In calling for increased funding to save what remained of these endangered repositories of much of earth's biodiversity, Myers et al. noted that "the mass extinction of species, if allowed to persist, would constitute a problem with far more enduring impact than any other environmental problem." We agree, for a species lost is a species gone forever. In fact, Kirchner and Weil (2000) contemporaneously calculated that fully ten million years are required for a somewhat analogous species to reappear on the scene. Hence, they too concluded that "today's anthropogenic extinctions will diminish biodiversity for millions of years to come."

Clearly, the grand problem facing the biosphere today, and the specter that will cast its gloomy shadow over the face of the earth for as far into the future as we can peer, is the threat of massive species extinctions. As Myers et al. said in their concluding remarks, "what we do (or do not do) within the next few decades will determine the long-term future of a vital feature of the biosphere, its abundance and diversity of species." And as we (Idso and Idso, 2000) wrote contemporaneously, the ongoing rise in the atmosphere's CO2 concentration "may well be one of the best allies we will ever have in our battle to preserve the planet's biodiversity." So how might it do so?

Consider Pimm and Raven's concluding statement. They say that "unless the large remaining areas of humid tropical forests are also protected, extinctions of those species that are still wide-ranging should exceed those in the hotspots within a few decades." This fact drove Andrew Lee of the Worldwide Fund for Nature to state that "we want to save species from all types of ecosystems" (Pearce, 2000). And this statement suggests that something far more wide-ranging and ubiquitous than hotspot protection must be done to preserve what little we might be able to save of the planet's biodiversity. It also suggests that it must be done now; and that's where anthropogenic CO2 emissions enter the biodiversity-preserving equation.

In a major review of plant-animal interactions in 51 terrestrial ecosystems, McNaughton et al. (1989) found that the biomass of plant-eating animals is a strongly-increasing function of aboveground primary production. Likewise, in a review of 22 aquatic ecosystems, Cyr and Pace (1993) found that the herbivore biomass of watery habitats also increases in response to increases in vegetative productivity. Hence, it is abundantly clear that greater plant productivity -- both terrestrial and aquatic -- leads to greater populations of plants, as well as the animals that feed upon the plants, which should therefore lead to greater ecosystem biodiversity, because each species of plant and animal must maintain a certain "critical biomass" to sustain its unique identity and insure its long-term viability.

Observations of the world of nature have confirmed the validity of this relationship again and again. In a study of the vascular plants of 94 terrestrial ecosystems from all across the globe, for example, Scheiner and Rey-Benayas (1994) found that ecosystem species richness is more positively correlated with ecosystem productivity than it is with anything else. It readily follows, therefore, that anything that enhances ecosystem production will also enhance ecosystem biodiversity; and that is what atmospheric CO2 enrichment does best, as has been demonstrated in literally thousands of laboratory and field experiments.

Viewed in this light, the ongoing rise in the air's CO2 content is seen to be a blessing in disguise. It's aerial fertilization effect provides a much-needed boost to the vitality of the vegetation that serves as the energetic basis of all ecosystems; and the elevated levels of primary production that elevated levels of CO2 induce in earth's plants -- and especially in its trees (Idso, 1999) -- provides the basis for greater populations of herbivores and carnivores at all higher levels of the planet's many food chains. And those greater numbers of individual plants and animals are what help to maintain the viability of their respective species.

Clearly, many other measures, in addition to allowing the air's CO2 content to continue to rise, must be taken to preserve earth's biodiversity. But equally as clear is the fact that all effective measures that can be taken, must be taken; for even in their entirety, all the things that man can do will still be too few and too late for many species that will shortly be reduced to mere memories (da Silva and Tabarelli, 2000; Pimm and Raven, 2000). Continued atmospheric CO2 enrichment, therefore, must play a major role in our crusade to save the many life forms that are currently in danger of being lost; and in this regard, the known biodiversity benefits of the ongoing rise in the air's CO2 content far outweigh the speculation that elevated CO2 concentrations might possibly lead to significant global warming in decades to come.

