Topsoil does not last forever. Records show that topsoil erosion, accelerated by human civilization and conventional agricultural practices, has outpaced long-term soil production. Earth's continents are losing prime agricultural soils even as population growth and increased demand for biofuels claim more from this basic resource.

What will be the lasting impression made by mankind - 100 million years hence? "From the perspective of 100 million years in the future --- a geologist's view --- the reign of humans on Earth would seem very short: we would almost certainly have died out long before then. What footprint will we leave in the rocks? What would have become of our great cities, our roads and tunnels, our cars, our plastic cups in the far distant future? What fossils would we leave behind?