THE DEFINITIVE BLOG FOR EVERYTHING YOU NEED TO KNOW ABOUT THE ENVIRONMENT YOU LIVE IN, WITH REFERENCE TO LIFE, EARTH AND COSMIC SPACE SCIENCES, PRESENTED BY ENVIRONMENTAL ENGINEER DORU INDREI, ENVIRONMENTAL QUALITY AND ENERGY SPACIALIST
"Life is not about what we know, but what we don't know, craving the unthinkable makes it so amazing, that is worth dying for."Doru Indrei
In itself, not much: Seven billion is just a one-digit flicker from 6,999,999,999. But the number carries a deep existential weight, symbolising themes central to humanity's relationship with the rest of life on Earth.
For context, let's consider a few other numbers. The first: 10,000. That's approximately how many homo sapiens existed 200,000 years ago, the date at which scientists mark the divergence of our species from the rest of homo genus, of which we are the sole survivors.
From those humble origins, humans -- thanks to our smarts, long-distance running skills, verbal ability and skill with plants -- proliferated at an almost inconceivable rate.
Some may note that, in a big-picture biological sense, humanity has rivals: In total biomass, ants weigh as much as we do, oceanic krill weigh more than both of us combined, and bacteria dwarf us all. Those are interesting factoids, but they belie a larger point.
Ants and krill and bacteria occupy an entirely different ecological level. A more appropriate comparison can be made between humans and other apex predators, which is precisely the ecological role humans evolved to play, and which -- beneath our civilised veneer -- we still are.
According to a back-of-the-envelope calculation, there are about 1.7 million other top-level, land-dwelling, mammalian predators on Earth. Put another way: For every non-human mammal sharing our niche, there are more than 4,000 of us.Environment Clean Generations
In short, humans are Earth's great omnivore, and our omnivorous nature can only be understood at global scales. Scientists estimate that 83 per cent of the terrestrial biosphere is under direct human influence. Crops cover some 12 per cent of Earth's land surface, and account for more than one-third of terrestrial biomass. One-third of all available fresh water is diverted to human use.
Altogether, roughly 20 per cent of Earth's net terrestrial primary production, the sheer volume of life produced on land on this planet every year, is harvested for human purposes -- and, to return to the comparative factoids, it's all for a species that accounts for .00018 per cent of Earth's non-marine biomass.
We are the .00018 per cent, and we use 20 per cent. The purpose of that number isn't to induce guilt, or blame humanity. The point of that number is perspective. At this snapshot in life's history, at -- per the insights of James C. Rettie, who imagined life on Earth as a year-long movie -- a few minutes after 11:45 pm on 31 December, we are big. Very big.
However, it must be noted that, as we've become big, much of life had to get out of the way. When modern Homo sapiens started scrambling out of East Africa, the average extinction rate of other mammals was, in scientific terms, one per million species years. It's 100 times that now, a number that threatens to make non-human life on Earth collapse.
In regard to that number, environmentalists usually say that humanity's fate depends on the life around us. That's debatable. Humans are adaptable and perfectly capable of living in squalor, without clean air or clean water or birds in the trees. If not, there wouldn't be 7 billion of us. Conservation is a moral question, and probably not a utilitarian imperative.
But the fact remains that, for all of humanity to experience a material standard of living now enjoyed by a tiny fraction, we'd need four more Earths. It's just not possible. And that, in the end, is the significance of 7 billion. It's a challenge.
In just a few minutes of evolutionary time, humanity has become a force to be measured in terms of the entirety of life itself. How do we, the God species, want to live? For the answer, check back at 8 billion.
Environmentalists agree on the issues facing us, including collapsing diversity, climate change and resource insecurity. We also agree on the causal factors, including pollution, invasive species, resource over-exploitation, waste, population growth, global industrialisation, unsustainable consumption and poor business practices. Solutions are harder. None will solve all our problems and all face obstacles and opposition. Environment Clean Generations
Technological solutions, such as biofuels, fracking, shale oil, GM foods and nuclear have side effects, while renewables have limited scope. Environmentally conscious lifestyles, including less waste, travel and consumption, are increasingly adopted, but the impact may by limited given the billions seeking to improve their low living standards. Changes to corporate and governmental practices have occurred, but are far from universal, particularly in the developing world.
