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Thoughts on Science, Technology, and Human Well-Being in the Next Fifty Years

By John P. Holdren, John F. Kennedy School of Government, Harvard University

Rather than trying to predict what the world will be like in 2048, I want to focus on what I think society ought to be STRIVING FOR, over the next 50 years, in terms of four threats to human well-being on which current science sheds light and to which future science and technology, intelligently applied, can help provide the answers. Posed as challenges, the four issues I want to address are:

  1. Eliminating weapons of mass destruction;
  2. Meeting global energy needs while limiting the atmospheric concentration of carbon dioxide to less than twice its preindustrial value;
  3. Sharply reducing the global rate of loss of biodiversity; and
  4. Preventing the population of the planet from exceeding 9 billion people.
These challenges are interrelated (in more ways than there is space here to discuss); and they are all essential parts of the larger agenda of fashioning, over the next half century, an environmentally sustainable and politically stabilizing prosperity for all of the world's inhabitants. Failure in meeting any one of the four challenges is likely to put at risk that larger agenda and, in so doing, to risk denying to large numbers of our descendants the life-enhancing benefits that the advance of science and technology along other fronts would otherwise be bringing.

Weapons of Mass Destruction

The end of the Cold War has brought with it a widespread but alas wholly unwarranted complacency about the dangers still posed to the human condition by chemical, biological, and nuclear weapons.

To be sure, a global ban on chemical weapons has recently been agreed, joining a similar ban on biological weapons agreed 25 years earlier; more than 180 nations are parties to the recently indefinitely extended Nuclear Non-Proliferation Treaty; a comprehensive ban on nuclear weapons testing has been signed by most of the world's nations; and the United States and Russia are embarked on nuclear-force reductions that - assuming implementation of the START II agreement - will reduce the number of nuclear weapons in these two nations' stockpiles to between one-third and one-fourth of their respective peak Cold War values.

But, the world does not yet have in place either the technology or the institutions for reliable monitoring and verification of compliance of either the chemical or the biological weapons convention; the safeguards on nuclear facilities that could be used to violate the Nuclear Non-Proliferation Treaty are far from comprehensive; it is quite clear that a number of countries have violated these agreements or intend to do so (and, of course, some others never signed them); even after START II the United States and Russia may retain something in the range of 10,000 nuclear weapons each; and the danger of "leakage" of nuclear bombs or bomb-usable materials into the hands of terrorists or black marketeers has quite clearly GROWN in the post-Cold-War era, largely because of reduced reliability of the protection for these deadly commodities under current conditions in Russia.

Meanwhile, the United States - while it denounces the aspirations of potential proliferator states to acquire weapons of mass destruction of any kind - continues to assert its own need and right to retain a nuclear arsenal of some size indefinitely, and so far has refused to renounce even the option of first use of its nuclear weapons against nonnuclear threats or attacks. We do not seem to be much troubled by the inconsistencies of asserting a need and right for the United States to wield weapons of mass destruction while denying that any nation besides us and the four other officially certified nuclear-weapon states has reason or right to possess such weapons - whether nuclear, chemical, or biological - including the reason of wanting them as a counter to ours.

I am not asserting here that there is no political or military advantage to the United States from being able to threaten to use nuclear weapons against a country that does not have them, as we have implicitly threatened Iraq more than once. I am simply asserting that those advantages come at too high a cost. The cost of ANY country's insisting on retaining weapons of mass destruction of ANY kind is the provision of a continuing incentive to MANY countries to acquire weapons of mass destruction of one kind or another.

I believe the logic of this is implacable. In the long run, we are either going to have a world in which NO nations have weapons of mass destruction, or a world in which MANY nations do. And, in a world in which many nations have these weapons, the probability that some of the weapons will be set off (whether by accident or by design, by nations or by terrorists) becomes much too large. If we cannot get rid of weapons of mass destruction in the next fifty years, there will be too high a chance that they will get rid of altogether too many of us.

Of course, to confidently verify a prohibition of nuclear weapons will require large improvements in the science and technology of verification, as well as a general increase in transparency and openness in scientific, industrial, and governmental activities around the world. The most pains-taking protection and monitoring of all nuclear-weapon-usable materials, including those in use in civilian energy systems, will be an essential part of the elimination effort. These ingredients of an adequate verification regime for elimination of nuclear weapons will not materialize overnight, but we are already moving in these directions in connection with the cuts in nuclear weaponry already achieved or under negotiation, and another half century should not be too little to accomplish all that is required.

Greenhouse Gases, Climate Change, and Sustainable Energy Supply

The greenhouse gas most responsible for the growing threat of human-induced disruption of climate is carbon dioxide, some of it emitted by deforestation but mostly coming from the combustion of fossil fuels. Before the industrial revolution, when no fossil fuels were being burned, the concentration of carbon dioxide in the global atmosphere was about 280 parts per million (ppm).

