Agriculture
Resources
Agriculture requires non-saline water, fertile land, seeds, labor. Of these, overall, water is often most scarce.
Artificial production
Research is on to produce meat in-vitro.
Demand and supply
Past
The discovery of agriculture enabled mass, reliable food production. For most of history, we have had a food surplus. When there was a famine in one country, one could rely on imports from another.
Forecast
Human population is growing.
Non vegetarian diet requires production of more grain, consumption of water, use of land. As people grow affluent in developing countries, the demand for meat grows higher. Eg: In 2010, India roughly consumed 400 units of grain per capita, while America consumed 1600 units of grain per capita.
Water scarcity
In many countries, people are pumping out water faster than nature can replenish the aquifers by precipitation. Also, people in many places have been inefficient in storing precipitated water - especially in modern times (unlike ancient rAjasthAna and kOlAra folk).
Land scarcity
Arable land is scarce. Some land is part of important nature reserves. Plus, there is competition from using it for growing ethanol producing crops.
Climate change
Because agricultural crops were domesticated when the climate was cooler, hotter climate leads to less yields. It is estimated that for wheat, every 1 degree increase corresponds to 10% reduction in yield. Besides, climate change produces more extremes.
Role of nations
Food supply affects social stability. Eg: food riots in 18th century France, 2011 Tunisia etc.. So, governments are very concerned with preserving adequate food supply.
Food exporters, in times of inflation, ban exports. Considering the fact that the food market is a seller’s market, they refuse to enter into long term agreements.
So, food importers have begun to purchase land and water supply abroad - especially Africa - to grow their own food. They have also begun to make deals directly with farmers.