Mankind was originally created in the image of God without sin and in direct relationship with Him.  The first male and female humans, Adam & Eve, walked and talked in the Garden of Eden with God.  When they chose to disobey God, they sinned, and it brought death to humanity and to the universe.  This sin broke their relationship with the perfect holy God, brought sin into the thoughts, emotions and actions of all humanity, and brought us physical death that results in eternal separation from God in hell.  The sin of mankind also broke the perfection of all of creation so that the universe is winding down in death, resulting in the unraveling of the basic building blocks of all that exists.  As a result, the environment, plants, animals are all in a state of progressive decay.