“Evil has become rife on the land and at sea because of men’s deeds; this in order that He may cause them to have a taste of some of their deeds; perhaps they will turn back (from evil).”
(Al-Qur’ān – 30:41)
This verse of the Qur’ān holds men’s deeds responsible for all the riots and killings, evils and corruption spread over the land and at sea. It also says that this spread of evil et al can cause the erring persons to realise their guilt, their sins, their crimes, ill consequences of their deeds, and above all the imperfectness of human thinking and behaviour. But for this they need to have the eyes that can see, the ears that can listen, and the heart that can realise the reality.
“Man’s own doings” means the wickedness and oppression and tyranny, which inevitably appear in human conduct and character as a result of adopting shirk(polytheism) and atheism and ignoring the Hereafter.
“Maybe they mend their ways” means that Allah shows the evil consequences of some of the acts of men in this world before the punishment of the Hereafter so that they understand the reality, feel the error of their conjectures and turn to the righteous belief, which the Prophets of Allah have been presenting before man since the earliest times, and besides adopting which there is no other way of ordering human conduct on sound foundations.
This subject has been presented at several places in the Qur’ān, e.g. in At-Taubah: 126, Ar-Ra’d: 31, As-Sajdah: 21, and Al-Tur: 47.