In my lifetime, human numbers have grown from 3 billion in 1960 to 7 billion today. By 2085, they are projected to grow to 10 billion. One can argue about the impact this makes, but it clearly does not help. We believe that a smaller population would help us to preserve the environment and live within the limit of renewable resources, as part of a comprehensive approach to the environment and sustainability. Environment Clean Generations.Most would agree that improving living standards for the poor, women’s rights and access to health, including family planning, are desirable and they all tend to lead to women choosing to have smaller families. We would argue that aid for family planning to developing countries should be prioritised, both for environmental reasons and because it contributes to poverty alleviation, women’s empowerment and better health. While individual consumption in those countries is low, growing populations do affect the environment and they will not always be poor as the world industrializes. Environment Clean Generations
In developed countries, too, many pregnancies are unplanned, and we believe that funding better sex and relationships education and family planning services would be a worthwhile investment in our future, particularly in countries such as the US and UK. For individuals, we would argue that having one or two children rather than three or four is an important part of an environmental lifestyle. Environment Clean Generations.By seeking to lower our numbers over time to a more sustainable level, we will be contributing to a future where we can live in harmony with nature, instead of the unachievable goal of seeking to exploit it ever more intensively.
Noted geneticist Snoop Dogg once said--and I’m paraphrasing here--that no matter where one goes in life, one’s surroundings during one's formative years stay with one for life. No matter where you go, you can’t change where you’re from (I think Prof. Dogg was actually calling back to an old Comrads lyric from the song Homeboyz--I’m sure you all will correct me in the comments). Findings published today in the International Journal of Epidemiology suggest that he may have been correct--socio-economic status and living standards early in life may actually cause changes to your DNA that you carry with you for life, regardless of how your living conditions change along the way.
In some ways, we already knew that. Some adult diseases--type 2 diabetes, coronary heart disease, etc.--have been linked to socio-economic disadvantages in early life. But we don’t really know why or how. Researchers in Canada and the UK may have just found the key.
Their sample size is admittedly small, but what they found was significant. In 40 research patients in the UK that are participating in an ongoing study that has documented many aspects of their lives, researchers looked at differences in gene methylation. Methylation is an epigenetic modification to one’s DNA that changes a gene’s activity, generally reducing that activity within the genome. Various factors can influence methylation, including environmental conditions.
In their sample, the researchers looked at DNA taken from the subjects at age 45. They chose subjects that had come from either very high or very low standards of living, and they looked at differences in DNA methylation across some 20,000 genes. They found that 1,252 methylation differences were associated with socio-economic circumstances in early life while just 545 were associated with socio-economic circumstances in adulthood, suggesting that where you come from really does make an impact on the very fiber of your biological being.
Moreover, the methylation patterns were clustered together in large swaths of DNA, suggesting an epigenetic pattern linked to humans’ early environments. That’s actually good news. If we know some diseases are linked to a person’t early upbringing, and we can see where there are changes happening in the DNA during early life, then we can narrow the window on where in the genome things like coronary heart disease and diabetes take root. Future research could peg where certain methylation differences are associated with specific diseases, then target those areas with drugs or other treatments.
Chronic low-level exposure to a compound found in a variety of plastic household items could pose a threat to women who overproduce a protein linked with breast cancer, say researchers at University of Alabama at Birmingham.
Environment-Clean-Generations
Coral Lamartiniere, Ph.D., professor in the Department of Pharmacology and Toxicology and senior scientist in the UAB Comprehensive Cancer Center, and postdoctoral fellow Sarah Jenkins, Ph.D., assessed the effect of chronic, oral exposure to the compound bisphenol A (BPA) in mice genetically modified to overproduce the protein HER2/erbB2, present in about 15-30 percent of women with breast cancer. The results were published online Oct. 12, 2011, by the journal Environmental Health Perspectives.
"We found the lower doses of BPA to be capable of activating several growth-factor-receptor pathways that previously have been implicated in cancer. This was not observed with the higher BPA doses," Jenkins says. "This is counterintuitive since BPA in low levels was presumed to be safe."
BPA is an industrial compound primarily used to manufacture polycarbonate plastic and epoxy resins and it is commonly found in household items including kitchen utensils, food storage containers, travel mugs and metal can linings.
Animal studies have linked BPA to a variety of health problems such as infertility, prostate cancer and breast cancer, but not without disagreement as to how and whether such findings can be extrapolated to humans. Most BPA research has been centered on early-life exposure in animals, linking low doses of BPA administered early in life -- prenatal, pre-pubertal or a combination of the two -- to an increased risk of mammary cancer later in life.
