"Refugees climb atop trains as blockades pepper European borders" is the title of this news article.
What does pepper mean?
Edit: this is the verb definition of pepper from Google definitions
1.sprinkle or season (food) with pepper. "peppered beef" synonyms: add pepper to, season, flavor "salt and pepper the potatoes"
2.cover or fill with a liberal amount of scattered items. "the script is peppered with four-letter words" synonyms: sprinkle, fleck, dot, spot, stipple; More
3.hit repeatedly with small missiles or gunshot. "another burst of enemy bullets peppered his defenseless body" synonyms: bombard, pelt, shower, rain down on, attack, assail, batter, strafe, rake, blitz, hit "a burst of bullets peppered the tank"
archaic 4.inflict severe punishment or suffering upon.
Edit: meaning of blockade from OALD
the action of surrounding or closing a place, especially a port, in order to stop people or goods from coming in or out
a naval blockade
to impose/lift a blockade
an economic blockade (= stopping goods from entering or leaving a country)
blockades of roads by truck drivers protesting over pay
a barrier that stops people or vehicles from entering or leaving a place
The police set up blockades on highways leading out of the city.