Ah yes! The devastation of crops and animals is similar to the bubonic plague aspect of the "hybrid" theory. If I remember correctly I believe the black plague caused a lot of land devastation, but I don't know if it was caused by the disease itself or by the chaos wrought by the dying populations. I believe the pneumonic (or bubonic) plague can be spread to animals and humans, which is why I think it fits with the blight (how it turns bears into berzerkarn and wolves into blight wolves). My memory on the plagues is rusty so please correct me if I misremembered anything.
And yes, I have absolutely no idea how I would explain the song aspect of it! I'm afraid I don't know much about the song theory so I think I'll have to leave that up to you and madrar for now! I was also wondering how I could explain Fiona's apparent regression of the blight... I have no idea. Any thoughts would be appreciated!
EDIT: The blight being one large lifeform is interesting. I'll have to put more brainpower into that, but that sounds really interesting. Let me know if you guys go into that any further & i'll see if I can add in things.
EDIT EDIT: I need to read more carefully before I post. I'll need to go google who Utha is, I don't remember reading anything about her. Was she in a book?
The most famous outbreak of plague, the Black Death, actually caused enormous amounts of farmland and villages to be reclaimed by natural forestation. It wasn't unknown for the plague to sweep through a village and wipe it clean, or for the handful of survivors to flee to a nearby city for shelter. Despite the usual wars, Europe looked to be entering a Golden Age during the High Middle Ages when the Black Death struck. Most of the available farmland was already being cultivated and there had been a population boom. The majority of the population were serfs, and not treated well either.
The Black Death killed most of the farmers, which led to a high demand for labor, which meant that the farmers were paid more for doing less back-breaking labor. Over the course of the plague, however, much of the farmland was lost. Forests grew over villages full of boil-covered corpses, which fit in with the trend in European art to be nihilistic and more than a little creepy. So, ironically, like Genghis Khan's armies, the plague was pro-environment. So the land-destroying disease part doesn't fit in yet, but the social impact could.
The Black Death hit Asia and the Middle East as well. The plague seems to follow the old trade route between East and West, and the plagues are likely native to Central Asia, like the Gobi desert. Some theorize it's present in Europe as well, and has sprung up before. But, starting with Justinian's Plague in the sixth century, in European history it seems to start in the Black Sea and move its way through the naval trade routes. I just don't focus on the East because I'm only starting to study and appreciate its history, as opposed to that of the West which I was practically weaned on.
There's a funny story that some Italian merchants from Genoa managed to upset the Mongol Khan in the Crimea enough that he laid siege to their trading post. When the Mongols started dropping dead from the plague, the ever practical Khan started launching them into the city. The disease spread into the ships before they fled back to Italy. A similar story is told about the Mongols marching on Baghdad. The Black Death is still being debated. I understand there's some controversy about which specific disease. I know that bubonic was the less-lethal version. The lethal version was the type that wiped out villages but died out, because, well, everyone died too quickly to spread it.
Minor tangent here.
Genghis Khan and his soldiers killed a lot of people.
A. Lot.
I've seen estimates where, adjusted for per capita of people alive before they got started, Genghis was responsible for more deaths relatively speaking than World War II. Even if you don't, it's way too goddamn close to have been achieved without aircraft, bombs, machine guns, or the Dovahkiin.
After the Khwarezmians rejected his overtures of peace and trade, the Mongols hit Kwarezm like the scourge of god. Most people have never heard of Kwarezm for this very reason.
There are regions in Iran and Uzbekistan that recovered population wise from the Mongol invasion in the early 1900's.
From a war in the 13th century.
This led to an explosion in livestock and prey animal population, it see-sawed back and forth, but eventually forests started to grow over the former farmland. In addition to being one of the most brilliant war-leaders to ever walk the earth, Genghis managed to do a lot for the environment. So there's that.
Likewise, Europe took many centuries to recover its pre-Black Death population. In part, because plague kept breaking out, and there were some gruesome wars, and people started using mercenaries, and then the religious schism, and the whole mess that was the Thirty Years War and the climate was worsening. Europe 1300-1820 is the stuff of nightmares. (Then again, so are most places most of the time.)
So what happens if we combine those two paradigm shifting, mass turmoil inducing events, but remove the forestation and replace it with the permanent devastation of incredibly valuable farmable land?
We get a Theodosian style Blight.
It goes a long way into explaining the crappy situation Thedas finds itself in all the time, and the lack of technological growth, and the constant warring with one another, and the religious fatalism. Certainly explains Zevran's lewd references to flagellation.