Foreign direct investment in agriculture went from an average US$ 600 million annually in the 1990s to an average US$ 3 billion in 2005-2007.

The shock created by the 2007-2008 global food price crisis led to the establishment or strengthening of further initiatives, such as the Aquila Food Security Initiative, the Global Agriculture and Food Security Program (GAFSP) or NEPAD’s Comprehensive Africa Agriculture Development Program (CAADP) in Africa. Governments are paying greater attention to agriculture than in the past.

The prophet Isaah said “all flesh is grass”, earning him the title of first ecologist, because virtually all energy available to organisms originates in plants. Because it is the first step in the production of energy for living things, it is called primary production . Herbivores obtain their energy by consuming plants or plant products, carnivores eat herbivores, and detritivores consume the droppings and carcasses of us all.

Figure 2 portrays a simple food chain, in which energy from the sun, captured by plant photosynthesis, flows from trophic level to trophic level via the food chain. A trophic level is composed of organisms that make a living in the same way, that is they are all primary producers (plants), primary consumers (herbivores) or secondary consumers (carnivores). Dead tissue and waste products are produced at all levels. Scavengers, detritivores, and decomposers collectively account for the use of all such “waste” — consumers of carcasses and fallen leaves may be other animals, such as crows and beetles, but ultimately it is the microbes that finish the job of decomposition. Not surprisingly, the amount of primary production varies a great deal from place to place, due to differences in the amount of solar radiation and the availability of nutrients and water.

For reasons that we will explore more fully in subsequent lectures, energy transfer through the food chain is inefficient. This means that less energy is available at the herbivore level than at the primary producer level, less yet at the carnivore level, and so on. The result is a pyramid of energy, with important implications for understanding the quantity of life that can be supported.

Usually when we think of food chains we visualize green plants, herbivores, and so on. These are referred to as grazer food chains, because living plants are directly consumed. In many circumstances the principal energy input is not green plants but dead organic matter. These are called detritus food chains. Examples include the forest floor or a woodland stream in a forested area, a salt marsh, and most obviously, the ocean floor in very deep areas where all sunlight is extinguished 1000′s of meters above. In subsequent lectures we shall return to these important issues concerning energy flow.

Finally, although we have been talking about food chains, in reality the organization of biological systems is much more complicated than can be represented by a simple “chain”. There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web. Food webs can be very complicated, where it appears that “everything is connected to everything else”, and it is important to understand what are the most important linkages in any particular food web.

Photosynthetic Equation: H2O + CO2 –> O2 + CHO’s

Since plants/algaes are the only organisms that can make organic energy out of the sun’s light, they are considered the primary producers in an ecosystem.

Let’s say that our incoming photons create 100 kilograms of algae in a pond. Why algae since you can’t even see it unless there is a lot? Most animal life in a pond either eats algae directly or eats smaller organisms that eat algae. Thus algae is the producer and everyone else is a consumer. Consumers which get their energy by eating (in other words they do not make their own energy) are heterotrophs. Consumers can be plant eaters (herbivores), meat eaters (carnivores), scavengers which eat dead things or detritus (detritivores), or they can eat just about anything (omnivores—humans, for example, are typically omnivores).

So you have 100 kilograms of algae to pass on to the algae eaters. About 90% of that available energy will be used up by those algae eaters just by their having to live: growth, respiration, energy lost as heat, energy required for movement, etc. So your 100 kilograms of algae can produce 10 kilograms of algae eaters. In other words, only 10% of the energy produced gets passed on from on trophic level (or level in the food web) to the next. Thus the more trophic levels you have, the less energy is available at the top. This is depicted as the trophic pyramid.

(from: Caduto, 1985)

The premise that people consume the same amount of calories all over the world means that one should be able to calculate the number of calories which need to be produced/grown by counting the number of people. To put it another way. Global food production is directly related to global population.

When the number of people increases, then they need more living space. This involves the conversion of arable land into villages, towns and cities. Since there is less arable land available for food production, this could result in food shortages in the futures. This coupled with potential environmental impacts like flooding / drought means that acts of god can have a huge impact on the amount of food available for consumption.