The IPCC’s new summary report has been released: “Climate Change 2013. The physical science basis“. The publication is available for free downloading or online reading. Probably the most significant conclusion of the study is that scientists are 95% certain that human activity is responsible for the ongoing episode of recent global warming. The details of the document cover the mechanics of greenhouse gas-driven warming given updated emissions data, and the physical consequences, including warming air temperatures, changes in precipitation (mostly rainfall), sea level rise, and other ocean changes. The report also explores predicted changes to biogeochemical cycles, the all-important pathways through which living systems interact with, influence and are influenced-by the physical and chemical environments.
So now the real work begins in a sense. Given this state-of-the-art report, it will now be up to biologists, economists, sociologists, policy makers and others to translate these findings and predictions of the physical world into impacts on the living world, including our human society. These will be challenging efforts, but necessary if we are to then move onto the next steps of formulating solutions, both mitigative and adaptive. Further down the road, and of particular personal scientific interest, will be studies to figure out how changes to the living world, both naturally driven and perhaps also based on human decisions, will feed back into the physical world. The work never ends!
Giving Out Corn to the People, During a Season of Scarcity.”: Chinese officials engaged in famine relief. Detail of engraving by G. F. Sargent.
I recently wrote a commentary on Erle Ellis’ op-ed in the NY Times, addressing human overpopulation, food, and ecosystems. I found it to be a rather poorly constructed article, and addressed it in my Food Weblog. Here is the full response: Overpopulation? No Problem!
“Tipping point” has become a part of modern jargon, referring to a sudden change in the state of a system (e.g. an explosive disease outbreak) in response to an external driving force (or “control parameter” in scientific jargon). There is a considerable body of mathematics underlying this jargon, and we can identify four key features of systems that possess tipping points. First, the driving force can be applied incrementally over a broad range of intensities and result in little change to the system. This can be caused by a natural resistance of the system to change, or resiliency so that after being disturbed the system returns to its pre-disturbance state. Second, there is a point at which the next incremental change of the controlling parameter results in a significant change in the system’s state. The straw has broken the camel’s back and the system “tipped”. Response to the driving force changed either because the intensity of the driver can now overcome the internal resistance or resiliency of the system, or had eroded it incrementally, setting in motion previously inert or insignificant processes. Alternatively, the intensity of the driver can be reduced to a point where internal processes become more effective controllers, rendering the driver ineffective. Third, the intensity of the disturbance at which the system tips differs according to whether intensity is increasing or decreasing. In other words, if you added 10 kg to tip your scale, you would have to remove more than 10 kg to regain balance! Finally, two similar states can nevertheless be divergent in their responses, i.e. are sensitive to initial conditions.
Tipping points in many physical systems are well understood and find application in physics and engineering. In other real-life situations with apparent tipping points, however, such as disease outbreaks, or socio-political upheavals, analysis is more difficult. Difficulties stem from an incomplete identification and understanding of the driving factors, limits on the precision with which those factors can be measured, and complex interactions among multiple drivers and the system’s state. Therefore, when change occurs, it often surprises.
Why then do some scientists argue that the biosphere is approaching a tipping point? Specifically, why identify population size and resource consumption as controlling parameters? Because the effective drivers that result from those parameters, e.g. climate change and ecosystem disruption, have caused biosphere transitions in the past, and are themselves capable of dramatic transitions. For example, there is considerable concern that the consequences of ongoing global warming will be manifested as sudden shifts in climatic regimes rather than gradual transitions[7]. Climate change in the geologic past altered the biosphere in diverse ways, including extinctions and outbursts of evolutionary diversification. Another agent of ancient biosphere transformation was planetary or ecosystem primary productivity. Primary productivity is the energy converted to food by plants and other photosynthesizers. Large increases of primary production in the past, fertilized by various processes such as volcanism, were associated with increases of biological richness and ecological diversity. Large disruptions or decreases of this energy supply, however, linked to events such as asteroid impacts, climate change and oceanographic changes, are associated with regional to global ecological collapses and extinctions[8]. Humans today utilize or influence 24-41% of global primary production through the agricultural cultivation of a rather low diversity of species and the direct utilization or alteration of productive terrestrial systems[9,10]. In the oceans, where microscopic organisms are responsible for up to 50% of the Earth’s primary production, there is growing concern about the effects of increasing ocean temperatures and acidity. More directly, when we reduce the amount of space available to species or biological communities, or reduce the connectivity among those spaces, the result is extinction or community collapse. Thus, despite difficulties inherent to predicting tipping points in a system as complex as the global biosphere, there is sufficient evidence at both long time scales and small spatial scales that the biosphere is capable of such transitions, and sufficient reason to be concerned. An important question then is, as we increase the amount of the biosphere affected by humans, will local and regional collapses interact synergistically to result in global collapse? Counterintuitively, potential solutions emerge when we acknowledge the fundamental roles of human population size and resource consumption.
