The baking summer temperatures of February 2009 have southern Australians thinking about climate change and their limited water supplies. As high temperatures led to grid collapse and massive blackouts followed by disastrous fires, they also had the opportunity to think about how dependent their lives are on technology and the resources that keep technology ticking. For me, a biologist interested in politics, the summer of 2008-2009 has been quite interesting for another, related reason; the more open discussion of the effect of population growth on our ability to mitigate climate change. As Kevin Rudd explained last December about emission reduction targets:

The EU's 20 per cent target announced over the weekend is equal to a 24 per cent reduction in emissions for each European from 1990 to 2020. Our 5 per cent unconditional target is equal to a 27 per cent reduction in carbon pollution for each Australian from 2000 to 2020 - and a 34 per cent reduction for each Australian from 1990. This is because Europe's population is not projected to grow between 1990 and 2020. By contrast, Australia's population is projected to grow by 45 per cent. If the Europeans were to adopt the same per capita effort as Australia is proposing, their cuts would be around 30 per cent by 2020.




So it seems that Australians will be required to make larger sacrifices in their energy use so that population growth can continue and we can, ultimately, achieve a lesser total reduction than the Europeans in any case. Part of me wants to believe that Rudd’s comment might be the first subtle move in a campaign to relieve us of the illusion that economic and population growth can continue for ever. However, the far more likely explanation is that the political leadership (of both major parties) believes so blindly in the benefits of population growth that they regard Rudd’s excuse for our failure to make larger cuts in CO2 emissions as acceptable and noble.

I do not know of any topic that evokes more heated, passionate, and opinionated argument than population. For a biologist the matter appears simple. There are numerous examples of species expanding their populations until they exceed their energy resources (i.e. food supply), after which starvation kicks in and the population crashes. Humans are clearly animals and if we do not get sufficient food then we starve too. But most of the scientifically under-educated population seems to think that humans are in some way exceptional, that we are too clever to starve. Either our technology or our ability to respond to crises, or both, will save us if food ever becomes limiting. I wish this were true but history - and a cold, objective look at the numbers involved - shows that this idea is just a comforting illusion.

For most of history the threatening shadow of hunger has been humanity’s constant companion. The oil driven “green revolution” of the 1960s and 1970s boosted food production at a time when it seemed our population might soon exceed its food resources (as predicted by the original dismal economist, Thomas Malthus).

The food price hikes and riots of 2008 led some commentators to declare that we need another green revolution but nobody can really say how this will be accomplished. Gene technology is sometimes cited as the saviour to come but this ignores the fact that most of the genetic gains in crop productivity in the last 40 years have been possible because we have been using stupendous volumes of oil energy to perform more and more tasks for the plants that they would otherwise have to spend energy doing for themselves. (For an excellent illustration of this see Folke Günther’sarticle “Making western agriculture more sustainable”).

By some estimates we use 10 times as much energy from oil to grow our food as is provided to us by the food itself. (Additional energy is then used in transport and distribution, processing, packaging, the driving involved in collecting it from the supermarket and then cooking it.)




What more can we do for our pampered plants? And how will we be able to keep them pampered in any case now that oil production seems to be set for rapid decline and phosphate fertiliser may disappear even faster?

Currently, the world’s population increases by 76 million people a year - the equivalent of almost four Australias. However, world food production (as illustrated by grain production) may have peaked in 2007-8 and grain per person peaked back in 1986. In fact, widespread drought may reduce world food production by more than 20 per cent in 2009. Water for agriculture is becoming increasingly scarce, unpredictable weather patterns resulting from climate change are decreasing agricultural production, fertilisers have been rapidly increasing in price as their raw materials become scarce, and our farmers are collapsing into financial crisis as volatile agricultural markets play havoc with their income. The world’s stocks of grain in reserve have now fallen close to critically low levels and are on a downward trend.

These problems have been exacerbated (until recently at least) by the trend to higher per capita consumption of meat in Asia as the region becomes (or, rather, became) wealthier. Eating meat is far less food-energy efficient since many grams of grain must be fed to any animal to return each gram of meat which then finds its way into a human mouth. Only the most optimistic fantasist could imagine that we could turn around these worldwide trends in time to increase food production to match the UN’s often-quoted estimate of a 40 per cent increase in world population by 2050. A realistic estimate based on projections of energy and other resources must see a crash in agricultural production before 2020 and declining population numbers before long thereafter.