86. Why Evolution of Animals Was Delayed By 2 Billion Years

The Earth span off the Sun some 4.6 billion years ago. It took about 1 billion years for the the prokaryotic cell organisms to develop on Earth.  But evolution of animals was delayed.  


The following report states that this delay may have been caused by oxygen deficiency and the presence of heavy metal molybdenum in the ancient deep oceans.  In a related story, the previous post reports on very recent research that points to early plants for oxygenization of ancient deep oceans and the atmosphere, necessary for evolution of animal life forms.  Together, they deepen our knowledge of the conditions and factors responsible for  the long evolutionary process that that has created the magic of the present-day living planet, including our species, Homo sapiens (see the post on The Gaia Hypothesis).  Is it not sheer arrogance and ignorance coupled with the drive for monetary gain that is rapidly destroy it, most significantly, through anthropogenic climate change? 

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Science Daily, Mar. 27, 2008 — Scientists from around the world have reconstructed changes in Earth's ancient ocean chemistry during a broad sweep of geological time, from about 2.5 to 0.5 billion years ago. They have discovered that a deficiency of oxygen and the heavy metal molybdenum in the ancient deep ocean may have delayed the evolution of animal life on Earth for nearly 2 billion years.

The researchers arrived at their result by tracking molybdenum in black shales, which are a kind of sedimentary rock rich in organic matter and usually found in the deep ocean. Molybdenum is a key micronutrient for life and serves as a proxy for oceanic and atmospheric oxygen amounts.

Following the initial rise of oxygen in the Earth's atmosphere 2.4 billion years ago, oxygen was transferred to the surface ocean to support oxygen-demanding microorganims. Yet the diversity of these single-celled life forms remained low, and their multicellular ancestors, the animals, did not appear until about 600 million years ago, explained Timothy Lyons, a professor of biogeochemistry in the Department of Earth Sciences at the University of California, Riverside, and one of the study's authors.

Suspecting that deficiencies in oxygen and molybdenum might explain this evolutionary lag, Lyons and his colleagues measured abundances of molybdenum in ancient marine sediments over time to estimate how much of the metal had been dissolved in the seawater in which the sediments formed.

The researchers found significant, firsthand evidence for a molybdenum-depleted ocean relative to the high levels measured in modern, oxygen-rich seawater.

Molybdenum is of particular interest  because it is used by some bacteria to convert the element nitrogen from a gas in the atmosphere to a form useful for living things -- a process known as "nitrogen fixation." Bacteria cannot fix nitrogen efficiently when they are deprived of molybdenum. And if bacteria can't fix nitrogen fast enough then eukaryotes -- a kind of organism that includes plants, pachyderms and people -- are in trouble because eukaryotes cannot fix nitrogen themselves at all.

"These molybdenum depletions may have retarded the development of complex life such as animals for almost two billion years of Earth history," Lyons said. "The amount of molybdenum in the ocean probably played a major role in the development of early life. As in the case of iron today, molybdenum can be thought of as a life-affirming micronutrient that regulates the biological cycling of nitrogen in the ocean.

"At the same time, molybdenum's low abundance in the early ocean tracks the global extent of oxygen-poor seawater and implies that the amount of oxygen in the atmosphere was still low.

"Knowing the amount of oxygen in the early ocean is important for many reasons, including a refined understanding of how and when appreciable oxygen first began to accumulate in the atmosphere," Lyons said. "These steps in oxygenation are what gave rise ultimately to the first animals almost 600 million years ago -- just the last tenth or so of Earth history."

Earth's oxygenation

For animal life to commence, survive and eventually expand on Earth, a threshold amount of oxygen -- estimated to be on the order of 1 to 10 percent of present atmospheric levels of oxygen -- was needed.

Past research has shown that Earth's oxygenation occurred in two major steps:

The first step, around 2.4 billion years ago, took place as the ocean transitioned to a state where only the surface ocean was oxygenated by photosynthesizing bacteria, while the deep ocean was relatively oxygen-free.