[7] Lenton, T. M. et al. 2008. Tipping elements in the Earth’s climate system. Proceedings of the National Academy of Sciences, 105: 1786-1793.
[8] Roopnarine, P. D. 2006. Extinction cascades and catastrophe in ancient food webs. Paleobiology, 32: 1-19.
[9] Haberl, H. et al. 2007. Quantifying and mapping the human appropriation of net primary production in Earth’s terrestrial ecosystems. Proceedings of the National Academy of Sciences, 104: 12942-12947.
[10] Roopnarine, P. D. 2008. Ecological Informatics: Catastrophe Theory. Encyclopedia of Ecology, Elsevier Press. p. 531-536.
The historical and lifetime experiences of humans accustom us to regularities in the Earth’s dynamics; e.g., tides ebb and flow, and species migrate annually. Civilizations, past and present, have always depended on those regularities. Disruptive episodes or events can sometimes be forecast, e.g. quasi periodic droughts, or they may come as a surprise, e.g. earthquakes. Our concern about those events depends on their frequencies, intensities, and purely psychological factors [2]. For example, massive earthquakes (moment magnitude 8.0 or greater) occur infrequently in densely populated areas, but past experience at local to regional scales makes them important to humans. Events that transform the entire biosphere, on the other hand, lie outside human historical experience, and our knowledge of them comes from the geological and fossil records. Those ancient events were driven by physical factors, ranging from massive volcanism to asteroid impacts to orbital fluctuations. They also have biological feedbacks, exemplified in the ice ages of the past 2.5 million years, in which the biologically-based carbon cycle controlled atmospheric levels of the greenhouse gas carbon dioxide. Mass extinctions are commonly associated with those events, such as the end Permian extinctions of 251 million years ago, when approximately 90% of Earth’s species became extinct [3] as a consequence of extensive Siberian volcanism, or the end Cretaceous asteroid impact of 65 million years ago, when roughly 70% of species became extinct [4]. The most recent global transformation occurred just 12,500 years ago at the end of the last ice age, when climate change and human expansion (Note: and possibly a meteor impact) caused the extinction of many large terrestrial animals [1]. Natural recurrence of any of those Earth-transforming events in the nearfuture is of low probability. For example, eruption of the Toba supervolcano in Sumatra 26,500 years ago, brought our own species to the brink of extinction (Note: but see), but the probability of a similar eruption in the next 50 years is estimated to be 0.1% or less [2].
Today the Earth is undergoing another transformation, with consequences for both biological diversity and human well-being, but this time humans are the agents of change. The ways in which we are transforming the planet are diverse, including: anthropogenic global warming; landscape alteration, fragmentation and destruction; species over-exploitation; pollution; and invasive species. Underlying all these factors, however, are two fundamental parameters of modern human society; population size and resource consumption. All other factors stem from the effects of a burgeoning global population and increased resource consumption. Needless to say we must continue to mitigate and perhaps halt our transformation of the atmosphere, species over-exploitation and landscape destruction, but these will bring temporary reprieves at best. As long as global population and resource consumption continue to increase, their effects will be translated into biosphere-transforming factors. Complicating the search for, and implementation of solutions are the feedbacks and synergistic relationships among the transforming factors (including population size and resource consumption). For example, clearing land for agriculture to feed a growing population is sometimes followed by a loss of vital ecosystem services, such as clean water, soil conservation and firewood production, prompting further clearing, the concentration of populations into denser collectives, and the importation of basic consumables such as water and fuel. Interestingly, the relationship between population size and resource consumption is a largely independent one! There is of course a base level of resource consumption necessary to sustain a population of any given size, though I suspect that the level is rather low and would not meet everyone’s expectations of a decent standard of living (imagine a gulag). Beyond that base level, resource consumption is mostly a matter of choices, and the biosphere transforming choices that we make often either have little to do with population size, or have an indirect connection. One simply looks to history’s record of over-exploited and exhausted resources, which predates the exponential increase of global population size which began in the 19th century. Plato bemoaned the final deforestation of Attica in the 5th century BCE [5], which fueled Athen’s silver mines. The Atlantic Gray Whale was extinct by the beginning of the 19th century CE after being whaled by coastal communities since at least the 16th century [6].
