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Natural disasters through the ages

A lecture given as part of the Mary Anning Weekend at Lyme Regis, 24 October 2010.

I begin with one central point. We and all living creatures live dangerously on Earth. Life itself is a strange phenomenon, so far as we know unique among billions of stars in our galaxy and among billions in other galaxies. It is only our limited knowledge of the past and the shortness of our lives which shield us from better understanding how vulnerable the Earth really is and always has been. The work of Mary Anning some 200 years ago opened the doors to that understanding.

We tend to classify most sudden change as disastrous. So it can be. The word disaster derives from an untoward event from the stars (the same 'astre' as in astronomy), and the stars certainly carry responsibility from time to time. But without disasters we would not be here. The history of living organisms, so far as we know it from the fossil evidence, shows a pattern of relative evolutionary stability, punctuated by relatively sudden departures of some species and the arrivals of others. Few ecosystems or species last more than a few million years. Extinctions are an essential element in evolution.

The cliffs around us today are remarkable obituaries of past species. They are a reminder not only of what happened in the past but of what could happen in the future. Indeed Lyme Regis is on the border of some unstable geology between East and West: to the East it is broadly stable; then comes Lucy's Ledge Fault between the Cobb and the mouth of the river; and to the West is a pattern of slides and faults of which the remains of the Great Landslip of February 1840 is a continuing witness.

First I shall speak about natural disasters down the ages from beyond the Earth; then about some from within the Earth system; and then about some caused by the small but destructive animal species which is ourselves. I will say something at the end about what, if anything, we can do to anticipate, prevent, mitigate or adapt ourselves to them and the sort of governance we need to do so.

Disasters from space range from the very big to the very small. They include meteorites, asteroids, planetesimals, and comets, many of them dating from the origins of the solar system.

The biggest of all was the object which hit the young Earth more than 4 billion years ago, and led to the creation of the Moon. Since then there has been an intermittent barrage. Only in the last quarter century have we come to understand the scale of the problem. A vivid illustration in July 1994 was the spectacle of the comet Shoemaker-Levy colliding with the planet Jupiter. As the comet entered Jupiter's gravitational field, it broke up into fragments, resulting in multiple impacts. One fragment alone created a fireball as big as the Earth.

Fortunately for us the atmosphere of the Earth acts as a protective shield for most Near Earth Objects, which burn up or explode at high altitudes. By contrast the larger ones can hit the Earth with devastating effects. The main ones are blast waves, tsunamis, injection of material into the atmosphere, and electromagnetic changes near the surface.

Here are some examples. The most famous is the Chicxulub event - or series of events - of 65 million years ago. It changed the history of life on Earth. An object with a diameter of about 10 kilometres hit Yucatan in Mexico, digging out a crater traceable today with a diameter of around 180 kilometres. It threw up a cloud of vaporized and molten rock over north America. The consequent dust in the upper atmosphere darkened and drastically cooled the whole Earth, damaging the process of photosynthesis on the surface.

When the dust settled, the temperature swung the other way. Water vapour and carbon dioxide in the atmosphere caused a runaway green house effect. The surface temperature of the Earth could have risen by as much as 10C for at least 500,000 years. It is no wonder that all living creatures were affected, and that a high proportion, including the dinosaur family, perished.

Extinctions of this magnitude are a disaster for some, but obviously an opportunity for others. Fortunately major impacts are extremely rare. But they have occurred at very roughly 100 million year intervals throughout the history of the Earth, and could, at least in theory, happen at any time.

Then there is the more recent Tunguska event of 1908. An object with a diameter of 60 metres broke up over Siberia, destroying some 2,000 square kilometres of forest. It lit up the night sky across most of the northern hemisphere, and in Belgium was likened to a great red glow after sunset as if from a huge distant fire. Had it struck London, there would have been little left. A witness described the sky as being split in two, with the northern part covered with fire, then a great heat and a mighty crash. Events of this kind are relatively frequent of the order of once every 250 years. We were lucky that an object of more than 300 metres in diameter missed the Earth by no more 120,000 km in 2003. We can expect another - Apophis - in 2029.

