The National Council for Planning and Building handed environmentalists a mammoth victory last week by rejecting a proposal to apply National Master Plan 35 to areas hitherto closed to construction.The plan had been to increase land for residential development, but at the cost of space from which such development had been previously prohibited. Parts of the Jerusalem Hills and the Sharon would have been in danger – and not only there.Urban sprawl has been the bane of modern life, especially in recent decades. Growing populations lead to the expansion of our cities through the incorporation of undeveloped or strictly rural land nearby.The process is relentless everywhere in the industrialized world, but all the more so in a country as narrow- waisted and densely packed at its center as Israel.Over the years, we have seen much farmland and wilderness disappear under multi-storied metropolitan housing projects. Much of this is unavoidable, especially if we wish to slow the rise in housing prices.At the same time, though, our “green lungs” – the open spaces that filter air and provide recreation opportunities for city-dwellers – have become increasingly scarce and congested.Environmentalists, whose opposition to the plan was a foregone conclusion, were not the only ones incensed by the plan to bite off more chunks of open-space. The Housing and Construction Ministry, the Union of Local Authorities and many municipalities, plus groups of architects and city planners, fervently fought the amendment that would have shrunk the remaining supply of unexploited land.Supporters of the quashed plan argue that great damage was wrought to the cause of affordable housing, which depends, first and foremost, on freeing up land for construction.But was this particular land truly indispensable? It is a fact that plenty of land has already been earmarked for development, with approved re-zoning and permits already issued. Such land would suffice for hundreds of thousands of housing units. However, in actuality development has not begun, despite the overcoming of legal obstacles.The reasons for the delay in using already available land vary. Some are bureaucratic but most are not. Plenty of land in private hands is kept dormant for speculative purposes. Disincentives for withholding these resources might be created, but this has not happened yet. In other cases, the available land is not in the most lucrative locations where demand is high.The greatest demand for housing is in the Greater Tel Aviv hub – what is colloquially dubbed the Gedera-Hadera bloc. There is populist temptation for the government to increase construction where most people live, but there is a clear downside to exacerbating the Central region’s overcrowding.The designations of center and periphery are not immutable. Israeli experience has amply shown that once unattractive sites sometimes evolved into sought-after real estate. Israelis who once did not commute do so today, and this new behavior has driven people farther away from core cities.Similar changes are likely in the future too, especially if public transport – rail transport above all – is improved so as to bring outlying areas closer to the country’s employment, business and cultural focal points.Population dispersal was and remains a key national interest, an interest that was certainly not served by the proposed expansion of the national master plan. Just as a delicate balance between population dispersal and increased building in popular centers is mandated, so too planners must find a tricky equilibrium between urban expansion and open spaces crucial that city residents crave for sustaining quality of life.It is all too easy to fill up vacant land with asphalt and concrete. In the short term the harm might not be evident, but in the long run there would be nowhere to escape to and the damage would have become irreversible.It does not have to be that way. Our land resources are strained, but rather than despoil scarce remnants of open space, we could provide more residential units simply by building higher and save the green lungs from the jaws of urban sprawl.