The desert of west Texas was in the Palaeozoic era covered by an inland sea, teeming with life. That rich ecosystem is playing a crucial role in the world economy 250m years later. Over the course of millennia the abundant flora and fauna of that sea were transformed into the oil reserves of the Permian basin, which is both the most prolific and most resilient of the US regions that produce tight oil. US production peaked in April and has since been drifting lower, dropping 274,000 barrels a day to 9.324m b/d in August, as a result of the sharp slowdown in drilling that followed last year’s crash in oil prices. The slowdown would have been sharper but for two factors: projects coming on stream in the Gulf of Mexico, where lead times are longer and reactions to price movements are slower; and the strength of production in the Permian basin.