In 1998 civilization's fossil fuel burning will release about 6.3 billion tons of carbon, and the atmospheric concentration will reach 365 parts per million, 30 percent above the preindustrial level. Under "business as usual", annual emissions from fossil-fuel burning in 2048 would total around 15 billion tons of carbon per year, and the atmospheric concentration of carbon dioxide would reach 500 to 550 parts per million. The momentum of the business-as-usual trajectory, moreover, would be carrying us rapidly toward a tripling or more of the preindustrial concentration in the second half of the next century.

Growth of this magnitude in carbon-dioxide concentrations, combined with hard-to-avoid increases in other greenhouse gases such as methane and nitrous oxide, is likely to entail severely disruptive changes in climate in many regions, including the United States. The productivity of farms and forests, the patterns of disease, the magnitude of damages from storms and floods, and the livability of our cities in summer are all likely to be adversely affected.

In the decades ahead we need simultaneously to try to better understand these climate-change liabilities, through increased investments in the science of climate and climate-change impacts, and to reduce the probability of intolerable outcomes by using advanced technologies to move off of the "business as usual" emissions trajectory to a much lower one. It will be extremely difficult to do much better than holding atmospheric carbon dioxide to a doubling of its preindustrial concentration; but it will be extremely dangerous to do much worse.

The needed technological improvements can be brought about through a combination of R&D to expand and improve the array of available emissions-reducing technologies plus incentives to deploy the best ones available. These technologies will sharply lower the energy intensity of economic activity by increasing the efficiencies with which energy is transformed and used, as well as lowering the carbon intensity of energy supply through use of lower-carbon and zero-carbon energy sources (renewables, fusion if we can make it work, and fission if we can fix the problems that have afflicted it) and through capture and sequestration of the carbon dioxide from the fossil fuels that continue to be used).


We do not even know the number of species on the planet to within a factor of three - it is thought that there are between 10 million and 30 million, of which fewer than two million have been identified and named. There is reason to believe that the rate of extinction of species is in the range of 1,000 times (give or take maybe a factor of 10) the average extinction rate prior to major human influence. The Global Biodiversity Assessment estimated that up to a third of the species in tropical forests - the largest reservoir of biodiversity on the planet - may be lost over the next several decades.

The species making up the biota are the indispensable foundation of the environmental goods and services on which, no less than on economic goods and services, the well-being of every person on the planet depends: the cycling of nutrients, the building and maintenance of soils, the purification of air and water, the natural control of many agents and vectors of human disease, and much more. This biodiversity also constitutes a vast library of genetic information, from which new food crops, drugs, vaccines, and other valuable products could come.

But since most of this genetic information has not even been cataloged, much less analyzed, it should be apparent that the current epidemic of extinctions amounts to burning down a unique and irreplaceable library without ever having read the books. I say "irreplaceable" because, notwithstanding the wonders of biotechnology, there is no reason now to think that we will be able to reconstruct the genetic information in species lost before they have been discovered, not to mention the information residing in the co-evolved complexity of the ecosystems of which these species were a part.

There is a tremendous task ahead for science -in building understanding of what the biodiversity of the planet is, how it works, and what it does - and a tremendous task for our technology and our institutions in arranging to meet human needs and aspirations for increased economic prosperity without destroying the indispensable foundation of well-being provided by the biota.


In mid-1998 there will be about 5.9 billion people on the planet, nearly two and a half times as many as in 1948. Because the rate of population growth has been falling, we will not see the same 2.5-fold growth in the next 50 years we saw in the last 50. Instead, barring nuclear war or global pandemic, the figure in 2048 will probably be between 8 billion and 10 billion people...and by 2098 between 9 and 12 billion. Most of the challenges that civilization will need to overcome in the next century - particularly the challenges of supplying sustainably the food, water, energy, housing, health care, education, employment opportunities, and other ingredients of a fulfilling life for all of the world's people - will be considerably more difficult if the 2048 population is at the high end of this range than if it is at the low end.

Accordingly, as part of our strategy for addressing all of these other challenges, we should strive for the lower end of the range of mid-21st century population possibilities...and for a peak population thereafter that does not exceed 9 billion. In doing so, we should bring to bear both the relevant insights of social science (about, for example, the effects on desired family size of economic and social development, including especially improvements in the status and education of women) and the capabilities of modern - and doubtless still improvable - contraceptive technologies to avoid unwanted births.


The sluggishness with which society is today addressing these problems, notwithstanding abundant information about their character and consequences, says something about the effectiveness (or, more accurately, the lack of it) of those of us who have long been laboring at the intersection of science, technology, and policy. It also says something about the inertia of the institutions of public-policy formation that would need to be energized in order to mount a serious attack on these problems. And it says something, finally, about our educational system, which clearly needs to do better in developing the skills of the populace in relation to numeracy, earth-system science, interdisciplinary thinking, and envisioning both the consequences of a "business as usual" future and pathways toward more promising alternatives.

Based on address at 150th Anniversary Meeting of the American Association for the Advancement of Science, Philadelphia, 15 February 1998.

John Holdren is Teresa and John Heinz Professor of Environmental Policy & Director, Program in Science, Technology, & Public Policy, Center for Science and International Affairs, John F. Kennedy School of Government, 79 JFK Street, Harvard University, Cambridge, MA 02138

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Editor: Barrett H. Ripin