On olemassa ilmastomalleja, joiden mukaan ns. pieni jääkausi koitui saaren puuston kohtaloksi.
Tähän piti ihan perehtyä. Pari tuoreehkoa tutkimusta löysin nopealla googlauksella:
Simulated climate variability in the region of Rapa Nui
during the last millennium (2011):
"Some first, very preliminary sensitivity studies on the
effect of (simulated) climate variations on the vegetation
change indicate no significant change in forest coverage on
Rapa Nui. Hence, we tentatively
conclude that large-scale
climate changes in the region of Rapa Nui might be too small
to explain strong vegetation changes on the island over the
last millennium. We cannot exclude, however, small-scale,
local effects on precipitation over the island in response to
changes in the local atmosphere-ecosystem system of the is-
land."
Drought, vegetation change, and human history on Rapa Nui (2008):
"
We see no evidence for such a rat outbreak effect in
the pollen records presented here. That said, it could be that
environmental transformation happened too quickly on this
small island to be evident in the relatively coarse stratigraphic
records now available."
"Without a history of frequent fire
disturbance, neither soil development nor the composition of
the island's vegetation had equilibrated to disturbance by fire.
Secondly, Rapa Nui's small size facilitated its rapid burning.
Windiness and seasonal droughtiness, combined with a gentle
topography devoid of natural firebreaks, probably allowed fires
to spread rapidly.
It may not have taken many fire ignitions to
burn most parts of this small island, even those distant from the
first garden plots that were cleared."
"In conclusion,
latitudinal shifts in the subtropical storm track
and resultant changes in the intensity and frequency of cyclonic
storms provide a feasible, though untested, climatological trig-
ger for radical changes in moisture balance on Rapa Nui."
Vaikeahan se on näin jälkeenpäin sanoa, että mikä katastrofin lopullinen syy. Todennäköisesti kaikki vaikutti kaikkeen. Jos ilmasto tuolloin muuttui merkittävästi, niin varmasti myös sillä oli vaikutusta puuston kohtaloon. En kuitenkaan ole vielä valmis jättämään ihmisiä pois yhtälöstä.
