From the beginning of September 2008, a renewed concern emanated from Western intelligence agencies to the effect that Al Qaeda terrorists were planning a “global fireball”, in a departure from its war on the West. Deliberately lighting forest fires in Europe, the US and Australia, would not only stretch emergency services, but would also leave insurance companies facing multi-billion dollar claims, as the credit crunch bites. The fires would also create a pollution disaster, with billions of tons of climate-change gases escaping into the atmosphere. The so-called “forest jihad” is being championed by Islamic scholars and Osama Bin Laden’s terror strategists who believe setting fire to dry woodlands will produce maximum damage at minimum risk.Read the whole thing.
Already back in November 2007, radical Islamic forums spelled out the terrorists’ mindset in graphic terms. One of the Arabic web sites affiliated with Al Qaeda’s ideas, called “Al-Ikhlas Islamic Network”, posted a long and detailed message, in which it was argued that lighting fires is an effective form of action, justified in Islamic law under the "eye for an eye" doctrine. The posting instructs remembering the "Forest Jihad" during the summer months, noting that "fires cause economic damage and pollution, tie up security agencies and can take months to extinguish.” Imagine, if after all the losses caused by such an event, a jihadist organization were to claim responsibility for the forest fires," the website says, "you can hardly begin to imagine the level of fear that would take hold of people in the United States, Europe, Russia and Australia."… 
Another Al Qaeda affiliated website,”Al-Jazeeratalk.net” posted a similar message on 27 December 2007, where supporters were reminded, “not to forget the summer forest jihad”. It added: “This is an invitation to the Muslims of Europe and America, Australia and Russia to burn forests.”  The message claims that the burning of trees, as a warfare method, is permitted in Islam and it quotes from the Qur’an to back it up. The “benefits” of the fires, are to cause casualties, hit tourist income, create timber shortages for domestic, industrial use and pharmaceuticals, and stretch emergency services.
In the late 1980s and early 1990s, arson comprised about one-third of all forest fires in Israel, which is a very large proportion. Some of the sources of this arson were identified as the work of criminals, whose sole aim was to collect the insurance money. However, many instances of arson in the late 1980s were directly related to the Palestinian uprising (the first Intifada). Palestinians have used arson in the past as an insurgency method, as early as the 1920s, 1930s and 1940s, but in the 1980s it was adopted as a highly visible action against Israel. Arson was found to be easy to execute: all one had to do was cross the old border between the West Bank and Israel, which was unguarded and open to all, start a fire in one of the many forests in the hilly areas near the border, and then disappear. According to the International Forest Fire News (IFFN), between 1988 and 1991 the number of fires attributed to arson rose to over 30%, which was explained by an increase in politically motivated arson associated with the Israeli-Palestinian conflict.
There were frequent occurrences of forest fires in areas adjacent to the old "Green Line" border between Israel and the West Bank, during the years 1988-1990. Between 288 and 388 forest fires were caused by arson, which occurred in areas near the old pre-1967 border. In some of the fires, which occurred in northern Israel, Israeli Arab Palestinians were found to be responsible. These fires were extraordinary, given the fact that in 1988, there was a great deal of rain and, as a result, the vegetation was highly combustible.
While it looks like the Carmel fires started more from negligence than arson, Al Qaeda is taking credit for them, which is consistent with the information above.
Forest fires are potentially potent weapons that need to be defended against.
(h/t Serious Black and O)