Revelation modifies the Exodus plague in that now only a third of the land and the trees are harmed, yet the affliction of all the grass remains unchanged, though the limitation to one third may be carried over from the previous clauses, as is more clearly the case in 8:11b. Although in one sense the trial has thus been limited in its effects, it has also been universalized in that it now has effect throughout the inhabited earth and not just within one nation (unless one adopts a preterist reading of the Apocalypse in which either Israel or the Roman Empire is the scene of the woes). Revelation also emphasizes that fire did the major harm, whereas Exodus gives this role to the hail. The addition of the element of “blood” may come from the first Egyptian plague, the Nile turning to blood, so that the first plague becomes an aspect of the first trumpet.16
This woe is not referring to literal fire that will burn up part of the earth. This is consistent with 1:1, where the visions are said to be a “communication by symbols.” Furthermore, “fire” elsewhere is used figuratively (so most clearly 4:5 and also in 1:14; 2:18; 10:1; and 19:12; see also on 9:17 and 11:5). 4:5 is especially relevant because there the “fire burning before the throne” in heaven receives a formal figurative interpretation, and the ordeals signaled by all the trumpets also have their origin “before God” (8:2) and therefore before the heavenly throne (8:3–4 explicitly equates “before the throne” with “before God”). The parts of the earth affected are associated with food supplies, which is clear from Exod. 9:25, 31–32. The Exodus plague destroyed only part of the food supply (Exod. 9:31–32: “flax and barley were smitten … but wheat and rye were not”). This is strikingly similar to the description in Rev. 6:6, where there is famine, and wheat and barley are scarce but still available.
G. K. Beale, The Book of Revelation: A Commentary on the Greek Text, New International Greek Testament Commentary (Grand Rapids, MI; Carlisle, Cumbria: W.B. Eerdmans; Paternoster Press, 1999), 473–474.