Category Archives: Article review

Running on empty

Will there be enough oil to sustain future food production? Why is current agriculture so dependent on fossil energy? To explore these questions it is perhaps a good idea to examine our ecological footprint from the very beginning of our history on earth.  Our planet originated 4,500 million years ago. Photosynthesis exists for about 3,500 million years but vertebrate land animals and plants only appeared about 400 million years ago. Dinosaurs were there between 230 and 65 million years ago. We humans have been on earth for merely 2 million years, and for most of that time we’ve been marauding around, hunting, gathering fruits and roots, and looking quite different than we do today.


Settling down

Between 10,000 and 5,000 years ago – on the last second of our existence you may say – we decided to set camp, became sedentary and started farming, in a period in which the climate became milder, warmer. Agriculture was a ‘successful’ strategy for our species, starting almost simultaneously in different parts of the world that were not connected by then, and leading to the first population boom. The expansion of our species, half-farming, half-hunting and gathering, led to profound modification of the previous ecosystems around the world. This period coincided approximately with the massive extinction of other species of megafauna (other than human) that took place during the Quaternary.

This moment of our history is seen by some scientists as a key period to study earth living system’s resilience, given that two important processes took place at the same time. Namely, human population growth and climate change – do these sound familiar? A couple of papers published by Barnosky a few years back tried to put some figures behind the dynamics of human and other megafauna populations over the last hundreds of thousands of years. Human expansion, according to Barnosky, is one of the major drivers of extinction of hundreds of megafauna species around the world.

Replacement and addition

If, as Barnosky explains, instead of the total number of individuals we consider the total biomass of humans and of all the extinct megafauna species, then we see a sort of ‘replacement’ of such species by humans. That is, the total biomass that went extinct coincides approximately with that of all humans. The sum of total megafauna biomass – human and non – represents the carrying capacity of Earth, as determined by the incoming solar radiation through plant photosynthesis. In other words, this is the capacity of the Earth to sustain the life of megafauna populations with plant biomass.

Total megafauna biomass declined rapidly during the massive extinctions of the Quaternary and it took about 10,000 years to reach again the level that corresponds to Earth’s carrying capacity. This level was achieved once again around the time of the industrial revolution, as can be seen in the figure below.

megafaunaWhat is most striking in this figure put up by Barnosky (2008) is that the beginning of the industrial revolution, when the world human population starts becoming increasingly urban, marks also the beginning of the expansion in numbers of another category of megafauna: domestic livestock. When we now add up humans, wild animals and livestock, the result is that we are currently keeping about ten times more megafauna biomass than the estimated carrying capacity of the Earth! How is this possible?

Eating fossil fuels

Earth’s carrying capacity, as mentioned above, is determined by the rate of plant photosynthesis. That is, by the ability of plants to turn solar energy into feed energy. Nowadays, to be able to sustain such numbers of animals and humans on Earth we are consuming not only the photosynthetic energy that is capture every year, but also all of that that was captured over hundreds of millions of years. All that energy is stored in fossil fuels: oil, charcoal, gas, tar, etc. These fossil fuels represent a net subsidy to our energy balance on Earth. For example, it is calculated that about 70% of the energy contained in a cereal grain produced using the methods of industrial agriculture comes from fossil fuels (check out this book that appeared already about a decade ago: Eating Fossil Fuels).

About 1500 oil equivalents per year are necessary to feed a person in the developed world. That represents about 6 barrels per person per year. At peak oil production, back in 1979, the maximum oil extraction rate was about 5.5 barrels per person per year, not even half of what is needed in the developed world. All predictions towards the future, both from the public and private sector, point to a reduction in the annual rates of extraction, even when new sources and methods of extraction are considered (e.g. shale gas/fracking). And we know that, as a resource becomes increasingly scarce, its price tends to go up (or so they said in the courses of Economics I ever took).

In conclusion, we are running on empty. And what’s worse, many of the recommendations made to ‘sustain’ agricultural production in the poorest areas of the world, may actually lead to an increased dependence of smallholder farmers on fossil fuels. An example of this is the recommendation to use synthetic nitrogen fertiliser, which requires large amounts of fossil energy to be produced. Do we want to make smallholder farmers dependent on a resource that is becoming increasingly scarce? What would this mean for future (and current!) global food security? We ought to come up with alternatives.

Food produced vs. food delivered

A relatively small proportion of the food produced in the high-yielding regions of the world is actually delivered to the food system. Not just because of waste, which accounts for anything between 30 and 50% from post-harvest and manufacturing through to trade and consumption. Here, ‘delivering’ means how much food enters the food system in the form of edible items (even before it is wasted). A global study by Cassidy et al. (2013) calculated this proportion using energy units.

They expressed the productivity of all the crops in calories per ha per year (to be able to compare apples and pears) and mapped them per region. They assumed that an average person requires 2700 Kcal per year. With these two pieces of information they calculated the number of people that could the fed per ha of agricultural land on the basis of its current productivity. Note that 2700 Kcal is greater than the actual human needs, which fluctuate according to physical constitution between 1800 and 2100 Kcal per person per year. By considering 2700 Kcal they are already assuming a certain level of inherent value chain inefficiency, which gives more conservative estimates.

Potential vs. actual delivery

The map they developed shows that the most productive areas of the world can potentially feed 8 to 10 people per ha on the basis of current productivity, while the least productive regions can feed barely 3 to 4. But then they produced another map, that estimates how many people are effectively fed per ha of land. They developed this new map by computing the fraction of the total energy contained in a crop that is delivered to the food system in the form of edible energy.

For example, in the case of maize (or corn), only ca. 25% of the energy contained in the crop is delivered as edible energy, be it in the form of maize grain, meal or flour, or transformed into meat, milk, fructose, bier or candies, etc. This is because maize is used as raw material by different non-food industries, such as paint additives, plastics or biofuels. But also, because a large proportion of the harvest is used to feed livestock, which is inherently inefficient, as we all know.

Maize represents perhaps the most extreme case. But when we consider all cereals together (maize, wheat, rice, barley, oats, rye, sorghum, millet, etc.) yet 46% is used directly as food (raw or processed), 34% to fed livestock, and 20% used by the non-food industry.

Source: ES Cassidy, PC West, JS Gerber, JA Foley, 2013. Redefining Agricultural Yields: From Tonnes to People Nourished per Hectare. Environmental Research Letters 8 (3), 8
Source: ES Cassidy, PC West, JS Gerber, JA Foley, 2013. Redefining Agricultural Yields: From Tonnes to People Nourished per Hectare. Environmental Research Letters 8 (click to enlarge)

Based on this information for the most important crops globally (not just cereals), Cassidy et al. built the above map, that shows the fraction of the total agricultural production delivered to the food system. In the most productive areas of the world, barely 20 to 30% of the food produced is delivered to the food system. In areas dominated by smallholder farming 80 to 100% of the food produced is delivered – i.e. consumed at home or traded locally. This does not mean though that food systems are necessarily more efficient, as post harvest losses can still be high in many of these regions.

These are – again – global estimates, based on a number of assumptions, and they may therefore be questioned. Yet they contribute further evidence to understand why increasing agricultural production in developed countries will continue to have a limited impact on achieving global food security (see also this previous post). Most of the non- or hardly renewable resources such as fossil fuels, rock phosphate, soils or (fossil) water are used in these regions to produce food that will never reach a human stomach.