There's the case global warming, there's the case of resources running short, the decaying ozon layer, the growing world population, decaying soil (thus food production) and the ever growing human 'needs' for more resources per person. And perhaps some more.
Most resourses arn't being consumed, their being randomized, instead of mining vains of ore, our ancestors will be mining landfills and the ruins of our cities.
The Aral lake is currently about half it's original size. And mismanagements of soils in Africa are making the food shortage even bigger.
Don't forget the Dead Sea is now two lakes, and Lake Chad is more or less a pond. China will collapse in the next 50 years or so, their population has depleated their aquifers so much all those rice fields will become virtual deserts (Chinese only needed to drill for water to a depth of 30 feet 50 years ago, now they need to go down to over 100.), and even if the whole world supplied food to china dailly, it wouldn't even dent the famine that would swamp them.
Canada might have a chance at greatness in another century with all our freash water, course we'd have to get a big kick in the ass to get ourselves in line to be an accual global power.
As said in the beginning: then the Europeans came and what they found were only about a 100 people, ignorant of their own history! After all, they didn't know where the moai came from. A civilization lost.
Don't forget they were using the Rongo Rongos as fire wood, the reason why only 50 or so survive. They didn't know what they were because the upper class wrote them in their own language, so when they went, the commoners had no idea what they were.
yes, Europe has one of the best climates to tolerate changes, deep soils, very varied terrain -we are truely lucky (which, btw is the reason why agriculture is still fine here while the Fertile Crescent is already ruined and the Great Plains will alos not survive 1000 years of intensive agriculture).
Russia would become a power house, some people are speculating that they are delaying in signing the Kyoto Accord because they reap nothing but benefits from a warmer climate.
Global Warming will not kill humanity, I don't take to the idea that we are the major cause of it, however it could and probably fill be a cause to the fall of modern civilization.
That theory on how the Easter Islander mismanaged (they couldn't really know better beforhand though) makes a load of sense!
One of the main reasons the Norse colonies failed in Greenland with Iceland meeting hard times was the extensive deforestation they did on those two islands without them, the Greenlanders were cut off and had no way to flee when the climate hit a cold spell and stopped most of their food production.
The same thing goes for Rapa Nui, except they were unable to flee the island the moment the tide grabbed them and pushed them ashore. They were doomed from the start, wheather or not the cut down all the trees to move the moai or just used them for fishing boards and everyday use, they used them to the extenction (the last stump died in the 50s or 60s I think).