I have referred to this subject on this blog before, in posts about climate change and immortality, but the sources keep popping up so I think it's time for a round-up of current thinking. One I made a note of was a BBC news report in March 2009 here: Global Crisis to Strike by 2030 . You can read it for yourselves, but this gives the flavour:
Growing world population will cause a "perfect storm" of food, energy and water shortages by 2030, the UK government chief scientist has warned... Demand for food and energy will jump 50% by 2030 and for fresh water by 30%, as the population tops 8.3 billion, he told a conference in London.
Much more detail was included in How Many People Can Live on Planet Earth, a BBC TV Horizon programme in December 2009 fronted by none other than the famous naturalist Sir David Attenborough, which examined the impact of the population growth on the planet's environment. To summarise the key points:
Growth is inevitable
The world's population is currently increasing by 80 million a year, and is projected to increase from 6.8 to 9 billion by the middle of this century. This is pretty well guaranteed to happen (barring a colossal disaster wiping out a substantial portion of the world's population) even if average family size drops sharply, because of the way in which the population structure is skewed towards the young: it is generated by a decrease in the death rate rather than an increase in the birth rate. There are already more than 1 billion teenagers in the world (an appalling thought, think of all that collective angst…pity it can't be harnessed as a power source) and most of them will inevitably produce their own children. So any attempts to control population will have to start from that 9 billion baseline - a 25% increase over the next four decades. Forecasts from that point make different assumptions about future family size and vary from the optimistic (eventually stabilising at around 8 billion by the mid-22nd century) to the pessimistic (10+ billion). Even the most optimistic projections therefore envisage a long-term total some 1.2 billion more than at present. That’s about as much as the entire population of China or India.
The USA is likely to increase in population from 300 to 400 million by 2050, the UK from 60 to 70 million. These figures are bad enough, but the growth rate in the developing world is slated to be much higher, with sub-Saharan Africa (already the world's biggest disaster area and also facing the worst effects of climate change) doubling in population.
The three key resources which will be put under most pressure by this increase in population are fresh water, food and oil.
The Water Problem
It's important to note that the total quantity of water on this planet is constant - there's no way of getting any more. Just 2.5% of the world's water is fresh, of which only 1% is available for use (the rest being in ice caps). Half of the available fresh water is already used and over 1 billion people are currently living in areas affected by water stress (i.e. water is being used up at a faster rate than the sources are being replenished). This number is projected to increase to more than 50% of the global population within 20 years. Some areas are already running out: to give one example, Mexico City has a population of 20 million of which more than 1 million are affected by daily water shortages. This number is growing all of the time as the reservoirs are running dry.
Even so, domestic use is not the major problem. Agriculture is one of the major users of water, and the numbers involved are astonishing. For instance, growing enough coffee beans to produce one cup of coffee uses up 120 litres of fresh water; growing enough cotton to make one shirt uses 3,000 litres.
Desalination of sea water is one way of obtaining more fresh water, but carries its own problems. It is very energy-intensive (and therefore expensive) and even in sunny regions where solar power can be used, it still results in the production of huge quantities of salts which have to be disposed of somehow without damaging the environment (which rules out pumping it back into the sea).
Probably the most promising measures are small-scale local ones intended to trap and store more water rather than let it run off to the sea, but these will only work in certain areas and will only postpone the problem unless something can be done to contain and preferably reverse population growth.
Next, agriculture. Needless to say, the quantity of land is pretty much constant too, except round the margins (where it may be reducing in the future as sea level rises). Virtually all productive land - amounting to 35-40% of the planet's land surface - is already being used. Furthermore, most of it is already being used intensively. During the 20th century, industrial countries tripled their food production by using better crops and industrial farming methods, with extensive use of machinery, fertiliser and pesticides. From the 1960s the developing world began to follow suit in the "Green Revolution", resulting in increases in yield of up to five times. However, yields are now levelling off globally.
Higher-yielding genetically-engineered crops are available, but they tend to use even more water - which takes us back to the previous section. Given the likely effects of climate change (one of which is drier continental interiors) the focus of genetic modifications may have to shift towards drought-resistant varieties, but they are unlikely to be as productive. Some of the richer nations (e.g. China) are trying to protect their future food supplies by buying farmland from poorer countries, particularly in Africa - even in countries like Ethiopia which already has a food shortage - and reserving its production for themselves. This is clearly likely to lead to tensions - to put it mildly - as existing food supplies come under increasing pressure from the growing population. The increasing taste for meat as countries develop exacerbates the problems, as growing crops for human rather than animal consumption is several times as productive in food value per hectare.
