LAND is another resource that is in increasingly short supply. (Click "Land degradation" for more details and causes than are given below.) In many areas, land suitable for cultivation is already under cultivation.

Globally, it is estimated that less than 25% of the approximately 14,900 million ha of land in the world is potentially productive at all, with only 9% potentially moderately or highly productive. About half of the potentially productive land is already under cultivation leaving 1,700 million ha of potentially productive land uncultivated (as forest or grassland). This then represents the maximum possible future expansion, but much of that is marginal, geographically inaccessible, infested with pests that transmit parasitic diseases -- and there will be competing social, economic, and ecological demands on its use!

Asia has very little suitable land that isn't already cultivated (although India has some potential for expanding irrigation), but Africa and Latin American still have some that could be brought under cultivation. However, we must realize that bringing new land under cultivation generally means a loss of natural ecosystems. The land is not simply sitting there "empty", waiting to be used! The UN Food and Agriculture Organization (FAO) estimates that cultivating ALL potential cropland in developing countries (excluding China) would reduce permanent pasture, forests and woodlands by 47%!!! (Think of the implications of this conversion for biodiversity and global climate change!) In fact, need for agricultural land is estimated to account for over 60% of the deforestation that is occurring world wide....

In the future, gains in cultivated acreage resulting from bringing new land under cultivation are likely to be counterbalanced by losses. Losses are already apparent. As we already saw, globally, total acreage cultivated has essentially plateaued in the past couple of decades (Figure 1).

Harvested grain acreage on a per capita basis has decreased greatly, as illustrated in the following Figure (updated version available in Course Documents on Blackboard):


Figure 5. (Modified from "Vital Signs 1997," World Watch Institute; updated available on Blackboard.)

Between 1950 and 1993, grain acreage per person decreased from 0.23 to 0.13 ha per person. At present only about half as much acreage is planted per person now as in 1950! Harvested acreage per capita fell 25% in just the decade between 1986 and 1996. (Note that in 1996, there was a slight increase in per capita harvested acreage, in contrast to the trend for previous years. This resulted from the increase in total grain acreage in that year, which was a response to high grain prices, as previously discussed.)

This trend in per capita acreage results from a combination of rising population and diminished agricultural lands.

You can see real time changes in acreage of productive land (not just grain land, but productive land, defined as arable land, pasture and forest) on a global basis at

In the past, loss of grainland was offset by increases in production per ha, but those increases were sluggish (or nonexistent) from about 1990 until just the past few years.

WHY are we seeing losses in productive agricultural lands [not restricting ourselves to just grainlands] both on a total and a per capita basis? Some of the reasons are cheery, while some are not so cheery.

(1) Competition from nonfarm uses

Since 1967, the US has lost over 25 million acres of farmland to urban sprawl. This is an area larger than New Hampshire + Vermont + Massachusetts + Connecticut + New Jersey!!

In the US, 90 ha (220 acres) of actual or potential farmland is taken out of production every HOUR (= 2160 HA PER DAY [~5300 ACRE PER DAY]. Graphically, this represents an annual loss of a strip of land 1 km wide running from New York to San Francisco! (This doesn't include losses of rangeland, which are about 600 ha (1500 acres) per day.) As of Feb. 2008, there were about 931 million acres of farmland in the US, which was a 1.5 million acre drop from the previous year, continuing a fairly long term trend. Meanwhile, the average size of a "farm" increased by ~ 3% between the start of 2007 and that of 2008 (to 449 acres per farm averaged for the US as a whole in 2008) -- and the number of farms decreased by 0.6% over that time period. For OR, WA, CA and ID, there was a 2% decrease in the number of farms over that time.

In 2001, the American Farmland Trust (the US's largest farmland conservation organization) identified the Willamette Valley of OR and the Puget Sound corridor as the 5th most threatened on its top 20 list of endangered agricultural lands, with the cause of threat being growing human population. (About 50,000 new residents per year move into Oregon from elsewhere.; the population of the Willamette Valley is projected to increase from the 2.3 million that lived here in 2001 to ~ 4 million by 2050 (nearly a doubling!) While Oregon has rigorous land use and zoning laws, including the "exclusive farm use" ("EFU") designation, which covers about 16 million acres in Oregon, between 1995 and 1998, Oregon counties approved ~600 new building developments in lands zoned EFU....

China has been losing 1 million acres of arable land per year for the last 3 decades to industry, housing, roads, and recently cemeteries. (This rate of loss is slightly less than US rate actually...) Between 1990 and 1994, the loss rate was 1% per year (from 90.8 down to 87.4 million cultivated hectares). (How does this compare to the rate of population growth in China? (Click "current" to review...)

The net result of population growth and loss of arable land in China is that per capita land area planted in grain is now less than HALF what it was when People's republic was founded in 1949 . The huge industrialization push in China, coupled with the growing population, is the main driver of this trend. Sounds awful, doesn't it? This matches the global trend in per cpaita acreage planted to grain (see Figure "E" from class and Figure 5, above).