"Although this study did not study breast cancer in humans, the results suggest that chronic low-level BPA exposure could pose a particular threat to women with breast cancer who overproduce this protein," Jenkins says.
A picture of the past, a memory of a nice afternoon, sitting on the grass doing homework with someone you love. An image or a movie takes up space on a computer's hard drive, so what causes the reactions to store these memories in our mind? Let's take a look at a couple of recently discovered molecules that might be able to impact human memory in the coming decades.
Our Understanding of Memory is still in its Infancy
Memories form because of interactions between several parts of the brain, with learning arising from the changes in neuron synapses.
We are still in the infancy of knowing exactly how a memory is formed and subsequently altered, with most conclusions coming from trial and error observations involving hormones.
For example, injections of cortisol, a steroid hormone released by the adrenal gland in response to stress, and adrenaline into subjects have been shown to increase the retention of short term memory.
Long-term stress situations, however, which would allow for streams of cortisol to be present, have be shown to hamper short term memory (with this showing that there is a delicate chemical balance in place to separate remembering and forgetting).
Additional work has looked at cell signaling and neurotransmitters, like dopamine, and what regions of the brain are populated by specific neurotransmitters.
Protecting our Memories
Using the small molecule P7C3, first mentioned in the journal article Discovery of a Pro-neurogenic, Neuroprotective Chemical, is a possibly way in which to aid in restoring memories. P7C3, due to its neuroprotective properties, could be used to ward off the later stages of Alzheimer's by aiding in the branching of neurons and protecting neurons from being degraded.
Exactly how P7C3 works, however, is not known. P7C3 and a more potent analogue, were discovered through a screen of over 1,000 individual molecules through in vivo assays. This is quite the "shotgun" approach, throwing a lot of previously synthesized molecules at a problem and seeing if any work. This is a common method used in drug discovery, and also shows that there is no "one" good way to design a memory enhancing molecule. Yet.
Can we Erase Bad Memories?
When the amount of the large molecule CaMKII (to give an idea of scale of CaMKII, it is about one thousand times larger than cortisol or P7C3) is spiked within in the brain of a mouse, the recall of a short term memory associated with fear decreases.
That's according to research reported in the journal article Inducible and Selective Erasure of Memories in the Mouse Brain via Chemical-Genetic Manipulation
However, as with stress induced cortisol release, too much CaMKII can lead to the impaired ability to recall memories, and extending past cortisol, the erasure of new and fear-induced memories specifically without harming other memories.
These experiments were only performed in mice, so implementation in humans might be years away or not possible at all, but it gives hope for research looking to radically change the memories on an individual for positive reasons.
CaMKII is also for sale as a reagent, increasing the accessibility and thus ease of research. It's not cheap, however, and if you do try to use it, it's not likely to be administered properly, so don't run out and buy it to black out your memories of the monsters that did live under your bed.
CaMKII release has recently been shown to be extremely specific and activated in the formation of dendritic spines, lending insight into how the molecule behaves and putting a bit of theory behind the molecule's ability to significantly alter neurochemistry enough to block memories.
If you play with your memories, are you changing who you are?
Would you want to erase a bad memory? In situations of physical abuse or harm, yeah, more than likely. But what about that test you failed or your first break-up? That time you drove home with the lights on in your car after watching a scary movie? These are the moments that help make us who we are, and in sum, condition us to change our decision-making in the future.
So before we go around erasing memories, we probably want to make sure we are erasing the right types. For example, if all memories of a certain type (like those pertaining to fear) were erased, we would probably have to spend time acclimating ourselves to our environment and possibly remembering why we don't put our hand on a hot stove. Further research to help us learn the mechanism for how the molecules work couldn't hurt either.
The mission is to boldly go where no man has gone before – on a flight to Mars.
The snag is that you’d never come back.
The U.S. space agency Nasa is actively investigating the possibility of humans colonising other worlds such as the Red Planet in an ambitious project named the Hundred Years Starship.
The settlers would be sent supplies from Earth, but would go on the understanding that it would be too costly to make the return trip.
NASA Ames Director Pete Worden revealed that one of NASA’s main research centres, Ames Research Centre, has received £1million funding to start work on the project.