The third resource problem is oil. The demand for this is projected to increase by 40% over the next 20 years due to a combination of increasing population and increasing industrialisation in the developing world. Oil is not just used for transport and industry, it is also vital in maintaining levels of food production because of its use in fertiliser and in the mechanisation of farming, which takes us back to the previous section.
There is much debate among petroleum geologists about the issue of "peak oil"; the point at which production starts to decline as the more productive fields are worked out. Some say we are more or less there already, others that there are still lots more oil reserves than official figures suggest. Whichever group is correct, it seems inevitable that oil will become more costly as a result of the projected increase in demand combined with the newer fields being more difficult to exploit.
Add them together…
These three key resources - fresh water, agricultural production and oil - are clearly interrelated. This leads to the concept of "carrying capacity"; the maximum population which a given environment can support. This does of course depend on the standard of living which is assumed. The standard method of measuring the productive biocapacity of the Earth is in "global hectares"; on average, each person uses about 2 of these hectares. There are big regional variations, however: in Africa the average use is 1.37, in India 0.89, China is right on the average at 2.0, each UK citizen uses 5.3 and each US citizen 9.42. The Earth's carrying capacity could therefore range from 15 billion if everyone lived at Indian levels of consumption, down to 1.5 billion if everyone enjoyed US standards.
If anything, these figures are optimistic because the current rates of consumption are already unsustainable in the long term; we need 1.5x the Earth's resources to sustain our current way of life. Which according to these calculations means that the maximum sustainable global population ranges from 1 billion at a high average standard of living to 10 billion at little more than subsistence level.
What can be done?
Attenborough listed three ways in which we could reduce the pressure on our resources:
1. Reduce our consumption
2. Change our technology
3. Reduce our population growth
The first is probably inevitable anyway as the increasing demands on resources have the effect of pushing up their cost. The second is already underway in many fields but is unlikely to achieve enough by itself. The third has been forcibly tried by China and India.
China instituted a "one child" policy in 1979. It has been highly unpopular but it has been estimated that without it their population would have been 400 million higher than at present. India attempted a vigorous sterilisation programme (including all criminals) but this was abandoned as a result of public resistance. It has long been noted that birth rates tend to fall naturally as the standard of living increases and death rates fall (but there is always a gap between the fall in death rates and in birth rates, during which the population soars to a higher base level).
The key element in the fall of birth rates is women: in countries where women have the same educational opportunities as men, have access to contraception and are fully emancipated with the same legal rights as men, the birth rate falls dramatically. A remarkable example is the Indian state of Kerala where education for girls as well as boys is compulsory. As a result, women choose to delay marriage until an average of 28 years old and have on average only 1.5 children, less than half the Indian average.
Finally a New Scientist article, Feeding the Nine Billion (21 November 2009), focused on the specific issue of the expected food shortage and examined four different ways to boost food production in the third world:
1. Holding on to water, by such measures as storage tanks (particularly useful in areas which suffer from seasonal floods and droughts) or agricultural practices such as mulching or building terraces.
2. Stop ploughing, as this damages soil and releases greenhouse gases. Instead, just scratch furrows in which to plant seeds, and keep pests at bay by crop rotation, herbicides or genetically-modified plants.
3. Go back to basics by ensuring that the agricultural system works more efficiently; there are crop varieties available which would bring substantial benefits but they are not distributed to where they are needed, also a significant percentage of crops grown are wasted because of inefficient transport or market arrangements.
4. Boost yields by genetically engineering crops, which could lead to a 25% increase in production.
In conclusion, we are now (a few isolated hermits possibly excepted) all too familiar with the problem of the effect of human activities in changing the world's climate. Just to add to this gloomy picture, a growing population will exacerbate a further, long-range problem which will hit the world even if CO2 production were successfully controlled and entirely sustainable power sources used. People's activities and their equipment produce heat. As society becomes more technologically developed, the quantity of heat produced per person rises. Eventually, this will begin to have a significant impact on global temperatures even if the current drivers of climate change are removed. The estimated effect is an increase in temperature of three degrees Celsius in 300 years. The only way to prevent it is to get all of our power from renewable energy sources, since these absorb solar energy (directly or indirectly) and therefore do not add to the heating of our environment.
In the past, each new generation in the developed world owed a debt to the previous ones for their successful efforts in gradually increasing living standards. Just consider how these changed from 1800 through 1900 to 2000; a particularly commendable achievement in the 20th century given it was racked by two devastating world wars and came close to a civilisation-annihilating third. Sadly, new generations reaching maturity from the middle of this century (if not earlier) are likely to be far less grateful for the legacy of their forebears (that’s us…). Human ingenuity will be stretched as never before in meeting the challenges they will be facing. Plenty of scope for good, fact-based SF stories here - or will readers prefer to shrink from painful reality into yet more fantasy?