Rachel's Democracy & Health News #868, August 16, 2006


[Rachel's introduction: "Species-area relationships lead to projections of the loss of fully two-thirds of all species on Earth by the end of this century.... And these projections do not include the inevitably negative effects of climate change, widespread pollution, and the destruction caused by alien species worldwide, among other factors."]

By Peter Montague

Peter H. Raven, a well-known biologist, was president of the American Association for the Advancement of Science (AAAS) during 2002. With 10 million members and affiliates, the AAAS is the largest scientific organization in the U.S.; it publishes Science magazine.

Dr. Raven's presidential address to the academy in 2002 is a succinct statement of where business as usual has carried us. In 2003, Dr. Raven presented a companion paper to the Natural History Museum in London, England. Here we summarize what he had to say in those two papers. [I have added a few comments in the text, inside square brackets. --P.M.]

[As you read through this description of the world we are handing to our children, ask yourself, "If the environmental movement got everything it is seeking, would it make a real difference in the problems described here? Have we set our sights high enough? Have we focused our minds on the real root causes?"]

Human Population

In 1950, the human population of Earth was 2.5 billion. A mere 50 years later it had grown to 6 billion. The human population is expected to level off at 9 billion some time during this century. [This will require 50% more of everything that we enjoy today -- 50% more cities, hospitals, roads, parks, prisons, parking lots, trucks, sewage treatment plants, farms and factories. If the human standard of living rises during that time, even more will be needed.]

[How will things look when the human population has grown 50% larger?]

To support 6 billion people, each year we are dousing our crops with 3 million metric tonnes (6.6 billion pounds) of pesticidal chemicals (1.1 billion pounds in the U.S. alone). Another byproduct of our industrial agricultural system, Dr. Raven says, is that "We also are poisoning the environment with the nitrogen we fix, our output now exceeding the total derived from natural processes." [This deserves a brief explanation: We "fix" nitrogen gas from the atmosphere, turning it into a solid, and mix it into soils as fertilizer to stimulate plant growth. Much of this nitrogen washes out of the soil and enters streams, eventually reaching the oceans, where it stimulates growth of algae, disrupting near-shore ecosystems with "red tides" and "brown tides," and contributes to the death of corals, among other disruptions. Humans are now putting more nitrogen into soils and water than all non-human natural processes combined. By this measure we humans are now more powerful than all the rest of nature -- quite an astonishing accomplishment for a single species among the 10 million (or more) species on earth.]

The Land

Human crops now require cultivated lands the size of South America. "Most of the land used for agriculture and grazing, especially in the tropics and subtropics, is being degraded by these activities and is therefore becoming less sustainable and productive in the face of increasing worldwide demand for high-quality food." Furthermore, "only limited potential remains for expanding the area of land under cultivation."

And, says Dr. Raven, "The rangelands on which some 180 million of us graze 3.3 billion cattle, sheep, and goats occupy about a fifth of the world's land surface; although there is a rapidly increasing demand for animal protein, "in almost every case, the lands on which they are being grazed are being progressively degraded to such an extent that they are unlikely to be able to maintain their present levels of productivity, much less of biodiversity, in the future," says Dr. Raven.

...[A]bout 20% of the arable land in 1950 has been lost subsequently, to salinization [from salt left in the soil by irrigation], desertification, urban sprawl, erosion, and other factors, so that we are feeding 6.3 billion people today on about four-fifths of the land on which we were feeding 2.5 billion people in 1950....

In sum, says Dr. Raven, "Over the past half century, we have lost about a fifth of the world's topsoil, a fifth of its agricultural land, and a third of its forests." By the middle of the present century, 95% of tropical moist forests are expected to be lost. Furthermore, "habitats throughout the world have [already] been decimated, with populations of alien plants and animals exploding and causing enormous damage throughout the world."

The Oceans

"About two-thirds of the world's fisheries are being harvested beyond sustainability," says Dr. Raven. And, "Almost all major fisheries are under severe pressure...."

The Atmosphere

"We have changed the composition of the atmosphere profoundly, first by adding about one sixth to the carbon dioxide that is contributing substantially to driving global temperatures upward and second, by depleting the stratospheric ozone layer by about 8 per cent."

Fresh Water

...[W]e [humans] are consuming more than half of the total renewable supplies of fresh water in the world, our use of water growing at about twice the rate of our population growth. Our demands for water are growing rapidly, while water tables across north China, India, and other critical, densely populated regions are dropping rapidly.

Agriculture accounts for about 90% of the total water actually consumed for human purposes, and it is not clear how we shall be able to find water for a human population 50% larger than at present, one with greatly increased demands for affluence. As it is, about half the human population, some 3.5 billion people, will be living in regions facing severe water shortages by 2025.


"The most troublesome environmental change of all, in that it is irreversible, is the loss of biodiversity." Historically, extinction has occurred naturally at the rate of about one species lost per million species each year. "Historical records over the past few centuries demonstrate that it has now risen by approximately three orders of magnitude, to perhaps 1,000 species per million per year (0.1 per cent of all species per year), and it continues to rise sharply, with the accelerating destruction of habitats throughout the world," Dr. Raven says.

"Species-area relationships, taken worldwide, lead to projections of the loss of fully two-thirds of all species on Earth by the end of this century.... And these projections do not include the inevitably negative effects of climate change, widespread pollution, and the destruction caused by alien species worldwide, among other factors."

[Did you get that? Two-thirds of all species on Earth may disappear during this century -- and this projection does not take into consideration the effects of climate change, widespread pollution, and the destruction caused by alient species worldwide.]

"The significance of such a loss for global stability as well as human progress is staggering," says Dr. Raven.

He goes on: "Striking is the fact that we are likely never to have seen, or to be aware of, the existence of most of the species we are driving to extinction. In tropical moist forest, we have catalogued so far probably fewer than one in twenty of the species present -- which is one reason that the losses are so tragic. The loss of so many species clearly will have a negative impact on future human prospects. We derive all of our food; most of our medicines; a major proportion of our building materials, clothing, chemical feedstocks; and other useful products from the living world."

In addition, the communities and ecosystems that it comprises protect our watersheds, stabilize our soils, determine our climates and provide the insects that pollinate our crops, among many other ecosystem services.

And finally, says Dr. Raven, these organisms are simply beautiful, enriching our lives in many ways and inspiring us every day. By any moral or ethical standard, we simply do not have the right to destroy them, and yet we are doing it savagely, relentlessly, and at a rapidly increasing rate, every day. Many believe, and I agree with them, that we simply do not have the right to destroy what is such a high proportion of the species on Earth. They are, as far as we know, our only living companions in the universe, Dr. Raven says.


"Summarizing, we can see that the world has been converted in an instant of time from a wild, natural one to one in which human beings, one of an estimated 10 million species of organisms (possibly many more), are consuming, wasting, or diverting an estimated 45 percent of the total net biological productivity on land and using more than half of the renewable fresh water."

Dr. Raven says, "The scales and kinds of changes in the Earth's life support systems are so different from what they have ever been before that we cannot base our predictions of the future, much less chart our future courses of action, on the basis of what has happened in the past."

[Continued next week.]