The relationship between population size and consumption is therefore an irregular one, based as much on socio-economic context, social norms and societal goals, as it is on need. Our current problems are generated by levels of resource consumption that either remain fixed or grow as population size increases. Drivers of negative biosphere transformation are thus created and exacerbated. The complexity of natural systems, such as climate or ecosystems, as well as the nonlinearity of their internal processes, raises the possibility that any such transformation could come as a tipping point, rather than gradually and incrementally. The irregularity of the population size-resource consumption relationship, however, also raises hope for avoiding, or at least adapting to, the transformation.
[1] Barnosky, A. et al. 2012. Approaching a stateshift in Earth’s biosphere. Nature 486:5258.
[2] Smil, V. 2008. Global Catastrophes and Trends. The MIT Press, Cambridge, USA. 307p.
[3] Chen, Z. And M. J. Benton. 2012. The timing and pattern of biotic recovery following the end Permian mass extinction. Nature Geoscience, 5: 375383.
[4] Schulte, P. et al. 2010. The Chicxulub asteroid impact and mass extinction at the Cretaceous Paleogene boundary. Science, 327: 12141218.
[5] Hughes, J. D. And J. V. Thirgood. 1982. Deforestation, erosion, and forest management in Ancient Greece and Rome. Journal of Forest History, 26: 6075.
[6] Bryant. P. J. 1995. Dating the remains of gray whales from the eastern North Atlantic. Journal of Mammalogy, 76: 857861.
I recently published a chapter in a book, Meer!, edited by Dutch parliamentarian, Marianne Thieme. Here is a summary (translated; my apologies) from the publisher, Uitgeverij Jan van Arkel:
MORE! has become the central theme of our society: more of everything and more than there is. In the last decades of unprecedented prosperity, the belief has taken hold that the growth of our economy is not only boundless, but also a prerequisite for happiness and prosperity. Where economics was once the science of the production and distribution of scarce goods, it has at the end of the 20th century turned into an exclusive focus on money and monetary issues. The systemic crisis that presented itself in 2008 as a banking crisis, is now clearly a monetary crisis and it is clear that we also have the biodiversity crisis, the climate crisis, the world food crisis and other scarcity problems that prosperity and well-being threatening to the core.
The book brought together a number of scientists, and asked us to contribute our views on the current econo-environmental crises facing the world, the sources of the crises, possible outcomes, and potential solutions. I will present an English version of my contribution over the next few posts on this blog. My chapter is entitled, “Tipping the Biosphere”. Here is the Introduction.
TIPPING THE BIOSPHERE
Peter D. Roopnarine
Department of Invertebrate Zoology & Geology, California Academy of Sciences, 55 Music Concourse Drive, San Francisco CA 94118 USA
The global biosphere comprises the Earth’s living organisms, their interrelationships, and their ecosystems. Any assessment of the biosphere’s state or condition includes at least the number of species on the planet (richness), their ecological diversities, i.e. the ways in which they make their livings, and the number of ecosystems into which richness and diversity are organized. When considering human well-being, measures of biosphere condition should also include the types and magnitudes of services provided to humans by the biosphere, such as renewable natural resources, and the types and magnitudes of human impacts on the biosphere. The state of the biosphere and human well-being have become inextricably intertwined over the course of human history, both as the ways in which humans use the natural world have become more diverse and increasingly sophisticated, and as the number of humans, all of whom depend ultimately on the biosphere for survival, has increased exponentially. The negative impacts of humans on the biosphere are today evident everywhere, from heavily urbanized areas to remote stretches of the open ocean, and there can be no doubt that we are transforming the planet. Of particular concern to many scientists is the possibility that increasing human pressure on the planet’s natural systems and resources is rapidly transforming it to a state of decreased richness and ecological diversity. A biosphere so transformed would represent a loss of adaptive evolutionary potential, as well as the reduction and loss of ecosystem services and other dependencies to human well-being. Of equal concern is the possibility that the transformation will not unfold smoothly and incrementally, but will instead behave as a tipping point, where the biosphere will transition rapidly between states [1].
