Which of the following is NOT a factor responsible for "Land degradation"?

None of the above

The correct answer is option 4: None of the above

Various factors responsible for land degradation are:

1.  loss of vegetation occuring due to deforestation
2.  unsustainable fuel wood and fodder extraction
3.  shifting cultivation
4.  encroachment into forest lands
5.  forest fires and over grazing
6.  non-adoption of adequate soil conservation measures
7.  improper crop rotation
8.  indiscriminate use of agro-chemicals such as fertilisers and pesticides
9.  improper planning and management of irrigation systems