The second step, around 600 million years ago, marked the occasion when the entire ocean became fully oxygenated through a process not yet fully understood.

"We wanted to know what the state of the ocean was between the two steps," said Clinton Scott, a graduate student working in Lyons's lab and the first author of the research paper. "By tracking molybdenum in shales rich in organic matter, we found the deep ocean remained oxygen- and molybdenum-deficient after the first step. This condition may have had a negative impact on the evolution of early eukaryotes, our single-celled ancestors. The molybdenum record also tells us that the deep ocean was already fully oxygenated by around 550 million years ago."

According to Scott, the timing of the oxygenation steps suggests that significant events in Earth history are related. Scientists have long speculated that the evolution of the first animals was linked somehow to the so-called Snowball Earth hypothesis, which posits that the Earth was covered from pole to pole in a thick sheet of ice for millions of years at a time. "The second oxygenation step took place not long after the last Snowball Earth episode ended around 600 million years ago," Scott said. "So one question is: Did this global glaciation play a role in the increasing abundance of oxygen which, in turn, enabled the evolution of animals?"

The study results appear in the March 27 issue of Nature.

Scott and Lyons were joined in the research by A. Bekker of the Carnegie Institution of Washington, DC; Y. Shen of the Université du Québec à Montréal, Canada; S.W. Poulton of Newcastle University, Newcastle upon Tyne, United Kingdom; X. Chu of the Chinese Academy of Sciences, Beijing, China; and A.D. Anbar of Arizona State University, Tempe, Ariz.

The research was supported by grants from the U.S. National Science Foundation Division of Earth Sciences and the NASA Astrobiology Institute.

More about molybdenum as a proxy for ocean chemistry

Molybdenum, a metal abundant in the ocean today but less so at times in the past, is an excellent tracer of ancient chemistry for two reasons. First, the primary source of molybdenum to the ocean is oxidative weathering of continental crust, requiring oxygen in the atmosphere. Second, molybdenum is removed primarily in marine sediments where oxygen is absent and sulfide is abundant. Thus the enrichment of molybdenum in ancient organic-rich shales requires oxygen in the atmosphere but high sulfur and very low or no oxygen in the deep ocean. This combination is relatively rare today but may have been common when oxygen was less abundant in the earlier atmosphere.

When oxygen is available in the atmosphere, the amount of dissolved molybdenum in seawater is determined by the extent of hydrogen-sulfide-containing sediments and bottom waters (the colder, more isolated, lowermost layer of ocean water). Where sulfidic environments are widespread, the pool of molybdenum remaining in seawater is small, growing as the sulfidic environments shrink. The amount of molybdenum in the seawater is reflected in the magnitude of molybdenum enrichment in shales deposited in the deep ocean.

The UCR-led team of researchers estimated the size of the oceanic reservoir, and thus the extent of sulfidic bottom waters and sediments, based on the concentration of molybdenum in ancient black shales. They did so by dissolving the samples in a cocktail of acids and analyzing the dissolved rock for concentration using a mass spectrometer. The amount of this metal in the shales tracks the oxygen state of the early ocean and atmosphere and also points to the varying abundance of this essential ingredient of life. Molybdenum limitations may have delayed the development of eukaryotes, including the first animals, our earliest multicellular cousins.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Riverside, via EurekAlert!, a service of AAAS.

85. Plants Kick-Started Evolutionary Drama of Earth's Oxygenation

Science Daily, October 9, 2010

An international team of scientists, exploiting pioneering techniques at Arizona State University, has taken a significant step toward unlocking the secrets of oxygenation of the Earth's oceans and atmosphere.

Evolution of the Earth's multitude of organisms is intimately linked to the rise of oxygen in the oceans and atmosphere. The new research indicates that the appearance of large predatory fish as well as vascular plants approximately 400 million years ago coincided with an increase in oxygen, to levels comparable to those we experience today. If so, then animals from before that time appeared and evolved under markedly lower oxygen conditions than previously thought.

