The Scientific Consensus on Maintaining Humanity’s Life Support Systems in the 21st Century

May 21, 2013. the Scientific Consensus on Maintaining Humanity’s Life Support Systems in the 21st Century

In the one month since it was written, 520 global scientists have signed on to this statement. You can, too. There is more information, including ideas for solutions, at Stanford University’s Millenium Alliance for Humanity & the Biosphere website.

Earth is rapidly approaching a tipping point. Human impacts are causing alarming levels of harm to our planet. As scientists who study the interaction of people with the rest of the biosphere using a wide range of approaches, we agree that the evidence that humans are damaging their ecological life-support systems is overwhelming.We further agree that, based on the best scientific information available, human quality of life will suffer substantial degradation by the year 2050 if we continue on our current path.

Science unequivocally demonstrates the human impacts of key concern:

  • Climate disruption—more, faster climate change than since humans first became a species.
  • Extinctions—not since the dinosaurs went extinct have so many species and populations died out so fast, both on land and in the oceans.
  • Wholesale loss of diverse ecosystems—we have plowed, paved, or otherwise transformed more than 40% of Earth’s ice-free land, and no place on land or in the sea is free of our direct or indirect influences.
  • Pollution—environmental contaminants in the air, water and land are at record levels and increasing, seriously harming people and wildlife in unforeseen ways.
  • Human population growth and consumption patterns—seven billion people alive today will likely grow to 9.5 billion by 2050, and the pressures of heavy material consumption among the middle class and wealthy may well intensify.

By the time today’s children reach middle age, it is extremely likely that Earth’s life-support systems, critical for human prosperity and existence, will be irretrievably damaged by the magnitude, global extent, and combination of these human-caused environmental stressors, unless we take concrete, immediate actions to ensure a sustainable, high-quality future.

As members of the scientific community actively involved in assessing the biological and societal impacts of global change, we are sounding this alarm to the world. For humanity’s continued health and prosperity, we all—individuals, businesses, political leaders, religious leaders, scientists, and people in every walk of life—must work hard to solve these five global problems, starting today: 1. Climate Disruption 2. Extinctions 3. Loss of Ecosystem Diversity 4. Pollution 5. Human Population Growth and Resource Consumption.

The full statement has been signed by 520 global scientists from 44 countries. Those signatures were obtained within a month of completion of the statement, by direct email requests from the authors and their close colleagues to a targeted group of well-regarded global change scientists.   The signers include 2 Nobel Laureates, 33 members of the U.S. National Academy of Sciences,   42 members of the American Academy of Arts and Sciences, and several members of various European scientific academies.

Since about 1950, the world has been changing faster, and to a greater extent, than it has in the past 12,000 years. 

Changes, all interacting with each other, are leading humanity in dangerous directions: climate disruption, extinction of biodiversity, wholesale loss of vast ecosystems, pollution, and ever-increasing numbers of people competing for the planet’s resources. Until now, these have often been viewed as “necessary evils” for progress, or collateral damage that, while unfortunate, would not ultimately stand in the way of serving the needs of people. Several recent comprehensive reports by the scientific community, however, have now shown otherwise. Rather than simply being inconveniences, the accelerating trends of climate disruption, extinction, ecosystem loss, pollution, and human population growth in fact are threatening the life-support systems upon which we all depend for continuing the high quality of life that many people already enjoy and to which many others aspire.

The vast majority of scientists who study the interactions between people and the rest of the biosphere agree on a key conclusion: that the five interconnected dangerous trends listed above are having detrimental effects, and if continued, the already-apparent negative impacts on human quality of life will become much worse within a few decades. The multitude of sound scientific evidence to substantiate this has been summarized in many recent position papers and consensus statements (a few samples are listed on pp. 28-29), and documented in thousands of articles in the peer-reviewed scientific literature. However, the position papers and consensus statements typically focus only on a subset of the five key issues (for example, climate change, or biodiversity loss, or pollution), and access to the peer-reviewed literature is often difficult for non-scientists. As a result, policy makers faced with making critical decisions can find it cumbersome both to locate the pertinent information and to digest the thousands of pages through which it is distributed.

Here we provide a summary intended to Clearly voice the consensus of most scientists who study these issues that climate disruption, extinction, ecosystem loss, pollution, and population growth are serious threats to humanity’s well-being and societal stability; and these five major threats do not operate independently of each other.

People have basic needs for food, water, health, and a place to live, and additionally have to produce energy and other products from natural resources to maintain standards of living that each culture considers adequate. Fulfilling all of these needs for all people is not possible in the absence of a healthy, well-functioning global ecosystem. The “global ecosystem” is basically the complex ways that all life forms on Earth—including us—interact with each other and with their physical environment (water, soil, air, and so on). The total of all those myriad interactions compose the planet’s, and our, life support systems.


Humans have been an integral part of the global ecosystem since we first evolved; now we have become the dominant species in it. As such, we strongly influence how Earth’s life support systems work, in both positive and negative ways. A key challenge in the coming decades is to ensure that the negative influences do not outweigh the positive ones, which would make the world a worse place to live. Robust scientific evidence confirms that five interconnected negative trends of major concern have emerged over the past several decades:
• Disrupting the climate that we and other species depend upon.

• Triggering a mass extinction of biodiversity.

• Destroying diverse ecosystems in ways that damage our basic life support systems.

• Polluting our land, water, and air with harmful contaminants that undermine basic biological processes, impose severe health costs, and undermine our ability to deal with other problems.

• Increasing human population rapidly while relying on old patterns of production and consumption.

