Bookmark and Share

World Scientists' Warning to Humanity

Union of Concerned Scientists


Earth has a limited capacity to provide for the human race. If we want to avoid our own demise, we urgently need to:

  • clean up our air and land
  • better manage our water and forestry resources
  • protect endangered and threatened species
  • avoid human overpopulation
  • help developing nations create environmental policies

November 1992

Note: Because some of the information in this article may be outdated, it has been archived.

Editor’s Note: Some 1,700 of the world’s leading scientists, including the majority of Nobel laureates in the sciences, issued this appeal in November 1992. Their message is still valid today.


Eld’s Deer, or The Manipur Brow-antlered Deer, is a rare and critically endangered species of deer. It is found in its last existing natural habitat at the Kaibul Lamjao National Park in Loktak Lake in Manipur. Photo: Animal Kingdom, Florida, Oksana Hlodan.

We are on a collision course to disaster if we continue to damage the planet.

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 is suffering critical stress:

  • The Atmosphere
    Stratospheric ozone depletion threatens us with enhanced ultra-violet 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.

By the end of the 21st century we may lose 1/3 of all species if we don’t clean up our air, water, and land resources.
  • Oceans 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.

  • Soil
    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.

  • Forests
    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.

Global warming has been linked to human activity and environmental damage.

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 planet cannot sustain human overpopulation.

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

Scientists need everyone’s support to reverse some of the damage already done.

Five inextricably linked areas must be addressed simultaneously:

  • 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 to implement.

  • We must halt deforestation, injury to and loss of agricultural land, and the loss of terrestrial and marine plant and animal species.

  • 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.

  • 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.

  • We must reduce and eventually eliminate poverty.

  • We must ensure sexual equality, and guarantee women control over their own reproductive decisions.

Industrialized nations are the worst polluters.

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.

Government funding should be diverted from other activities to improve the planet’s health.

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
  • We require the help of the world’s business and industrial leaders
  • We require the help of the worlds religious leaders
  • We require the help of the world’s peoples
  • We call on all to join us in this task

The World Scientists’ Warning to Humanity was written and spearheaded by the late Henry Kendall, former chair of the board of directors of the Union of Concerned Scientists. UCS is an advocacy organization of citizens and scientists who are concerned about environmental and other scientific issues.

World Scientists' Warning to Humanity

Union of Concerned Scientists

Find out about current environmental issues and how this organization is working to solve the problems.

U.S. Patent Information

Search a free database to discover information about registered patents.

Save our Earth and Make a Difference

This site describes why everyone should be more aware of how people contribute to environmental problems. It gives sound advice on what people can do to become more eco-conscious. Take the eco-quiz while you’re there

Environmental knowledge quiz

“Compare your knowledge of the environment with adults across the nation by taking this environmental quiz… Two out of three adults who took the quiz didn’t make the passing mark.”


An environmental portal providing full text searches of reviewed Internet content, news, links and more at the international level.

Global Environment Outlook 3

From the United Nations Environment Programme (May 2002). This major report collated the thoughts of more than 1,000 contributors to assess the environmental impact of the last 30 years and outline policy ideas for the next three decades. It concluded that, without action, the world may experience severe environmental problems within 30 years. The entire report can be read online at no cost or can be purchased.

Emissions calculator

Quiz and calculator to find out how much air pollution you are responsible for in a given month.


The World Resources Institute’s new interactive website provides timely and accurate global environmental and sustainable development information. EarthTrends contains something for policy-makers in government and private industry, NGOs, educators, students, and the general public on ten topics, such as marine ecosystems and biodiversity.

Environmental news and organizations

EnviroLink offers links to various resources and updates.

Population quiz

How much do you know about world population? Explanatory answers provided. Click on number 7 “Applied” on home page and choose “quiz” from the scroll down menu.

Read a book

TerraViva! World Resourcesis a book/CD-ROM tool that lets you compare over 200 countries around the world “using hundreds of environmental, social, economic, and political variables.” From the World Resources Institute, 2003.

E, “The Environment Magazine”

UCS Action Network

You can help shape policy at all levels of government through the UCS Action Network. UCS will contact you when needed (email or post) with information on pivotal issues in need of your action — typically a call, email message or fax to an elected official.

Hands on the Land

Hands on the Land (HOL) is a network of field classrooms stretching across America. HOL provides a national network of field classrooms to enhance kindergarten through high school student-learning.

20/20 Vision

“We give citizens the information they need to get involved on important [environmental] issues. Our ‘20 minute’ monthly alerts tell you how to contact politicians and corporate officials and quickly and easily tell them you’re watching them on an urgent issue.”

Ask a scientist about nature

Choose from several categories to ask scientists questions about animals, habitats, and conservation.

Earth Share Organization

This organization manages workplace-giving campaigns for national environmental charities. You can choose to donate to one or several organizations on their list. Also check out the Earth Saving Tips page with suggested actions to take to help the environment.


For teachers and school administrators: add your school to the International Environmental and Education Partnership, a worldwide program offering students the opportunity to learn from environmental research scientists and to find resources for classroom activities.


Students and youth can become members of this grassroots organization, dedicated to environmental and social justice action. SEAC’s calendar of events is shown on its home page.

KIDLINK global networking for youth 10-15

This grassroots organization is trying to get young people involved in a global dialog about the environment, through activities, projects, and chats. Registration is required

Recycling for school fundraising

Toner Donation, a program of U.S. Recycling, is just an example of how schools can raise funds and help the environment at the same time by recycling inkjet & toner cartridges. “Almost 9 cartridges are discarded every second in the US alone.” What other programs are available in your area? Probably many. Try “recycle cartridges” or “recycling cartridges” in a search engine.

Friends of the Earth

Friends of the Earth is one of the largest international networks of environmental groups. Their site gives details about current environmental campaigns worldwide. original lesson

This lesson has been written by a science educator to specifically accompany the above article. It includes article content and extension questions, as well as activity handouts for different grade levels.

Lesson Title: Global Resources: What Will You Do with Your Power?
Levels: high school - undergraduate
Summary: This lesson examines human impact on natural resources. Students prepare a presidential speech on the state of the environment, rate nations according to their effectiveness in environmental problem-solving, conduct a natural resources scavenger hunt/simulation game… and more.

Download/view lesson. (To open the lesson’s PDF file, you need Adobe Acrobat Reader free software.)

Lessons for middle school

The following links will take you to middle school lessons available on other web sites:

  • » Our World, Our Future (Nuestro Mundo, Nuestro Futuro) Downloadable teaching kit of activities (English version only) from Population Connection. The Spanish version must be ordered by mail.
  • » Nurturing an Environmental Ethic Students learn about “the nature, character, and processes of the immediate lifespace environment — natural and built (human-made) in nature.”

Useful links for student research

In addition to the links in the “learn more” section above:


Understanding Science