The research team has also received an additional $100,000 from Nasa.
Astronauts would be marooned on the planet's surface and would never be able to return home due to cost.
‘You heard it here,” Worden said at ‘Long Conversation,’ an event in San Francisco. ‘We also hope to inveigle some billionaires to form a Hundred Year Starship fund.’
He added: ‘The human space program is now really aimed at settling other worlds. Twenty years ago you had to whisper that in dark bars and get fired.’
Worden said he has discussed the potential price tag for one-way trips to Mars with Google co-founder Larry Page, telling him such a mission could be done for $10 billion.
He said said: ‘His response was, “Can you get it down to $1 [billion] or $2billion?” So now we're starting to get a little argument over the price.’
Depending on the position of Mars in its orbit around the sun, its distance from Earth varies between 34million and 250million miles.
The most recent unmanned mission there was Nasa’s Phoenix lander, which launched in August 2007 and landed on the planet’s north polar cap in May the following year.
Experts say a nuclear-fuelled rocket could shorten the journey to about four months.
Of all the planets in the solar system, Mars is the most likely to have substantial quantities of water, making it the best bet for sustaining life. But it is a forbidding place to set up home.
Temperatures plummet way below freezing in some parts. The thin atmosphere would be a problem as it is mostly carbon dioxide, so oxygen supplies are a must.
Worden also suggested that new technologies such as synthetic biology and alterations to the human genome could also be explored ahead of the mission.
And he said that he believed the mission should visit Mars’ moons first, where scientists can do extensive telerobotics exploration of the planet. He claims that humans could be on Mars' moons by 2030.
News of the Hundred Years Starship comes as new research found that a one-way human mission to Mars is technologically feasible and would be a cheaper option than bringing astronauts back.
Writing in the Journal of Cosmology, scientists Dirk Schulze-Makuch and Paul Davies, say that the envision sending four volunteer astronauts on the first mission to permanently colonise Mars.
They write: ‘A one-way human mission to Mars would not be a fixed duration project as in the Apollo program, but the first step in establishing a permanent human presence on the planet.’
The astronauts would be sent supplies from Earth on a regular basis but they would be expected to become self-sufficient on the red planet’s surface as soon as possible.
They say: There are many reasons why a human colony on Mars is a desirable goal, scientifically and politically. The strategy of one-way missions brings this goal within technological and financial feasibility.
‘Nevertheless, to attain it would require not only major international cooperation, but a return to the exploration spirit and risk-taking ethos of the great period of Earth exploration, from Columbus to Amundsen, but which has nowadays being replaced with a culture of safety and political correctness.’
An artist's impression of the 100 Year Starship, the craft that would take astronauts to colonise other planets
NASA's Mars Exploration Rover Spirit work on the planet's surface. One day humans could be working alongside the robotic probe
They admit that the mission would come with ‘ethical considerations’ with the general public feeling that the Martian pioneers had been abandoned to their fate or sacrificed.
But they argue that these first inhabitants of Mars would be going in much the same spirit as the first white settlers of North America – travelling to a distant land, knowing that they will never return home.
They say: ‘Explorers such as Columbus, Frobisher, Scott and Amundsen, while not embarking on their voyages with the intention of staying at their destination, nevertheless took huge personal risks to explore new lands, in the knowledge that there was a significant likelihood that they would perish in the attempt.’
Cities have existed for thousands of years and can be traced back to the river valley civilizations of Mesopotamia (present-day Iraq), Egypt, India, and China. At first, these settlements depended largely on agriculture and domestic cattle, but as they grew in size they became centers for merchants and traders.
Urban growth, also known as urbanization, accelerated dramatically with the advent of industrialization some 200 years ago. At that time, large numbers of people moved to cities in search of jobs, mostly in factories. But the most rapid growth has taken place over the past 50 years. While less than one-third of the world's population lived in cities in 1950, about two thirds of humanity is expected to live in urban areas by 2030. Most of that urbanization is taking place in Asia, Africa, and Latin America.
Urban is defined as "that which is characteristic of a city." But what exactly is a city? In the past, walls may have defined a city. But today's city boundaries are often blurred. Are suburbs, which are often called metropolitan areas, part of cities? Depending on the boundaries used, Tokyo can have a population of anywhere between 8 and 40 million people.
