Read the given passage and answer the questions that follow.
Have you ever taken the time to stop and consider the dirt under your feet? Leonardo da Vinci said, “We know more about the movement of celestial bodies than about the soil underfoot.” Yet, our very survival as humans – and life on this planet – is intimately linked with the health of a thin layer of soil enveloping the earth.
Soil provides society with essential food, feed, fibre and raw materials, as well as being home to a quarter of the earth’s biodiversity. Soils are also the largest organic carbon reservoir on Earth and although highly dynamic, are very fragile. Chop a forest down and it might grow back in 50 years, but lose 10 cm of soil and get ready to wait 1,000 years to get it back. Without soil, our planet would be unrecognisable to us, and more like the barren and inhospitable surface of the Moon or Mars.
Until recently, we did not even know how deep the soil is below our feet. Like the best mysteries, a bit of digging is required for soils to be fully understood and for their history to be laid bare.
When they are visible, a range of questions arise. What does the variation in colour with depth mean? How much carbon is stored? Is the soil dense or light, damaged or healthy? Answering these questions is important, but presents a significant challenge and may require years of training.
Mankind’s survival, according to the passage, solely depends on _________ .