聯合國世衛組織在發表年終宣言時指出，2005年因海嘯、颶風、颱風、山崩、地震、火山爆發、蟲害、以及流行性疾病等所造成眾多的死亡人數不能完全歸咎於自然災害。諸如森林消退、溫室氣體排放等人類活動也必須負部分責任。
世衛組織指出有多項因素造成去年的高死傷人數，諸如：人為因素所造成的氣候變遷及全球暖化；社會經濟失衡問題迫使窮人們必須定居在危險的區域；政府及一般民眾對於災害防範的教育普遍不足。設立於美國華府的「泛美衛生組織」（PAHO）急難防治救助區域顧問烏加特（Ciro Ugarte）說：「我不太喜歡用『天災』來形容這些事件。」
根據世衛組織流行病學研究中心（CRED）的資料，2005年1月到10月間，全球超過9萬7,400人在災害中喪生，其中有8萬8,000人是死於天然災害，並且從1875年以來此類別死亡人數便持續增加。CRED是世衛組織中掌管天然災害資料庫的單位，辦公室設於比利時。
回顧2005年，最嚴重的悲劇包括：2004年12月26日的南亞地震和大海嘯、侵襲中北美洲並淹沒紐奧良市近80%土地的卡崔娜颶風、以及10月8日發生在巴基斯坦和印度的強震。另外，非洲國家尼日遭遇蝗害，農作被洗劫一空而爆發嚴重飢荒；薩爾瓦多則是遭史坦颶風侵襲後接續發生火山爆發。
不過，據烏加特觀察，自然現象並非全然會造成人類的災難，2005年有幾個發生在南美洲的強烈地震，其強度足以和去年10間震動巴基斯坦北部和部份印度地區的驚人強震相提並論，但卻因人煙稀少所以並未造成多大的危害。
顯然，人口是一重要因素。目前的全球人口約有65億，根據聯合國估計在2050年將突破91億人口，所以未來的自然現象諸如地震和颶風將會影響更多的人口。
世衛指出，人們決定住所之時也冒著相當的風險。該組織引用最早的災害數據說，西元79年維蘇威火山爆發，火山灰掩埋了羅馬帝國的龐貝城，造成約莫一萬人死亡，如果發生在今天，同樣的區域範圍內恐將造成200萬人罹難。
另一個重要的因素是環境的破壞，根據世衛組織「危機衛生行動部」發言人寇奇克（Marko Kokic）指出，加勒比海及印度洋海域風暴之所以造成慘重死傷，原因在於森林的過度砍伐及海岸植被的消失。
寇奇克同時指出，災害也是工業化與開發下的必然結果，在歐洲，專家深信當今法國及德國和過去相比是最為水患所苦的國家，原因在於境內的主要河流，如：萊因河，均以商務運輸便利為由遭到人為工程截彎取直。
災害專家並指出，預警系統和教育在預防及減輕天然災害的影響中是不可或缺的一環。在2005年世界災害報告中指出：紅十字和紅新月國際聯合會提及：當2004年的巨大海嘯侵襲印度時，一通簡單的電話通知就可以及時挽救數千條的人命。
The high death toll in 2005 from tsunamis, hurricanes, typhoons, mudslides, earthquakes, volcanoes, locusts and pandemics can not be blamed entirely on natural disaster, the United Nations health agency said in a year end statement. Human activities such as deforestation and emission of greenhouse gases also play a part.
The World Health Organization (WHO) blames a wide variety of factors for last year's high death toll - climate change, global warming influenced by human behavior, socioeconomic factors causing poorer people to live in risky areas, and inadequate disaster preparedness and education on the part of governments as well as the general population. "I don't like to use the term natural disasters," said Ciro Ugarte, regional advisor for emergency preparedness and disaster relief with the Pan American Health Organization (PAHO) in Washington, DC.
From January to October 2005, over 97,400 people were killed in disasters globally, with some 88,000 of those deaths resulting from so-called natural disasters, according to the Center for Research on the Epidemiology of Disasters (CRED), a WHO institution that operates a global disaster database in Belgium. Such deaths have been increasing since 1975.
The year 2005 was marked by the tragic aftermath of the December 26, 2004 earthquake and tsunami waves in Asia, as well as hurricanes in central and north America, notably Katrina, which flooded about 80 percent of the U.S. city of New Orleans, and the October 8 earthquake in Pakistan and India. Famine struck after crops were destroyed by locusts in Niger, and in El Salvador a volcanic eruption was followed by Hurricane Stan.
But natural phenomena do not always generate human disasters. Dr. Ugarte observed that in 2005, several earthquakes that struck in South America were of a higher magnitude than the one that devastated northern Pakistan and parts of India in October, but these hit sparsely populated areas and so they caused less damage.
In the future, natural phenomena such as earthquakes and hurricanes are likely to affect more people because the global population that now stands at about 6.5 billion people is projected to reach 9.1 billion people in 2050, according to UN figures.
People are taking risks in deciding where to live, WHO pointed out, citing one of the earliest recorded disasters, the eruption of Mount Vesuvius in 79 AD, which buried the ancient Roman city of Pompeii, killing about 10,000 people. Today, two million people live within its possible range.
Another important factor is environmental degradation, according to Marko Kokic, spokesperson for WHO's Health Action in Crisis Department, who said natural storm events in Caribbean and Indian Ocean lands were amplified because of deforestation and stripping of vegetation from coastlines.
Disasters are also a consequence of development and industrialization, said Kokic. In Europe, experts believe that countries such as France and Germany are more adversely affected by floods today than in the past because major rivers, such as the Rhine, have been straightened to ease commercial traffic.
Disaster experts say early warning systems and education are essential to prevent and mitigate against the effects of natural disasters. In its World Disasters Report 2005, the International Federation of Red Cross and Red Crescent Societies notes that a simple phone call saved thousands of lives when the giant tsunami waves hit India in 2004.
