The God Species: How Humans Really Can Save the Planet.... Mark Lynas

Чтение книги онлайн.

СКАЧАТЬ Major volcanic eruptions may release trillions of tonnes of carbon dioxide over just a few thousand years, outstripping the capacity of the Earth system to mop up the additional CO₂ via rock weathering and other processes of sequestration, and leading to extreme global warming events. Mass extinctions happen because changing circumstances outstrip the adaptability of existing species before evolution can work its magic. Over millions of years new species can appear, but only from the diminished gene pool of the survivors – and a return to true pre-extinction levels of biodiversity may take much longer, if it ever takes place at all.

      This time-lag effect was cleverly demonstrated in a modelling simulation undertaken by two British researchers, Hywell Williams and Tim Lenton (both at the University of East Anglia; Lenton is a member of the planetary boundaries expert group).² In a computer-generated world – entirely populated by evolving micro-organisms living in a closed flask – Williams and Lenton found that the closing of nutrient loops emerged as a robust property of the system nearly every time the model was run. As in the real world, the emergence of self-regulation came about because evolution allowed new species to appear that could use the waste of one species as food for themselves, recycling nutrients and leading to a stable state. Moreover, the more species that evolved, the greater the amount of recycling and the greater the overall biomass the system could support. ‘Flask world’ had discovered the value of biodiversity.

      But this world also had a dark side, for several simulations illustrated that the flaw in self-regulation – the time gap between a disturbance and the evolved correction – might occasionally be fatal. In just a few model runs, an organism appeared that was so spectacularly successful in mopping up nutrients that its numbers exploded and its wastes built up to toxic levels before other organisms were able to evolve a response. Williams and Lenton dubbed these occasional rogue species ‘rebel organisms’. They were unusual, but their impact was invariably catastrophic: the explosive initial success of the rebels changed the simulated global environment so suddenly and dramatically that their compatriots were killed, and – with no other life-forms around to recycle their wastes – they were themselves condemned to die too. As the last lonely rebels perished, their whole biosphere went extinct, evolution ceased, self-regulation failed, and life wiped itself out.

      Like Lovelock’s Gaia, Flask world – and its rebel organisms – might just be a clever idea, more of a metaphor than a true representation of reality. But the parallels with our species are unsettling. We have transformed our environment within just a few centuries in ways that are wiping out other life-forms at a shocking speed – the changes so rapid that evolution has no time to adapt and thereby allow other organisms to survive. Like a rebel organism, our species discovered a colossal new source of energy, which had lain hidden and undisturbed for millions of years, and which no previous life-form had found a use for. It is the sheer rapidity in the rise of the waste from the exploited new energy source of buried carbon – largely in the form of gaseous carbon dioxide – plus the other combined wastes and environmentally transformative impacts that fossil fuels allowed humanity to achieve, that have now begun to overwhelm the self-regulatory capacity of the Earth system. This single element holds the key to a possible future mass extinction.

      Flask world is now our world. Consider that our wastes are accumulating so fast in the oceans that no species can consume them; instead, massive dead zones are spreading around the world’s coasts, from China to the Gulf of Mexico, where the recent BP oil spill adds to the toll. We have produced novel organic chemicals and synthetic polymers that no microbes have yet learned to digest, and which are poisonous to most organisms – often including ourselves. And we are steadily eating our way through global biodiversity – from fish to frogs – consuming voraciously, and moving on to the next species when one is extinguished. Those species that are not edible we ignore and displace, whilst those that threaten or dare to compete with us we pursue mercilessly and annihilate. Thus is our rebel nature revealed.

      There is a paradox however. Even as a putative rebel organism, humanity is a product of Darwinian evolution, like every other naturally generated life-form sharing our planet today. Moreover, we did not evolve the biological capacity to eat coal and drink oil – the energy from these abundant ‘nutrients’ is combusted outside the body rather than metabolised within it. Why us, then? Our mastery of fire was a product of the adaptability and innovativeness with which evolution had already equipped us long before, and that no other species had heretofore possessed. Humanity’s Great Leap Forward was not about evolution, but adaptation – and could therefore move a thousand times faster.

      I don’t want to oversimplify: the Stone Age did not end in 1764 with James Watt’s invention of the steam engine. Clearly great leaps in human behaviour and organisation took place over preceding millennia with the advent of language, trade, agriculture, cities, writing and the myriad other innovations in production and communications that laid the foundations for humanity’s industrial emergence. But I would argue that the true Anthropocene probably did begin in the second half of the eighteenth century, for it was then that atmospheric carbon dioxide levels began their inexorable climb upwards, a rise that continues in accelerated form today. This date also marks the beginning of the large-scale production of other atmospheric pollutants and the planet-wide destabilisation of nutrient cycles that also characterise this new anthropogenic geological era.

      Take population. When humans invented agriculture, some 10,000 years ago, the global human population was somewhere between 2 and 20 million³. There were still more baboons than people on the planet. By the time of the birth of Christ, the globe supported perhaps 300 million of us. By 1500, that population had increased to about 500 million – still a relatively slow growth rate. A global total of 700 million was reached in 1730. Then the boom began. By 1820 we numbered a billion. That total rose to 1.6 billion by 1900, and the growth rate continued to accelerate. By 1950 we were 2.5 billion strong, and by 1990 had doubled again to more than 5 billion. In 2000 the 6 billion mark was passed. At the time of writing, in late March 2011, we number an astonishing 6.88 billion individuals.⁴ Through the process of writing this book, another 225 million people were added to the total – just under half the entire world population of 500 years ago, now appearing in just three years.

      But this still doesn’t answer the puzzle: Why us? And why were buried stores of carbon the ‘nutrients’ that allowed our species to proliferate so explosively? A satisfactory response requires a brief digression into the evolutionary origins of this remarkable hominid, for it is our past that holds the key to our present and future. This is the story of a species whose biological characteristics combined with an accident of fate to have world-shattering consequences. And it is a story that might shed some light on the central question of this book – whether we are rebel organisms destined to destroy the biosphere, or divine apes sent to manage it intelligently and so save it from ourselves.

      Perhaps the environmentalist and futurist Stewart Brand put it best when he wrote these words: ‘We are as gods and have to get good at it.’⁵ Amen to that.

      THE DESCENT OF MAN

      Listening to some environmentalists talk, it is easy to get the feeling that humanity is somehow unnatural, a malign external force acting on the natural biosphere from the outside. They have it wrong. We are as natural as coral reefs or termites; our inherited physiology is entirely the product of selective pressures operating over millions of years within living systems. Our inner ear, for example, was once the jawbone of a reptilian ancestor. Babies in the womb begin life with tails, expressing in the earliest stages of life genes that illustrate our long evolutionary history. Our key biological characteristics – including those that have allowed us to emerge as ‘sapient’ beings – exist only because they conferred on our ancestors some selective advantage as they ate, fought, played and reproduced over millions of years within the natural biosphere.

      The СКАЧАТЬ