Though the Syrian civil war can be used to illustrate this, a better example is the india - bangladesh fenced wall. Bangladesh is one of the first country and most severely impacted by climate change and this wall has been put in place to stop people bangladesh migrating away from climate change consequences into India.
https://www.newyorker.com/culture/photo-booth/indias-fence-o...
http://indianexpress.com/article/india/laser-walls-smart-sen...