[1] Barnosky, A. et al. 2012. Approaching a state-shift in Earth’s biosphere. Nature 486:52-58.
From Science Today: “Recently, researchers discovered other effects of acidification on oysters and what the breakdown of the oysters’ calcium carbonate shells could mean for the acidic balance. Science Today sat down with the Academy’s own oyster expert, Dr. Peter Roopnarine, curator and chair of Invertebrate Zoology and Geology, to get some perspective on these recent studies.”
The following is a guest post by Darko D. Cotoras Viedma.
Imagine that somehow you have the chance to travel to the future. A time when you will be alone on this planet and humanity is part of a history that nobody will read. Your mission is to do a biodiversity inventory and try to answer one question: What was the signature of the presence of humans on Earth?
Enclosed on its natural environment the endangered Mauna Kea silversword (Argyroxiphium sandwicense subsp. Sandwicense) is protected with a fence from introduced feral animals. South slope of Mauna Kea. Big Island, Hawai’i.
Right before that future, humanity never took real responsibility for the environment. It centered its efforts on promoting a strongly industrial development which deepened social inequalities. However, this didn’t affect every aspect of life. The interest in market expansion favored the worldwide access to a whole “family” of products and services associated mostly with entertainment and luxury. Immediate desires related to those things could be satisfied in the same way pretty much anywhere in the world. In that sense the world became more “equal”.
As many science fiction authors predicted, the world became dominated by big corporations. In some places it was easier to get access to their products and services than to any other basic needs. Also the movement of people became extremely easy; the average person lived in three different cities during his/her life and one third of world’s population owned a second house.
Humanity gained complete independence from seasonality and weather. Everybody could get any kind of vegetable or fruit year around. Cities were founded in the middle of the deserts or deep in jungles. But, this way of life couldn’t last for long. When it spread to the entire world it was a matter of a century to reach a point of no return. Hundreds of thousands of years after that event your mission starts.
The first thing you notice is the reduction in species diversity. The long announced “Sixth mass extinction” happened and an important part of the biological patrimony was lost forever. In some cases whole branches of the Tree of Life were lost, while in others only some species. But, what really commanded your attention were the survivors. You expected to find hundreds of different species that evolved from the wide spread agricultural plants and animals, however they were all extinct. The domestication of these organisms made them absolutely dependent on us. On the other hand, other organisms dispersed unintentionally by humans had the distribution pattern you expected. The New World was populated by many new species of grasses coming from Europe, while the islands in Oceania were full of new species of rats, geckos and land snails coming from Africa, South America and Asia.
At the same latitude most of the low elevation environments had a similar biodiversity. The same thing happened in shallow waters in the ocean. Everywhere between 100 meters below to 1,500 meters above sea level, you were able to describe a very well defined biological community, the “Human-impacted community”. Interestingly within this community you found some species originally endemic to those very areas. They are the result of past human conservation efforts. Somehow, by establishing biological interactions with all the rest of introduced species they managed to survive.
Outside of the “Human-impacted community” there is another kind of survival species. Those areas weren’t affected directly by humans, but because of global changes extinctions also occurred. The survival species then had very small population sizes restricted to reduced patches of habitat in comparison to their original distributions.
At some point, standing in the middle of what once was a city you look around and only see an extensive forest, a forest comprised of species that initially were on the sidewalks of the streets or in the backyards of houses. This forest is replicated in all the former cities at this latitude, but now after thousands of years, each one has its own species that evolved from once widely spread ornamental plants.
The world you saw in the future was definitely a different place. Somehow less diverse, somehow more diverse. The same as five times before, life was able to recover from a cataclysmic event. After a period of exponentially rapid change, ecosystems evolved into a new configuration that was stable over units of geologic time.
In a geologic perspective it seems clear that life followed its own course. The main consequences of our activities affected us and the unfortunate species that happened to co-exists with us. The preservation of the environment it is not only a problem of sustainability for our own benefit, it is also a matter of respect for others and I am not talking about other humans.
Darko on Molokai
Darko Cotoras, originally from Chile, is a Ph.D. candidate in the Integrative Biology dept at UC Berkeley. He is interested in the historical processes that shape biodiversity, in particular on insular environments. For his dissertation he is studying the temporal dynamic of the adaptive radiation of an endemic group spiders (genus Tetragnatha) from the Hawaiian archipelago. He has also researched terrestrial invertebrates on the Juan Fernández Islands and Rapa Nui.