Another intriguing question that was asked early in current century was How much land can ten billion people spare for nature? It 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) 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."

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 hundred years, simply by taking their land. Global warming, by comparison, pales in significance. Its impact is nowhere near as severe, being possibly 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.

What parts of the world are likely to be hardest hit by this human land-eating machine? Tilman et al. (2001) note that developed countries are expected to actually withdraw large areas of land from farming over the next fifty years, leaving developing countries to shoulder essentially all of the growing burden of feeding our expanding species. 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 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 at the turn of the century, 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 is 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-rise in crop yields was declining, as the genetic ceiling for maximal yield potential was being approached. This observation, they said, "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 suggested 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 the study 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 terrestrial 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% (Saxe et al. 1998; Idso and Kimball, 2001). In fact, since the inception of the Industrial Revolution, we calculate, on the basis of the work of Mayeux et al. (1997) and Idso and Idso (2000), that the 100-ppm increase in atmospheric CO2 concentration that has been caused by the historical burning of fossil fuels has likely increased agricultural production per unit land area by 70% for C3 cereals, 28% for C4 cereals, 33% for fruits and melons, 62% for legumes, 67% for root and tuber crops, and 51% for vegetables. 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. Consequently, 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.

It would thus 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 next century, if world agricultural output is not dramatically increased. This unfathomable consequence will occur simply because we will need more land to produce what is required to sustain us and, in the absence of the needed productivity increase, because we will simply take the needed 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, 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 entire species. And to allow, nay, to cause the extinction of untold millions of unique and irreplaceable species has got to rank close to the top of all conceivable immoralities.

We humans, as stewards of the earth, have got to get our science and 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 have got to let the air's CO2 content continue to rise. Any policies that stand in the way of that objective, therefore, are not only immoral, they are obscene.

Writing in Science, in another paper that comes to bear upon the issue of land use and animal extinctions, Ceballos et al. (2005) conducted what they described as "a global examination of mammal distributions to evaluate conservation priorities based on (i) range size distribution, (ii) global patterns of species richness, (iii) political endemism (i.e., the proportion of species restricted to one country), (iv) the minimum area required to preserve one population or 10% of the range of each species, and (v) conservation conflicts in priority areas." In the course of their analyses, the five scientists found that approximately one fourth of all terrestrial mammal species in the world are at risk of extinction, and that to preserve 10% of the range of each species would require 11% of the planet's ice-free land surface. They also found that 80% of the specific land area in question has been affected to some degree by agriculture, with 20% of it having lost from 26 to 100% of its natural vegetation to agriculture.

This loss of land to agriculture appears to be the greatest single threat to the survival of earth's mammals; and in the same issue of Science, Foley et al. (2005) reported that "human activities now appropriate nearly one-third to one-half of global ecosystem production." Others have come to the same conclusion with respect to both land (Tilman et al., 2001, 2002) and water (Wallace, 2000), with Green et al. (2005) wondering how humanity will meet the two- to three-fold increase in food demand that will exist by 2050 without usurping all the land that is currently available to what they call "wild nature."

The only answer to this question that we foresee on the horizon is that after all that man can do to become more efficient and productive in the agricultural arena, he will still fall short of the food production capacity that will be required by 2050, and he will have to rely on the aerial fertilization and water conservation (anti-transpiration) effects of the ongoing rise in the air's CO2 content to make up the difference (Idso and Idso, 2000), in order to preserve some land (which at best will not be much) for earth's wild plant and animal species. Consequently, if anthropogenic CO2 emissions are not allowed to pursue the course that is dictated by the natural evolution of technological development, i.e., if we mandate the type of CO2 emissions reductions that radical environmentalists want to see enforced, most of earth's wild animals have but a few decades left before their only remaining representatives will be those fortunate enough to be incarcerated in zoos, with mammals being some of the first to go.

