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World Scientists' Warning to Humanity

Some 1,700 of the world's leading scientists, including the majority of Nobel laureates in the sciences, issued this appeal on November 18, 1992. The Warning was written and spearheaded by UCS Chair Henry Kendall.

Human beings and the natural world are on a collision course. Human activities inflict harsh and often irreversible damage on the environment and on critical resources. If not checked, many of our current practices put at serious risk the future that we wish for human society and the plant and animal kingdoms, and may so alter the living world that it will be unable to sustain life in the manner that we know. Fundamental changes are urgent if we are to avoid the collision our present course will bring about.

The Environment

The environment is suffering critical stress:

The Atmosphere

Stratospheric ozone depletion threatens us with enhanced ultraviolet radiation at the earth's surface, which can be damaging or lethal to many life forms. Air pollution near ground level, and acid precipitation, are already causing widespread injury to humans, forests and crops.

Water Resources

Heedless exploitation of depletable ground water supplies endangers food production and other essential human systems. Heavy demands on the world's surface waters have resulted in serious shortages in some 80 countries, containing 40% of the world's population. Pollution of rivers, lakes and ground water further limits the supply.


Destructive pressure on the oceans is severe, particularly in the coastal regions which produce most of the world's food fish. The total marine catch is now at or above the estimated maximum sustainable yield. Some fisheries have already shown signs of collapse. Rivers carrying heavy burdens of eroded soil into the seas also carry industrial, municipal, agricultural, and livestock waste -- some of it toxic.


Loss of soil productivity, which is causing extensive Land abandonment, is a widespread byproduct of current practices in agriculture and animal husbandry. Since 1945, 11% of the earth's vegetated surface has been degraded -- an area larger than India and China combined -- and per capita food production in many parts of the world is decreasing.


Tropical rain forests, as well as tropical and temperate dry forests, are being destroyed rapidly. At present rates, some critical forest types will be gone in a few years and most of the tropical rain forest will be gone before the end of the next century. With them will go large numbers of plant and animal species.

Living Species

The irreversible loss of species, which by 2100 may reach one third of all species now living, is especially serious. We are losing the potential they hold for providing medicinal and other benefits, and the contribution that genetic diversity of life forms gives to the robustness of the world's biological systems and to the astonishing beauty of the earth itself.

Much of this damage is irreversible on a scale of centuries or permanent. Other processes appear to pose additional threats. Increasing levels of gases in the atmosphere from human activities, including carbon dioxide released from fossil fuel burning and from deforestation, may alter climate on a global scale. Predictions of global warming are still uncertain -- with projected effects ranging from tolerable to very severe -- but the potential risks are very great.

Our massive tampering with the world's interdependent web of life -- coupled with the environmental damage inflicted by deforestation, species loss, and climate change -- could trigger widespread adverse effects, including unpredictable collapses of critical biological systems whose interactions and dynamics we only imperfectly understand.

Uncertainty over the extent of these effects cannot excuse complacency or delay in facing the threat.


The earth is finite. Its ability to absorb wastes and destructive effluent is finite. Its ability to provide food and energy is finite. Its ability to provide for growing numbers of people is finite. And we are fast approaching many of the earth's limits. Current economic practices which damage the environment, in both developed and underdeveloped nations, cannot be continued without the risk that vital global systems will be damaged beyond repair.

Pressures resulting from unrestrained population growth put demands on the natural world that can overwhelm any efforts to achieve a sustainable future. If we are to halt the destruction of our environment, we must accept limits to that growth. A World Bank estimate indicates that world population will not stabilize at less than 12.4 billion, while the United Nations concludes that the eventual total could reach 14 billion, a near tripling of today's 5.4 billion. But, even at this moment, one person in five lives in absolute poverty without enough to eat, and one in ten suffers serious malnutrition.

No more than one or a few decades remain before the chance to avert the threats we now confront will be lost and the prospects for humanity immeasurably diminished.


We the undersigned, senior members of the world's scientific community, hereby warn all humanity of what lies ahead. A great change in our stewardship of the earth and the life on it, is required, if vast human misery is to be avoided and our global home on this planet is not to be irretrievably mutilated.

