Collapse: How Societies Choose to Fail or Succeed (22 page)

of rongo-rongo was inspired by the islanders' first contact with writing during the Spanish landing of 1770, or else by the trauma of the 1862-63 Peruvian slave raid that killed so many carriers of oral knowledge.

In part because of this history of exploitation and oppression, there has been resistance among both islanders and scholars to acknowledging the
reality of self-inflicted environmental damage before Roggeveen's arrival in
1722, despite all the detailed evidence that I have summarized. In essence, the islanders are saying, "Our ancestors would never have done that," while
visiting scientists are saying, "Those nice people whom we have come to
love would never have done that." For example, Michel Orliac wrote about
similar questions of environmental change in Tahiti, "... it is at least as
likely
—if not more so—that environmental modifications originated in
natural causes rather than in human activities. This is a much-debated
question (McFadgen 1985; Grant 1985; McGlone 1989) to which I do not
claim to bring a definitive solution, even if my affection for the Polynesians
incites me to choose natural actions [e.g., cyclones] to explain the damages suffered by the environment." Three specific objections or alternative theo
ries have been raised.

First, it has been suggested that Easter's deforested condition seen by
Roggeveen in 1722 was not caused by the islanders in isolation but resulted
in some unspecified way from disruption caused by unrecorded European
visitors before Roggeveen. It is perfectly possible that there were indeed one
or more such unrecorded visits: many Spanish galleons were sailing across the Pacific in the 1500s and 1600s, and the islanders' nonchalant, unafraid,
curious reaction to Roggeveen does suggest prior experience of Europeans,
rather than the shocked reaction expected for people who had been living
in total isolation and had assumed themselves to be the only humans in the
world. However, we have no specific knowledge of any pre-1722 visit, nor is it obvious how it would have triggered deforestation. Even before Magellan
became the first European to cross the Pacific in 1521, abundant evidence attests to massive human impacts on Easter: extinctions of all the land bird
species, disappearance of porpoises and tuna from the diet, declines of forest tree pollen in Flenley's sediment cores before 1300, deforestation of the Poike Peninsula by around 1400, lack of radiocarbon-dated palm nuts after
1500, and so on.

A second objection is that deforestation might instead have been due
to natural climate changes, such as droughts or El Nino episodes. It would
not surprise me at all if a contributing role of climate change does eventu
ally emerge for Easter, because we shall see that climatic downturns did

exacerbate human environmental impacts by the Anasazi (Chapter 4),
Maya (Chapter 5), Greenland Norse (Chapters 7 and 8), and probably many
other societies. At present, we lack information about climate changes on Easter in the relevant period of
a.d.
900-1700: we don't know whether the climate got drier and stormier and less favorable to forest survival (as pos
tulated by critics), or wetter and less stormy and more favorable to forest
survival. But there seems to me to be compelling evidence against climate change by itself having caused the deforestation and bird extinctions: the
palm trunk casts in Mt. Terevaka's lava flows prove that the giant palm had
already survived on Easter for several hundred thousand years; and Flen-
ley's sediment cores demonstrate pollen of the palm, tree daisies, toromiro,
and half-a-dozen other tree species on Easter between 38,000 and 21,000
years ago. Hence Easter's plants had already survived innumerable droughts
and El Nino events, making it unlikely that all those native tree species finally chose a time coincidentally just after the arrival of those innocent hu
mans to drop dead simultaneously in response to yet another drought or El
Nino event. In fact, Flenley's records show that a cool dry period on Easter
between 26,000 and 12,000 years ago, more severe than any worldwide cool
dry period in the last thousand years, merely caused Easter's trees at higher
elevation to undergo a retreat to the lowlands, from which they subsequently recovered.

A third objection is that Easter Islanders surely wouldn't have been so foolish as to cut down all their trees, when the consequences would have
been so obvious to them. As Catherine Orliac expressed it," Why destroy a
forest that one needs for his [i.e., the Easter Islanders'] material and spiri
tual survival?" This is indeed a key question, one that has nagged not only Catherine Orliac but also my University of California students, me, and everyone else who has wondered about self-inflicted environmental dam
age. I have often asked myself, "What did the Easter Islander who cut down
the last palm tree say while he was doing it?" Like modern loggers, did he
shout "Jobs, not trees!"? Or: "Technology will solve our problems, never fear, we'll find a substitute for wood"? Or: "We don't have proof that there aren't palms somewhere else on Easter, we need more research, your pro
posed ban on logging is premature and driven by fear-mongering"? Similar
questions arise for every society that has inadvertently damaged its envi
ronment. When we return to this question in Chapter 14, we shall see that
there is a whole series of reasons why societies nevertheless do make such
mistakes.

