Why did Angkor fall? According to the annals of Siam, we understand that the Kingdom of Angkor fell because of the relentless Burmese or Siam invaders. Recently, scientists have come to believe that it was the collapse of the city’s waterworks that resulted in its demise. For those unfamiliar with the topic, you can read my previous post here for more information, but in brief, Angkor’s temple complexes had a network of hundreds of kilometers of canals and massive reservoirs that appear to have been used both for irrigation, religious ceremonies, plumbing, and sewage. In one of the great mystery’s of human history, it was abandoned by the 16th century and its history forgotten. I witnessed these abandoned waterworks when I visited Cambodia in 2003.

Recently, more evidence has emerged that suggest that a “megadrought” preceded the abandoning of the city. Looking at the tree rings of centuries-old conifers that survived the Angkor era, Professor Brendan Buckley of Columbia University reveals a sharp weakening of Asia’s summer monsoon from 1362 to 1392 A.D., and and again from 1415 to 1440 A.D. This occurred just as the “Little Ice Age” that drastically affected Europe was setting in, suggesting a greater global link to climate change. This was shortly before the Khmer kingdom was approaching its fall and collapse.

But there were also warning signs before the two droubts. Archaeological and pollen findings indicate that Angkor’s great reservoirs and storage ponds began operating at sharply reduced capacity several decades before the back-to-back droughts. So it wasn’t just droubt, but climate instability in general, along with an inflexible plumbing and sewage system, that brought about the collapse and abandonment of the city.

All this information comes from a recent article in Science, published on February 20, 2009. And it ends with this warning:

Both Younghusband and I have traveled to Cambodia on separate trips in 2003 and traveled the country. We visited Angkor Wat, saw landmine museums, played chess with German ex-pats, and shot AK-47s at the cost of a few dollars. Prostitution was advertised regularly and I was told that drugs were readily available for purchase. There was not a hint of high-rises or skyscrapers in the city of a quarter of a million, with the tallest building being perhaps 8 stories high. In talks with my very learned, bilingual and friendly hotel proprietor, he revealed that he used to be a bureaucrat for the Ministry of Economy, but left when the government couldn’t afford to pay his salary for six months. Compared to nearby Thailand, Malaysia, and even Vietnam and Laos, Cambodia was still poor and chaotic.

But things are changing. The Wall Street Journal recently published an article on Phnom Penh that said it is “tamed and transformed.”

Today, Phnom Penh still has plenty of rough edges and crime. At certain places, visitors can still order “happy pizza,” or pizza with marijuana topping. But in other ways, it’s a different city entirely. But the government has destroyed 200,000 or more firearms through a program in which citizens voluntarily lay down their guns. It has also shut down the military-hardware market and closed some of the most infamous brothels. Foreign cash is pouring in, with some investors calling Phnom Penh “The New Ho Chi Minh City” after the city that’s Vietnam’s emerging center of consumption. Property values have soared and Phnom Penh is getting its first skyscrapers. One Cambodian developer even wants to dredge the Mekong River all the way to Vietnam, some 60 or so miles south, to create a deepwater megaport, and other financiers are planning a satellite city with offices and malls.

All that activity has brought more well-heeled visitors and more hotels. The Quay Hotel along the riverfront, opened earlier this year, which calls itself Phnom Penh’s first “carbon-friendly” hotel (it measures carbon emissions and then buys “offsets” through carbon-reduction programs) and features minimalist décor of the “2001: A Space Odyssey” variety, spaces “infused with aromatherapy” and a rooftop wine bar. Other new hotels include the Pavilion, an elegant boutique property in a colonial mansion hidden behind the Royal Palace.

Some have complaints. Many of the hardened expats who have turned Cambodia into their adopted home are upset at the gentrification. Tuk-tuks, the ramshackle taxis used for short trips around town, now sometimes cost $2 instead of $1. Rents have soared and the average Cambodian hasn’t yet seen the benefits, and their incomes remain the lowest in the region. But it’s a start on what should be positive changes.