Previously in this course, we have been discussing the human population situation (click on history or current to review notes on the history of human population growth or the current situation with regard to that topic).

Now we will spend the next few weeks talking about how we are attempting to feed all these people, and about the environmental consequences of those attempts.

That is, we'll be discussing impacts of human agriculture on ecosystems. The US Department of Agriculture tracks many trends related to agriculture in the US (land, water, fertilizer and pesticide use, etc.) and assesses public policies that affect conservation and environmental quality in agriculture. The site is updated periodically, and is available at: "Agricultural Resources and Environmental Indicators.


A traditional environmental science course wouldn't necessarily include discussion of agricultural issues.

Traditionally, the study of agriculture ("agronomy") has been considered to be an applied discipline, and its practitioners for the most part have felt that they had nothing to learn from academic ecologists, much less environmental scientists.

Similarly, ecologists and environmental scientists have felt that agricultural systems are inherently uninteresting, in part because they aren't "natural" and in part because they are so simplified. Until recently, most ecologists have not recognized that an agroecosystem (an agricultural ecosystem) is a complex place -- and a good home for both theoretical and applied research.

Ecologists have also come to recognize that agroecosystems dominate much of the land area of the globe, and that by ignoring them, they are ignoring a great deal.

In fact, about 25 - 33% (depending on who you read and their definitions) of the land area of the world is used directly in agriculture of various types, including grazing lands.

Cereal (grain) fields are now one of the largest terrestrial ecosystems of the temperate zone!

Agriculturists and ecologists should be talking to each other, and are beginning to do so more and more. They have much to learn from and offer to each other.

Better communication between the two disciplines can help to ensure that we continue to be able to feed ourselves, and that we do not do that at the expense of our children.


First, in terms of demand for food, experts are anticipating something close to a doubling of demand for food globally by 2050.

This doubling in demand is expected to occur as population increases and as urbanization and income increase with expanded development. Increased incomes often are associated with changes in diet, notably with an increase in animal-derived products. Much grain is used to feed livestock, and thus diets richer in meat and dairy require increased gain production for animal feed. (We'll talk about efficiencies of various kinds of diets later.)

The prospect of feeding an increasing (and increasingly affluent) population didn't seem to present much of a problem until relatively recently. World wide, per capita food production increased steeply until recently. As an example, per capita grain production increased 40% between 1950-1984! (See Figure 3, under "Trends ..." below.)

The increase was not sustained, however. Global per capita grain production peaked in 1986 and has "wobbled around" near or slightly below that since that time, as the following numbers indicate:

Total grain harvests have continued to increase, generally, but the increase has barely been fast enough to keep up with population growth (remember, we've been adding something on the order of ~ 80 million people per yr for some time now); this combination has resulted in a struggle to maintain per capita yields.

Basically, increases in global grain harvests are struggling to keep up with population growth, despite the fact that there were record global grain harvests in 2007 and 2008! For some individual countries or regions of the world, the picture is gloomier -- for example, it is predicted that Africa will be able to feed only ~ 40% of its population with its own food production by about 2025.

We've explored the population part of this equation already. Over the next couple of weeks, we'll explore the reasons for both the rapid increases in production that have occurred and for the reasons for concern about whether production can keep up with population growth.

How many people starve each year across the globe (on average)?

more than 5 million children per year die of hunger (this is about 1 every 5 seconds...) [WorldWatch 2005, citing FAO's "Annual State of Food Insecurity"]

about 40 million persons of all ages die each year from starvation and diseases related to malnutrition

Numbers like these are difficult to grasp. But they become more real if we cast them in terms of something more familiar. The 40 million persons dying from starvation and diseases related to malnutrition is roughly equivalent to 300 JUMBO JETS EACH CARRYING 400 PEOPLE CRASHING EVERY DAY!

This is only the numbers who actually die. It is impossible to estimate accurately the number who are severely malnourished, but estimates are that about 1 in 8 are not fed well enough to be considered as having "enough" food each day (that is, lack enough calories to satisfy their basic bodily requirements; that is, they regularly consume fewer than 1,800 Kcal per day).

In 2004, the UN Food and Agriculture Organization (FAO) estimated that there were at least ~ 850 million undernourished hungry people in the world (this is the ~ 1 in 8 people referred to above). This is about 18 million more than were in this condition in the mid 1990's, and the estimate for 2004 was an increase over previous estimates for the first time since FAO began keeping track in the 1970's. As of 2010, the estimated number of people who "lack sufficient dietary energy availability" was ~ 1 billion, or 1 out of 7 [Science 12 Feb '10]. Rises in prices for food during 2007 - 2008 surely exacerbated this problem -- poverty is a big cause of hunger, at least on one level.

