Look at the smokestacks, how they proliferate, fanning the wastes of original waste over greater and greater masses of city.
-- Thomas Pynchon, Gravity's Rainbow
During the 1990s, armed escort vehicles began to proliferate in Lima and cars ceased stopping at red traffic lights. Professional companies fitted more and more electric fences round high- and middle income settlements.
-- Alan Gilbert, The mega-city in Latin America
Proliferate is a back-formation from the biology term proliferation, circa 1873.