Rats responsible for Easter Island's demise?

http://news.yahoo.com/s/usatoday/20051206/tc_usatoday/dideasterislandgetrattedout

rats!

aha, i was just about to post that here :D

that's crazy, though - imagine if they found new york 500 years from now and decided that the subway rats had indirectly/directly caused the civilization to die off? i once read that iceland used to be completely forested, but the scandinavian presence and their livestock somehow caused deforestation.

"Hunt counters that deforestation of palm trees by Polynesian rats occurred on the Hawaiian islands. And the Easter Island palms were uniquely vulnerable because the rats had no predators and the trees didn't grow at elevations too high for them to reach."

Jared Diamond also refers to the Polynesian rat as a problem (although not with the same emphasis).

20 million rats (or 100,000) on one Island could create havoc, if too small to catch easily and no other predators.

I think Easter Island only had chickens as domesticated animals.

Mahalo for the thought-provoking post.

On 2005-12-06 18:57, christiki295 wrote:
"because the rats had no predators."

[ Edited by: filslash 2008-09-15 15:23 ]

I dunno. I liked the theory about deforestation caused by transporting and erecting hundreds of giant Tikis better, as a cautionary tale for all of us Tiki collectors, to not carry it too far!

Here is an interesting model re issues of rats on Easter Island:

1. Rats have a positive effect on people births. The birth rate of people will increase with more rats (and the birth rate will decrease if rats are low).

2. Rats have a negative effect on human death. The death rate of people will increase if rats are too low.

3. People have a positive effect on the harvesting of trees. People cut down more trees because they need them for fishing and to cultivate land for crops.

4. Rats have a negative effect on the rate of palm fruit germination. The percentage of new palm seeds that germinate successfully is decreased by the number of rats because the rats chew on the seeds.

5. Palm trees have a positive effect on rat births, because the rats eat the palm fruit.

http://web.pdx.edu/~rueterj/courses/casestudies/easterisland/case1-easterisland.html

Mahalo, Filslash.

This model is so grossly oversimplified, I hope it's not presented as science in that course. Rats have a negative effect on human death, unless they compete with the humans for the same resources that are either consumed for food or consumed as tools in getting food, in which case they have a positive effect on human death? Either way, where is the justification for the inference of actual causal effect, with the predictive value they assign? At least on the webpage where this is described as an assignment, it says "Think of some questions you have about information that was oversimplified or left out of the model above." One would hope that this was the real point of this case study, to explore how oversimplified models are the enemy of real scientific analysis. While we're oversimplifying, why not just reduce it to a model with one rule?

1. Humans have a positive effect on human death.

This may or may not be universally true over time, but for the context of Rapa Nui it could be, IF you use the same methodology as that other model applies in its five rules - combining scraps of direct evidence with heaps of speculation and unabashed logical leaping.

-Randy

Aloha,

On 2005-12-07 18:57, christiki295 wrote:
Mahalo, Filslash.

[ Edited by: filslash 2008-09-15 15:23 ]

Saw a show about Easter Island on the History channel last night, which reminded me of this thread again, and it occurred to me that no one seems to talk about the REAL explanation for the island's demise.

Whether they were representative of deceased ancestors or of something else, the moai were acting as guardians of the island and its inhabitants. Once toppled, the moais' guardianship ended and that precipitated the decline of the population. Disrespect the moai at your own peril!

Seems pretty obvious to me.

-Randy