Cities make a lot of sense for humans. People are concentrated in a small space rather than being spread out over a large territory. This allows the government and others to provide more service such as water, electricity, and transportation to a larger number of people. Schools and shops are more easily accessible than in rural areas.
Cities have always been at the center of economic growth and technological advances. The promise of jobs and prosperity pulls people to cities. But their rapid growth has also brought with it many negative things: violence, poverty, overcrowding, health problems, and pollution. Many cities in developing countries in particular are growing too rapidly for their own good, with many residents unable to find jobs and forced to live in slums.
Urban expansion is also encroaching on wildlife habitats everywhere. Increasingly people live and work in close proximity to wild animals whose native habitats have been lost or broken up. Many animals—from mice and cockroaches to pigeons and squirrels—have adapted to city life, taking advantage of abundant food and warmer temperatures.
A verdant expanse of grass rippling in the wind, interspersed by a few trees casting umbrellas of shade with their branches is the likely landscape over which humans and their ancestors learned to walk. Open woodlands and savanna dominated the East African homeland of the human species as we diverged from other primates, said researchers in a recent edition of the journal Nature.
"Wherever we find human ancestors, we find evidence for open habitats similar to savannas – much more open and savanna-like than forested," said Thure Cerling, a University of Utah professor of geology, geophysics and biology, and lead author of the study, in a press release.
The researchers found that large areas of grassland and open woodland were consistently present for the past 7.4 million years. Understanding ancient vegetation patterns could help scientists resolve some questions about what kind of environment humans evolved in and the pressures that influenced development of features like our upright stance and dexterous hands.
"Currently, many scientists think that before 2 million years ago, things were forested [in East Africa] and savanna conditions have been present only for the past 2 million years," Cerling said. "This study shows that during the development of bipedalism [about 4 million years ago] open conditions were present."
"We conclude there have been open savannas all the time for which we have hominin fossils in the environments where the fossils were found during the past 4.3 million years,” which is when the first accepted ancestors of humans branched off from other primates, said Cerling.
"In some periods, it was more bushy, and other times it was less bushy," Cerling said. "Hardly anything could have been called a dense forest, but we can show some periods where certain environments were consistently more wooded than others. We find hominins (early humans, pre-humans and chimp and gorilla relatives) in both places. How early hominins partitioned their time between 'more open' and 'more closed' habitats is still an open question."
The researchers used a recently developed technique for analyzing the isotopes locked in fossilized soil to determine what kind of plants had been taking root over the years. They found that the large parts of East Africa had less than 40 percent tree cover over the past 7.4 million years.
Isotopes such as carbon-12 and carbon-13 are variations of a chemical element, in this case carbon. Because tropical grasses and sedges tend to absorb the rare isotope carbon-13, while trees, bushes, and herbs, which dominate woodlands and forests, tend to stick with the standard carbon-12 the ecologists were able to map the past landscapes based on the isotopes in the fossilized soil and current botanical knowledge.
"This study is based on the geological axiom that the present is the key to the past," said Cerling. "We assume soils in the past had similar relationships to vegetation as what we observe today."
This technique of estimating the types of plants growing in the ancient past based on the ratios of the isotopes in the soil provides “a new way to quantify the openness of tropical landscapes," Cerling added. "This is the first method to actually quantify the amount of canopy cover, which is the basis for deciding if something is savanna."
To understand what kind of landscape correlated to what carbon isotope ratio, the scientists looked at the carbon isotope ratios in 3,000 modern soil samples. The study looked at 75 tropical sites, half of which were in Africa. Satellite photos then helped the researchers determine how to classify the areas by their amount of tree cover.
The researchers defined grasslands as having less than 40 percent tree cover; woodlands as having between 40 and 80 percent; and anything with more than that as forests.
The modern soil samples were then compared to 1,300 fossil soil samples from areas near where human ancestors were found. Seventy percent of the sites had less than 40 percent trees and other woody plants. That puts them within the definition of grassland or wooded grassland. Only one percent of the samples exceeded 70 percent forest cover, meaning dense forests seem to have been rare.
The researchers note that this does contradict finds that show human ancestors lived in some wooded or forested areas, such as the Middle Awash, nor does it refute previous observations that savannas expanded about 2 million years ago. But it does show that for the entire time humans were evolving from other primates, East Africa had extensive grasslands in the same places human ancestors were found.