We celebrate Endangered Species Day on May 18th. We have reasons to celebrate because though human activities have many species on the brink of annihilation, there is serious commitment ranging from individuals to nations states to both protect those species, and to bring them back from the brink. Nevertheless, the threats to species are growing in number and severity. The following essay will not be cheery, and I hope to convince you that avoiding extinction is a very difficult problem and its consequences are severe. I will therefore begin with the optimistic message: The fact that we humans are the cause of the current species crisis is reason to be hopeful. We cannot save species from devastating physical events such as asteroids and volcanoes, but we can save them from ourselves.
It is well known, based on the fossil record, that the majority of species that have ever existed are now extinct. That’s why you will often hear the phrases, “99% of all species that have ever existed are extinct”, and “extinction is the fate of all species”. Let’s examine these statements for a moment. The first is a somewhat factual measure. No one knows if 99% is the correct figure, but we do know that most species that have ever evolved are now extinct. The reason that the Earth is still teeming with millions of species is, of course, because new ones evolve all the time. The second statement is a bit more problematic though; it’s an assumption, not an observation. To scientifically predict the fate of a thing is to presume that we know and understand all the forces controlling it, and that we know what those forces will do in the future. That of course is certainly not the case here. Even more problematic is the fact that even though changing conditions might cause the extinction of a species, changing conditions also drive evolution! In a sense then, extinction is an evolutionary failure. Okay, it’s not quite that simple, but here’s what I mean. Under what circumstances does evolution fail and lead to extinction?
Such cool headgear (Wikipedia)
Imagine that you are lucky enough to be a spectacular dinosaur living somewhere on the planet 65 million years ago (some of you know what’s coming…). You are the culmination of archosaurian evolution which got started some 175 million years before, in the wake of the devastating end Permian mass extinction. Unfortunately for you, today is the day that a giant asteroid from outer space collides with the Earth somewhere in the vicinity of today’s Yucatan Peninsula. The energy released by the collision is some 19,000 times greater than the explosive force of the world’s current nuclear weapons arsenal. The survival of your species depends on enough of its members surviving the ensuing environmental catastrophe, and that could happen in two ways. First, you could have the individual capacity to acclimatize to the changes happening around you. For example, it’s possible that many animals survived by taking advantage of underground dwellings, or their abilities to enter into some sort of resting phase. Second, your species could adapt to the changes. In either case, evolution is at work. The capacity to acclimatize is generally a function of the physiology, behaviors and so on that evolved in your ancestry, while adaptation is the result of current genetic variation and natural selection. Extinction will occur if the magnitude or severity of the environmental changes overwhelm your capacity to acclimatize, or your species’s capacity to adapt (e.g. limited genetic variation) or the rate at which it can adapt. Sadly, non-avian dinosaurs neither acclimatized nor adapted, and today exist only as fossils or in the movies. This has happened repeatedly during the history of life. The end Permian mass extinction of 251 million years ago resulted from overwhelming changes of climate, ocean conditions and atmospheric composition. Ultimately, it was driven by massive volcanism in the Siberian region. The mass extinction 65 million years ago was also the result of significant changes in climate, driven by massive volcanism in India’s Deccan region, coupled with that rock from outer space. That collision would have heated large regions of the North American continent, darkened the skies for months, and subsequently cooled the planet for years.
Today the Earth is on the brink of another mass extinction, but this time we humans are the volcanoes and asteroids. Driven by an exploding population and rapidly increasing rates of resource consumption, we are sequestering landscapes and habitats or destroying them outright, over-exploiting wild species, and changing the climate at rates that overwhelm the ability of species to acclimatize or adapt. Climate change is by far the most dangerous of the bunch because while we can confer protection from exploitation on landscapes and species, we cannot protect them from changing temperatures, seasons, patterns of rainfall and ocean acidification. Even as we work to curb our climate-changing habits by developing alternatives to fossil fuels, engineering more efficient transportation systems and planning our own socio-economic adaptations, species must also acclimatize and adapt. This will be accomplished either by species movement to track favourable climates, or staying put and acclimatizing and adapting. Unfortunately, there are severe limitations to each.