Additional evidence that earth's mammals are in a world of hurt is provided by the study of Schipper et al. (2008). In this review paper -- authored by 130 researchers employing data compiled by over 1700 experts in the field, they present, in their words, "the results of the most comprehensive assessment to date of the conservation status and distribution of the world's mammals, covering all 5,487 wild species recognized as extant since 1500."

So what did they find?

First of all, they determined that 25% of all mammals for which adequate data are available are threatened with extinction, with the percentage for marine mammals rising to 36%. These figures include 188 critically endangered species that face what they call "a very high probability of extinction," as well as 29 species for which they say "it may already be too late."

What are the primary causes of the possible near-term mammal extinctions?

The international team of experts states that "worldwide, habitat loss and degradation (affecting 40% of species assessed) and harvesting (hunting or gathering for food, medicine, fuel and materials, which affect 17%) are by far [our italics] the main threats to [land] mammals." With respect to marine mammals, however, they say "the dominant threat is accidental mortality (which affects 78% of species), particularly through fisheries by-catch and vessel strike," while "pollution (60% of species) is the second most prevalent threat."

So what factor is most important to maintaining mammal species richness and preventing wholesale extinctions?

As stated in the table of contents tag line to the article, the comprehensive assessment of the 130 researchers "shows that primary productivity [our italics] drives species richness on land and sea," while in the article itself the authors write that "as with land species, marine richness seems to be associated with primary productivity," noting that "whereas land species' richness peaks toward the equator, marine richness peaks at around 40°N and S, corresponding to belts of high oceanic productivity."

Shipper et al. conclude their review by stating that their results "paint a bleak picture of the global status of mammals worldwide." And so they do. However, we can reduce the loss and degradation of habitat and animal harvesting on land, as well as accidents and pollution at sea, but only if we truly dedicate ourselves to doing so. On the other hand, attempting to prevent catastrophic mammal extinctions by trying to change the world's climate -- as Al Gore, James Hansen and others claim we must do by restricting CO2 emissions -- is even worse than wishful thinking, for it simply cannot be done. What is more, literally thousands of experimental studies stand as solemn testaments to the fact that atmospheric CO2 enrichment significantly increases primary productivity, both on land and at sea; and this phenomenon is the greatest known force for maintaining earth's mammal species richness that has ever been identified.

Clearly, the combination of these elements of the problem's solution -- protecting mammal habitat from loss, degradation and pollution, while curtailing willful and accidental animal harvesting, plus allowing the atmosphere's CO2 concentration to pursue its historical upward course without overt curtailment -- is the only hope we realistically have of saving what yet remains of earth's endangered mammals.

In a sad addendum to the above observations, Sir John Houghton, formerly of the IPCC, has recently championed "very large growth in renewable energy sources," among which he lists biomass in second place (after solar) as a moral imperative, in an attempt to make people think they would be helping mankind (and thereby doing God's work) by growing plants for the purpose of producing large amounts of biofuels to replace large amounts of fossil fuels. This crusade, however, is misguided in the extreme, as indicated by thoughts expressed in a Science editorial by Borlaug (2007) that sheds further light upon the matter.

Borlaug begins his mini-treatise on "feeding a hungry world" by noting that "some 800 million people still experience chronic and transitory hunger each year," and that "over the next 50 years, we face the daunting job of feeding 3.5 billion additional people, most of whom will begin life in poverty."

Discussing a bit of history, the father of the Green Revolution recounts how "over a 40-year period, the proportion of hungry people in the world declined from about 60% in 1960 to 17% in 2000," primarily because of the effectiveness of the movement he was instrumental in initiating. Had that movement failed, he says that environmentally fragile land would have been needed to be brought into agricultural production, and the resulting "soil erosion, loss of forests and grasslands, reduction in biodiversity, and extinction of wildlife species would have been disastrous." And that same result is what awaits the world of tomorrow if the scheme of Sir John Houghton is ever implemented.

