There's only so much space.
There's only so many resources.
Some places have more safety and resources than others.
People that live in areas with limited opportunity and resources are naturally going to gravitate to those places with the most resources, opportunities, and security.
People that already live in areas where there are more opportunities, resources and security are naturally going to feel threatened by newcomers that they see as a threat to what they feel are their (already diminishing) opportunities, resources, and security.
Does anyone profit from the chaos?
From "The Seven Loose Pieces of the Global Jigsaw Puzzle", (an essay by Subcomandante Marcos)
snip--
The results of this world war of conquest was a great ring of millions of migrants in all the world "Foreigners" in the world "without borders" which the victors of the Third World War promised. Millions of people suffered xenophobic persecution, precarious labor conditions, loss of cultural identity, police repression, hunger, prison, death.
"From the American Rio Grande to the "European" Schengen space,
a double contradictory tendency is confirmed. On one side the borders are closed officially to the migration of labor, on the other side entire branches of the economy oscillate between instability and flexibility, which are the most secure means of attracting a foreign labor force" (Alain Morice, Op. Cit.).
With different names, under a judicial differentiation, sharing an equality of misery, the migrants or refugees or displaced of all the world are "foreigners" who are tolerated or rejected. The nightmare of migration, whatever its causes, continues to roll and grow over the planet's surface. The number of people who are accounted for in the statistics of the UN High Commission on Refugees has grown disproportionately from some 2 million in 1975 to 27 million in 1995.
With national borders destroyed (for merchandise) the globalized market organizes the global economy: research and design of goods and services, as well as their circulation and consumption are thought of in intercontinental terms. For each part of the capitalist process the "new world order" organizes the flow of the labor force, specialized or not, up to where it is necessary. Far from subjecting itself to the "free flow" so clucked-over by neoliberalism, the employment markets are each day determined more by migratory flows. Where skilled workers are concerned, whose numbers are not significance in the context of global migration, the "crossing of brains" represents a great deal in terms of economic power and knowledge. Nevertheless, whether skilled labor, or unskilled labor,
the migratory politics of neoliberalism is oriented more towards destabilizing the global labor market than towards stopping immigration.
(more)
http://flag.blackened.net/revolt/mexico/ezln/1997/jigsaw.html