Carbon Dioxide and Earth's Future: Pursuing the Prudent Path
How much land can ten billion people spare for nature? This provocative question was posed by Waggoner (1995) in the title of an essay designed to illuminate the dynamic tension that exists between the need for land to support the agricultural enterprises that sustain mankind and the need for land to support the natural ecosystems that sustain all other creatures. As noted by Huang et al. (2002), human populations "have encroached on almost all of the world's frontiers, leaving little new land that is cultivatable." And in consequence of humanity's ongoing usurpation of this most basic of natural resources, Raven (2002) has stated that "species-area relationships, taken worldwide in relation to habitat destruction, lead to projections of the loss of fully two-thirds of all species on earth by the end of this century," which problem has been noted and discussed by a number of other scientists as well, including Conway and Toenniessen (1999), Wallace (2000), Pretty et al. (2003), Foley et al. (2005), Green et al. (2005), Khush (2005), Hanjra and Qureshi (2010), Lele (2010) and Zhu et al. (2010)
If one were to pick the most significant problem currently facing the biosphere, this would probably be it: a single species of life, Homo sapiens, is on course to completely annihilate fully two-thirds of the ten million or so other species with which we share the planet within a mere ninety years, simply by taking their land. Global warming, by comparison, pales in significance, as its impact is nowhere near as severe, likely being nil or even positive. In addition, its root cause is highly debated; and actions to thwart it are much more difficult, if not impossible, to both define and implement. Furthermore, what many people believe to be the cause of global warming, i.e., anthropogenic CO2 emissions, may actually be a powerful force for preserving land for nature.
So what parts of the world are likely to be hardest hit by this human land-eating machine? Tilman et al. (2001) stated that developed countries are expected to actually withdraw large areas of land from farming by the mid-point of this century, leaving developing countries to shoulder essentially all of the increasingly-heavy burden of feeding the still-expanding human population. In addition, they calculate that the loss of these countries' natural ecosystems to cropland and pasture will amount to about half of all potentially suitable remaining land, which "could lead to the loss of about a third of remaining tropical and temperate forests, savannas, and grasslands," along with the many unique species they support.
What can be done to alleviate this bleak situation? In another analysis of the problem, Tilman et al. (2002) introduced a few more facts before suggesting some solutions. They noted, for example, that by 2050 the human population of the globe was projected to be 50% larger than it was in 2000, and that global grain demand could well double, due to expected increases in per capita real income and dietary shifts toward a higher proportion of meat. Hence, they but stated the obvious when they concluded that "raising yields on existing farmland is essential for 'saving land for nature'."
So how is it to be done? Tilman et al. (2002) suggested a strategy that was built around three essential tasks: (1) increasing crop yield per unit of land area, (2) increasing crop yield per unit of nutrients applied, and (3) increasing crop yield per unit of water used.
With respect to the first of these requirements, Tilman et al. noted that in many parts of the world the historical rate of increase in crop yields was declining, as the genetic ceiling for maximal yield potential was being approached. This observation, as they put it, "highlights the need for efforts to steadily increase the yield potential ceiling." With respect to the second requirement, they noted that "without the use of synthetic fertilizers, world food production could not have increased at the rate it did [in the past], and more natural ecosystems would have been converted to agriculture." Hence, they said that the ultimate solution "will require significant increases in nutrient use efficiency, that is, in cereal production per unit of added nitrogen, phosphorus," and so forth. Finally, with respect to the third requirement, Tilman et al. noted that "water is regionally scarce," and that "many countries in a band from China through India and Pakistan, and the Middle East to North Africa either currently or will soon fail to have adequate water to maintain per capita food production from irrigated land." Increasing crop water use efficiency, therefore, is also a must.
Although the impending biological crisis and several important elements of its potential solution are thus well defined, Tilman et al. (2001) reported that "even the best available technologies, fully deployed, cannot prevent many of the forecasted problems." This was also the conclusion of Idso and Idso (2000), who -- although acknowledging that "expected advances in agricultural technology and expertise will significantly increase the food production potential of many countries and regions" -- noted that these advances "will not increase production fast enough to meet the demands of the even faster-growing human population of the planet."
Fortunately, we have a powerful ally in the ongoing rise in the air's CO2 content that can provide what we can't. Since atmospheric CO2 is the basic "food" of essentially all plants, the more of it there is in the air, the bigger and better they grow. For a nominal doubling of the air's CO2 concentration, for example, the productivity of earth's herbaceous plants rises by 30 to 50% (Kimball, 1983; Idso and Idso, 1994), while the productivity of its woody plants rises by 50 to 75% or more (Saxe et al. 1998; Idso and Kimball, 2001). Hence, as the air's CO2 content continues to rise, so too will the land use efficiency of the planet rise right along with it. In addition, atmospheric CO2 enrichment typically increases plant nutrient use efficiency and plant water use efficiency. Thus, with respect to all three of the major needs noted by Tilman et al. (2002), increases in the air's CO2 content pay huge dividends, helping to increase agricultural output without the taking of new lands from nature.