There is a fairly constant hail of small objects into the upper atmosphere. In 2000 an object of around five metres in diameter exploded at an altitude of 25 kilometres over Lake Tagish in the Yukon. It caused a long and bright fireball, a loud bang, a shower of fragments, and an electromagnetic pulse which caused a temporary loss of power transmission on the ground below.

Then there are the trails of dust left behind by comets through which the Earth passes from time to time. Such dust can provide the nuclei for ice crystals to form at the top of the troposphere some 10 to 15 kilometres above the surface of the Earth. This has the effect of reflecting solar radiation back into space, and could, with other factors, help to trigger variations in the climate below.

We must also reckon with other much neglected influences on the Earth from space. Events inside and outside our galaxy, for example the explosion of a supernova, can generate bursts of immensely destructive radiation, but without such explosions life as we know it could not exist. We are literally star dust.

Then there are variations in radiation from the sun, our friendly neighbourhood hydrogen bomb. Occasional coronal ejections, or concentrated solar flares as in 1859 and 1989, could have dangerous effects of all kinds, including the disruption of electronic communication systems. Finally there are the changing relationships in the Earth's orbit - variations in wobble, tilt and spin known as the Milankovitch effect - which profoundly affect the Earth's climate, and its current propensity to dip in and out of ice ages.

This brings me to disasters from within the Earth. The slow movement of the tectonic plates usually gives time for ecosystems and the species which compose them to move or adapt to change. But passing over thresholds can sometimes have dramatic effects on the behaviour of winds and ocean currents, and of course the living organisms adapted to them.

A good example is the joining of north and south America some four million years ago, which led to drastic changes in the direction of ocean currents. Another example, also linked to oceans, is the Younger Dryas event of some 12,000 years ago, which caused a thousand-year reversion to glacial conditions in the northern hemisphere.

Associated with tectonic plate movements are volcanoes and earthquakes. We are unused to major volcanic eruptions. The eruptions of the Siberian Traps some 250 million years ago, and the Deccan Traps 65 million years ago, both possibly associated with extra terrestrial impacts, changed the surface conditions of the planet.

The eruption of Mount Toba in Indonesia some 73,000 years ago, which put enormous quantities of volcanic dust into the atmosphere, may have helped trigger a renewal of glacial conditions within the last ice age, and changed the development of our own species. By comparison the eruption of Tambora in 1815, which led to the famous 'year without a summer', that of Krakatoa in 1883, that of Mount St Helens in 1980, that of Mount Pinatubo in 1991, and that of Eyjafjallajokull in Iceland this year, each with its specific global effects, were relatively minor.

Earthquakes are part of the same pattern. Mostly their effects, however destructive, are local. Some 10,000 people a year are killed by earthquakes, usually by buildings falling in on them. But sometimes they can combine with tsunamis to cause much greater damage. Underwater landslides can be precipitated by many factors, including Earth tremors. One such off Norway caused a wave to hit Scotland reaching far up the Firth of Forth some 9,000 years ago. Recently there has been concern about the possibility that part of the Cumbre Vieja volcano in the Canaries might collapse into the sea, creating a tsunami with a height of up to 40 metres, which could hit the east coast of the United States.

Then there are disasters in the living world. As I have said they can be catastrophic for some ecosystems, but are the opportunity for others. If the wide spread extinctions at the Permian/Triassic boundary 250 million years ago, and those of the Cretaceous/Tertiary boundary 65 million years ago, had not taken place, nothing like the world we know today, and the human species within it, could have existed.

One point is worth adding, the product of recent and continuing research. To a considerable extent, and operating on Darwinian principles, organisms tend to create and maintain the living environment most favourable to them. Thus they can offset and mitigate the consequences of catastrophes through complex systems of feedback. The Earth system behaves as a single, self regulating system, comprised of physical, chemical, biological and even human components. In a word this is Gaia theory. At present we are pressing Gaia hard without fully understanding the possible consequences.

