Natural evil is evil for which “no non-divine agent can be held morally responsible for its occurrence.” By contrast, moral evil is “caused by human activity.” The existence of natural evil challenges not only belief in the omnibenevolence or the omnipotence of God, but also belief in the existence of God.
Nature of natural evil
Moral evil results from a perpetrator, or one who acts intentionally and in so doing has flouted some duty or engaged in some vice. Natural evil has only victims, and is generally taken to be the result of natural processes. The "evil" thus identified is evil only from the perspective of those affected and who perceive it as an affliction. Examples include cancer, birth defects, tornadoes, earthquakes, tsunamis, hurricanes, acts of God, and other phenomena which inflict suffering with apparently no accompanying mitigating good. Such phenomena inflict "evil" on victims with no perpetrator to blame.
In the Bible, God is portrayed as the ultimate perpetrator, for the “sun, moon and stars, celestial activity, clouds, dew, frost, hail, lightning, rain, snow, thunder, and wind are all subject to God's command.” Examples of natural evils ascribed to God follow:
- Floods: God brought “a flood of waters on the earth” (Genesis 6:17).
- Thunder, hail, lightning: God “sent thunder and hail, and fire came down” (Exodus 9:23).
- Destructive Wind: God sent a “great wind” that destroyed Job’s house and killed his family (Job 1:19).
- Earthquake: By the Lord “the earth will be shaken” (Isaiah 13:13).
- Drought and Famine: God will shut off rains, so neither land nor trees yield produce (Leviticus 26:19-20).
- Forest fires: God says, “I will kindle a fire in you, and it shall devour every green tree in you and every dry tree” (Ezekiel 20:47).
Traditional theism (e.g. Thomas Aquinas) distinguishes between God's will and God's permission, claiming that while God permits evil, he does not will it. This is echoed by some modern open theists, e.g. Gregory A. Boyd, who writes, "Divine goodness does not completely control or in any sense will evil." Aquinas partly explained this in terms of primary and secondary causality, whereby God is the primary (or transcendent) cause of the world, but not the secondary (or immanent) cause of everything that occurs in it. Such accounts explain the presence of natural evil through the story of the Fall of man, which affected not only human beings, but nature as well (Genesis 3:16–19).
Especially since the Reformation the distinction between God's will and God's permission, and between primary and secondary causality, has been disputed, notably by John Calvin. Among modern inheritors of this tradition, Mark R. Talbot ascribes evil to God: “God’s foreordination is the ultimate reason why everything comes about, including the existence of all evil persons and things and the occurrence of any evil acts or events.” Such models of God's complete foreordination and direct willing of everything that happens lead to the doctrines of double predestination and limited atonement.
Natural versus moral evil
Jean Jacques Rousseau responded to Voltaire's criticism of the optimists by pointing out that the value judgement required in order to declare the 1755 Lisbon earthquake a natural evil ignored the fact that the human endeavour of the construction and organization of the city of Lisbon was also to blame for the horrors recounted as they had contributed to the level of suffering. It was, after all, the collapsing buildings, the fires, and the close human confinement that led to much of the death.
The question of whether natural disasters such as hurricanes might be natural or moral evil is complicated by new understandings of the effects, such as global warming, of our collective actions on events that were previously considered to be out of our control. Nonetheless, even before the beginning of the Industrial Revolution (which many believe was the beginning point of global warming), natural disasters (e.g., earthquakes, volcanoes, tsunamis, flooding, fires, disease, etc.) occurred regularly, and cannot be ascribed to the actions of humans. However, human actions exacerbate the evil effects of natural disasters. The World Wide Fund for Nature (WWF) says human activity is a key factor that turns “extreme weather events into greater natural disasters.” For example, “deforestation and floodplain development” by humans turn high rainfall into “devastating floods and mudslides." When humans damage coastal reefs, remove mangroves, destroy dune systems, or clear coastal forests, "extreme coastal events cause much more loss of life and damage.” Damage by tsunamis varied “according to the extent of reef protection and remaining mangrove coverage.” 
In the United States, wildfires that destroy lives and property aren't "entirely natural.” Some fires are caused by human action and the damage inflicted is sometimes magnified by building “in remote, fire-prone areas.” Dusty conditions in the West that “can cause significant human health problems” have been shown to be “a direct result of human activity and not part of the natural system."
In sum, there is evidence that some "natural" evil results from human activity and, therefore, contains an element of moral evil.
Challenge to religious belief
Natural evil (also non-moral or surd evil) is a term generally used in discussions of the problem of evil and theodicy that refers to states of affairs which, considered in themselves, are those that are part of the natural world, and so are independent of the intervention of a human agent. Both natural and moral evil are a challenge to religious believers. Many atheists claim that natural evil is proof that there is no God, at least not an omnipotent, omnibenevolent one, as such a being would not allow such evil to happen to his/her creation. However, the deist position states that intervention by God to prevent such actions (or any intervention) is not an attribute of God.
- James R. Beebe, “The Evidential Problem of Evil” in The Internet Encyclopedia of Philosophy (IEP) at http://www.iep.utm.edu/evil-evi/#SH4b.
- Michael Martin, Atheism: A Philosophical Justification (Temple University Press, 1992), 412.
- Baker's Evangelical Dictionary, s.v. “Providence of God.”
- David Bentley Hart, The Doors of the Sea: Where Was God in the Tsunami? (William B. Eerdmans, 2005), pp. 82–89.
- Gregory A. Boyd, God at War: the Bible and Spiritual Conflict (InterVarsity Press,1997) 20.
- Mark R. Talbot, “All the Good That Is Ours in Christ,” in Suffering and the Sovereignty of God, ed. John Piper and Justin Taylor, 43-44 (Crossway Books, 2006). Available online at http://www.desiringgod.org/ResourceLibrary/OnlineBooks/ByTitle/.
- David Bentley Hart, The Doors of the Sea: Where Was God in the Tsunami? (William B. Eerdmans, 2005), pp. 89–91.
- http://www.expatica.com/fr/news/local_news/Natural-disasters-made-worse-by-human-activity-_43194.html Accessed August 30, 2014.
- “Natural Disasters Made Worse by Human Activity” (May 20, 2008), Expatica.com, accessed December 2, 2009.
- “UN Says Poor Construction to Blame for Earthquake Deaths — May 19, 2008,” Expatica.com, accessed December 2, 2009.
- “Southern California Forest Fires,” Time.Com, accessed December 2, 2009.
- “Dust in West up 500 Percent in Past 2 Centuries, says CU-Boulder Study,” Eurekalert.org, accessed December 2, 2009.