Of this ~ 1 billion hungry people, about 10% are "acutely" hungry -- that is wasting away from starvation -- and the remainder are "chronically" hungry -- lack enough calories to satisfy basic bodily requirements. Most of the hungry are in Asia, but the largest percentage of the population in this condition is in subSaharan Africa, where about 30% of the population is hungry; most of these are from small-scale, subsistence farming families. In some nations, chronic hunger affects as much as half of the population [Vital Signs 2011).

Basically, global increases in food production are still keeping up with population growth in most years, but with little to no margain of comfort, and it is not clear that this can continue. .

Differences between trends in grain production and population growth differ by region of the world, of course. Africa is about the worst off, in general, in terms of trends in per capita grain production. As of 2004, it was projected that Africa will be able to feed only about 40% of its population from its own food production by 2025.

The Consultative Group on International Agricultural Research (CGIAR); a consortium of 16 international agricultural research centers, estimated in 1992 that about 70% of developing countries have rates of population growth that are outstripping their gains in food production. I haven't read an update of this statistic, but I suspect that it is still approximately correct.

Food prices skyrocketed during 2007 - 2008, which undoubtedly led to much more world hunger. What do I mean by "sky rocketed?" The Global Food Price Index is a monthly measure of price changes in major food commodities that are traded internationally. In 2005, the Index averaged 117, while in March 2008, it was up to 220 (Time May 19, 2008). The global costs of rice, corn and wheat increased by 20, 50, and 100% between Jan. 07 and Jan. 08 (Conser. Mag. Jan/March 08). Why did prices increase so steeply?

(1) Global cereal stocks (reserves) were at lowest levels in 25 years (UNFAO) -- production wasn't great enough to provide a buffer against massive droughts and other weather instabilities.

(2) The decrease in these cereal stocks caused some countries to impose export restrictions, which increase prices.

(3) The price of oil has risen dramatically, and agriculture depends heavily on oil.

(4) Increasing proportions of food crops are being diverted from food uses to production of ethanol, which drives prices up (as an example of this diversion, in 1997, 5% of corn raised in the US was used to make ethanol; by 2007, that had increased to 24% and by 2010, it was up to 41%!).

(5) Demand for milk and meat is increasingly rapidly in some industrializing nations, notably (because of their population size) China and India. Production of milk and meat takes a lot of grain, adding to demand, which drives prices up. As an example, in 1980, the average yearly meat consumption per capita in China was 44 pounds; in 2007, that was up to 110 pounds.


(1) The immediate problem of feeding the world's people now

(2) The longer term problem of meeting future food needs, and, closely related to that,

(3) Preventing the deterioration of the resources that agriculture depends on

These challenges are great. For example, every year farmers have to feed ~ 80 million more people with billions of tons less topsoil (about 25 billion tons are lost per year to erosion alone) and trillions of gallons less water. How can this be done? Can it be done?


In the US, we are generally well-fed, and we are rich in agricultural resources. It often seems to us that these problems are not ours.

However, food crises elsewhere in the world have implications for agricultural methods and production goals in the US, for global climate, and for biodiversity. Further, changes in our agricultural practices have huge implications for agriculture elsewhere in the world -- a noted case in point is the increased emphasis of US corn growers on growing corn for production of ethanol, which we'll explore in more detail later in our discussion of agriculture, and also when we talk about policies related to global climate change.

Production goals in the US (and hence the agricultural practices that are used here) depend on global grain markets, such that agricultural reform in the US is, to some extent, limited by the need to feed people in other countries!

We cannot view food problems as belonging only to others -- they are our problems in the US as well.

In 2005, a large international group of scientists, economists, anthropologists, policy makers and others met to discuss future world food and agricultural prospects, and to try to formulate some international policies related to those topics (see Science 18 Apr 08 for more information on the effort). Funded by the UN, the World Bank, and several nations, the group produced a document that you might be interested in, entitled International Assessment of Agricultural Science and Technology for Development. As is true for many such efforts, time will tell if it actually leads to new accomplishments. (IAAST).

Click ">>" at the bottom of this page to move to a look at a brief history of the Green Revolution, or click "Navigate," here for a reminder on how to move around and within these documents.

Page last update Oct. 29, 2012. Page maintained by Patricia Muir at Oregon State University.