I don't know why I didn't realize this before, but the other day it finally dawned on me that the 4 angels standing on the 4 corners of the earth holding back the winds so that they don't blow on the earth, on the sea nor on any tree while another angel is sealing the 144,000 in the forehead with the seal of the living God in Rev. 7:1-4 are the same first 4 angels who sound the first 4 trumpets in Rev. 8:7-12.

The other angel who seals the 144,000 in the forehead tells the 4 angels holding the winds back in Rev. 7:2-3 not to hurt the earth nor the sea nor the trees until the servants of God are sealed in the forehead. In fact, he says "until we have sealed" according to the Bible verses below:

Rev. 7:2-3, "And I saw another angel ascending from the east, having the seal of the living God: and he cried with a loud voice to the four angels, to whom it was given to hurt the earth and the sea, Saying, Hurt not the earth, neither the sea, nor the trees, till we havesealed the servants of our God in their foreheads." 

Then after each of the first 4 angels sound their trumpets the earth, trees and sea receive destruction as shown in the Bible verses below: 

Rev. 8:7-12,"The first angel sounded, and there followed hail and fire mingled with blood, and they were cast upon the earth: and the third part of trees was burnt up, and all green grass was burnt upAnd the second angel sounded, and as it were a great mountain burning with fire was cast into the sea: and the third part of the sea became blood; And the third  part of the creatures which were in the sea, and had life, died; and the third part of the ships were destroyed. And the third angel sounded, and there fell a greatstar from heaven, burning as it were a lamp, and it fell upon the third part of the rivers, and upon the fountains of waters; And the name of the star is called Wormwood: and the third part of the waters became wormwood; and many men died of the waters, because they were made bitter. And the fourth angel sounded, and the third part of the sun was smitten, and the third part of the moon, and the third part of the stars; so as the third part of them was darkened, and the day shone not for a third part of it, and the night likewise."  

On the third part of the earth where the trees and grass will be destroyed, there will be no grass to feed the animals which men slaughter to eat, and the fruit trees and the nut trees won't be producing any fruit or nuts for men and animals because they will have been destroyed.  There will be no water to grow crops or for men nor beast on the third part of the earth where the water turns bitter and undrinkable, and there will be no fish in the sea in the third part that is destroyed for men to eat. And with the sun not shining for a third part of the day that will also affect plant growth as well. 

Does the sun not shining for a third part of the day and the moon and stars not shining for a third part of the night mean that there will be so much debris & dark pollution in the air from the smoke of a third part of the trees burning up along with all the grass, from a volcano eruption shooting debris into the air as the volcano slides into the sea and from an asteroid striking a third part of the waters so that the sun, moon and stars can't be seen for a third of the day and a third of the night?