This graph shows proposed commercial roads across the Serengeti and surrounding region in 2010. However, following intense international pressure, the Tanzanian Government announced in 2011 that it will favour an alternative route to the South, outside the park. Some projections suggest that if the road were built, numbers may fall to less than 300,000 (Dobson and Borner, 2010), others that the herd could decline by a third (Holdo et al., 2011), which in turn to loss of populations in other areas and a possible break-down of parts of the Serengeti ecosystem. While a road would not cause a complete failure of any migration, there is ample evidence today that even roads, apparently passable, can cause avoidance, reduce crossings or delay or hinder migrations.
From collection: Living Planet: Connected Planet, Rapid Response Assessment
Riccardo Pravettoni, UNEP/GRID-Arendal