The genesis of this dilemma hearkens back to a provocative question posed by Waggoner (1995): How much land can ten billion people spare for nature? This was the title of an essay he wrote to illuminate the dynamic tension that exists between (1) the need for land to support the agricultural enterprises that sustain mankind and (2) 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 noted 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." In addition, Wallace (2000) has calculated that we will need to divert essentially all usable non-saline water on the face of the earth to the agricultural enterprises that will be required to meet the food and fiber needs of humanity's growing numbers even well before that.

So what parts of the world are likely to be the hardest hit by the great land-grabbing and water-consuming machine that is us? Tilman et al. (2001) report that developed countries are expected to actually withdraw large areas of land from farming between now and the middle of the century (2050), leaving developing countries to shoulder essentially all of the growing burden of feeding our numerically-expanding species. In addition, they calculate that the losses of these countries' natural ecosystems to crops and pasture represent 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.

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 two-thirds of the ten million or so other species with which we share the planet within the next several decades, simply by taking their land and water. Global warming, by comparison, pales in significance, as its impact is nowhere near as severe, being possibly nil or even positive. In addition, its chief 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 main cause of global warming -- anthropogenic CO2 emissions -- may actually be a powerful force for preserving land and water for nature.

So what can be done to alleviate this bleak situation? In a subsequent 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 is 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 built around three essential tasks: (1) increasing crop yield per unit 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. note that in many parts of the world the historical rate of increase in crop yields is declining, as the genetic ceiling for maximal yield potential is being approached. This observation, in their words, "highlights the need for efforts to steadily increase the yield potential ceiling." With respect to the second requirement, they indicate 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 say 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. remind us 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) noted 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" -- stated that these advances "will not increase production fast enough to meet the demands of the even faster-growing human population of the planet." So what can possibly be done?

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 80% 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 identified 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 land and water from nature.

In conclusion, 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 and water to produce what is required to sustain us, and (2) we will simply take that land and water from "wild 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, 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.

That certain forces continue to resist this reality is truly incredible. More CO2 means life for the planet; less CO2 means death ... and not just the death of individuals, but the death of species. And to allow -- nay, to cause -- the extinction of untold millions of unique and irreplaceable species of plants and animals has got to rank close to the top of all conceivable immoralities.

We humans, as stewards of the earth, have got to get our priorities straight. We have got to do all that we can to preserve nature by helping to feed humanity; and to do so successfully, we must let the air's CO2 content rise. Any policies that stand in the way of that objective -- such as those included in the proposed Senate Energy Bills -- are truly obscene.

Sherwood, Keith and Craig Idso

References
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Idso, C.D. and Idso, K.E. 2000. Forecasting world food supplies: The impact of the rising atmospheric CO2 concentration. Technology 7S: 33-55.

Idso, K.E. and Idso, S.B. 1994. Plant responses to atmospheric CO2 enrichment in the face of environmental constraints: a review of the past 10 years' research. Agricultural and Forest Meteorology 69: 153-203.

Idso, S.B. and Kimball, B.A. 2001. CO2 enrichment of sour orange trees: 13 years and counting. Environmental and Experimental Botany 46: 147-153.

Kimball, B.A. 1983. Carbon dioxide and agricultural yield: an assemblage and analysis of 430 prior observations. Agronomy Journal 75: 779-788.

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