Since the lower regions of the cable are moving slower than the higher ones, a rising car will lag behind the orbiting anchor, causing a drag on the cable that could destabilize the entire assembly.

Most of Africa is urbanizing at a lower level of income than other regions of the world did.

The areas that are now desert were, like all arid regions, very susceptible to cycles of higher and lower levels of rainfall, resulting in major, sudden changes in distributions of plants and animals.