Exploitation of Food Resources Of 250,000 species of plants described only 100 are used to feed the worldOf 250,000 species of plants described only 100 are used to feed the world 15 plants and 8 animal species supply 90% of our food15 plants and 8 animal species supply 90% of our food –Primary food crops: –Wheat - staple food of over 1/3 of global pop. –Rice - large yield, grows continuously, tropics –Corn / Maize - staple in S. America & Africa, fed to cattle in US –Potato - in developed countries

Other foods consumed Fish, meat and animal products (milk, eggs, cheese) - EXPENSIVE!Fish, meat and animal products (milk, eggs, cheese) - EXPENSIVE! 80% of meat and milk produced is consumed by only 20% of global population80% of meat and milk produced is consumed by only 20% of global population –Meat consumption per capita per year: –US: 110 kg –UK: 75 kg –China: 21 kg –India: 1.1 kg

Inefficiencies in terrestrial systems More than one third of grain harvest (37%) is used for animal feed - not human consumption This is very inefficient as the energy of assimilation is only about 10% (Fig. 3) One calorie of grain-fed steak requires at least 10 calories for production One calorie of chicken requires 12 calories Meat production is very inefficient!

Terrestrial versus aquatic systems Most food from terrestrial systems is harvested from lower trophic levels - producers and herbivores Food from aquatic systems is harvested from higher trophic levels Efficiency of fixation of solar energy is lower in aquatic systems because of absorption and reflection by water

Improving use of food resources Maximize yield Improve storage Improve distribution methods Change eating habits (i.e. eat less meat) Population control