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The Pampa del Tamarugal, which runs from the latitude of Pisagua to the River Loa, differs from the desert tracts on either side of it in having more abundant ground water and a higher water table. In the Lagunas salar it is only three and a half feet from the surface. Today the Pampa still retains fragments of what appears to have been a more extensive thorn-woodland cover, characterized by tamarugos, algar- robos, and other drought-resisting species, that is represented on some of the older maps and described in carly records. Frézier reports that in 1712 there was near Calama a forest of algarrobos where vegetation is now almost entirely absent San Roman saw in the southern Desert of Atacama dead for- ests of algarrobo in the sand. They were dug up for firewood. Plagemann notes the existence of algarrobo forests sixty or seventy vears ago close to the village of Tarapaca where now is complete desert. People of that village supported their troops of sheep by allowing them to eat the fruits of the trees. Much of the wood appears to have been cleared in the latter part of the eighteenth century to aid in a new desert industry, the exploitation of nitrate from Tirana for the local—and illegal— production of gunpowder and also for the reduction of ores. The present exploitation of wood at Tarapacaé depends chictly upon algarrobo trees brought down by mountain streams where the shifting of piedmont stream channels had under- mined algarrobales, that is patches of algarrobo woodland. One should not make the mistake of thinking that this means necessarily a change of climate. A shift in a piedmont stream might leave a long tongue of algarrobo forest without water and kill it off, floods of a later epoch burying the fallen trunks. The drifting of sand, the alleged increase of salt deposits, and possibly a change of climate have helped bring about the disappearance of the forests.