These five trends interact with and exacerbate each other, such that the total impact becomes worse than the simple sum of their parts. Ensuring a future for our children and grandchildren that is at least as desirable as the life we live now will require accepting that we have already inadvertently pushed the global ecosystem in dangerous directions, and that we have the knowledge and power to steer it back on course—if we act now. Waiting longer will only make it harder, if not impossible, to be successful, and will inflict substantial, escalating costs in both monetary terms and human suffering.

Background Information: Dangerous Trends in Our Life Support System

Biological extinctions cannot be reversed and therefore are a particularly destructive kind of global change. Even the most conservative analyses indicate that human-caused extinction of other species is now proceeding at rates that are 3-80 times faster than the extinction rate that prevailed before people were abundant on Earth28, and other estimates are much higher29-32. If the current rate of extinction is not slowed for species and their constituent populations, then within as little as three centuries the world would see the loss of 75% of vertebrate species (mammals, birds, reptiles, amphibians, and fish), as well as loss of many species of other kinds of animals and plants28. Earth has not seen that magnitude of extinction since an asteroid hit the planet 65 million years ago, killing the dinosaurs and many other species. Only five times in the 540 million years since complex life forms dominated Earth have mass extinctions occurred at the scale of what current extinction rates would produce; those mass extinctions killed an estimated 75%-96% of the species known to be living at the time. !

Currently, sound scientific criteria document that at least 23,000 species are threatened with extinction, including 22% of mammal species, 14% of birds, 29% of evaluated reptiles, as many as 43% of amphibians, 29% of evaluated fish, 26% of evaluated invertebrate animals, and 23% of plants33-35. Populations—groups of interacting individuals that are the building blocks of species—are dying off at an even faster rate than species. The extinction of local populations, in fact, represents the strongest pulse of contemporary biological extinction. For example, since 1970 some 30% of all vertebrate populations have died out36, and most species have experienced loss of connectivity between populations because of human-caused habitat fragmentation. Healthy species are composed of many, interconnected populations; rapid population loss, and loss of connectivity between populations, are thus early warning signs of eventual species extinction.

Ecosystem Transformation

As humans have become more abundant, we have transformed large parts of the Earth’s surface from their pre-human “natural” state into entirely different landscapes and seascapes58. Some of these transformations have been necessary to support basic human needs; others have been inadvertent and unanticipated$!! As of 2012, somewhat more than 41% of Earth’s ice-free lands (36% of total land surface) have been commandeered for farms, ranches, logging, cities, suburbs, roads, and other human constructs59-61. This equates to an average of a little less than 2 acres of transformed land for each person on Earth. Conversion for agriculture accounts for most of the landscape change, with crops covering about 12% and pastureland about 26% of ice-free land (the percentages are about 10% and 22%, respectively, for the proportion of all Earth’s land). Urban lands account for another 3%. On top of that are vast road networks that fragment habitats across some 50% of the entire land surface, dams that modify water flow in more than 60% of the world’s large rivers and in many smaller ones62, and continuing deforestation that has been proceeding at the rate of about 30,000 square kilometers (=11,000 square miles) per year for the past 16 years63. This per-year loss is roughly the equivalent of clear-cutting the entire country of Belgium or in the United States, the states of Massachusetts or Hawaii in one year.

Measuring the percentage of the oceans that have been transformed is much more challenging, but it is clear that pollution, trawling, and ship traffic and noise have caused major changes along most of the world’s coastlines64,65. For example, bottom trawling alone has been estimated to annually destroy an area of seabed equivalent to twice the area of the continental United States66. Human debris, particularly plastics, also is ubiquitous in ocean waters, even far offshore67. The human footprint extends even outside of the ecosystems that have been transformed wholesale by people. Nearly every terrestrial ecosystem in the world now integrates at least a few species that ultimately were introduced by human activities68-70, sometimes with devastating losses in ecosystem services71, and invasive species now number in the hundreds in most major marine ports72,73 and in the thousands on most continents70,74,75. All told, 83% of the entire land surface exhibits human impact defined as influenced by at least one of the following factors:
human population density greater than 1 person per square kilometer (=1 person per 0.4 square miles, or 247 acres); agricultural activity; built-up areas or settlements; being within 15 kilometers (9.3 miles) of a road or coastline; or nighttime light bright enough to be detected by satellites76,77. Adding in the effect of climate change, every place on Earth exhibits at least some human impact, even the most remote parts of the land and oceans78.



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2 Responses to The Scientific Consensus on Maintaining Humanity’s Life Support Systems in the 21st Century

  1. Jeff Strahl says:

    Isn’t it interesting that out of the blue, Lockheed today claims a “breakthrough” in fusion energy, promises a commercial reactor in 10 years! One wonders how Lockheed beat out all the other efforts, such as the IERR facility, by decades. The article in Reuters, where this is reported, noted that Lockheed is shopping around for new business since its military contracts with the US government are not yielding as much money as they used to.

  2. Jeff Strahl says:

    Well, i was pretty skeptical of the Lockheed claim, but it turns out i wasn’t skeptical nearly enough.
    “One of the top scientists at the International Thermonuclear Experimental Reactor (Iter) told the Guardian: “Let’s just say that since they don’t provide any technical details of what their ‘breakthrough’ actually involves, I am very sceptical. It’s amazing how much publicity you can generate with minimal information.”
    It appears that this is because the reactor in question has not been built and tested yet. “Some key parts of the prototype are theoretical and not yet proven,” Nathan Gilliland, CEO of General Fusion who are working on their own fusion reactor, told Wired.”

    See if you can get anyone to buy a car whose braking system, steering system and/or engine are “theoretical.”

    A friend of mine, who found the Guardian article, said “Yep, pure, unadulterated BS, especially since the world will be very much different ten years from now, probably even sooner, and not in a good way.”