The episode is known as the Younger Dryas, because in Scandinavia abundant pollen from a tundra flower called the mountain avens, Dryas octopetala, reappears in soil from this date, indicating that the forest had once more given way to tundra.

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And other factors driving global change, like radiation, soil erosion, changing soil conditions and demographic pressures, are also very noticeable in mountain regions.

UNESCO: 83e

As we head back out into the paddy fields, he lights a clove-scented cigarette and points to the shadowy, still-active volcano that shares its name with him - Gunung Agung, the tallest, most sacred mountain on Bali, from which rivers are said to flow and the volcanic soil gains its rich fertility.

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The pigs are smallish, curious mottled animals, which range freely over the mountain, feeding on the acorns from the cork and holm oaks that flourish in the parched soil.

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The mountain is a giant, putrid layer-cake, with dozens of strata of rubbish separated by soil and plastic liners designed to contain the brew of noxious chemicals that would otherwise leach into groundwater.

ECONOMIST: A history of waste