The researchers, including collaborators from Harvard, Denmark, Sweden and the United Kingdom, made use of a method developed at ASU by Ariel Anbar, a professor in the department of chemistry and biochemistry and the School of Earth and Space Exploration in the College of Liberal Arts and Sciences, and his research group. The method can be used to estimate global oxygen levels in ancient oceans from the chemical composition of ancient seafloor sediments.

Their important findings are presented in a paper published in the Proceedings of the National Academy of Sciences (PNAS), titled "Devonian rise in atmospheric oxygen correlated to radiations of terrestrial plants and large predatory fish."

"There has been a lot of speculation over the years about whether or not

oxygen in the atmosphere was steady or variable over the last 500 million years," explained Anbar, who leads ASU's Astrobiology Program. "This is the era during which animals and land plants emerged and flourished. So it's a profound question in understanding the history of life. These new findings not only suggest that oxygen levels varied, but also that the variation had direct consequences for the evolution of complex life."

The Earth is 4,500 million years old. Microbial life has probably thrived in the oceans for most of that time. However, until about 2,300 million years ago, the atmosphere contained only traces of oxygen. During that time, some microbes in the oceans likely produced oxygen as a byproduct of photosynthesis. But the quantities they produced were insufficient to accumulate much in the atmosphere and oceans. The situation changed with the "Great Oxidation Event," 2,300 million years ago. Oxygen levels rose again around 550 million years ago. The first animals appear in the fossil record at this time, marking the beginning of an era that geologists call the "Phanerozoic" -- a Greek word meaning "evident animals." This new work explores how oxygen levels changed during the Phanerozoic.

The new study was led by Tais W. Dahl while he was a postdoctoral scholar at Harvard. Dahl spent several months in Anbar's lab at ASU during his graduate research learning how to make the necessary measurements from Gwyneth Gordon, Ph.D., who is also an author of this paper. Other authors include geochemist Don Canfield, Dahl's Ph.D. mentor at the University of Southern Denmark, and paleontologist Andrew Knoll, Dahl's postdoctoral mentor at Harvard.

Dahl returned to ASU to perform the measurements for this study, which involved measuring the relative amounts of different isotopes of the element molybdenum in rocks called "black shales." These rocks are formed from ancient ocean sediments.

Isotopes are atoms of an element, in this case molybdenum, that differ only in their mass and therefore can be easily distinguished from one another. Molybdenum has seven stable isotopes. Chemical reactions fractionate heavy from light isotopes. For example, carbon 12 is enriched by three percent in plants relative to the carbon in carbon dioxide in the atmosphere. Similarly, molybdenum isotopes are fractionated during their removal from seawater into ocean sediments. The magnitude of this fractionation is sensitive to the presence of oxygen.

The data Dahl obtained at ASU reveal that there were at least two stages of oxygenation during the Phanerozoic, separated by the oxygenation event 400 million years ago. This inference from molybdenum isotopes is corroborated by the appearance of large (up to 30 feet long) predatory fish in the fossil record 400 million years ago, coincident with the rise in oxygen. Animals of that size consume energy rapidly, requiring high levels of oxygen for their metabolism. "Tais's data indicate that early animals evolved in an environment with less oxygen than today," said Anbar. The newly discovered oxygenation event therefore explains the puzzling appearance of these fish in the fossil record. "It's always satisfying when we can demonstrate how an environmental change drove biological evolution," Anbar explained.

"But the real kicker is that these data also show us the reverse -- that biological innovation can drive environmental change" continued Anbar. He points to the fact that vascular plants also appear in the fossil record around 400 million years ago. The bodies of such plants decompose with difficulty, making it easier for organic carbon to be buried in sediments. When that happens, the organic carbon -- produced by photosynthesis -- is not available for reaction with oxygen. The consequence is a rise in the amount of oxygen in the environment.

"It's a push-me-pull-you situation," explained Anbar. The biological innovation of vascular plants led to more carbon burial, and therefore to more oxygen. Then, the rise in oxygen made it possible for larger animals to evolve. "This is a great example of what we call the "co evolution" of life and the environment," enthused Anbar "Geoscientists talk about this idea a lot, but we rarely find such nice examples."

