Israel’s critics say the fact that the conditions in Gaza do not rival the problems in sub-Saharan Africa only makes the political and human rights crisis here all the more tragic — and solvable. Israel, they note, still controls access to sea, air and most land routes, and its security policies have consciously strangled development opportunities for an educated and potentially high-achieving population that is trapped with no horizon. Pressure needs to be maintained to end the siege entirely, they say, and talk of improvement is counterproductive.

The recent changes stem from a combination of Israeli policy shifts and the chaos in Egypt. The new Egyptian border policy has made little difference, but Egypt’s revolution and its reduced policing in the Sinai have had a profound effect.

For the past year, Israel has allowed most everything into Gaza but cement, steel and other construction material — other than for internationally supervised projects — because they are worried that such supplies can be used by Hamas for bunkers and bombs. A number of international projects are proceeding, but there is an urgent need for housing, street paving, schools, factories and public works projects, all under Hamas or the private sector, and Israel’s policy bans access to the goods to move those forward.

So in recent months, tunnels under the southern border that were used to bring in consumer goods have become almost fully devoted to smuggling in building materials.

Sacks of cement and piles of gravel, Turkish in origin and bought legally in Egypt, are smuggled through the hundreds of tunnels in double shifts, day and night, totaling some 3,000 tons a day. Since the overthrow of President Hosni Mubarak, the Egyptian security authorities no longer stop the smugglers. Streets are being paved and buildings constructed.

“Mubarak was crushing us before,” said Mahmoud Mohammad, a subcontractor whose 10-man crew in Gaza City was unloading steel bars that were carried through the tunnels and were destined for a new restaurant. “Last year we were sitting at home. The contractor I work for has three major projects going.”

Nearby, Amer Selmi was supervising the building of a three-story, $2 million wedding hall. Most of his materials come from the tunnels.