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Road access for all would be costly, but not so much for the climate

One of the UN’s Sustainable Development Goals aims to ensure access to transport infrastructure for all.

A team of researchers led by the Potsdam Institute for Climate Impact Research (PIK) has now brought together various data sets to quantify the economic costs as well as climate implications of achieving this goal by providing universal road access. The result: While such road extension would weigh very heavily on individual countries’ budgets, on the global CO2 emissions budget it would not. To connect almost all the world’s population, the global road network would only need to be extended by 8 per cent, causing a total CO2 emissions of about 1.5 per cent of what we can emit while keeping global warming below 2 degree Celsius.

The research team from PIK and the Mercator Research Institute on Global Commons and Climate Change (MCC) finds that currently, ca. 14 per cent of the world’s population live more than 2 km from a road. “We compute how many kilometres of roads would have to be built in each country, how much the construction might cost, and finally, how many CO2 emissions would ensue the construction and increased traffic on those roads,” explains Leonie Wenz from PIK, lead author of the study and deputy head of the research department on complexity science at the Potsdam Institute for Climate Impact Research. To connect 97.5 per cent of the population in each country, about 4 million km of additional roads would need to be constructed. Access gaps are biggest in sub-Saharan Africa and Southeast Asia. Angola or Indonesia are cases where currently over half of the population lives more than 2 km away from a road.

The study finds the economic costs of constructing those roads as very significant, especially when compared with the individual countries’ national economic output: USD 3,000 billion would be needed to provide access to almost all of world population. “Much like in logistics, the last mile to cover, or rather the last household to connect, is the most expensive,” Jan Steckel, Head of the working group on Climate and Development at MCC lays out. “For comparison, connecting only 90 per cent of the population in each country would require only about USD 700 million. Aiming at 97.5 per cent would mean facing costs more than half of their current national economic output for some countries – especially in Africa and the Middle East, where both need and costs are highest.”

Roads’ climate impact is moderate

Regarding the climate impact of construction of and traffic on the new roads, however, the outlook is brighter: Until 2100, resulting emissions will be around 16 gigatonnes of CO2, the researchers calculate. This presumes that all roads be built by 2030 employing today’s carbon-intensive modes of provision. The total carbon budget, i.e. the amount of carbon humankind can still emit to keep global warming below 2 degrees Celsius, is a little over 1,070 gigatonnes. Thus, the fraction necessary for road construction and additional traffic are ca. 1.5 per cent of that budget. “Connecting the vast majority of people to the road network, which is considered to spur prosperity, would not drastically inflate our greenhouse gas emissions,” Leonie Wenz says. “From this perspective there is no trade-off between economic development goals and climate protection.”

However, there might still be other sources of CO2 emissions from roads and additional environmental and societal concerns associated with road building. Steckel explains: “Streets crossing through new territories can ensue deforestation and fragmentation and hence loss of carbon sinks and biodiversity, or have negative health impacts. All these issues are also covered in the Sustainable Development Goals.” To overcome potential trade-offs in the SDG agenda, with regard to road construction the authors propose to shift the focus from mere road availability to travel times and a more strategic road planning.

“With our geographically explicit data set, we hope to provide a useful starting point for further analyses – both into the concrete situation of individual countries, and in the further interactions between fulfilling the Sustainable Development Goals within our planetary boundaries,” Wenz concludes.


Potsdam Institute for Climate Impact Research (PIK) 2020

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