This work was supported by the Danish National Research Foundation, Danish Council for Independent Research, the Swedish Research Council, the NASA Astrobiology Institute team at ASU and the NASA Exobiology Program.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Arizona State University, via EurekAlert!, a service of AAAS. The original article was written by Jenny Green.

Journal Reference:

T. W. Dahl, E. U. Hammarlund, A. D. Anbar, D. P. G. Bond, B. C. Gill, G. W. Gordon, A. H. Knoll, A. T. Nielsen, N. H. Schovsbo, D. E. Canfield. Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1011287107

84. First Marine Census Completed, Revealing a World of Wonders, Commercial Destruction

By John Collins Rudolf, The New York Times, October 4, 2010

After a decade of research and more than 540 ocean expeditions, scientists presented the world with the first-ever census of marine life on Monday. The census involved the work of 670 institutions and 2,700 researchers and made direct observation of 120,000 marine species, including some 6,000 newly discovered species.

“We’re like the people in London and Paris 200 years ago, putting together the first dictionaries and encyclopedias,” Jesse H. Ausubel, co-founder of the census project and a professor of environmental studies at the Rockefeller University in New York, said in an interview. “Ten years ago, there was simply no list anywhere of the world’s marine species.”

The project has conclusively overturned a once-common belief that the open ocean and deep seafloor were relatively barren. “There are no ocean deserts,” Mr. Ausubel said. “Everywhere we looked we found life.”

The census also documented the wide travels of some species, which can migrate thousands of miles across the globe, and rise and descend thousands of feet of ocean in a single day. The world’s polar oceans, meanwhile, were found to be important “incubators” for new species.

The project brings the estimate of known marine species to nearly 250,000, a figure that still represents only a fraction of the species that inhabit the seas. The full number of species could be nearly one million, researchers said. If microscopic life like bacteria and viruses are included, that number could be in the hundreds of millions, or billions.

One of the most remarkable new species uncovered by researchers during the census is the so-called “yeti crab” from the Pacific Ocean south of Easter Island, which features long, extravagantly furry claws.

“It looks like it’s wearing big white mittens that look like they belong in Aspen during ski season,” Mr. Ausubel said.

With the human influence on the oceans only accelerating, the marine census helps establish a baseline to judge the impact of industrial fishing, pollution and the changes brought about by steadily warming ocean waters.

Already, the abundance of most large species — from sea turtles to tuna — has dropped by 90 percent or more, the survey found.

“We hope that the 21st century will be the era of the great restoration of sea life,” Mr. Ausubel said.

==> For a New York Times slide show click here.

83. The Other Debt Crisis: Climate Debt

Bolivia has spearheaded a campaign to confront the climate change in the United Nations meetings.  It has also organized an international conference in April as an alternative venue for voices that were mostly sidelined or even barred from the UN meeting in Copenhagen last year.  Avi Lewis from Al Jazeera's Fault Lines traveled to Bolivia to explore its role in the climate change movement.  It is an informative show. Readers unfamiliar with the World People's Conference on Climate Change and the Rights of Mother Earth may want to visit its website and may want to  read my analysis of the Copenhagen conference. 

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Al Jazeera
Fault Lines 

The climate crisis in Bolivia is not a headline or an abstraction - it is playing out in people's lives in real time. Melting glaciers are threatening the water supply of the country's two biggest cities. Increasing droughts and floods are playing havoc with agriculture.

So it is no surprise that in climate negotiations, Bolivia is emerging as a leader in the global south - advancing both radical solutions and analysis that make rich countries distinctly nervous.

On this edition of Fault Lines, Avi Lewis travels to Bolivia to explore the country's climate crusade from the inside. 

