Michel al-Maqdissi, former director of Syria's Archaeological Excavations Department, has spoken with authority about severe threats to Syria's cultural heritage.
Al-Maqdissi places most blame on the Syrian government and military which have "destroyed a lot with its incessant bombing." And even if Assad ultimately prevails, Syria's cultural heritage will remain at risk from a government more interested in grandiose building projects (that will no doubt enrich the dictator's cronies) than in caring for its cultural heritage. As an example, al-Maqdissi mentions longstanding plans for a hotel and tourist center to be built right over the ruins of an important Phoenician site.
In response to a question, Al-Maqdissi states that looting is a serious problem, particularly at Apamea. However, al-Maqdissi rightly notes that rebels and the "real terrorists" of ISIS are far more likely to make quick cash from easy to sell commodities, like "hot oil." Simply, antiquities are not very "liquid"-- it's hard to sell them fast and for top dollar. And then there is the real question whether the iconoclasts of ISIS would rather smash than sell what they find anyway.
Revealingly, al-Maqdissi has little good to say about UNESCO and its tired group of experts who use the same cookie-cutter approach to every "cultural heritage crisis."
Instead, what's needed is outside funding for site guards (which would be difficult given international sanctions) and more realistically, effective policing of Turkey's border, something CPO suggested awhile ago.