In light of these observations, it would appear that the extinction of two-thirds of all species of plants and animals on the face of the earth is essentially assured within the current century, if world agricultural output is not dramatically increased. This unfathomable consequence will occur simply because (1) we will need more land to produce what is required to sustain us and (2) in the absence of the full productivity increase required, we will simply take that land from nature to keep ourselves alive. It is also the conclusion of scientists who have studied this problem in depth that the needed increase in agricultural productivity is not possible to achieve, even with anticipated improvements in technology and expertise. With the help of the ongoing rise in the air's CO2 content, however, Idso and Idso (2000) have shown that we should be able -- but just barely -- to meet our expanding food needs without "bringing down the curtain" on the world of nature in the process.
What Idso and Idso (2000) did, in this regard, was to develop and analyze a supply-and-demand scenario for food in the year 2050. Specifically, they identified the plants that at the start of the new century supplied 95% of the world's food needs and projected historical trends in the productivities of these crops 50 years into the future, after which they evaluated the growth-enhancing effects of atmospheric CO2 enrichment on these plants and made similar yield projections based on the increase in atmospheric CO2 concentration likely to have occurred by that future date. This exercise revealed that world population would likely be 51% greater in the year 2050 than it was in 1998, but that world food production would be only 37% greater if its enhanced productivity comes solely as a consequence of anticipated improvements in agricultural technology and expertise. However, they further determined that the consequent shortfall in farm production could be overcome -- but only just barely -- by the additional benefits anticipated to accrue from the aerial fertilization effect of the expected rise in the air's CO2 content, assuming no Kyoto-style cutbacks in anthropogenic CO2 emissions.
In light of the above, it is remarkable that many people actually characterize the ongoing rise in the air's CO2 content as the greatest threat ever to be faced by the biosphere, or that the U.S. Environmental Protection Agency has actually classified CO2 as a dangerous air pollutant. It is also disturbing to hear some people claim that we must do now whatever it takes, at whatever the price, to stop the upward trend in the concentration of this supposedly diabolical trace gas of the atmosphere. Representatives of the nations of the world, for example, meet regularly to consider the issue and talk of the moral imperative we have to do something about it. But as they tilt at this greatest of all environmental issues ever to be created by the mind of man -- for as demonstrated in the pages of this treatise it is by no means clear that it is, or ever will be, a bone fide threat in the real world -- they also weaken our chances of successfully dealing with a host of environmental problems that truly do vex us, such as the food security and extinction threats described above. And there are a great many more threats that are literally crying out for attention.
In the most recent World Energy Outlook Report (2010), produced by the International Energy Agency, for example, the following is reported:
"Despite rising energy use across the world, many poor households in developing countries still have no access to modern energy service. The numbers are striking: we estimate that 1.4 billion people - over 20% of the global population - lack access to electricity and that 2.7 billion people - some 40% of the global population - rely on the traditional use of biomass for cooking."
Furthermore, in an editorial in Science entitled "Science and Sustainability," Leshner (2002) wrote that:
"One billion people throughout the world have no access to clean water. Two billion people have inadequate sanitation. Almost 1.5 billion people, mostly in cities in the developing world, are breathing air below the standards deemed acceptable by the World Health Organization."
And things have not changed in the interim.
Where in the world are our priorities? We agonize over a future hypothetical scenario -- CO2-induced global warming, which many knowledgeable scientists are convinced will never occur -- while billions of people suffer from a host of very real energy- and health-related hazards in the here-and-now.
Why would anyone in their right mind give the governments of the world a mandate to totally restructure human society to fight a hypothetical problem of vastly greater complexity than the very real and clearly-identified problems we currently face? Why should we not rather confront these genuine energy and health threats with all due haste and with every modern tool we have at our disposal?
Whatever the answers to these disturbing questions might be, it is clear that the current brouhaha over atmospheric CO2 emissions and imagined catastrophic global warming has relegated the very real environmental and human concerns of our day to second- and third-class status. This situation is truly regrettable; for unless the more immediate and weighty matters we have mentioned are forthrightly addressed in a timely manner, whatever earth's climate may do in the future will be pretty much a moot point, especially for the millions of species of plants and animals that will have suffered extinction in the interim, as well as the millions of human beings who will have died prematurely as a consequence of environmental problems wholly unrelated to the air's CO2 content that could have been solved but weren't.
We humans, as stewards of the earth, have got to get our priorities straight. We must do all that we possibly can, in order to preserve nature by helping to feed humanity and raise living standards the world over; and to do so successfully, we have got to let the air's CO2 content maintain its natural upward course for many decades to come. This is the prudent path we must pursue.