At least five mass extinctions may have occurred in the history of our planet, meaning that in a relatively short period of time, a large number of species have disappeared. Probably the most famous one took place 65 million years ago at the end of the Cretaceous period, when the dinosaur domination reached its end.
There is an interesting, yet highly controversial theory, claiming that it might not have been only the huge asteroid impact, but also a massive dose of cosmic radiation, produced by the galaxy itself at a supposedly regular interval.
According to Adrian Melott, professor of physics and astronomy at Kansas University, the circular movement of our solar system within the galaxy, regularly exposes Earth "to an onslaught of cosmic rays on a schedule that is synchronized to the mass extinctions."
Mellott and colleague Mikhail Medvedev "hypothesize that the leading, north side of the Milky Way generates a shock wave as the galaxy plunges through the
universe". The Kansas researchers discovered that high rates of extinction in the cycle coincide almost perfectly with periodic "excursions" of the solar system outside the central plane of the Milky Way galaxy. "When the solar system periodically journeys up to the boundary of the galaxy [in the direction of its movement across the Universe] -- about once every 64 million years -- the galactic shock wave exposes Earth to a huge dose of high-energy radiation."
According to them, our planet is rapidly heading for the bad galactic neighborhood: "We've just passed the mid-plane of the galaxy," said Melott. "We're on the way up and we'll reach a peak in about 10 or 12 million years. That's when the radiation should start getting bad again -- if our idea is right."
However, there are some problems with this theory, that make it at least hasty if not clearly undocumented; that doesn't necessarily mean that the scientists don't know what they're talking about, it may just mean that they are making some assumptions without scientifically proven evidence.
First of all, there is strong evidence of the impact that caused the extinction of the dinosaurs, so the cosmic rays are at best a secondary cause. An adjacent proposal says that cosmic rays are not the only cause of such an extinction, and that the galactic shock wave also produces much more numerous asteroids and comets, disrupting them and making them speed in the opposite direction to the galactic movement. Maybe the one that hit us and caused the dinosaurs to disappear was one of those "disturbed" asteroids...maybe not.
But the most important counter argument is the fact that we should have observed the effects of the cosmic radiation in plants and other animals that survived the dinosaur die-off. Animals that suffered mutations would have been less significant in percentage, it's true, but the mutations should have been passed on to the descendants, and we should have seen this kind of evidence by now.
It is highly unlikely for a massive dose of radiation to wipe out entire species, yet leave no trace in the surviving ones. Furthermore, if cosmic radiation was the cause of the dinosaur apocalypse, could it really have happened instantly?
Presuming that Earth is indeed heading for a danger zone, filled with radiation, there are some aspects that do not add up. It is hard to believe that the radiation is so localized, that the planet would simply enter its area of influence in an instant, so rapidly that we wouldn't even know what hit us.
Again, there is no clear limit between the "safe" and the "bad" zones, so early effects should be noticed by humans, if dinosaurs did not have the technological means to do that. And last, but not least, the speed of the Earth in space - resulting from both its movement in the galaxy and the galaxy's movement in the Universe - is not so great, so the influence of these cosmic rays would have been felt for at least a few million years, since the galactic waves form on an important part of the galaxy's circumference.
So, the bottom line is, as much as humans enjoy apocalyptic scenarios (and this can be clearly seen in so many Hollywood movies) I really doubt the making of another one, called: "Cosmic Rays of Doom" or something like that. It was a good try, though, and the two scientists got their 15 minutes of fame...
There is little doubt left in the minds of professional biologists that Earth is currently faced with a mounting loss of species that threatens to rival the five great mass extinctions of the geological past. As long ago as 1993, Harvard biologist E.O. Wilson estimated that Earth is currently losing something on the order of 30,000 species per year — which breaks down to the even more daunting statistic of some three species per hour. Some biologists have begun to feel that this biodiversity crisis — this “Sixth Extinction” — is even more severe, and more imminent, than Wilson had supposed.
Extinction in the past
The major global biotic turnovers were all caused by physical events that lay outside the normal climatic and other physical disturbances which species, and entire ecosystems, experience and survive. What caused them?
About 30,000 species go extinct annually.
First major extinction (c. 440 mya): Climate change (relatively severe and sudden global cooling) seems to have been at work at the first of these-the end-Ordovician mass extinction that caused such pronounced change in marine life (little or no life existed on land at that time). 25% of families lost (a family may consist of a few to thousands of species).
