When nature bites back

The Nazca of Peru and the Polynesian residents of Easter island both paid the ultimate price for their environmental sins, according to our modern eco-morality tales.

The residents of Easter Island chopped down trees as well as creating the 'moai' stone stautes.

Stories of the dire fate that befalls evil-doers are a mainstay of most religions - and no wonder: with their vivid imagery and dramatic denouements, they make otherwise abstract threats seem real. Lately environmentalists have turned to a similar device to convince the world to change its consumerist ways. It's the eco-morality tale, in which those who treat the environment in a cavalier fashion come to a sticky end. From the desertification of north Africa by Roman wheat farmers to the collapse of fish stocks off Newfoundland in the 1990s, there is a rich seam of such stories to mine. Now there is a new one from Peru, which centres on the fate of the Nazca people, forerunners of the Incas. After their emergence in southern Peru around 2,000 years ago, the Nazca thrived for several centuries until, around AD500, their culture underwent some kind of collapse and fell into sharp decline.

Suspicion has long focused on some kind of climatic catastrophe, with the most likely culprit being the notorious El Nino phenomenon, in which part of the Pacific becomes abnormally warm, triggering severe weather events worldwide - and especially around the coastline of Peru. Research suggests that a particularly severe El Nino event did indeed take place around AD500 and appears to have devastated the Nazca culture by triggering severe flooding. But a new study looks set to transform the event into a new eco-morality tale, by suggesting that the environmental sins of the Nazca themselves left them vulnerable to nature's wrath. A team led by the archaeologist Dr David Beresford-Jones at Cambridge University has examined the pollen record in the area occupied by the Nazca, and found evidence of severe deforestation caused by changing agricultural practices. Over time, the source of pollen switched from small, hardy trees with long roots to crops such as cotton and maize.

According to the team, the results are consistent with the Nazca cutting down the trees to create farms, thus robbing the soil of the root system that held it firm against wind, rain and floods. The result was rapid soil erosion, leading to the collapse of agriculture in the area, which eventually turned to the arid desert seen today. Dr Beresford-Jones and his team are cautious about claiming to have found the explanation for the collapse of the entire Nazca culture, which continued to eke out a living beyond the one valley they have so far examined. Even so, their findings, published in the current issue of the journal Latin American Antiquity, are being hailed as yet further proof of the perils facing those who fail to live in harmony with the planet. In particular, parallels have been drawn with the best-known of all eco-morality tales: the fate of Easter Island. Made famous by the American biogeographer Jared Diamond in his best-selling book Collapse: How Societies Choose to Fail or Succeed, the story of this remote Pacific island does seem strikingly similar. Colonised around AD800 by settlers from elsewhere in Polynesia, Easter Island thrived until around AD1200, when the inhabitants began chopping down the island's extensive forests to make dwellings and to create the famous network of huge stone statues, the "moai". According to Prof Diamond and others, the population then soared to around 15,000 and deforestation took place at a furious rate.

Within 250 years, virtually all the trees had gone. Unable to support the population, the island's eco-system collapsed, triggering famine, war and even cannibalism. By the time Dutch explorers reached the island, on Easter Sunday 1722, the population had plunged by at least 80 per cent. Professor Diamond described the fate of the islanders as "the clearest example of a society that destroyed itself by overexploiting its own resources", adding that: "The parallels between Easter Island and the whole modern world are chillingly obvious." Yet as so often with the environmental debate, these parallels aren't as clear-cut as they are claimed to be. For a start, there are grave doubts about the size of the original population, and thus about the supposed population "collapse". The widely-cited figure of 15,000 is just a guess based on estimates of the manpower needed to erect the moai. Recent carbon dating of debris found on the coast of Easter Island in fact suggests that the first Polynesian settlers arrived up to 400 years later than the date cited by Prof Diamond. Only an implausibly high rate of population growth is then capable of producing the 15,000 supposedly occupying the island during the deforestation. That said, there's little doubt that deforestation did take place. So if the depredations of the islanders were not responsible for it, what was? Researchers have found huge numbers of ancient rat bones on the island, suggesting that the first human settlers did not come unaccompanied. As the inhabitants of other Pacific islands have discovered, rats are quite capable of triggering deforestation, by eating the seeds of trees, preventing regeneration. Whatever the true cause, the impact of the deforestation on the islanders appears to have been overplayed. Archaeologists have found no convincing evidence for warfare, cannibalism or general chaos before the Dutch arrived. Indeed, the explorers remarked on how healthy the islanders looked, considering the bleakness of their island home. In short, far from being a salutary tale of "ecocide", the story of the Easter Islanders is one of the astonishing ability of humans to adapt to their environment and thrive in the face of adversity. If there is a lesson to be drawn from their experiences - and now those of the Nazca - it is that life can be made a whole lot easier by preserving trees. But that's hardly a radically new idea. Since the 19th century, many countries have begun mass tree-planting campaigns, with more than 30 having annual "Arbor Days" to highlight the importance of trees to the environment. Many countries have benefited from the results, among them the UAE. For example, since the mid-1970s, more than 150,000 hectares of drought-resistant trees have been planted in the Al Gharbia region of Abu Dhabi. Despite what some environmentalists seem to think, not all of us need scary stories to prompt us to do the right thing. Robert Matthews is Visiting Reader in Science at Aston University, Birmingham, England