The rule of twelfth Imam will be based on religious sovereignty and refusal of laicism and secularism. Imam Mahdi (PBUH) will rule on the basis of Quran and his goal is to fully realize justice, not just in a limited domain but on the whole world.
At the time of arrival of the savior, the nature will act differently. The animals will cooperate with men. The paradise in which Adam and Eve dwelled and were expelled from, will be founded again on the earth.