Borlaug notes, for example, that "for the foreseeable future, plants -- especially the cereals -- will continue to supply much of our increased food demand, both for direct human consumption and as livestock feed to satisfy the rapidly growing demand for meat in the newly industrializing countries." In fact, he states that "the demand for cereals will probably grow by 50% over the next 20 years [our italics], and even larger harvests will be needed if more grain is diverted to produce biofuels."

Noting that most food increases of the future "will have to come from lands already in production [our italics]," and that "70% of global water withdrawals are for irrigating agricultural lands," Borlaug's facts suggest that crop water use efficiency (biomass produced per unit of water used) will have to be increased dramatically if we are to meet humanity's food needs of the future without creating the disastrous consequences he outlines above; and it should be evident to all but those most blinded to the truth that this requirement can only be met if biofuels are not a part of the picture, while the aerial fertilization and anti-transpiration effects of atmospheric CO2 enrichment are the future.

Although Borlaug notes that conventional plant breeding, improvements in crop management, tillage, fertilization, and weed and pest control, as well as genetic engineering, will help significantly in this regard, we will in all likelihood need the beneficial biological byproducts of concomitant increases in the atmosphere's CO2 concentration in addition. Without them, to borrow a chilling phrase from Borlaug, "efforts to halt global poverty will grind to a halt," and much of the world of nature will be no longer.

Last of all, in a lengthy discourse entitled "Energy, Food, and Land -- The Ecological Traps of Humankind," Haber (2007) contends that energy, food and land are the principal resources required by contemporary human societies, and that "the absolutely decisive resource in question is land, whose increasing scarcity is totally underrated."

Expanding on this theme, Haber writes that the energy trap is "formed by a quasi-return to renewable energy suppliers for which we need very vast, hardly available tracts of land," that the food trap is "formed by increased use and demand of arable and pasture land with suitable soils," and that the land trap is "formed by the need of land for urban-industrial uses, transport, material extraction, refuse deposition, but also for leisure, recreation, and nature conservation." All of these needs, as he continues, "compete for land." And good soils, as he adds, are becoming "scarcer than ever ... scarcer than coal, oil and uranium."

As if this were not enough, Haber notes that "we are preoccupied with fighting climate change and loss of biodiversity," and he says that "these are minor problems we could adapt to, albeit painfully." In fact, he states that "their solution will fail [our italics] if we are caught in the interrelated traps of energy, food, and land scarcity," which are looming menacingly before us just a few short decades down the road.

"Land and soil," as Haber continues, "have to be conserved, maintained, cared for, [and] properly used, based on reliable ecological information and monitoring, planning and design." We agree; and we have reported, in this regard, that a switch to biofuels to help meet our energy needs will result in our taking unconscionable amounts of land and freshwater resources from nature to produce them, and that the simple task of growing enough crops to meet the food needs of the world's population in the year 2050 will require our using so much more land than we do now, that the resulting loss of habitat will drive unnumbered species of plants and animals to extinction.

So what's the solution? As we have noted in many of our other writings on this question, it is to let the air's CO2 content continue to climb as the world's scientists and engineers devise ways of meeting mankind's growing energy needs without usurping the remaining habitat of "wild nature." We say this because of two things. First, some of the world's most prominent ecologists have concluded that even with all agricultural advancements they can anticipate over the next few decades, we may still not be able to grow sufficient food to sustain the planet's human population without appropriating for this purpose vast amounts of land and water that are currently needed to support the other species with which we share the earth. Second, we have calculated that the crop yield enhancements and water-use efficiency increases that should be caused by the expected increase in the atmosphere's CO2 concentration between now and the year 2050 should be sufficient, but only barely, to enable us to grow the crops we will need at that time on the lands and with the water that we currently use for this purpose.

