The Islamic State and its allies have defeated the Kurdish peshmerga and taken control of the Mosul Dam, north of Mosul itself on the Tigris River, as well as Sinjar, a town to the west of Mosul that is home to many of Iraq’s Yazidi people. They now also control the Batma and Ain Zalah oil fields, which aren’t big, but they’re not nothing, either. This is the first major blow that the Kurds have suffered due to IS expansion, which to this point had actually boosted the cause of Kurdish independence by weakening Baghdad. The peshmerga was thought, including by yours truly, to be a match for IS’s fighters, so this certainly calls that into question. But to be fair to the Kurds, the dam and Sinjar were Kurdish-controlled enclaves surrounded by IS-controlled territory, so defending them was more difficult than defending, say, Kirkuk would be.
Today’s IS successes, if they stick, have a couple of huge humanitarian implications. For one thing, control of the Mosul Dam gives IS considerably control over the Tigris itself. They could, in theory, turn off the spigots and watch the farmland that depends on water from the Tigris dry up, or they could open them entirely and inundate parts of southern Iraq. So that could be a major catastrophe, hypothetically. If you prefer not to think about hypotheticals, then consider the plight of the Yazidi people. The Yazidis are a Kurdish community that practices a unique religion that seems to be a product of parts of several other religions, including clear influences of Zoroastrianism, Islam, and Christianity. They are vulnerable both because the community is so small and because the central figure of their faith is an archangel named Melek Taus, who was given responsibility to care for Earth by God, who for the Yazidis is basically an impersonal Creator. Christians and Muslims believe that Melek Taus is actually Satan, which makes the Yazidis literal devil-worshipers if you believe in that sort of thing.
Syria Comment has the best summary of the very real threat that the Yazidis are under right now as IS extremists have taken over Sinjar, which has been a home to the Yazidis for centuries and has protected them against periodic attempts by regional powers to exterminate them. They’re not only fleeing for their lives with no supplies, putting them at risk physically, but they’ve also now lost their homeland and its religious sites, which threatens the community in less tangible ways. There are reports that IS has already destroyed a Shiʿa holy site in the town, which are unconfirmed but certainly in line with what IS does, and that doesn’t bode well for the Yazidi shrines in the area. The Yazidi community may have a very difficult time coming back from this; while IS’s extremism may be creating opposition in Deir ez-Zor, in Syria, and their harsh treatment of religious shrines in Mosul may be starting to cost it support there as well, the Yazidis don’t have any kind of support network to draw upon in order to resist the destruction of their heritage. There’s no network of Yazidi tribes ready to support resistance to IS, and no Yazidi militias prepared to counter IS’s military actions. These folks are just refugees now, and it’s not at all clear what will happen to them in the future.