82. The Search for Other Living Planets

In the final installment of David Attenborough's The Living Planet, he lets various voices air their view of the future of the Earth and its imperiled biodiversity. A zoologist, who is the director of a zoo in Florida, comments on the future of the tiger, as few are left in the wild.  She comforts her audience by declaring that tigers continue to live and breed in captivity.  She further suggests that it would be possible to freeze their DNA so that some day in the future, when it is possible to create a habitat for them on the moon, we can recreate a "wild habitat" for the tiger! 

Cosmologists have been searching for other planets that can sustain life for decades.  And once in a while a candidate is found.  As Stephen Hawking recently stated, it probable that our living planet, the Earth, is not alone.  This statement should not be taken lightly as the conditions that led to emergence of life on Earth are extremely improbable to assemble (see my posts about the Gaia Hypothesis and Biodiveristy).  But if it did happen on Earth, it could have happened in one or more of billions of other planets in the universe.  

However, the general attitude remains that human society can one day "colonize the space" (The Obama administration has already taken steps to privatize it) to allow room for the excess population, to search for new resource once those on the Earth are exhausted or if a nuclear war force the survivors to find a new home!   This sort of ideological madness should not be taken lightly. It create a false sense of the "long term" for the ruling elites and many ordinary folks who look to technology to save them from the worst.  How else can we explain the inaction of the world governments in the face of majority scientific consensus on the societal-caused climate change or continued decline of biodiversity? Or the passivity of even the more informed sectors of society?  

As one scientist pointed out--if you want to find life you need not peer into the night sky.  Just take the time to look all around on our home planet. It is full of life.  Alas many species are disappearing even before being discovered by us due to our social mode of existence.

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New Planet May Be Able to Nurture Organisms

by Dennis Overbye, The New York Times, September 29, 20101

It might be a place that only a lichen or pond scum could love, but astronomers said Wednesday that they had found a very distant planet capable of harboring water on its surface, thus potentially making it a home for plant or animal life.

Enlarge This Image

National Science Foundation and NASA

A planet, as depicted in this rendering, orbits the habitable zone of a star 20 light years from Earth, meaning it could have water on its surface.

Astrophyisical Journal

Nobody from Earth will be visiting anytime soon: The planet, which goes by the bumpy name of Gliese 581g, is orbiting a star about 20 light-years away in the constellation Libra.

But if the finding is confirmed by other astronomers, the planet, which has three to four times the mass of Earth, would be the most Earthlike planet yet discovered, and the first to meet the criteria for being potentially habitable.

“It’s been a long haul,” said Steven S. Vogt of the University of California, Santa Cruz, who, along with R. Paul Butler of the Carnegie Institution of Washington, led the team that made the discovery. “This is the first exoplanet that has the right conditions for water to exist on its surface.”

In a recent report for the National Academy of Science, astronomers declared the finding of such planets one of the major goals of this decade. NASA’s Kepler satellite — which was launched in March 2009 as a way to detect Earthlike bodies — is expected to harvest dozens or hundreds.

Gliese 581g (whose first name is pronounced GLEE-za) circles a dim red star known as Gliese 581, once every 37 days, at a distance of about 14 million miles. That is smack in the middle of the so-called Goldilocks zone, where the heat from the star is neither too cold nor too hot for water to exist in liquid form on its surface.

“This is really the first Goldilocks planet,” Dr. Butler said.

Other astronomers hailed the news as another harbinger that the search for “living planets,” as Dimitar D. Sasselov of the Harvard-Smithsonian Center for Astrophysics calls them, is on the right track.

“I’m getting goose bumps,” said Caleb Scharf of Columbia University.

But they expressed caution about this particular planet, noting uncertainties about its density, composition and atmosphere, and the need for another generation of giant telescopes and spacecraft in order to find out anything more about it. Other Goldilocks planets have come and gone in recent years.

The discovery was announced at a news conference Wednesday in Washington, and the findings have been posted on the National Science Foundation’s Web site and will be published in The Astrophysical Journal.

The authors said the relative ease by which planet was found — in only 11 years — led them to believe that such planets must be common.

“Either we have just been incredibly lucky in this early detection, or we are truly on the threshold of a second Age of Discovery,” they wrote in their paper.