What We Must Do

Five inextricably linked areas must be addressed simultaneously:

  1. We must bring environmentally damaging activities under control to restore and protect the integrity of the earth's systems we depend on. We must, for example, move away from fossil fuels to more benign, inexhaustible energy sources to cut greenhouse gas emissions and the pollution of our air and water. Priority must be given to the development of energy sources matched to third world needs -- small scale and relatively easy too implement. We must halt deforestation, injury to and loss of agricultural land, and the loss of terrestrial and marine plant and animal species.
  2. We must manage resources crucial to human welfare more effectively. We must give high priority to efficient use of energy, water, and other materials, including expansion of conservation and recycling.
  3. We must stabilize population. This will be possible only if all nations recognize that it requires improved social and economic conditions, and the adoption of effective, voluntary family planning.
  4. We must reduce and eventually eliminate poverty.
  5. We must ensure sexual equality, and guarantee women control over their own reproductive decisions.

The developed nations are the largest polluters in the world today. They must greatly reduce their over-consumption, if we are to reduce pressures on resources and the global environment. The developed nations have the obligation to provide aid and support to developing nations, because only the developed nations have the financial resources and the technical skills for these tasks.

Acting on this recognition is not altruism, but enlightened self-interest: whether industrialized or not, we all have but one lifeboat. No nation can escape from injury when global biological systems are damaged. No nation can escape from conflicts over increasingly scarce resources. In addition, environmental and economic instabilities will cause mass migrations with incalculable consequences for developed and undeveloped nations alike.

Developing nations must realize that environmental damage is one of the gravest threats they face, and that attempts to blunt it will be overwhelmed if their populations go unchecked. The greatest peril is to become trapped in spirals of environmental decline, poverty, and unrest, leading to social, economic and environmental collapse.

Success in this global endeavor will require a great reduction in violence and war. Resources now devoted to the preparation and conduct of war -- amounting to over $1 trillion annually -- will be badly needed in the new tasks and should be diverted to the new challenges.

A new ethic is required -- a new attitude towards discharging our responsibility for caring for ourselves and for the earth. We must recognize the earth's limited capacity to provide for us. We must recognize its fragility. We must no longer allow it to be ravaged. This ethic must motivate a great movement, convince reluctant leaders and reluctant governments and reluctant peoples themselves to effect the needed changes.

The scientists issuing this warning hope that our message will reach and affect people everywhere. We need the help of many.

We require the help of the world community of scientists -- natural, social, economic, political;<

We require the help of the world's business and industrial leaders;

We require the help of the worlds religious leaders; and

We require the help of the world's peoples.

We call on all to join us in this task.


