The economics comes from all of the above. Demand from customers for snake means no snakes left to eat the rats - a classic externality. The demand from consumers for more goods and rampant materialism leads to greater CO2 emissions and hence climate change that may have contributed to the recent flooding. The Chinese government building the three gorges dam that cost billions so that it could be used to control the floods but may also have contributed to the increase in rats. Finally, the ability of the Chinese to substitute rat for other meat and for it to have a cost.
One point of clarification, it appears that what us Brits call mice, the Chinese call rats. What do the Chinese call rats?
This Guardian article is great - it goes straight for the economics. Forget the human misery, lets talk business.
'Rats' on the menu after China swamped by 2 billion rodents [Guardian]
The business management philosophy that one person's crisis is another's opportunity may perhaps never have been taken to such bizarre extremes.
A plague of 2 billion mice in central China was described just days ago as being so bad that it resembled a scene from a horror movie with roads and hillsides turned black with rodents.
But in a remarkable display of entrepreneurship, businessmen are catching, shipping and selling the eastern field mice, also known locally as rats, to the southern city of Guangzhou, where restaurants are reportedly offering rodent banquets to diners notorious for their unusual tastes.
According to Beijing News, businessmen from Guangzhou - the provincial capital of Guangdong - were offering 6 yuan (40 pence) for a kilogramme of live rodents.
The Guardian then decides to mention as an aside the fact that:
The infestation was caused by some of the worst flooding in 50 years in central China. In the past two weeks, more than 400 people have died, 105 are missing and more than 3 million have been forced to evacuate their homes as a result of the deluge.
Another externality (in addition to the eating of owls and snakes):
In the ensuing war on rodents, local people beat hundreds of mice to death. Some used ferrets, others so much poison that more than 1,000 cats and chickens were also killed.
Assuming that the cats were trained rat killers the use of poison would appear to be rather hasty.
Finally, forget the great wall of China, the great mouse wall of Hunan could be the next great tourist hotspot. Is £400,000 a lot? We need to get the Contingent Valuation guys on the job.
Hunan province is attempting to raise more than 6m yuan (£400,000) to build a 24-mile wall to prevent future mice invasions.
H/T: Treehugger - who conclude their article with a fine "economics" phrase.
Two Billion Rats Invade China: From Eco-Disaster To Exotic Delicacy
Rats are being sold in greater numbers at live food markets in Changde, at the western end of the lake. From there, animals make their way to un-distinguished plates in restaurants in neighboring Guangdong province. The government has denied the news, saying that bans on wild animals still stand. But Guangdong, the home of Cantonese cuisine, is known for its exotic taste for everything from turtles to sharks to cats. And in China, where there's demand, there's supply -- and vice versa.