Because of all the industry they have there. Also because of all the mountains and how little space they have due to the huge population of Japan.
A cliff collapse could affect the environment by exposing new rock (previously covered by the cliff) to the elements, which could result in runoff of a different nature when it rains. Additionally, the cliff would collapse upon whatever life/features existed at the base of the cliff. One of the most drastic effects could be the shaking of the earth. Cliff failures can result in earthquakes or, if the cliff collapses into a large body of water, massive tsunamis which radically impact coastal environments.
Odd number go north and south and even number go east and west.
I don't believe that that is true due to the fact you can see soil even if there are no plants in it although im not 100% sure as soil and key components in it may be considered organic