Pressed during the news conference about the possibility of life on Gliese 581g, Dr. Vogt protested that he was an astronomer, not a biologist. Then he relented, saying that, speaking strictly personally, he believed that “the chances of life on this planet are almost 100 percent.”

Asked the same question, Dr. Butler squirmed and said, “I like data.” After a pause he added: “And what the data say is that the planet is the right distance from the star to have water and the right mass to hold an atmosphere. What is needed simply to find lots and lots of these things is lots and lots of telescope time.”

The latest results from Gliese 581 were harvested from observations by two often competing teams, using telescopes in Chile and Hawaii to measure the slight gravitational tugs the star gets as its planets swing by.

This is hardly the first time around the block for Gliese 581, which is a longtime favorite of planet hunters and now is known to have six planets in its retinue. It is a dwarf star about one-third the mass of the Sun and only about one-hundredth as bright, allowing planets to huddle closer to the campfire. “It hauntingly reminds us of our own solar system,” Dr. Butler said.

Two of Gliese’s planets have already had their moment in the limelight as possible Goldilocks planets. One, known as Gliese 581c, circles just on the inner edge of the habitable zone and was thus thought to be habitable three years ago. But further analysis suggested that the greenhouse effect would turn it into a stifling hell. Another planet, just on the outer edge of the Goldilocks zone, is probably too cold.

“One is on the hot side, the other is on cold side,” and the new planet is right in between, Dr. Vogt said. “It’s bookended.”

He and his colleagues estimated the average temperature on the surface of Gliese 581g to be between 10 and minus 24 degrees Fahrenheit, about the same as a summer day in Antarctica.

But that means very little, he said, because the planet, like all the others in that system, keeps the same face to the star all the time. So the temperature could vary wildly from the day-side to the night-side of the planet, meaning that an organism could perhaps find a comfortable zone to live in.

But nobody really knows what is going on on Gliese 581g, said Sara Seager, a planetary astronomer at the Massachusetts Institute of Technology. “If it was all carbon dioxide, like Venus, it would be pretty hot,” she said, adding that she would give the planet a 90 percent chance of holding water.

That, she pointed out, is faint praise in scientific circles. “Sounds high, but would you fly on a plane that only had an 8 or 9 chance out of 10 of making it?” she asked.

“Everyone is so primed to say here’s the next place we’re going to find life,” Dr. Seager said, “but this isn’t a good planet for follow-up.”

81. Billions Face Water Insecurity, Study Finds

By Richard Black, BBC, September 29, 2010

About 80% of the world's population lives in areas where the fresh water supply is not secure, according to a new global analysis.

Researchers compiled a composite index of "water threats" that includes issues such as scarcity and pollution.

The most severe threat category encompasses 3.4 billion people.

Writing in the journal Nature, they say that in western countries, conserving water for people through reservoirs and dams works for people, but not nature.

They urge developing countries not to follow the same path.

Continue reading the main story

“Start Quote

What we're able to outline is a planet-wide pattern of threat”

Charles VorosmartyCity College of New York

Instead, they say governments should to invest in water management strategies that combine infrastructure with "natural" options such as safeguarding watersheds, wetlands and flood plains.

The analysis is a global snapshot, and the research team suggests more people are likely to encounter more severe stress on their water supply in the coming decades, as the climate changes and the human population continues to grow.

They have taken data on a variety of different threats, used models of threats where data is scarce, and used expert assessment to combine the various individual threats into a composite index.

The result is a map that plots the composite threat to human water security and to biodiversity in squares 50km by 50km (30 miles by 30 miles) across the world.

Changing pictures

"What we've done is to take a very dispassionate look at the facts on the ground - what is going on with respect to humanity's water security and what the infrastructure that's been thrown at this problem does to the natural world," said study leader Charles Vorosmarty from the City College of New York.

"What we're able to outline is a planet-wide pattern of threat, despite the trillions of dollars worth of engineering palliatives that have totally reconfigured the threat landscape."