Anatole Abragam, Physicist; Fmr. Member, Pontifical Academy of Sciences; France
Carlos Aguirre President, Academy of Sciences, Bolivia
Walter Alvarez Geologist, National Academy of Sciences, USA
Viqar Uddin Ammad, Chemist, Pakistani & Third World Academies, Pakistan
Claude Allegre, Geophysicist, Crafoord Prize, France
Michael Alpers Epidemiologist, Inst. of Med. Research, Papua New Guinea
Anne Anastasi, Psychologist, National Medal of Science, USA
Philip Anderson, Nobel laureate, Physics; USA
Christian Anfinsen, Nobel laureate, Chemistry; USA
How Ghee Ang, Chemist, Third World Academy, Singapore
Werner Arber, Nobel laureate, Medicine; Switzerland
Mary Ellen Avery, Pediatrician, National Medal of Science, USA
Julius Axelrod, Nobel laureate, Medicine; USA
Michael Atiyah, Mathematician; President, Royal Society; Great Britain
Howard Bachrach, Biochemist, National Medal of Science, USA
John Backus, Computer Scientist, National Medal of Science, USA
Achmad Baiquni, Physicist, Indonesian & Third World Academies, Indonesia
David Baltimore, Nobel laureate, Medicine; USA
H. A. Barker, Biochemist, National Medal of Science, USA
Francisco J. Barrantes, Biophysicist, Third World Academy, Argentina
David Bates, Physicist, Royal Irish Academy, Ireland
Alan Battersby, Chemist, Wolf Prize in Chemistry, Great Britain
Baruj Benacerraf, Nobel laureate, Medicine; USA
Georg Bednorz, Nobel laureate, Physics; Switzerland
Germot Bergold, Inst. Venezolano de Investigaciones Cientificas, Venezuela
Sune Bergstrom, Nobel laureate, Medicine; Sweden
Daniel Bes, Physicist, Argentinean & Third World Academies, Argentina
Hans Bethe, Nobel laureate, Physics; USA
Arthur Birch Chemist, Australian Academy of Science, Australia
Michael Bishop, Nobel laureate, Medicine; USA
Konrad Bloch, Nobel laureate, Medicine; USA
Nicholaas Bloembergen, Nobel laureate, Physics; USA
David Mervyn Blow, Wolf Prize in Chemistry, Great Britain
Baruch Blumberg, Nobel laureate, Medicine; USA
Bert Bolin, Meteorologist, Tyler Prize, Sweden
Norman Borlaug, Agricultural Scientist, Nobel laureate, Peace; USA & Mexico
Frederick Bormann, Forest Ecologist; Past President, Ecological Soc. of Amer.; USA
Raoul Bott, Mathematician, National Medal of Science, USA
Ronald Breslow, Chemist, National Medal of Science
Ricardo Bressani, Inst. of Nutrition, Guatemalan & Third World Academies, Guatemala
Hermann Bruck, Astronomer, Pontifical Academy of Sciences, Great Britain
Gerardo Budowski, Natural Resources, Univ. Para La Paz, Costa Rica
E. Margaret Burbidge, Astronomer, National Medal of Science, USA
Robert Burris, Biochemist, Wolf Prize in Agriculture, USA
Glenn Burton, Geneticist, National Medal of Science, USA
Adolph Butenandt, Nobel laureate, Chemistry; Fmr. President, Max Planck Inst.; Germany
Sergio Cabrera, Biologist, Univ. de Chile, Chile
Paulo C. Campos, Medical scientist, Philippine & Third World Academies, Philippines
Ennio Candotti, Physicist; President, Brazilian Soc. Adv. of Science; Brazil
Henri Cartan, Wolf Prize in Mathematics, France
Carlos Chagas, Biologist; Univ. de Rio de Janeiro; Fmr. President, Pontifical Academy of Sciences; Brazil
Sivaramakrishna Chandrasekhar, Center for Liquid Crystal Research, India
Georges Charpak, Nobel laureate, Physics; France
Joseph Chatt, Wolf Prize in Chemistry, Great Britain
Shiing-Shen Chern, Wolf Prize in Mathematics, China & USA
Christopher Chetsanga, Biochemist, Affican & Third World Academies, Zimbabwe
Morris Cohen, Engineering, National Medal of Science, USA
Stanley Cohen, Nobel laureate, Medicine; USA
Stanley N. Cohen, Geneticist, Wolf Prize in Medicine, USA
Mildred Cohn, Biochemist, National Medal of Science, USA
E. J. Corey, Nobel laureate, Chemistry, USA
John Cornforth, Nobel laureate, Chemistry; Great Britain
Hector Croxatto, Physiologist, Pontifical & Third World Academies, Chile
Paul Crutzen, Chemist, Tyler Prize, Germany
Partha Dasgupta, Economist, Royal Society, Great Britain
Jean Dausset, Nobel laureate, Medicine; France
Ogulande Robert Davidson, Univ. Res. & Dev. Serv., African Acad., Sierra Leone
Margaret Davis, Ecologist, National Academy of Sciences, USA
Luis D'Croz, Limnologist, Univ. de Panama, Panama
Gerard Debreu, Nobel laureate, Economics; USA
Pierre-Gilles de Gennes, Nobel laureate, Physics; France
Johann Deisenhofer, Nobel laureate, Chemistry; Germany & USA
Frederica de Laguna, Anthropologist, National Academy of Sciences, USA
Paul-Yves Denis, Geographer, Academy of Sciences, Canada
Pierre Deligne, Mathematician, Crafoord Prize, France
Frank Dixon, Pathologist, Lasker Award, USA
