The study used crowd-sourced data covering 36 million kilometers to map the extent of roads around the world.
The researchers found roads have essentially fragmented the Earth’s land surface into 600,000 pieces. Only 7 percent of roadless areas are larger than 100 square kilometers, and only 9 percent of these are protected.
The study’s authors and an outside expert caution that the area affected by roads is likely much higher, since some regions are not thoroughly mapped.
The study recommends governments place higher importance on preserving the world’s remaining roadless areas.
Roads can present big problems for wildlife by severing populations, degrading and fragmenting habitat, opening up wildnerness to poachers, and directly killing animals that stray into the paths of oncoming vehicles. A new study published late last week in Science looked into the extent of roads, finding they have effectively divided the planet’s surface into 600,000 fragments.
Of these, the researchers found only 7 percent are larger than 100 square kilometers, and half are smaller than one square kilometer. To put this in perspective, the U.S. city of Cincinnati comprises around 200 square kilometers of land area.
The authors found that of these last-remaining large fragments, just 9 percent are officially protected.
The study was carried out by an international team of researchers who analyzed a crowd-sourced, global road dataset covering 36 million kilometers called OpenStreetMap. Its findings revealed the largest tracts of roadless land are found in the tundra and boreal forests of Eurasia and North America, as well as some tropical regions of South America, Africa, and Southeast Asia.
The researchers admit that the dataset may not be perfect, but say it was the most thorough resource available.
“This was the best available source of information to produce a global map for roadless areas although it was clear to us the data were incomplete. Our figures overestimate roadless areas, and we know many of the areas have already gone or been reduced in size,” Monika Hoffmann, coauthor from Eberswalde University for Sustainable Development who carried out the spatial analyses, said in a statement.
This concern was echoed by William Laurance of James Cook University in Australia who has researched and written extensively about the impacts of roads.
“As alarming as the study by Ibisch and colleagues sounds, it still probably underestimates the problem, because it is likely that the researchers missed half or more of all the roads on the planet,” Laurance wrote in a reaction essay for The Conversation.
Laurance says the study’s authors aren’t at fault for this underestimation. Instead, he blames the rapid development of roads and the fact that satellite-based detection systems don’t always register them. He writes that because of this, crowd-sourced platforms like OpenStreetMap that rely on eyes on-the-ground are often more accurate – with a big caveat.
“As the authors acknowledge, human mappers have worked far more prolifically in some areas than others. For instance, wealthier nations like Switzerland and Australia have quite accurate road maps,” Laurance writes. “But in Indonesia, Peru or Cameroon, great swathes of land have been poorly studied.
“A quick look at OpenStreetmap also shows that cities are far better mapped than hinterlands. For instance, in the Brazilian Amazon, my colleagues and I recently found 3km of illegal, unmapped roads for every 1km of legal, mapped road.”
In addition to direct effects like the deforestation required to build roads through forested areas and animals deaths from car collisions, roads can have powerful cascading impacts. These include opening up areas to poaching, logging, and other human disturbances. Roads are so influential that a 2014 study published in the journal Biological Conservation found nearly 95 percent of deforestation in the Brazilian Amazon happened within 5.5 kilometers of a road or navigable river.
The consequences of this forest loss can be severe. In India, proposed infrastructure development projects are being panned by conservationists as damaging to tiger habitat and, thus, limiting efforts to boost their numbers. In Southeast Asia, road expansion has been implicated as one of the biggest drivers of habitat loss and poaching in the region, which scientists say may push 21 to 48 percent of its native mammal species to extinction by 2100.
These impacts don’t just pertain to large roads plied by heavy traffic. Small roads – like those used for logging – can also come with a bevy of collateral damages.
“All roads affect the environment in some shape or form including timber extraction tracks and minor dirt roads, and the impacts can be felt far beyond the road edge. The area most severely affected is within a 1-km band on either side of a road,” said Nuria Selva of the Institute of Nature Conservation of the Polish Academy of Sciences in Krakow, Poland and co-author of the new Science study.
The study also warns of “contagious development,” in which roads beget more roads, opening up increasingly large areas to human encroachment.
The study’s authors analyzed data in respect to the UN’s Sustainable Development Goals (SDGs), which cover a broad range of issues from ending poverty to combatting climate change. They write their research revealed conflicts of interest between goals for generating economic growth and safeguarding biodiversity, with economic goals threatening remaining roadless areas and biodiversity goals ignoring the importance of preserving them.
“Roads are explicitly mentioned in the Sustainable Development Goals only for their contribution to economic growth, promoting further expansion into remote rural areas, and consideration is given neither to the environmental nor the social costs of road development,” the study states.
But where the researchers see shortfalls, they also see opportunity. The protection of ecological valuable roadless areas could help achieve SDGs, they write, by helping halt land degradation and fostering sustainable industry. They recommend that governments take into consideration the value of keeping these places roadless.
“As roads continue to expand, there is an urgent need for a global strategy for the effective conservation, restoration and monitoring of roadless areas and the ecosystems they comprise,”said co-author Pierre Ibisch in a statement. “We urge governments to avoid the costly building of roads in remote areas, which would be ecologically disastrous.”
- Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. “High-Resolution Global Maps of 21st-Century Forest Cover Change.” Science 342 (15 November): 850–53. Data available on-line from:http://earthenginepartners.appspot.com/science-2013-global-forest. Accessed through Global Forest Watch on December 19, 2016. www.globalforestwatch.org
- Ibisch, P. L., Hoffmann, M. T., Kreft, S., Pe’er, G., Kati, V., Biber-Freudenberger, L., … & Selva, N. (2016). A global map of roadless areas and their conservation status. Science, 354(6318), 1423-1427.
- OpenStreetMap with contributions from the Logging Road Initiative. “Congo Basin logging roads” Accessed through Global Forest Watch on December 19, 2016. www.globalforestwatch.org