Desertification and Population Pressure

My last post on climate change evidence concerned the doubt that still surrounds the issue of man-caused global warming. Personally, I can't see how we could possibly not have influenced the climate – we can’t even brush out teeth without damaging consequences.

That’s not necessarily an exaggeration, either. Desertification of farmland in semi-arid areas poses an increasingly ominous threat to the wellbeing of both our environment and the human race. UNEP reckon about 20 million hectares of land are lost to desertification each year. That’s around 200,000 km² or a little 1% of the world’s estimated arable land. It doesn’t take a genius to realize that isn’t going to leave us with much in around 100 years or so.

You might be tempted to think that this is a strictly developing world phenomenon, but you'd be wrong. In fact the most rapid desertification is happening in Australia, Spain and the USA. What’s causing it? Like I say: brushing your teeth.

Causes of Desertification

Okay, so it’s not quite that simple. Our ecosystem is both fragile and complex and any number of things can tip it out of balance. The main cause of desertification is poor soil conservation. The top layer of any soil is important and failing to maintain a healthy layer of humus is one of the prime reasons for the failure of arable land.

Crop rotation, composting and responsible use of fertilizer are all ways of getting the best out of soil but many farms practice intensive monoculture and use excessive chemical inputs to get the most out of the land. This inevitably leads to short term profit and long term soil degradation. Often such practices come about because of western business models that emphasis profit over responsibility. The gluttony of the developed world could well be contributing to the slow death of developing countries with marginal farmland.

Deforestation is another direct contributor. Reducing the concentration of trees affects the thermal properties of the land and often leads to reduced rainfall. Without an adequate water supply, the humus layer begins to degrade rather quickly and the soil begins to thin and die.

In developed countries with high urban densities and efficient water systems this same effect can be produced by excessive water consumption. Tapping into the aquifer and draining the water table can intensify the effects of dry periods and cause degradation on the surface. Excessive water demands from urbanization and tourism in countries such as Spain are putting large areas of farmland in danger – the UN reckons around 12% of Europe is in immediate danger of desertification and as much as 60% on the Iberian peninsula.

Which brings me back to brushing your teeth. You can use 12 gallons on water when you run a tap for 3 minutes - switching the tap off while you brush can save a lot of water over the year. There's a lot more you could be doing, too - taking shorter showers and showering more often than bathing, for example. But the toothbrushing fact is a nice clean tagline which media men (and me) like to seize upon. I guess it emphasises just how important some of our most banal actions are. Water conservation isn’t just a key issue in Sub-Saharan Africa; it’s an important principle that should apply to everybody and which needs to be taken seriously.

Feedback from Population Growth

It gets worse, too. Because of the impact of intensive farming and urbanization on the rate of desertification, the rate of damage theoretically increases as a population grows. The UN estimated the Earth’s population to be around 6.8 billion at the end of 2009 and the current rate of increase is around 100 million per year.

An optimistic blog post by Fat Knowledge estimates the ultimate carrying capacity of the Earth to be anything from 30 billion to 100 billion people – if all available farmland were used and everybody ate corn. But this estimation does nothing to take account of the effect that population growth will have on available farmland.

The agricultural capacity of the planet is already in decline and will continue to trend that way as the population grows. Sooner or later we’re not only going to be in a sticky situation; we'll have more people than the planet can support and our ability to support them is going to go into rapid decline. If Thomas Malthus is to be believed we'll probably keep on breeding past this point too, until something cataclysmic happens.

There are examples of this from history. History tells us that the pre-renaissance population crash in the UK was the result of the Black Death, but such a simplistic estimation fails to recognise that the population was already in steep decline before plague hit. The Black Death certainly helped, a large part of the near 3 million reduction in population was the result of crop failure.

I’m not going to try and translate that into a global context. The mesasge however if fairly clear; desertification is a very real threat and sooner or later the degradation of farmland coupled with excessive population growth is going to lead to a major and rather terrible global food crisis.

Not that I want to ruin your morning or anything.