Johanna Dobereiner, Biologist, First Sec., Brazilian Academy of Sci.; Pontifical & Third World Academies, Brazil
Joseph Doob, Mathematician, National Medal of Science, USA
Renato Dulbecco, Nobel laureate, Medicine; USA
Heneri Dzinotyiweyi, Mathematician, African & Third World Academies, Zimbabwe
Manfred Eigen, Nobel laureate, Chemistry; Germany
Samuel Eilenberg, Wolf Prize in Mathematics, USA
Mahdi Elmandjra, Economist; Vice President, African Academy of Sciences; Morocco
Paul Ehrlich, Biologist, Crafoord Prize, USA
Thomas Eisner, Biologist, Tyler Prize, USA
Mohammed T. El-Ashry, Environmental scientist, Third World Academy, Egypt & USA
Gertrude Elion, Nobel laureate, Medicine; USA
Aina Elvius, Astronomer, Royal Academy of Sciences, Sweden
K. O. Emery, Oceanographer, National Academy of Sciences, USA
Paul Erdos, Wolf Prize in Mathematics, Hungary
Richard Ernst, Nobel laureate, Chemistry; Switzerland
Vittorio Ersparmer, Pharmacologist, Accademia Nazionale dei Lincei, Italy
Sandra Faber, Astronomer, National Academy of Sciences, USA
Nina Federoff, Embryologist, National Academy of Sciences, USA
Herman Feshbach, Physicist, National Medal of Science, USA
Inga Fischer-Hjalmars, Biologist, Royal Academy of Sciences, Sweden
Michael Ellis Fisher, Physicist, Wolf Prize in Physics, Great Britain & USA
Val Fitch, Nobel laureate, Physics; USA
Daflinn Follesdal, President, Norwegian Academy of Science; Norway
William Fowler, Nobel laureate, Physics; USA
Otto Frankel, Geneticist, Australian Academy of Sciences, Australia
Herbert Friedman, Wolf Prize in Physics, USA
Jerome Friedman, Nobel laureate, Physics; USA
Konstantin V. Frolov Engineer; Vice President, Russian Academy of Sciences; Russia
Kenichi Fukui, Nobel laureate, Chemistry; Japan
Madhav Gadgil, Ecologist, National Science Academy, India
Mary Gaillard, Physicist, National Academy of Sciences. USA
Carleton Gajdusek, Nobel laureate, Medicine; USA
Robert Gallo, Research Scientist, Lasker Award, USA
Rodrigo Gamez ,Instituto Nacional de Biodiversidad, Costa Rica
Antonio Garcia-Bellido, Biologist, Univ. Auto. Madrid, Royal Society, Spain
Leopoldo Garcia-Collin, Physicist, Latin American & Third World Academies, Mexico
Percy Garnham, Royal Society & Pontifical Academy, Great Britain
Richard Garwin, Physicist, National Academy of Sciences, USA
Murray Gell-Mann, Nobel laureate, Physics; USA
Georgii Georgiev, Biologist, Lenin Prize, Russia
Humam Bishara Ghassib, Physicist, Third World Academy, Jordan
Ricardo Giacconi, Astronomer, Wolf Prize in Physics, USA
Eleanor J. Gibson, Psychologist, National Medal of Science, USA
Marvin Goldberger, Physicist; Fmr. President, Calif. Inst. of Tech., USA
Maurice Goldhaber, Wolf Prize in Physics, USA
Donald Glaser, Nobel laureate, Physics; USA
Sheldon Glashow, Nobel laureate, Physics; USA
James Gowans, Wolf Prize in Medicine, France
Roger Green, Anthropologist, Royal Society, New Zealand
Peter Greenwood, Ichthyologist, Royal Society, Great Britain
Edward Goldberg, Chemist, Tyler Prize, USA
Coluthur Gopolan, Nutrition Foundation of India, Indian & Third World Academies, India
Stephen Jay Gould, Paleontologist, Author, Harvard Univ., USA
Roger Guillemin, Nobel laureate, Medicine; USA
Herbert Gutowsky, Wolf Prize in Chemistry, USA
Erwin Hahn, Wolf Prize in Physics, USA
Gonzalo Halffter, Ecologist, Inst. Pol. Nac. ,Mexico
Kerstin Hall, Endocrinologist, Royal Academy of Sciences, Sweden
Mohammed Ahmed Hamdan, Mathematician, Third World, Academy, Jordan
Adnan Hamoui, Mathematician, Third World, Academy, Kuwait
A. M. Harun-ar Rashid, Physicist; Sec., Bangladesh, Academy of Sci., Bangladesh
Mohammed H. A. Hassan, Physicist; Exec. Sec., Third World Academy of Sciences; Sudan & Italy
Ahmed Hassanli, Chemist, African Academy of Sciences, Tanzania & Kenya
Herbert Hauptman, Nobel laureate, Chemistry; USA
Stephen Hawking, Mathematician, Wolf Prize in Physics, Great Britain
Elizabeth Hay, Biologist, National Academy of Sciences, USA
Dudley Herschbach, Nobel laureate, Chemistry, USA
Gerhard Herzberg, Nobel laureate, Chemistry; Canada
Antony Hewish, Nobel laureate, Physics; Great Britain
George Hitchings, Nobel laureate, Medicine; USA
Dorothy Crowfoot Hodgkin, Nobel laureate, Chemistry; Great Britain
Roald Hoffman, Nobel laureate, Chemistry; USA
Robert Holley, Nobel laureate, Medicine; USA
Nick Holonyak, Electrical Engineer, National Medal of Science, USA
Lars Hormander, Wolf Prize in Mathematics, Sweden
Dorothy Horstmann, Epidemiologist, National Academy of Sciences, USA

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