China's industrialization push also means competition for water with agriculture. The Yellow River supplies water to the Shandong Province, which historically has produced about 1/5 of China's wheat. It commonly runs dry for several weeks in the spring and early summer, as cities pull more and more water from it!

In addition, the greater affluence associated with industrialization means more meat consumption. In 1978, China fed 7% of its grain to livestock, in 1990 the percentage was up to 20%. The average person in China ate 44 pounds of meat per year in 1980, and that was up to an averge of 110 pounds per person by 2007. (Click on "sustainable" for insights into how eating meat affects food prospects and agricultural impacts.)

China's difference between consumption and production is widening, and the question is: who will meet her demand?? Consumption is going up, while production is decreasing. (See article addressing this topic that is listed on the study guide for more information on the situation in China.)

One dramatic example of this conflict involves eggs. The official government target was that each Chinese person will eat 200 eggs per year by the year 2000. The population of China in the year 2000 was about 1.3 billion persons. If each hen lays 200 eggs per year, that means China will need 1.3 billion hens. The grain required to feed that many hens is equal to the total Canadian grain export to all nations combined!

The same question about resolving discrepancies between trends in consumption and production is relevant for other industrializing and growing nations. Patterns in China are similar to what happened in Japan, S. Korea and Taiwan when they industrialized.

Japan lost 52% of its grainland in the last few decades and has had a 33% reduction in total grain production since its peak. Japan now must import 77% of its grain consumption. [A tiny part of this loss is that, with greater affluence, people eat more fruits and vegetables, so some land has been converted from growing grain to growing fruits and vegetables.]

Additional reasons for land limitations include the following:

(2) Systematic land retirement programs are another force behind losses of cultivated acreage. Examples from the US are retirements of land to decrease surpluses or to protect against erosion. In the US, government set-asides of land to decrease surpluses were eliminated in the 1996 Farm Bill, with the only government-supported set-asides now being for environmental reasons. These will be discussed in more detail later.) (Click on "sustainable" for a look now, if you wish.)

(3) Land that is badly degraded gets abandoned. See "Feeding Nine Billion" in your assigned readings for some data on this, or jump to notes on land degradation from here. Something on the order of 10 million ha (~ 24 million acres) of productive, arable land are serverly degraded and abandoned each year.


This is marginally relevant here, but it is SUCH an important issue, and I'm not sure how much time we'll have to talk about it by the time we discuss policy related to global climate change, so I'll put it here! While this doesn't actually pull land out of grain production, it uses the land for production that isn't food...

As you have undoubtedly heard -- and detected in food prices -- increasing acreages of coarse grains, particularly corn, are being devoted to raising crops from which ethanol is made (and that is then used as a substitute for fossil fuel). As mentioned previously, in 1997, only 5% of US corn production was used thusly; by 2007, 24% of our corn was being fed to distilleries instead of to livestock or people, and by 2010, ~ 41% of our corn was used this way (Congressional Research Service, "Renewable Energy Programs and the Farm Bill: Status and Issues," Sept 2011). Total corn production jumped in response to the increasing market for grain-based ethanol -- in 2007, Iowa alone saw a 22% increase in corn acreage (Leopold Letter winter 07). Between 2005 and 2008, the number of acres devoted in the US to growing corn to produce ethanol increased by 4.9 million hectares, this including some formerly retired land that was put back into production. US law (at least as of 2009) mandates that we produce 740% more biofuel (across feedstock sources) by 2022 than we did in 2006 (BioScience Oct '09).

Globally, by 2011, 17% of grain produced was being used to make ethanol and other fuels (WorldWatch 15 Nov '11, citing FAO), For context, this percentage was 5% as recently as 2008.

People were pretty excited about this early on -- "free us from dependence on fossil fuels!", but they hadn't really thought it through, sadly -- and many still haven't. (Sorry, but some Muir opinion will leak in here...). This use of crops that could otherwise feed people or livestock to produce fuel has been, aptly in my mind, referred to as "a crime against humanity."

What is so criminal about it? I'll give just a few examples:

Swaziland is receiving emergency food aid and 40% of its population faces acute food shortages. Yet its government exported biofuel made from a staple crop -- cassava -- and the government has allocated several thousand hectares of land for this purpose -- when its people are starving! (Conserv. Mag. Jan/March 08).

In the US, the 2008 Farm Bill (scroll fairly far down on the page to find farm bill info, if you use this link) calls for increased biofuel production (biofuels include ethanol and biodiesel and other fuels based on recently living material, as opposed to ancient previously living material, as embodied in fossil fuels) and provides substantial subsidies for production of cellulosic ethanol. The subsidies will go to both the growers and the refiners. So what?