There is no doubt that many species are now on the move in response to climate change. Most pronounced are expanding ranges of many tropical or warm temperate species as tropical air and water temperatures expand outward from the equator. Examples include the Humboldt squid, normally restricted to waters of the tropical and south eastern Pacific, but is now a frequent and abundant species in waters as far north as Alaska. The increasing incidence of normally tropical diseases such as West Nile virus are also testimony to increasingly favourable conditions in regions that were previously too cool. Habitat expansion for those species occurs at the expense of other habitats of course. Regions of cooler temperatures are shrinking, leaving no room for migration of the species there. In alpine regions many species are moving upward, but of course can go no higher than the highest mountains. Polar species are not only faced with changing habitats, such as the drastic reductions of summer ice coverage in the Arctic Ocean, but must deal with the newcomers from warmer regions. And therein lies the another limitation. Given the rate at which conditions are changing, on a timescale of decades, there is absolutely no guarantee that a species will have the genetic capacity to evolve and adapt rapidly enough to survive. For scientists, the answer will in many cases be a wait and see experiment. The results will no doubt be intriguing and valuable, but that will be small comfort for any species that come up short.
There is a final limitation, and that’s based on relationships. No species exists in isolation, humans included. Every species interacts with other species and is dependent on other species for survival. That’s how we evolved! Species adapt to changing conditions, and in turn their new adaptations alter the world around them. We are united in a gigantic global network of biological relationships which includes production, predation, competition, parasitism, reproductive services, habitat engineering, and recycling. When species move, when they change, some of those relationships are disrupted. Even now we see the synchrony of spring flowerings, fruitings, nesting etc. becoming de-synchronized. And these relationships are not formed on the fly! They are the evolutionary result of species interactions occurring over time, and indeed the systems or networks that they produce are likewise products of evolution. In studies by myself and colleagues (see Further Resources below) of ecosystems in the wake of the end Permian mass extinction, we found that while the number of species recovered very quickly within a million years of the extinction, the networks of relationships so formed were unstable and weak. It took several million more years before system robustness recovered to pre-extinction levels. And during that time, the dominant vertebrates of the land, the ancient relatives of humans and other mammals, were eclipsed by the rise of the dinosaurs. They would have to wait another 175 million years before another opportunity for dominance would present itself. Those timescales would try the most patient of humans.
So what do we do? I believe that we must become better stewards of the planet. I know that some will argue that we should not be stewards at all, but consider this. Humans already occupy to varying extents some 48% of the planet’s dry surface and we directly utilize or otherwise co-opt 24-41% of global photosynthetic production. We are already stewards of the planet! The real problem is that we are rather poor stewards. We either absolve ourselves collectively of this responsibility or we embrace it. The choice is ours, and the fates of an uncounted number of species now depend on us. Therefore, let us indeed celebrate Endangered Species Day, for while it is a reminder of the dire state of our environment, it also recognizes our acceptance of an awesome responsibility.
Further Resources
Some of these are fairly technical (sorry!), but please feel free to submit any and all questions.
News from Nature.
“Global average temperatures are now higher than they have been for about 75% of the past 11,300 years, a study suggests. And if climate models are any indication, by the end of this century they will be the highest ever since the end of the most recent ice age.”
It’s no longer news that warming temperatures are not the only negative consequence of the increasing concentrations of atmospheric greenhouse gases. Add increased weather variance, changing rainfall patterns and sea level rise to the list. One of the most dire impacts, however, and one that seems to be rather inescapable, is ocean acidification. Ocean waters become more acidic as the amount of carbon dioxide dissolved in the water increases. This has been happening as the amount of carbon dioxide in the atmosphere has been increasing. The oceans have a tremendous capacity to absorb carbon dioxide, but we are rapidly exhausting that capacity. When the gas dissolves in seawater, it triggers a complicated set of reversible chemical reactions, sort of chain from carbon dioxide, to carbonic acid, to bicarbonate and hydrogen ions, to carbonate and more hydrogen ions. Normally, the system is driven toward the carbonate end of things, resulting in very moderate acidity (high pH, which is a measure of the concentration of reactive hydrogen ions in the water), and conditions suitable for the precipitation of carbonate minerals, most notably calcium carbonate. Calcium carbonate is the material used most commonly by marine organisms for building skeletons, for example animals such as corals, snails, clams, and numerous microscopic plankton. One of the great dangers that we face as the oceans become more acidic is that all these organisms, and the ecosystems that they are parts of, will decline.
The Science Today team at the California Academy of Sciences recently produced a very nice short video discussing these topics. View the full video, and leave comments here, or for the Sci Today team!
