Rev. 6:7-8 (ESV)
When he opened the fourth seal, I heard the voice of the fourth living creature say, "Come!"  And I looked, and behold, a pale horse! And its rider's name was Death, and Hades followed him. And they were given authority over a fourth of the earth, to kill with sword and with famine and with pestilence and by wild beasts of the earth.
The Green Horse and rider is given the name death, Hades follows him. The four riders are given a fourth of the earth to kill, sword, famine, pestilence and wild beasts. The only thing left out is old age! A fourth of the earth, this should remind us that they don’t have the final say. They are only given partial reign. We see death all around us. People all over the earth die of these things. Yet death is limited in its reign. And Christ will make these four riders look like boys on hobby horses when he comes.