Why Was Easter Fragile?

■ ■ ■

We still have not faced the question why Easter Island ranks as such an
extreme example of deforestation. After all, the Pacific encompasses thou
sands of inhabited islands, almost all of whose inhabitants were chop
ping down trees, clearing gardens, burning firewood, building canoes, and
using wood and rope for houses and other things. Yet, among all those
islands, only three in the Hawaiian Archipelago, all of them much drier
than Easter
—the two islets of Necker and Nihoa, and the larger island of Niihau—even approach Easter in degree of deforestation. Nihoa still sup
ports one species of large palm tree, and it is uncertain whether tiny Necker,
with an area of barely forty acres, ever had trees. Why were Easter Islanders
unique, or nearly so, in destroying every tree? The answer sometimes given,
"because Easter's palm and toromiro were very slow-growing," fails to ex
plain why at least 19 other tree or plant species related to or the same
as species still widespread on East Polynesian islands were eliminated on
Easter but not on other islands. I suspect that this question lies behind
the reluctance of Easter Islanders themselves and of some scientists to ac
cept that the islanders caused the deforestation, because that conclusion
seems to imply that they were uniquely bad or improvident among Pacific
peoples.

Barry Rolett and I were puzzled by that apparent uniqueness of Easter. Actually, it's just part of a broader puzzling question: why degree of defor
estation varies among Pacific islands in general. For example, Mangareva
(to be discussed in the next chapter), most of the Cook and Austral Islands,
and the leeward sides of the main Hawaiian and Fijian Islands were largely
deforested, though not completely as in the case of Easter. The Societies and
Marquesas, and the windward sides of the main Hawaiian and Fijian Is
lands, supported primary forests at higher elevation and a mixture of sec
ondary forests, fernlands, and grasslands at low elevation. Tonga, Samoa, most of the Bismarcks and Solomons, and Makatea (the largest of the
Tuamotus) remained largely forested. How can all that variation be explained?

Barry began by combing through the journals of early European explorers of the Pacific, to locate descriptions of what the islands looked like then. That enabled him to extract the degree of deforestation on 81 islands as first
seen by Europeans
—i.e., after centuries or millennia of impacts by native Pa
cific Islanders but before European impacts. For those same 81 islands, we
then tabulated values of nine physical factors whose interisland variation

we thought might contribute to explaining those different outcomes of deforestation. Some trends immediately became obvious to us when we just
eyeballed the data, but we ground the data through many statistical analyses
in order to be able to put numbers on the trends.

What Affects Deforestation on Pacific Islands?

Deforestation is more severe on:

dry islands than wet islands;

cold high-latitude islands than warm equatorial islands;

old volcanic islands than young volcanic islands;

islands without aerial ash fallout than islands with it;

islands far from Central Asia's dust plume than islands
near it;

islands without makatea than islands with it;

low islands than high islands;

remote islands than islands with near neighbors; and

small islands than big islands.

It turned out that all nine of the physical variables did contribute to the
outcome (see the table above). Most important were variations in rainfall
and latitude: dry islands, and cooler islands farther from the equator (at
higher latitude), ended up more deforested than did wetter equatorial is
lands. That was as we had expected: the rate of plant growth and of seedling
establishment increases with rainfall and with temperature. When one
chops trees down in a wet hot place like the New Guinea lowlands, within a
year new trees 20 feet tall have sprung up on the site, but tree growth is
much slower in a cold dry desert. Hence regrowth can keep pace with mod
erate rates of cutting trees on wet hot islands, leaving the island in a steady
state of being largely tree-covered.

Three other variables
—island age, ash fallout, and dust fallout—had ef
fects 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 is
lands. 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 explo-

sions. 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 be
yond the Andesite Line, the main aerial input of nutrients to renew soil fer
tility 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 macerating my hands on a coral boulder if
I touched it while thoughtlessly extending my hands to maintain my bal
ance. 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, dis
tance, 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 is
landers 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 is
lands, 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.