Those "trillions of dollars" are represented by the dams, canals, aqueducts, and pipelines that have been used throughout the developed world to safeguard drinking water supplies.

Their impact on the global picture is striking.

Continue reading the main story

Natural Managed

Looking at the "raw threats" to people's water security - the "natural" picture - much of western Europe and North America appears to be under high stress.

However, when the impact of the infrastructure that distributes and conserves water is added in - the "managed" picture - most of the serious threat disappears from these regions.

Africa, however, moves in the opposite direction.

Continue reading the main story

Related stories

• Water - another global 'crisis'?
• Mapping future water stress
• Water policies suffer sinking feeling

"The problem is, we know that a large proportion of the world's population cannot afford these investments," said Peter McIntyre from the University of Wisconsin, another of the researchers involved.

"In fact we show them benefiting less than a billion people, so we're already excluding a large majority of the world's population," he told BBC News.

"But even in rich parts of the world, it's not a sensible way to proceed. We could continue to build more dams and exploit deeper and deeper aquifers; but even if you can afford it, it's not a cost-effective way of doing things."

According to this analysis, and others, the way water has been managed in the west has left a significant legacy of issues for nature.

Whereas Western Europe and the US emerge from this analysis with good scores on water stress facing their citizens, wildlife there that depends on water is much less secure, it concludes.

Concrete realities

One concept advocated by development organisations nowadays is integrated water management, where the needs of all users are taken into account and where natural features are integrated with human engineering.

One widely-cited example concerns the watersheds that supply New York, in the Catskill Mountains and elsewhere around the city.

Continue reading the main story

“Start Quote

We would argue people should be even more worried if you start to account for climate change and population growth”

Peter McIntyreUniversity of Wisconsin

Water from these areas historically needed no filtering.

That threatened to change in the 1990s, due to agricultural pollution and other issues.

The city invested in a programme of land protection and conservation; this has maintained quality, and is calculated to have been cheaper than the alternative of building treatment works.

Mark Smith, head of the water programme at the International Union for the Conservation of Nature (IUCN) who was not involved in the current study, said this sort of approach was beginning to take hold in the developing world, though "the concrete and steel model remains the default".

"One example is the Barotse Floodplain in Zambia, where there was a proposal for draining the wetland and developing an irrigation scheme to replace the wetlands," he related.

"Some analysis was then done that showed the economic benefits of the irrigation scheme would have been less than the benefits currently delivered by the wetland in terms of fisheries, agriculture around the flood plain, water supply, water quality and so on.

"So it's not a question of saying 'No we don't need any concrete infrastructure' - what we need are portfolios of built infrastructure and natural environment that can address the needs of development, and the ecosystem needs of people and biodiversity."

Dollars short

This analysis is likely to come in for some scrutiny, not least because it does contain an element of subjectivity in terms of how the various threats to water security are weighted and combined.

"This study, for the first time, brings all our knowledge together under one global model of water security and aquatic biodiversity loss."Nevertheless, Mark Smith hailed it as a "potentially powerful synthesis" of existing knowledge; while Gary Jones, chief executive of the eWater Co-operative Research Centre in Canberra, commented: "It's a very important and timely global analysis of the joint threats of declining water security for humans and biodiversity loss for rivers.

For the team itself, it is a first attempt - a "placeholder", or baseline - and they anticipate improvements as more accurate data emerges, not least from regions such as Africa that are traditionally data-scarce.

Already, they say, it provides a powerful indicator that governments and international institutions need to take water issues more seriously.

For developed countries and the Bric group - Brazil, Russia, India and China - alone, "$800bn per year will be required by 2015 to cover investments in water infrastructure, a target likely to go unmet," they conclude.

For poorer countries, the outlook is considerably more bleak, they say.

"In reality this is a snapshot of the world about five or 10 years ago, because that's the data that's coming on line now," said Dr McIntyre.

"It's not about the future, but we would argue people should be even more worried if you start to account for climate change and population growth.

"Climate change is going to affect the amount of water that comes in as precipitation; and if you overlay that on an already stressed population, we're rolling the dice."