This brings me to the role of our own little animal species, and our influence on the condition, living and otherwise, of the Earth's surface. A periodical visitor from outer space would find more change in the preceding 250 years than in the preceding 2000, and more change in the last 20 years than in the last 250. The association between humans and their environment, including the micro-world in and around them, has changed at every stage of human evolution: from hunter gatherers to farmers, from country to city dwellers, and from tribal groups to complex hierarchical societies.

But the most radical divide was the beginning of the industrial revolution in Britain. Before then the effects of human activity were local, or at worse regional, rather than global. All the civilizations of the past cleared land for cultivation, introduced plants and animals from elsewhere, and caused a variety of changes. It is no wonder that there are now proposals to reclassify the geological past so that the Holocene epoch would end some 250 years ago, and a new Anthropocene epoch to mark the changes brought about by our own species would follow it.

Our ability to influence other species has given us a profound conceit of ourselves. Yet our use of other species is coupled with an amazing ignorance of how natural systems work, their awe inspiring interconnectedness, and our total reliance on natural services. There have been some 30 urban civilizations before our own. All eventually crashed. Why? The reasons range from damage to the environmental base on which they rested to the mounting costs in human, economic and organizational terms of maintaining them.

What of our civilization? Some of you may have heard of some remarkably gloomy predictions about the future from the Astronomer Royal Lord Rees. In his recent book Our Final Century (the publishers removed the question mark after the title), he explores the dangers arising from human inventiveness, folly, wickedness and sheer inadvertence. The ramifications of information technology, nano-technology and nuclear experimentation and the rest have still to be understood and explored. His conclusion is to give our civilization only a 50 percent chance of survival beyond the end of this century.

For the moment there are six main things for us to think about:

Of these factors population issues are often ignored as somehow too embarrassing or mixed up with religion and the ideology of development. Most people are broadly aware of land and waste problems, although far from accepting the remedies necessary. Water issues have had a lot of publicity, and already affect most people on this planet. Climate change with its many uncertainties is also broadly understood, apart from by those who do not want to hear about it. How we generate energy while fossil fuel resources diminish and demand increases is another conundrum. But damage to the diversity of life has somehow escaped most public attention. All these issues are linked and all concern the future of humanity.

You may think I am exaggerating. But the Earth has never been in this situation before. These points were well brought out in a remarkable Declaration published by some 1500 scientists from the four great global research programmes at Amsterdam in July 2001. They stated squarely that:

"Human activities have the potential to switch the Earth's System to alternative modes of operation that may prove irreversible and less hospitable to humans and other life ... the Earth's System has moved well outside the range of the natural variability exhibited over the last half million years at least. The nature of changes now occurring simultaneously in the Earth's system, their magnitudes and rates of change are unprecedented. The Earth is currently operating in a no-analogue state" .

It would be tedious to enumerate the consequences of this combination of factors for human society. They suggest a dysfunctional world of increasing risks to the wellbeing of our society. Such risks include greater possibilities for conflict over resources, with use of dangerously destructive weapons, wider division between rich and sophisticated and poor and uneducated, larger flows of refugees both within and between countries, evolution of new and the return of old diseases, extinction of key ecosystems, and social and economic breakdown of a kind that can already be seen in parts of Africa.

I do not want to leave you expecting doom. There is something that we can do about all the categories of catastrophe I have described. But there has be a common theme to any response. These are global problems which will require concerted global solutions.

Let us look first at the kind of disaster which looks furthest from human control: impacts from outer space. I was once a member of a Government Task Force to look into this problem.

What then can we do? Let us suppose that with the help of a greatly improved telescope network, we could with reasonable accuracy predict the next range of extra terrestrial events. We would have to reckon not only with the size and composition of an incoming object, but also with the possibility that it might enter into ever diminishing orbit round the Earth before colliding with it. Our response would fall into two categories.

More promising are the possibilities of deflection through modification of the object's orbit. What would be needed is a steady gentle push, not an explosive jolt. For example the mounting of sails on the object to harness the Sun's radiation pressure to push it from its course. Another possibility would be the use of mass drivers whose source of power would again be the Sun. A number of major engineering problems would have to be solved, but with adequate warning time this should not be impossible.

