Welcome to the age of diminishing returns

Tuesday, April 17, 2012

Getting our land back

Lorenza Zambon, actress and gardener, tells the story of a couple who decided to demolish some property of theirs and return the area to fertile soil. A few square meters gained, about one trillion still to recover.

It is not easy to determine the area of the world covered by human-made artifacts, that is by roads, houses, parkings, buildings, commercial centers and all the rest. But much work has been performed in recent times and the estimates are starting to converge on reasonable values. The results for the fraction of area covered with permanent structures range from about 0.5% (Schneider et al., 2009) to about 3% (Global Rural-Urban Mapping Project, 2004). Translated into areas, these values correspond to a minimum of 700,000 square km and to a maximum of about three million square km. To visualize these areas, think that the first one compares to France (550,000 square km) and the second to India (3.2 million square km).

No matter which result we should consider as the most reliable, the data clearly show that building takes place mostly in flat and fertile areas. There, the fractions covered by human-made structures are much larger than the world average. For instance, recent data for Europe indicate that, in January 2012, the most urbanized European states were Holland and Belgium with, respectively, 13.2% and 9.8% of the surface. As you see below (From Schneider et al.), urbanization in Europe is, indeed, concentrated in the fertile plains. Apparently, we are engaged in the task of destroying the land that supports our physical existence.

We have no data telling us how fast this paving of land has been going on up to now but, if it is proportional to the production of cement, growth has been spectacular (data from USGS).

It is impressive that the curve shows no sign of abating whatsoever. Maybe there will be a peak in the coming years, but cement is a form of "persistent pollution." Reducing its production - or even stopping it - won't automatically return built environment to fertile soil. But we can't eat concrete. Will we ever get our land back? 

Restoring to fertility land covered with concrete is an enormous task, but not an impossible one. So, Lorenza Zambon, actress and gardener, tells the story of a couple in Turin, Italy, who decided to give to their children a patch of fertile land as a gift. They obtained it by demolishing a few concrete garages they had inherited.

It was a lot of work; concrete had to be cut and broken to pieces and the rubble carried away. Then, restoring the fertility of the soil took truckloads of dirt, charcoal, and more. Zambon doesn't tell us how long the task took nor how much it cost, but surely it was slow, messy and expensive. It was also a subversive idea: in the generally accepted view, paving the land means "developing" it, and that means making money. So, destroying property to restore the fertile soil is something that nobody in his/her right mind would - normally - do.

But someone did it. The end result was a patch fertile soil where grass and flowers grow. Just a few tens of square meters, not much in comparison to the trillion remaining to be recovered. But it is a first step!

This post was inspired by a talk given by Lorenza Zambon in Florence on March 24, 2012. If you want to hear Lorenza speaking on these matters, you can find one of her presentations here, unfortunately it seems that she does that only in Italian.


  1. The cement production data are just bonkers.

  2. I tore up part of my driveway for my garden. http://offthegridmpls.blogspot.com/2011/07/garden-tour.html

    The City went after me for that. They said I couldn't have anything there but asphalt, bitumin, or pavers. After that, after having been nearly condemned twice in the previous year, I left a voicemail with the inspector, telling him if this kept up, I'd be filing some kind of harassment charge. Haven't heard from them since.

  3. There was an EU report some years ago: "In the European Union (EU) about 1,000 km² were annually subject to land take for housing, industry, roads or recreational purposes between 1990 and 2006. This is exceeding the size of Berlin. About half of this surface is actually sealed by buildings, roads and parking lots." read more on

    In Denmark urban and developed land is estimated to 21 percent according to a report from 2004. One challenge in the figures is how to classify. e.g. in many cities only about 50% of the land is actually paves, the rest may be gravel, grass, golf courses allotments and football field. Also in some countries the areas of dams is part of "built" areas.

    1. In a way, I'd say that golf courses and football fields are built areas indeed, just somewhat easier to bring back to fertile land.

    2. Yes, the problem is how to classify areas. The paper by Schneider et al. that I cite in the text has an interesting discussion on this point. If I understood correctly, they superimpose a grid to the map. Each element of the grid is considered paved/unpaved if it contains more/less than 50% of the area covered by buildings. Of course, the measurement will be more precise, the smaller the elements of the grid. They have something like 500 m grid. At the limit, making the elements smaller, you would be able to count even flower pots in balconies! But the result should converge much earlier, I figure.

    3. Anyhow, if we keep the exponential increase in cement production, we should arrive to fully covering the planet with concrete structures in some decades....

    4. As the existing concrete infrastructure expands, the concrete necessary for maintenance also expands. (I.e., someone may use some concrete to repave a sidewalk or street.)
      So the area becoming newly paved and the production of concrete are not *strictly* proportional. There's probably a formula somewhere that describes their relationship, but I would not know where to find it.

  4. In the one day and still beautiful Canary Islands, there are people concerned about the sealing of the fertile soils of this archipelago.

    The long haul tourism, consisting in about 12 million people flying like ducks form 3 to 5,000 Km distance in average stays of one week, which means flying ducks in low cost planes at the rate of 200,000 per week, are the main reason for the spoiling of the fertile soil.

    They arrive and are transported form the airport to hotels, where they are placed an ankle bracelet to have free drinks during all the stay and enjoy in swimming pools, or jacuzzis, make some touristic trips to the vulcanos or so and taking sunbaths at the beah or in the terrace of the hotels

    In the past, these islands were living on their own (basically as everybody else in preindustrial times), with their famous potatoes, bananas, tomatoes and cereals in the driest islands closer to Africa.

    Today, 2 million Canarians attend basically to touristic activities. Little remain of the banana, tomato or potato crops. The islands are coped from the sea level to about 800 m. over the sea level and have naturally (?) occupied the most fertile volcanic soils, like the magnificent (in the past) valle de la Orotava.

    I told them in a conference, who will take care when these flying ducks cannot fly any longer from remote places to spend some moeny here? At least 400,000 employments are directly related with tourism there. Where will you cultivate now?

    Lanzarote, a fully volcanic island has now 140,000 inhabintats. Almost all the potable water is desalinated by a plant, that works with electricity of a power plant, that is fed with fuel oil coming in a tanker once a month. Should this tanker fail, they will have no water within about 60 days and iether will have to evacuate 140,000 people or take potable water tankers to feed them. In the past, they used very little water per person and was all of it collected in aljibes (artificial wells collecting the scarce rain in the island).

    Will they grow bananas in the jacuzzis? Perhaps tomatoes in the hotel terraces, like Incas in the Sacred Valley in Peru? Will the have to make good the 68 slogan in Paris ("below the paving stones is the earth")?

    Quo Vadis?

    1. You should see the island of Capri, facing Naples in the Mediterranean sea. Practically all paved for touristic activities. Fortunately, you don't need a plane to go there and you can escape from it without a plane. But the mainland is not much better

  5. Apparently the EU Commission released some guidelines about "soil sealing"
    and there is an upcoming conference about it:

    1. As usual, we arrive too late and what we plan is too weak. A crucial problem for our survival and all what the commission can produce is a working document with "guidelines." Nay, we learn only by hitting our nose hard against the problem. Ah.... and also a closed door conference, open only to "high level" people. Great.