The density of roads across a landscape gives a good indication of how fragmented the landscape is. Unfortunately, most current maps that show road density throughout the world are limited by resolution, geographic bias, or simply outdated information.
The Global Roads Inventory Project (GRIP) was initiated to gather and integrate multiple existing roads datasets into one consistent dataset that spanned the entire globe. This was achieved through analysis of nearly 60 geospatial datasets that were publicly available and contained the most recent available data. Ultimately, researchers mapped more than 21 million km of roads over 222 countries at a resolution of 5 x 5 arcminute (approximately 8 x 8 km at the equator).
The results of the project provide unprecedented detail of road densities. Several patterns and predictions about road densities emerged from analysis, including:
- The 21.6 million km of roads mapped is almost certainly an underrepresentation of the total length of roads around the globe, which may be as high as 32 million km.
- Global road length is conservatively estimated to increase by 14-23% (3.0-4.7 million km) by 2050.
- The largest increases in road length are predicted to be in developing nations in some of the world’s last remaining wilderness areas, such as the Amazon, Congo basin, and New Guinea.
The resulting maps and global dataset provide critical information for spatial planners to understand where road densities are likely to contribute to future habitat fragmentation. Maintaining landscape connectivity in the face of current and future road developments will be key to protecting biodiversity in high density regions.
Meijer JR, Huijbregts MAJ, Schotten KCGJ, and Schipper AM. 2018. Global patterns of current and future road infrastructure. Environmental Research Letters 13: 064006.