The fourth horseman is because of the eating and raising of animals for food, which has caused death (it is unhealthy to eat meat)
Actually it is unhealthy to eat too much meat. (Proverbs 23:20-21)
God gave Noah permission to eat the flesh of animals after the flood. He does not state the reason, but after that event, man's lifespan diminished from hundreds of years down to the 70 or eighty we now live on average. Perhaps the change in earth's atmosphere required additional protein?
This is also the time God instilled a fear of man in animals so that they would have an option to flee as man would now have to hunt for his food instead of just growing it.
On coming out of the ark......
"God went on to bless Noah and his sons and to say to them: “Be fruitful and become many and fill the earth. 2 A fear of you and a terror of you will continue upon every living creature of the earth and upon every flying creature of the heavens, upon everything that moves on the ground and upon all the fish of the sea. They are now given into your hand. 3 Every moving animal that is alive may serve as food for you. Just as I gave you the green vegetation, I give them all to you." (Genesis
9:1-3)
pestilence, and famine...
Pestilence and famine are both often caused by man. The spread of disease by epidemic (poor prevention practices or bad sanitation) or by an unhealthy lifestyle, continues to take its toll by the millions in all the world. Compromised immune systems cannot stave off infections. No one has a perfect diet and our bodies are no longer perfect.
Famine is mostly the result of man's mismanagement of this earth. He has altered his environment by clearing vast amounts of land, and altered the climate as a result. There is an abundance of food, but rather than spend money feeding the starving people of the world, good food is ploughed back into the ground and wasted because of greed. Western nations throw away as much food as would feed the rest of the world.
This is what I believe the horsemen picture......not what God is doing, but what man is doing in these last days. An accounting is coming. (Revelation 11:18)
Hades is included, as it is also morally wrong to kill life.
Death is followed by hades, which is the common grave, not "hell" as Christendom teaches it. Hades gobbles up the victims of man's stupidity and greed. It is never full.
Revelation 1:18 ....I have the keys of Death and of Hades.
Hades is a realm in this verse; therefore death is also something that can be accessed, like computer code, as death is removed at the end.
Revelation 20:14 Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire.
Yes, I believe that "the keys to death and hades" means that Jesus has the authority to eliminate death (as the last enemy of mankind...1 Corinthians 15:26) and to release all who are in hades. (the grave)
John 5:28-29 says....
"Do not be amazed at this, for the hour is coming in which all those in the memorial tombs will hear his voice 29 and come out, those who did good things to a resurrection of life, and those who practiced vile things to a resurrection of judgment."
Jesus will free all who sleep in death and raise them back to life by calling them out of their tombs, just as he did Lazarus (John 11:11-14)
It will be amazing to welcome back our lost loved ones.