and hydroelectric dam projects will impact 32 protected areas including numerous key habitats of threatened species such as the proboscis monkey (Nasalis larvatus), Sarawak surili (Presbytis chrysomelas), Bornean orangutans (Pongo pygmaeus) and tufted ground squirrel (Rheithrosciurus macrotis). Under its slated development trajectory, the local and trans-national forest connectivity between Malaysian Borneo and Indonesian Borneo would also be substantially diminished. Nearly ~161 km of the Pan-Borneo Highway in Sarawak will traverse forested landscapes and ~55 km will traverse carbon-rich peatlands. The 13 hydroelectric dam projects will collectively impact ~1.7 million ha of forest in Sarawak. The consequences of planned highway and hydroelectric dams construction will increase the carbon footprint of development in the region. Moreover, many new road segments and hydroelectric dams would be built on steep slopes in high-rainfall zones and forested areas, increasing both construction and ongoing maintenance costs. The projects would also alter livelihood activities of downstream communities, risking their long-term sustainability. Overall, our findings identify major economic, social and environmental risks for several planned road segments in Sarawak—such as those between Telok Melano and Kuching; Sibu and Bintulu; and in the Lambir, Limbang and Lawas regions—and dam projects—such as Tutoh, Limbang, Lawas, Baram, Linau, Ulu Air and Baleh dams. Such projects need to be reviewed to ensure they reflect Borneo’s unique environmental and forest ecosystem values, the aspirations of local communities and long-term sustainability of the projects rather than being assessed solely on their short-term economic returns.
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The Heart of Borneo initiative has promoted the integration of protected areas and sustainably-managed forests across Malaysia, Indonesia, and Brunei. Recently, however, member states of the Heart of Borneo have begun pursuing ambitious unilateral infrastructure-development schemes to accelerate economic growth, jeopardizing the underlying goal of trans-boundary integrated conservation. Focusing on Sabah, Malaysia, we highlight conflicts between its Pan-Borneo Highway scheme and the regional integration of protected areas, unprotected intact forests, and conservation-priority forests. Road developments in southern Sabah in particular would drastically reduce protected-area integration across the northern Heart of Borneo region. Such developments would separate two major clusters of protected areas that account for one-quarter of all protected areas within the Heart of Borneo complex. Sabah has proposed forest corridors and highway underpasses as means of retaining ecological connectivity in this context. Connectivity modelling identified numerous overlooked areas for connectivity rehabilitation among intact forest patches following planned road development. While such ‘linear-conservation planning’ might theoretically retain up to 85% of intact-forest connectivity and integrate half of the conservation-priority forests across Sabah, in reality it is very unlikely to achieve meaningful ecological integration. Moreover, such measure would be exceedingly costly if properly implemented–apparently beyond the operating budget of relevant Malaysian authorities. Unless critical road segments are cancelled, planned infrastructure will fragment important conservation landscapes with little recourse for mitigation. This likelihood reinforces earlier calls for the legal recognition of the Heart of Borneo region for conservation planning as well as for enhanced tri-lateral coordination of both conservation and development.
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The island of New Guinea hosts the third largest expanse of tropical rainforest on the planet. Papua New Guinea—comprising the eastern half of the island—plans to nearly double its national road network (from 8,700 to 15,000 km) over the next three years, to spur economic growth. We assessed these plans using fine-scale biophysical and environmental data. We identified numerous environmental and socioeconomic risks associated with these projects, including the dissection of 54 critical biodiversity habitats and diminished forest connectivity across large expanses of the island. Key habitats of globally endangered species including Goodfellow’s tree-kangaroo (Dendrolagus goodfellowi), Matchie’s tree kangaroo (D. matschiei), and several birds of paradise would also be bisected by roads and opened up to logging, hunting, and habitat conversion. Many planned roads would traverse rainforests and carbon-rich peatlands, contradicting Papua New Guinea’s international commitments to promote low-carbon development and forest conservation for climate-change mitigation. Planned roads would also create new deforestation hotspots via rapid expansion of logging, mining, and oil-palm plantations. Our study suggests that several planned road segments in steep and high-rainfall terrain would be extremely expensive in terms of construction and maintenance costs. This would create unanticipated economic challenges and public debt. The net environmental, social, and economic risks of several planned projects—such as the Epo-Kikori link, Madang-Baiyer link, Wau-Malalaua link, and some other planned projects in the Western and East Sepik Provinces—could easily outstrip their overall benefits. Such projects should be reconsidered under broader environmental, economic, and social grounds, rather than short-term economic considerations.
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The island of New Guinea harbours one of the world’s largest tracts of intact tropical forest, with 41% of its land area in Indonesian Papua (Papua and Papua Barat Provinces). Within Papua, the advent of a 4000-km ‘development corridor’ reflects a national agenda promoting primary-resource extraction and economic integration. Papua, a resource frontier containing vast forest and mineral resources, increasingly exhibits new conservation and development dynamics suggestive of the earlier frontier development phases of other Indonesian regions. Local environmental and social considerations have been discounted in the headlong rush to establish the corridor and secure access to natural resources. Peatland and forest conversion are increasingly extensive within the epicentres of economic development. Deforestation frontiers are emerging along parts of the expanding development corridor, including within the Lorentz World Heritage Site. Customary land rights for Papua’s indigenous people remain an afterthought to resource development, fomenting conditions contrary to conservation and sustainable development. A centralised development agenda within Indonesia underlies virtually all of these changes. We recommend specific actions to address the environmental, economic, and socio-political challenges of frontier development along the Papuan corridor.