Batgung

I've griped about it myself: pollution and a general indifference to the environment in Hong Kong. But in one way, at least, Hong Kong is surely one of the world's most environmentally-sound cities. How can that be, you ask, through a haze of air pollution, standing next to a harbor that's a toxic soup?

Well, we get told over and over that using up too much land for development is one of the primary environmental sins. You constantly hear about the terrible 'footprints' we humans leave on the earth's surface. Clearing land to build on lies behind deforestation, species extinction, and so on.

I started thinking about this the other day as I was jogging around my ultra-high-rise neighborhood in Hong Kong. What kind of 'footprint' was I leaving on the earth's surface, i.e. how much space was I taking up?

Uncharacteristically, I started doing some mental calculations.

I live in a 15-tower housing estate. Each tower has -- and I started rounding figures here strictly for convenience -- 50 stories. Each storey has eight flats. Let's say an average of three people lives in each flat (a bit low, I think, but I don't want to be accused of overstatement).

My little brain then put together the following equation:

3 people x 8 flats x 50 stories x 15 towers = 18,000 people in my housing estate

That's a nice big number, isn't it?

Next, I reckoned my estate occupies a plot of land that's around 400 meters long, and averages just under 100 meters wide - let's say 90. Again, these are rough figures, and again I think I've erred on the generous side.

By now you, clever reader, have no doubt jumped ahead and calculated the Tall Estate's area: 36,000 square meters.

At this point, we can complete a simple operation: 36,000 square meters divided by 18,000 residents means each member of Mr Tall's housing estate occupies just about exactly two square meters of the earth's surface.

Appropriately, if I arrange my two square meters end-to-end, this is just enough room for me to lie down all stretched out and comfy. I find this symmetry extremely satisfactory.

I would hate for such a lovely little number to go otherwise unused, so let's just follow things out a little further, shall we? What would it be like, for example, if everyone on earth occupied the same amount of space I do?

Well, there are 7 billion of us tormenting our planet at the moment, give or take a few foul polluting meat puppets here and there, so that's 14 billion square meters we'll need. We all know that one square kilometer covers exactly 1 million square meters. (At least I know this, thanks to Jimmy Carter forcing me to learn the metric system when I was 10.)

Anyway, now we divide 14 billion by 1 million, and -- we thankfully have a lot fewer zeros to confuse us. I come up with 14,000.

That is, to house the world in Mr Tall style, we need a housing estate that covers 14,000 square kilometers. That might sound like a lot of land, but really we just need to stake out a nice square plot that measures around 120 km on all sides -- that's just 75 miles per side, for us Americans -- and that has room for some very large sewage pipes to be installed beneath it.

To put this into some perspective, Ireland comprises 70,000 square km, so our estate would take up just one-fifth of that one small island. To translate back into American, we could fit our entire estate -- every Mr and Mrs and Child Tall in the whole wide world -- into the only-just-barely-a-state of Connecticut, with room left over for one hell of a strip mall.

And, oh yeah, the rest of the whole world would be free for a farm or two, and maybe for some parks and wildlife preserves.

Now, even I'll admit that this is a simplistic and extreme way of looking at the problem. So let's consider a much more plausible alternative.

If we dig out the actual population density figures for cities around the world, unsurprisingly, you don't need to go far down the list to find us: Hong Kong has about 6,200 people per square kilometer.

That's already pretty crowded, but allow me to add a couple of points of context to this figure. Hong Kong's population density is based on the entire area of the SAR, not just its actual urban areas, as it is for other cities on this list. I've seen various estimates of how much of Hong Kong's land is actually built up, ranging from 10-20%, but let's again be conservative, go for the highest figure, and say that all of Hong Kong's people live on about 20% of its land.

This means that the real population density here is much closer to 31,000 people/square kilometer (i.e. 6,200/.20).

Also keep in mind that much of the 80% of Hong Kong that's not built up is essentially wild. So if we were to ask everybody around the world to live in quarters as close as those in Hong Kong, we're not committing them to a soulless, stark urban wasteland. The great majority of our imaginary territory could be left completely to nature, or used in enviro-friendly ways.

Okay, now back to our numbers. How much space would it take to house the world at the Hong Kong standard, i.e. at an actual density of 31,000/square km, in an urban area that took up 20% of a broader area that could remain unspoiled?

Using our figure of 7 billion people, I come up with an overall area of roughly 1.1 million square kilometers. That comes out to just .74% -- i.e. not even one percent -- of the world's total land area (which is 148,000,000 km2).

Again to put these numbers into context: countries of just over a million km squared include the big-but-not-enormous Ethiopia, Bolivia and South Africa. By comparison, China and the USA are both around 9 million square km.

But remember, only 225,000 square km of this area - i.e. 20% of 1.1. million square km -- would need to be built up at a density equivalent to Hong Kong. So our actual urban area would be smaller than the already-cozy UK, which covers 241,000 square km. We'd need just .15% -- less than two-tenths of one percent -- of the world's total land area.

Think about that for a minute: 99.85% of the world's land without buildings of any sort.

But I wonder how many self-proclaimed 'environmentalists' around the world are willing to live this way, i.e. in tightly-packed urban centres that genuinely minimize land use, and that make widespread public transport not only possible but profitable? Maybe more of them should investigate life in Hong Kong -- here we certainly have the opportunity to practice what we preach when it comes to saving space!

--------------------------------------------------------------------------------

Postscript: for a far less cranky overview of urban densities, in which discussion of Hong Kong population features prominently, see these two articles (note that they are .pdf files). They were written by a visitor to HK, and despite a few howlers (e.g. the main road from Kowloon to Tseung Kwan O passes over a hill, not through a tunnel; HK locals don't eat at restaurants that take credit cards) they are generally well-observed and accurate. It's interesting to have an outsider's view sometimes, since it's easy for those of us who've lived here a long time to forget just how unusual Hong Kong really is.