"We have clear evidence now that Angkor was big enough to have caused environmental problems," Damian Evans said.
"But we need finer-grained detail to determine for sure how severe those problems were, and whether or not the local population was able to deal with them or not," said Evans, deputy director of the Greater Angkor Project at the University of Sydney.
His group published its findings in this week's online edition of Proceedings of the National Academy of Sciences.
They reveal that Angkor, during its zenith between the 9th and 14th centuries, was "the world's most extensive preindustrial low-density complex" and far larger than previously thought. It included an elaborate water management network encompassing nearly 1,000 square kilometers (390 square miles).
Extending rice fields to support a population of more than 1 million resulted in serious ecological problems, including deforestation, topsoil degradation and erosion.
The study's conclusions supported a theory in the early 1950s by Bernard-Philippe Groslier, a prominent French archaeologist, that the collapse of Angkor stemmed from over-exploitation of the environment.
The study produced a comprehensive digital mapping database detailing tens of thousands of individual features across nearly 3,000 square kilometers (1,160 square miles).
Previously, there were around 800 known temple sites in the mapped area, Evans said in an e-mail, adding that the number will likely be between 950 and 1,000 once results from the excavations have been verified on the ground."