Earth's surface is shattered by roads into over 600,000 fragments - more than half of which are smaller that one square kilometre - severely reducing the ability of ecosystems to function effectively, a new study has found.
Roads have made it possible for humans to access almost every region but this comes at a very high cost ecologically to the planet's natural world.
Despite substantial efforts to conserve the world's natural heritage, large tracts of valuable roadless areas remain unprotected, researchers said.
The researchers from the Eberswalde University for Sustainable Development in Germany used a dataset of 36 million kilometres of roads across the landscapes of the earth. They are dividing them into more than 600,000 pieces that are not directly affected by roads.
Of these remaining roadless areas only seven per cent are larger than 100 square kilometres. The largest tracts are to be found in the tundra and the boreal forests of North America and Eurasia, as well as some tropical areas of Africa, South America and Southeast Asia.
Only nine per cent of these areas undisturbed by roads are protected.
Roads introduce many problems to nature. For instance, they interrupt gene flow in animal population, facilitate the spread of pests and diseases, and increase soil erosion and the contamination of rivers and wetlands.
Then there is the free movement of people made possible by road development in previously remote areas, which has opened these areas up to severe problems such as illegal logging, poaching and deforestation.
Most importantly, roads trigger the construction of further roads and the subsequent conversion of natural landscapes, a phenomenon the study labels "contagious development."
"Our global map provides guidance on the location of the most valuable roadless areas," said Pierre Ibisch, from the Eberswalde University.
In many cases they represent remaining tracks of extensive functional ecosystems, and are of key significance to ecological processes, such as regulating the hydrological cycle and the climate," said Ibisch.
The researchers used a large data base generated through crowd-sourcing platform to produce a global map for roadless.
"Our figures overestimate roadless areas, and we know many of the areas have already gone or been reduced in size," said Monika Hoffmann from Eberswalde University.
"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," said Nuria Selva, from the Institute of Nature Conservation of the Polish Academy of Sciences in Poland.
"The area most severely affected is within a one kilometre band on either side of a road," said Selva.