Well, with regard to corn-based ethanol, if the US stops putting as much corn into the food stream, food prices climb sharply -- exacerbating world hunger. In addition, those high prices encourage conversion of non-agricultural land to grow crops -- e.g., encourage deforestation in the tropics, conversion of native grasslands to agriculture, and so on. These conversions aren't all to grow corn itself -- for example, as increasing farm acreage in the US is devoted to corn for ethanol, that means we grow less soy (land that was used for soy is used for corn). That drives soybean prices up, so farmers in Brazil clear land to plant soy -- you get the picture?


Initially, people thought that biomass-based ethanol, including cellulosic ethanol and ethanol derived from corn, would not only free us from dependence on foreign oil, but that it would also diminish production of heat-trapping CO2, one of the primary contributors to global climate change. However, the picture is not so rosy. Why? In a nutshell (the following summarized from Science 29 Feb 08 and Science 3 Oct. 08):

(1) If you compare CO2 emissions from growing -- or mining, in the case of fossil fuels -- the fuel feedstock, refining it, and burning the fuel in a vehicle, ethanol results in higher emissions than fossil fuels. (Think of all the ways we depend on fossil fuels to raise crops -- fertilizers, pesticides, irrigation, machinery, etc). So, that doesn't sound so good, if we're trying to save fossil fuel energy and decrease CO2 emissions. Doesn't look so rosy, BUT.....

(2) When you also take into account the fact that the crops used to make ethanol were busy pulling CO2 out of the atmosphere and storing some of it in their biomass, then bio-based ethanol CAN result in lower net CO2 emissions than do fossil fuels. Now does look rosy, right? BUT.....

(3) If farmers do what they've already begun doing, converting grassland or forest land into cropland to replace the area now devoted to biofuel crops, the picture changes radically. In this case, the storage ("sequestration") of carbon in soils and in vegetation (the latter particularly for forests, of course) is greatly diminished -- essentially, this lost carbon storage should be counted as additional emissions; it incurs a "carbon debt." Further, when land conversion is followed by burning, as often happens in the case of tropical forests, CO2 emissions are huge -- and tillage speeds decomposition in soils, so soil-related CO2 emissions also increase. Under this scenario, net CO2 emissions from plant-based ethanol production are estimated to be about double those from fossil fuels!!

(4) For cellulosic ethanol in particular (that is, not grain-based ethanol), the environmental and energetic impacts all depend on the materials used and how and where they are produced. While it is more likely that cellulosic ethanol can be produced with lower net CO2 emissions than fossil fuels and grain-based ethanol, it is more expensive to make cellulosic than grain ethanol (the raw material is less expensive, but pretreatment costs and enzymes required to "digest" it are more expensive), so grain ethanol will probably continue to be competitive with cellulosic ethanol for quite some time, unfortunately. It is important that environmental sustainability of production for both grain-based and cellulosic ethanol be kept in mind; it is estimated that to produce a significant amount of biofuel-based energy as much land as is now devoted to row-crop agriculture may be required! How can environmental costs of cellulosic ethanol be minimized? Here's just a short list -- see Science 3 Oct. 08 for more details. (1) Use no-till production methods along with cover crops to sequester soil carbon. (2) Use perennial rather than annual crops. Perennials don't need much chemical input once established (including energetically expensive fertilizers) and certainly don't require tillage. They build up root biomass that stores carbon. (3) Use mixtures of perennial species rather than monocultures, which will promote landscape level biodiversity and associated ecosystem services. (4) Grow these perennial mixtures on marginal, previously degraded lands rather than on prime farm land or on land that currently supports forest or healthy grasslands. This avoids competition with land needs for food production, and also avoids incurring a carbon debt associated with clearing land. (5) Seek plant species that do not require additional inputs of water or fertilizer -- this is particularly important if they are to be grown on marginal lands. (6) Do not plant species that have potential to become invasive!

The upshot? Dedicating land to crops for biofuel production can potentially decrease CO2 emissions ONLY if doing so increases the carbon sequestration that the land is capable of -- which may be possible on marginal, degraded, eroded sites. Recent studies also make apparent that we should think not only about CO2 emissions, but also about emissions of N2O, another important "greenhouse gas." This gas has many sources, but one is related to the applicationof nitrogen fertilizer -- SO, if these biofuel crops are grown with added nitrogen fertilizer, consequent emissions of N2O could be very important in terms of accelerating global climate change [Science 4 Dec '09].

The Energy Independence and Security Act of 2007 (EISA, P.L. 110-140) expanded the renewable fuels standard to focus increasingly on non-corn starch biofuels ("advanced biofuels), which may help to diminish the (in Muir's view) insane use of corn for this purpose. Under EISA and the energy provisions of the 2008 Farm Bill, minimum use of advanced biofuels must grow from zero in 2008 to 21 million gallons by 2022 (Congressional Research Service, "Renewable Energy Programs and the Farm Bill: Status and Issues, Sept 2011).

Page maintained by Patricia Muir. Last updated Oct. 29, 2012.

The next section (">>" at the bottom) discusses use of fossil fuels in agriculture.