If we are to prevent the extinctions of innumerable species of plants and animals that many see occurring only half a human lifespan from now, we must pursue a course of action that is congruent with the one we outline here. And above all, we must never forget that those decades to come will determine the fate of earth's biosphere for the millions of years that follow. Let's be certain, therefore, that we are not "biting the hand that feeds us" -- and that feeds the rest of the biosphere as well -- before we enact any measures to curtail life-sustaining and species-preserving anthropogenic CO2 emissions to the atmosphere.

References
Borlaug, N. 2007. Feeding a hungry world. Science 318: 359.

Ceballos, G., Ehrlich, P.R., Soberon, J., Salazar, I. and Fay, J.P. 2005. Global mammal conservation: What must we manage? Science 309: 603-607.

Cyr, H. and Pace, M.L. 1993. Magnitude and patterns of herbivory in aquatic and terrestrial ecosystems. Nature 361: 148-150.

Da Silva, J.M.C. and Tabarelli, M. 2000. Tree species impoverishment and the future flora of the Atlantic forest of northeast Brazil. Nature 404: 72-74.

Foley, J.A., DeFries, R., Asner, G.P., Barford, C., Bonan, G., Carpenter, S.R., Chapin, F.S., Coe, M.T., Daily, G.C., Gibbs, H.K., Helkowski, J.H., Holloway, T., Howard, E.A., Kucharik, C.J., Monfreda, C., Patz, J.A., Prentice, I.C., Ramankutty, N. and Snyder, P.K. 2005. Global consequences of land use. Science 309: 570-574.

Green, R.E., Cornell, S.J., Scharlemann, J.P.W. and Balmford, A. 2005. Farming and the fate of wild nature. Science 307: 550-555.

Haber, W. 2007. Energy, food, and land -- the ecological traps of humankind. Environmental Science and Pollution Research 14: 359-365.

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, S.B. 1999. The long-term response of trees to atmospheric CO2 enrichment. Global Change Biology 5: 493-495.

Kirchner, J.W. and Weil, A. 2000. Delayed biological recovery from extinctions throughout the fossil record. Nature 404: 177-180.

Mayeux, H.S., Johnson, H.B., Polley, H.W. and Malone, S.R. 1997. Yield of wheat across a subambient carbon dioxide gradient. Global Change Biology 3: 269-278.

McNaughton, S.J., Oesterheld, M., Frank, D.A. and Williams, K.J. 1989. Ecosystem-level patterns of primary productivity and herbivory in terrestrial habitats. Nature 341: 142-144.

Myers, N., Mittermeier, R.A., Mittermeier, C.G., da Fonseca, G.A.B. and Kent, J. 2000. Biodiversity hotspots for conservation priorities. Nature 403: 853-858.

Pearce, F. 2000. Spread the wealth: When ecofunds are scarce, just what should we conserve? New Scientist 165(2227): 12.

Pimm, S.L. and Raven, P. 2000. Extinction by numbers. Nature 403: 843-845.

Scheiner, S.M. and Ray-Benayas, J.M. 1994. Global patterns of plant diversity. Evolution and Ecology 8: 331-347.

Schipper, J. and 129 coauthors. 2008. The status of the world's land and marine mammals: Diversity, threat, and knowledge. Science 322: 225-230.

Tilman, D., Cassman, K.G., Matson, P.A., Naylor, R. and Polasky, S. 2002. Agricultural sustainability and intensive production practices. Nature 418: 671-677.

Tilman, D., Fargione, J., Wolff, B., D'Antonio, C., Dobson, A., Howarth, R., Schindler, D., Schlesinger, W.H., Simberloff, D. and Swackhamer, D. 2001. Forecasting agriculturally driven global environmental change. Science 292: 281-284.

Wallace, J.S. 2000. Increasing agricultural water use efficiency to meet future food production. Agriculture, Ecosystems & Environment 82: 105-119.