Environmental changes have also been considered as a factor in the empire’s decline.

There has been debate around the decline of Angkor coinciding with an era of rapid climate change known as the ‘Little Ice Age’, which began in around 1300 following the Medieval Warm Period.

The natural transition of global temperatures had wide-ranging impacts across the globe. In Europe, rivers froze regularly, and crop harvests diminished. In South-East Asia, the steady pattern of wet–dry seasons became volatile. Regular rainfall gave way to decades-long drought followed by unusually heavy, destructive downpours. The climatic volatility decreased the productivity of traditional Khmer rice cultivation areas. To counteract the low productivity, farmers increased the size of their fields. Old-growth forest was cleared for use as farmland; however, during the heavy rains, sediment once held in place by the forest eroded and washed into the barays. The barays and canals became clogged with soil and the earth dykes were continually battered and damaged by floodwaters. Angkor and its people relied on the baray and canal systems to sustain them. Some scholars have proposed that, towards the end of the empire, the silt build-up in the canals that fed and drained the lakes was so extensive that many became unusable or inefficient at supporting the population. With less food, mustering the manpower to clear them became an increasingly difficult task.

Internal pressures, too, were causing instability. Break-ups within the fabric of the empire were causing pressure on the government. For centuries, the people of the Khmer Empire had varied spiritual pursuits, but most people worshipped the Hindu god Shiva and/or practised Mahayana, a form of Buddhism. These philosophies espoused the virtues of honouring ancestors and family and were the basis of royal power. Over time, there was a shift among the people and ruling elite of the empire towards Theravada Buddhism. This more conservative form of Buddhist belief promoted an austere life, personal sacrifice and social equality. This sat at odds with a royal court and a class system in which an elite group administered those below them.

Learning activities

1. How might the shift towards Theravada Buddhism have undermined the position of the royal court? Research the tenets of Theravada Buddhism and consider how this shift would have disrupted the government.
2. Consider the argument that the change in climate played a part in the downfall of the Khmer Empire. How might this have impacted the empire?
3. The Earth’s climate has fluctuated many times throughout history in a natural cycle. Have there been any other empires whose decline has coincided with these cycles? What reasons have been given for their collapse?
4. With the Earth’s climate changing more rapidly than any other time in history, what might this mean for future stability of global food production?
5. Suppose Canberra disappeared one day and everyone who lived and worked there had to leave. Speculate what problems would arise from that. What would have to happen for the country to continue to function? What would it mean for the economy? How would it impact people in other cities? (Activity could be scaled down to state level.)