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By Root 1955 0

that we hadn’t anticipated, because we hadn’t been familiar with the scientific literature on the maintenance of soil fertility. Old islands that hadn’t experienced any volcanic activity for over a million years ended up more deforested than young, recently active volcanic islands. That’s because soil derived from fresh lava and ash contains nutrients that are necessary for plant growth, and that gradually become leached out by rain on older islands. One of the two main ways that those nutrients then become renewed on Pacific islands is by fallout of ash carried in the air from volcanic explosions. But the Pacific Ocean is divided by a line famous to geologists and known as the Andesite Line. In the Southwest Pacific on the Asian side of that line, volcanoes blow out ash that may be wind-carried for hundreds of miles and that maintains the fertility even of islands (like New Caledonia) that have no volcanoes of their own. In the central and eastern Pacific beyond the Andesite Line, the main aerial input of nutrients to renew soil fertility is instead in dust carried high in the atmosphere by winds from the steppes of Central Asia. Hence islands east of the Andesite Line, and far from Asia’s dust plume, ended up more deforested than islands within the Andesite Line or nearer to Asia.

Another variable required consideration only for half a dozen islands that consist of the rock known as makatea—basically, a coral reef thrust into the air by geological uplift. The name arises from the Tuamotu island of Makatea, which consists largely of that rock. Makatea terrain is absolute hell to walk over; the deeply fissured, razor-sharp coral cuts one’s boots, feet, and hands to shreds. When I first encountered makatea on Rennell Island in the Solomons, it took me 10 minutes to walk a hundred yards, and I was in constant terror of lacerating my hands on a coral boulder if I touched it while thoughtlessly extending my hands to maintain my balance. Makatea can slice up stout modern boots within a few days of walking. While Pacific Islanders somehow managed to get around on it in bare feet, even they had problems. No one who has endured the agony of walking on makatea will be surprised that Pacific islands with makatea ended up less deforested than those without it.

That leaves three variables with more complex effects: elevation, distance, and area. High islands tended to become less deforested (even in their lowlands) than low islands, because mountains generate clouds and rain, which descends to the lowlands as streams stimulating lowland plant growth by their water, by their transport of eroded nutrients, and by transport of atmospheric dust. The mountains themselves may remain forest-covered if they are too high or too steep for gardening. Remote islands became more deforested than islands near neighbors—possibly because islanders were more likely to stay home and do things impacting their own environment than to spend time and energy visiting other islands to trade, raid, or settle. Big islands tended to become less deforested than small islands, for numerous reasons including lower perimeter/area ratios, hence fewer marine resources per person and lower population densities, more centuries required to chop down the forest, and more areas unsuitable for gardening remaining.

How does Easter rate according to these nine variables predisposing to deforestation? It has the third highest latitude, among the lowest rainfalls, the lowest volcanic ash fallout, the lowest Asian dust fallout, no makatea, and the second greatest distance from neighboring islands. It is among the lower and smaller of the 81 islands that Barry Rolett and I studied. All eight of those variables make Easter susceptible to deforestation. Easter’s volcanoes are of moderate age (probably 200,000 to 600,000 years); Easter’s Poike Peninsula, its oldest volcano, was the first part of Easter to become deforested and exhibits the worst soil erosion today. Combining the effects of all those variables, Barry’s and my statistical model predicted that Easter, Nihoa, and Necker