Nature's Evil

Emerging from the forests, the barbarians put out this fire. By the seventh century, the level of energy harnessed per person fell by a factor of two. Only many centuries later did the mass consumption of Dutch peat and British coal allow societies to exceed the energy consumption reached by the Romans. Like any other activity, extracting fuel requires energy. The production of a kilogram of firewood or coal takes about 5 megajoules. When wood is burnt, it produces three times the amount of energy used to produce it. For coal, the figure is up to a hundred times greater and, for oil, up to a thousand times. Different forms of stored energy have very different characteristics, and they shaped different societies. Cities heated by wood, such as Rome, are organised differently from cities heated by peat, such as Amsterdam, and from cities heated by coal, such as London. The Romans dreamt of gold, of miraculous machines and voyages to other worlds. None of them could have guessed that the peaty sludge and black stone they found in their chilly colony would turn out to be the greatest miracles of the new world.

Ships

Humans’ earliest sources of energy were renewable. The wind filled sails, sending adventurers off in search of raw materials or their substitute, gold. Commodities floated downstream, and animals hauled goods upstream. Always on the front line of technology, shipbuilding sent people back to the forests. Ships required timber of the highest quality and of various sorts: straight oak for the planking, crooked oak for the ribs, pine for the masts, beech and spruce for the decks. And ships needed other products from the northern lands – tar for caulking the hull planks, hemp for ropes and linen for sails. But, in Southern Europe, forests remained only in the most inaccessible areas, on islands or on mountainsides. Wars were fought over these vital supplies of timber, and they were turned into colonies – Cyprus and Sicily, Istria and Macedonia, and later the Tyrol and Galicia. Sawmills and quays had to be constructed at river estuaries. All this activity depended on the population living on the river banks and sea coasts. But the imperial exploitation of the forests came into conflict with the native ways of using them and led to the policing of increasingly distant and inhospitable lands.

The Roman trireme had a wooden hull and deck, about 200 oars and two masts. Building such ships required thousands of trees of rare species. The Vikings’ ships were simpler and lighter, but more seaworthy thanks to their use of tar. This sticky, impermeable substance, produced by the dry distilling of pine or birch wood, protected the craft from leaks and rotting. The Vikings dug a big clay pit, filled it with chunks of pine, covered them with turf, and set them alight. After several hours, tar trickled down out of an opening at the bottom of the pit. The sailors of antiquity also knew the recipe for making tar, but it required pine trees in quantities which they could hardly obtain. The Vikings produced tar on an industrial scale, 300 litres at one go; two such distillations would produce enough tar to caulk one craft. The sails, which the Vikings made out of wool, were also soaked in tar – they turned black. It is only thanks to the archaeologists who found these tar pits that we understand why the Vikings were better seafarers than the Romans or the Phoenicians. 8

Republics and empires alike were preoccupied by the shortage of oak for hulls, beech for decks and pine for masts. It took up to 2,000 oak trunks, preferably from hundred-year-old trees, to build one large warship; but oaks grow in rich soil suitable for agriculture, and they were always in short supply. The Venetians invested in planting and protecting forests along the Adriatic. 9 Powerful religious orders – Benedictines in the Alps, the Teutonic order on the Baltic – cleared forests at the European frontier, pushing it to the north and the east. Combining wood and metal, new implements – axes, yokes, wheels and ploughs – increased the productivity of the cleared land. Later, wooden palisades and stockades – no match for firearms – were replaced by clay and stone. But there was nothing to replace the floating fortresses built from choice timber.