Second major extinction (c. 370 mya): The next such event, near the end of the Devonian Period, may or may not have been the result of global climate change. 19% of families lost.
Third major Extinction (c. 245 mya): Scenarios explaining what happened at the greatest mass extinction event of them all (so far, at least!) at the end of the Permian Period have been complex amalgams of climate change perhaps rooted in plate tectonics movements. Very recently, however, evidence suggests that a bolide impact similar to the end-Cretaceous event may have been the cause. 54% of families lost.
Fourth major extinction (c. 210 mya): The event at the end of the Triassic Period, shortly after dinosaurs and mammals had first evolved, also remains difficult to pin down in terms of precise causes. 23% of families lost.
Fifth major extinction (c. 65 mya): Most famous, perhaps, was the most recent of these events at the end-Cretaceous. It wiped out the remaining terrestrial dinosaurs and marine ammonites, as well as many other species across the phylogenetic spectrum, in all habitats sampled from the fossil record. Consensus has emerged in the past decade that this event was caused by one (possibly multiple) collisions between Earth and an extraterrestrial bolide (probably cometary). Some geologists, however, point to the great volcanic event that produced the Deccan traps of India as part of the chain of physical events that disrupted ecosystems so severely that many species on land and sea rapidly succumbed to extinction. 17% of families lost.
The previous mass extinctions were due to natural causes.
How is the Sixth Extinction different from previous events?
At first glance, the physically caused extinction events of the past might seem to have little or nothing to tell us about the current Sixth Extinction, which is a patently human-caused event. For there is little doubt that humans are the direct cause of ecosystem stress and species destruction in the modern world through such activities as:
transformation of the landscape
overexploitation of species
pollution
the introduction of alien species
And because Homo sapiens is clearly a species of animal (however behaviorally and ecologically peculiar an animal), the Sixth Extinction would seem to be the first recorded global extinction event that has a biotic, rather than a physical, cause.
The current mass extinction is caused by humans
Yet, upon further reflection, human impact on the planet is a direct analogue of the Cretaceous cometary collision. Sixty-five million years ago that extraterrestrial impact — through its sheer explosive power, followed immediately by its injections of so much debris into the upper reaches of the atmosphere that global temperatures plummeted and, most critically, photosynthesis was severely inhibited — wreaked havoc on the living systems of Earth. That is precisely what human beings are doing to the planet right now: humans are causing vast physical changes on the planet.
We are bringing about massive changes in the environment.
What is the Sixth Extinction?
We can divide the Sixth Extinction into two discrete phases:
Phase One began when the first modern humans began to disperse to different parts of the world about 100,000 years ago.
Phase Two began about 10,000 years ago when humans turned to agriculture.
The first phase began shortly after Homo sapiens evolved in Africa and the anatomically modern humans began migrating out of Africa and spreading throughout the world. Humans reached the middle east 90,000 years ago. They were in Europe starting around 40,000 years ago. Neanderthals, who had long lived in Europe, survived our arrival for less than 10,000 years, but then abruptly disappeared — victims, according to many paleoanthropologists, of our arrival through outright warfare or the more subtle, though potentially no less devastating effects, of being on the losing side of ecological competition.
Everywhere, shortly after modern humans arrived, many (especially, though by no means exclusively, the larger) native species typically became extinct. Humans were like bulls in a China shop:
They disrupted ecosystems by overhunting game species, which never experienced contact with humans before.
And perhaps they spread microbial disease-causing organisms as well.
Humans began disrupting the environment as soon as they appeared on Earth
The fossil record attests to human destruction of ecosystems:
Humans arrived in large numbers in North America roughly 12,500 years ago-and sites revealing the butchering of mammoths, mastodons and extinct buffalo are well documented throughout the continent. The demise of the bulk of the La Brea tar pit Pleistocene fauna coincided with our arrival.
The Caribbean lost several of its larger species when humans arrived some 8000 years ago.
Extinction struck elements of the Australian megafauna much earlier-when humans arrived some 40,000 years ago. Madagascar-something of an anomaly, as humans only arrived there two thousand years ago-also fits the pattern well: the larger species (elephant birds, a species of hippo, plus larger lemurs) rapidly disappeared soon after humans arrived.
Wherever early humans migrated, other species became extinct.
