The temperate and mixed forests of the world are the most divided by roads.
LONDON, Jan. 18, 2017 – European, Brazilian and US scientists have delivered a new map of humanity’s mark on the world. Roads now fragment the terrestrial landscape and divide it into 600,000 patches – and only 7% of the roadless areas are larger than 100 square kilometres.
More than half of the patches are less than 1 sq km and four-fifths are less than 5 sq km. The implication is that humans are getting everywhere, and bringing with them noise, pollution, damage to wildlife and biological invaders.
About the only regions in which roads are few are the tundra, the deserts and the rock- and ice-covered highlands. The temperate and mixed forests of the world are the most divided by roads.
Pierre Ibisch, of Eberswalde University for Sustainable Development in Germany, and colleagues report in Science that they used citizen science and internet datasets, and reviewed 282 studies, to make the maps.
They allowed a 1km buffer zone along each road, because the construction of any road creates disturbance, including the loss of timber. And they conclude that a third of the world’s roads are now in regions with low biodiversity, low ecological function and low ecosystem resilience.
They see those areas still beyond the reach of cars, trucks and tractors as vulnerable.
Such studies are fresh ways of illustrating what scientists call the “Great Acceleration”: one human lifetime ago, the world was home to only 2.5bn people, and very few of them had cars.
UN scientists predict a population of at least 9bn people this century, and possibly a much higher number before 2100. The cities are expanding, and new built-up areas will cover more than 1 million sq km between now and 2040.
One team of researchers has just calculated that the human “technosphere” – the sum of all things humans have built or excavated – has reached a mass of 30 trillion metric tons.
By 2050, the world will build an estimated 25 million kilometres of new road lanes, most of them in the developing world.
Andrew Balmford, a professor of conservation science at the University of Cambridge in the UK, and colleagues argue in a separate study in the Public Library of Science journal Biology that it should be possible to devise a highway strategy that makes the best use of existing farmland, serves the greatest number of people and yet conserves the natural ecosystems that deliver services of profound value to all humanity.
Among these are water management, carbon storage, crop pollination, and plants and animals that could be the source of new foods and medicines.
The researchers tested their argument in the Greater Mekong region of south-east Asia, a landscape that includes Vietnam, Laos, Cambodia and some of Myanmar. It is home to 320 million people, 20,000 plant species, 2,000 terrestrial vertebrate species and 850 varieties of freshwater fish, and it has lost a third of its tropical forest in the past four decades.
“The Mekong region is home to some of the world’s most valuable tropical forests. It’s also a region in which a lot of roads are going to be built, and blanket opposition by the conservation community is unlikely to stop this,” says co-author Xu Jianchu, professor of ethnoecology at the Kunming Institute of Botany in China and regional coordinator for the World Agroforestry Centre.