NPR's Audie Cornish talks to Peter Van der Auweraert, senior regional expert on humanitarian assistance at the International Organization for Migration, about the new options to get across Europe.

AUDIE CORNISH, HOST: Europe could be at another pivotal moment in the journey thousands of migrants are making across the continent.

ROBERT SIEGEL, HOST: Many had been going through Hungary, but after closing its border crossings and erecting fences, Hungary today used tear gas and water cannon to turn people away. So they're already seeking different routes, encountering new countries and new dangers.

CORNISH: To find out what might come next, we're joined by Peter Van der Auweraert with the International Organization for Migration. I asked him how these thousands of people on the move even know which way to turn.

PETER VAN DER AUWERAERT: Many people that I have seen have maps all the way from where they came to where they want to go in Europe. And they will ask you, for example, when you encounter them on the motorway. For example, yesterday when I was driving from Belgrade to the border between Serbia and Hungary, we saw probably about 150 migrants walking alongside the motorway. And we stopped the car to talk to them, and they were asking me, on the map that they had in their hands, can you tell us where exactly we are?

CORNISH: Some, at this point, may be considering finding an alternate route to Western Europe. And one of those people have talked about is going west through Croatia and Slovenia. Can you talk about that path, what people would encounter?

VAN DER AUWERAERT: I can. People have already started to go to Croatia. And as soon as the news of the border closings made its way to Macedonia from where people enter Serbia, instead of going to Hungary, people are taking the bus to go to Croatia. The Croatian border is not without its dangers. There are still mines that are leftovers from the Yugoslav Wars in the 1990s.

CORNISH: Landmines.

VAN DER AUWERAERT: Landmines. There is a very difficult geographical terrain in parts of the border terrain. So far, we have seen, today, I think, a few hundred migrants crossing the border from Serbia into Croatia. The Croatian government is very much aware of the difficult circumstances on their side of the border when it comes to landmines, and they have already dispatched teams to make sure that the landmines are well indicated and that there are no accidents.

One of the difficulties that the migrants will face is that they have two options to go from Croatia to Germany. Either they go through Hungary, or they go through Slovenia. And thirdly, after what happened today at the Hungarian border and the fact that it is quite likely that the border between Croatia and Hungary will be closed quickly as well, it seems, for us, more likely that people will be traveling through Slovenia to reach Austria and then move on to Germany.

CORNISH: You talk about people being deterred because of the poor treatment in Hungary, because of Hungary closing its doors. Is there a chance that it would also deter people from heading toward Europe at all?

VAN DER AUWERAERT: That is a very good question and the question that I think none of us have a handle on how much that will affect what people are currently talking about. My general sense is that it will not deter people. It will simply change the routes. All the people that I have met at the border yesterday and this morning - and many of these people are middle-class people, educated people from Syria, from Iraq. These people have set themselves a goal and that is very clear, to get to Europe, to get to Germany, specifically, some to Sweden, to start a new life.

The situation in their countries of origin is so desperate and without any solution in sight that we believe that these movements will continue and that new walls might be erected or new controls might be introduced. But the effect will simply be to make people change the route through which they try to reach the land that they want to reach.

People - individuals will do so but also the smugglers. The smugglers are very well organized, and I am sure that they are already planning today alternative routes for if this country would close the border or that country would close the border. So it will be very difficult, unless there is a drastic situation in the places where people currently are outside Europe, to stop this movement from happening.

CORNISH: Peter Van der Auweraert - he's with the International Organization for Migration. Thank you so much for speaking with us.

VAN DER AUWERAERT: You're welcome. Thank you very much for speaking to me.

First published in NPR.org