Indeed only in places where earlier hominid species had lived (Africa, of course, but also most of Europe and Asia) did the fauna, already adapted to hominid presence, survive the first wave of the Sixth Extinction pretty much intact. The rest of the world’s species, which had never before encountered hominids in their local ecosystems, were as naively unwary as all but the most recently arrived species (such as Vermilion Flycatchers) of the Galapagos Islands remain to this day.
Why does the Sixth Extinction continue?
The invention of agriculture accelerated the pace of the Sixth Extinction.
Phase two of the Sixth Extinction began around 10,000 years ago with the invention of agriculture-perhaps first in the Natufian culture of the Middle East. Agriculture appears to have been invented several different times in various different places, and has, in the intervening years, spread around the entire globe.
Agriculture represents the single most profound ecological change in the entire 3.5 billion-year history of life. With its invention:
humans did not have to interact with other species for survival, and so could manipulate other species for their own use
humans did not have to adhere to the ecosystem’s carrying capacity, and so could overpopulate
Humans do not live with nature but outside it.
Homo sapiens became the first species to stop living inside local ecosystems. All other species, including our ancestral hominid ancestors, all pre-agricultural humans, and remnant hunter-gatherer societies still extant exist as semi-isolated populations playing specific roles (i.e., have “niches”) in local ecosystems. This is not so with post-agricultural revolution humans, who in effect have stepped outside local ecosystems. Indeed, to develop agriculture is essentially to declare war on ecosystems - converting land to produce one or two food crops, with all other native plant species all now classified as unwanted “weeds” — and all but a few domesticated species of animals now considered as pests.
The total number of organisms within a species is limited by many factors-most crucial of which is the “carrying capacity” of the local ecosystem: given the energetic needs and energy-procuring adaptations of a given species, there are only so many squirrels, oak trees and hawks that can inhabit a given stretch of habitat. Agriculture had the effect of removing the natural local-ecosystem upper limit of the size of human populations. Though crops still fail regularly, and famine and disease still stalk the land, there is no doubt that agriculture in the main has had an enormous impact on human population size:
Earth can’t sustain the trend in human population growth. It is reaching its limit in carrying capacity.
Estimates vary, but range between 1 and 10 million people on earth 10,000 years ago.
There are now over 6 billion people.
The numbers continue to increase logarithmically — so that there will be 8 billion by 2020.
There is presumably an upper limit to the carrying capacity of humans on earth — of the numbers that agriculture can support — and that number is usually estimated at between 13-15 billion, though some people think the ultimate numbers might be much higher.
This explosion of human population, especially in the post-Industrial Revolution years of the past two centuries, coupled with the unequal distribution and consumption of wealth on the planet, is the underlying cause of the Sixth Extinction. There is a vicious cycle:
Overpopulation, invasive species, and overexploitation are fueling the extinction.
More lands are cleared and more efficient production techniques (most recently engendered largely through genetic engineering) to feed the growing number of humans — and in response, the human population continues to expand.
Higher fossil energy use is helping agriculture spread, further modifying the environment.
Humans continue to fish (12 of the 13 major fisheries on the planet are now considered severely depleted) and harvest timber for building materials and just plain fuel, pollution, and soil erosion from agriculture creates dead zones in fisheries (as in the Gulf of Mexico)
While the human Diaspora has meant the spread, as well, of alien species that more often than not thrive at the detriment of native species. For example, invasive species have contributed to 42% of all threatened and endangered species in the U.S.
Can conservation measures stop the Sixth Extinction?
Only 10% of the world’s species survived the third mass extinction. Will any survive this one?
The world’s ecosystems have been plunged into chaos, with some conservation biologists thinking that no system, not even the vast oceans, remains untouched by human presence. Conservation measures, sustainable development, and, ultimately, stabilization of human population numbers and consumption patterns seem to offer some hope that the Sixth Extinction will not develop to the extent of the third global extinction, some 245 mya, when 90% of the world’s species were lost.
Though it is true that life, so incredibly resilient, has always recovered (though after long lags) after major extinction spasms, it is only after whatever has caused the extinction event has dissipated. That cause, in the case of the Sixth Extinction, is ourselves — Homo sapiens. This means we can continue on the path to our own extinction, or, preferably, we modify our behavior toward the global ecosystem of which we are still very much a part. The latter must happen before the Sixth Extinction can be declared over, and life can once again rebound.
Posted in: bacteria,biomass,earth,environment clean generations,homo sapiens,humans,seven billion people
