Montag, 13. Oktober 2008

long summer 1

As previously mentioned, The Long Summer, by Brian Fagan, chronicles the advance of civilisation through our planet's turbulent climatic history. As global weather patterns have shifted and swung, reacted and counteracted, mankind has responded in both his movement around, and his settlement of land.

I wanted to go through the book chronologically, stopping at places which I found particularly interesting. The first stop is the story of the Laurentide ice sheet, which covered most of Canada and parts of the USA at the end of the last Ice Age, before cycles of growth and melting began which ultimately had a major influence on global climate, and therefore human civilisation.

A direct consequence of gradual melting was the opening of a corridor between the Laurentide and Cordilleran ice sheets, initially about 11,500BC. The corridor offered the first portal in to the hitherto unsettled American continents. An image of a huge, narrow canyon, with steep walls of ice to either side, stretching far into the distance and enticing curious hunter gatherers into its mysterious inner recesses and beyond is tempting, but colonisation was undoubtedly a gradual process.
If Paleo-Indian populations from the north did indeed pass through the widening defile, they must have moved southward not in a deliberate migration, but as a result of the annual round. The opening corridor was some 1,500km long, not a distance people would walk in a single summer and fall, but one that migh be traversed over some generations by small bands moving with the seasonal migrations of bison, caribou, and other animals. Some groups may have followed prey south of the ice sheets, then followed them back north. Generations of such movements would have extended even further southward, until some groups were living permanently south of the corridor, in much more hospitable territory.
Nevertheless, it marks an exciting turning point in mankind's colonisation of the globe, when the forces of expansion pressed against an impassable climatic barrier, and trickled through to finally gain access to the most distant corners of our planet.

Another effect of the ice sheets gradual retreat was more global in its implications. In a process which should cause concern for the future of our remaining ice sheets on Greenland and Antarctica, long term warming of the ice caused the bottom layers to melt more quickly than the top, thus lubricating the base and causing sudden, catastrophic collapse. Some of these, so called Heinrich events, expelled huge amounts of ice and meltwater into the Atlantic...
The intrusion of millions of gallons of glacial freshwater into the northern Atlantic Ocean had the effect of shutting down the circulation of warmer water in the Gulf Stream, which depends on the downwelling of saltwater in the Labrador Sea. The inevitable result: a deep freeze in Europe as the prevailing warm westerly winds faltered. Cold, dry, and windy conditions settled over a broad region across North America and Europe, and extended as far south as subtropical Asia and Africa. Much of the world became drier, because the cooling reduced the amount of water vapor as storm tracks moved southward. A Heinrich event, then, is a feedback loop - a quick warming that causes its own end in a quick cooling.
A Day After Tomorrow scenario? Similar in effect was the emptying of Lake Agassiz, a huge freshwater lake which grew along the western edge of the elting Laurentide until about 11,000BC. Then, in a matter of months, the lake outgrew the ice sheet, and began eating into eat, eventually carving a passage through which it emptied itself in to the Atlantic. This marked the beginning of a thousand year event known as the Younger Dryas; global sea level rise, sudden climatic oscillations across the world, and drought to the Fertile Crescent, where a previously benign climate had allowed both massive population growth, and created conditions for the first settled communities, such as the Abu Hureyra.
At first, the people adjusted to drier conditions by turning to small-seeded grasses and other standby foods. In about 10,000BC, they took the next logical step - attempting to grow grasses to expand the wild harvest. The first domesticated seeds appear in the village - rye, einkorn, and lentils - but they were not enough to feed everyone. After years of good living, the village had swelled to perhaps three or four hundred inhabitants, a population density far beyond the constraints imposed by a mobile existence. A permanent settlement like Abu Hureyra was no longer viable in the absence of the nut harvests and in the face of a severe drought that made even less desirable foods even scarcer. We can imagine the cold months of winter, hungry families huddled in their dwellings, with even firewood in short supply in an arid landscape no longer forested. Despite the experiments with cereal grasses, Abu Huryra was a community under stress from protracted drought. A few generations after the experiments began, the village was abandoned. Whether the abandonment was deliberate or gradual we have no means of knowing. But with fellow kin unable to help, food supplies faltering, and no end to the drought in sight, the ancient strategy of mobility was the only option, whatever the cost.
The passage nicely sums up the main thread of the book; the delicate dance of population size and carrying capacity, social flexibility and environmental stability. A land rich in resources allows the hunter gatherer, previously wandering where the seasons took him, to settle down and sire a large family. Sudden climatic changes, caused by invisible, unimaginable forces, take the plenty away from a now much larger, and less mobile population. Do they downsize, dispand and go back to constant movement? Or do they explore new method of land-use, enter a new relationship with their territory which allows them to maintain, even develope, the new lifestyle? Of course both happened. The first experiments, such as Abu Hureyra, may have failed, but eventually changes in climate caused by events such as the Younger Dryas forced us to play the ace up our sleeve; agriculture.
N An appropriate comment by George Monbiot. In particular the following is fitting:

Ecology and economy are both derived from the Greek word oikos - a house or dwelling. Our survival depends on the rational management of this home: the space in which life can be sustained. The rules are the same in both cases. If you extract resources at a rate beyond the level of replenishment, your stock will collapse. That's another noun which reminds us of the connection. The Oxford English Dictionary gives 69 definitions of "stock". When it means a fund or store, the word evokes the trunk - or stock - of a tree, "from which the gains are an outgrowth". Collapse occurs when you prune the tree so heavily that it dies. Ecology is the stock from which all wealth grows.

The two crises feed each other. As a result of Iceland's financial collapse, it is now contemplating joining the European Union, which means surrendering its fishing grounds to the common fisheries policy. Already the prime minister, Geir Haarde, has suggested that his countrymen concentrate on exploiting the ocean. The economic disaster will cause an ecological disaster.

I think what Fagan is talking about is exactly this scenario proposed by Monbiot, where Iceland seeks to enter a larger, more inflexible but stable, economy, at the cost of autonomous control of it's territory.

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