Why God is not Merciful to eradicate all this problems?
Bible Gives the Answer:
The earth is defiled under the inhabitants thereof; because they have transgressed the laws, changedthe ordinance, broken the everlasting covenant.
Therefore hath the curse devoured1 the earth, and they that dwell6 therein are desolate.
His name shall be called Wonderful, Counsellor,6 The mighty God, The everlasting Father, The Prince of Peace.
Of the increase of [his] government and peace [there shall be] no end
The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them.
And the cow and the bear shall feed; their young ones shall lie down together: and the lion shall eat4 straw like the ox.
And the sucking child shall play on the hole of the asp, and the weaned child shall put1 his hand on the cockatrice' den.
They shall not hurt nor destroy in all my holy mountain: for the earth shall be full of the knowledge of the LORD, as the waters cover18 the sea.
And in that day there shall be a root of Jesse, which shall stand6 for an ensign of the people; to it shall the Gentiles seek:4 and his rest shall be glorious.
God Bless You