We are more used to disasters within the Earth system. There the remedies are less exotic. It is well within our capabilities to improve prediction and take measures to mitigate catastrophes. Disasters such as the earthquakes in Turkey in 1999, in Iran in 2002 and 2003, and in China, Haiti and Chile in 2009 and 2010 seem to pull people in communities together as never before, while those in other countries are often willing to send relief to those they have never seen or are never likely to meet.

Larger scale catastrophes would require international effort and administrative skills which are at present lacking. Obviously human ability to cope would depend on the resilience and good health of society in general. A world riven by war and degradation could easily be overwhelmed. Much would depend on the abilities of individual governments to manage at least within the areas of their responsibility.

Now I turn to human damage to the current life system of the planet. This is not inevitable, but faced with self-induced disaster we tend to attitudes, and even policies, of denial. Yet most of the solutions to the problems we have caused are well known.

Take human population increase. The overall rate is still rising, but in several parts of the world it is levelling off. The main factors are improvement in the status of women, better provision for old age, wider availability of contraceptive devices, lower child mortality, and better education, especially for girls and young women.

Take degradation of land and water. We know how to look after them both if we try. We do not have to exhaust top soils, watch them erode into the sea, rely upon artificial aids to nature, eliminate the forests with their natural wealth of species, or poison the waters, fresh and salt. Take the atmosphere. We do not have to rely on systems of energy generation which will affect climate and weather in such a fashion that change could put an overcrowded world at risk.

In short we have to learn to think differently before it is forced upon us. Our ability to do so depend on several factors, high among them change in our value system. A system that gives primacy to market forces, exploitation of resources and ever rising consumption is simply unworkable. At present we seem to want to attach monetary value to almost everything.

Of course some rule-of-thumb method of assessing and comparing values would indeed be useful, not least in giving comfort to economists. But somehow we have to bring in the factor of environmental costs. As has been well said, markets are superb at setting prices but incapable of recognizing costs. In addition to the traditional costs of research, process, production, employment, and so on, prices should reflect the costs involved in replacing a resource or substituting for it; and the costs of the associated environmental problems.

In looking for some form of global institutional framework for the common good, there is much that needs to change. Global institutions are still feeble. Yet change in them is vital if we are to improve our understanding of natural ecosystems and rethink our value system. On the one hand there are the World Trade Organization, the International Monetary Fund and the World Bank which are all institutions with real mechanisms for influencing government policy. They are much stronger on trade than the environment, and tend to be driven by vested interests looking for short-term profitability.

By contrast the 200 or more environmental agreements are dispersed and poorly coordinated, with different hierarchies of reference and accountability, and look principally to the long term. I have long argued for the creation of a World Environment Organization to balance - and be a partner of - the World Trade Organization. A former Director of the World Trade Organization took the same view.

We could also create a global organization on Risk Management. Its job would mainly be to promote coordination, so far sadly lacking, between national agencies. It would cooperate with such bodies as the UN Committee on the Peaceful Uses of Outer Space. Like the Intergovernmental Panel on Climate Change, it would also suggest and if necessary direct action to cope with specific risks.

We have much to do, but there is at least one thing we can say for ourselves. We are the only animal species which could conceivably hope to do anything about the problems I have discussed. Our long term prospects for survival cannot be assured.

I sometimes wonder how long it would take for the Earth to recover from the human impact. How soon would our cities fall apart, soils regenerate, the animals and plants we have favoured find a more normal place in the natural environment, the waters and seas become clearer, the chemistry of the air return to what it was before we polluted it? Life itself, from the top of the atmosphere to the bottom of the seas, and even below that, is so robust that the human experience could become no more than an episode.

Above all let us remember how small and vulnerable we are. We are like microbes on the surface of an apple, on an insignificant tree, in an insignificant orchard, among billions of other insignificant orchards stretching over horizons beyond our sight or even our imagining.


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