American farmers could be one of the biggest losers if President-elect Donald Trump starts a trade war with China, a former chief economist for the Agriculture Department said today.

The United States currently exports about $20 billion to $24 billion worth of agricultural exports to China each year, and that’s expected to “grow even more over the next 10 years,” Joe Glauber, a visiting senior research fellow at the International Food Policy Research Institute, said at a discussion on U.S.-China farm trade hosted by the U.S. Chamber of Commerce. “That’s a pretty big vulnerability.”

Trump has threatened to use a variety of trade measures to defend the U.S. manufacturing sector and try to bring jobs back to the United States, raising the prospect of a tit-for-tat trade war with the world’s second largest economy.

In the short-term, it would be hard for China to replace all of the soybeans and other agricultural products it imports from the United States.

“But there are other sources,” Glauber said. “I think Brazil and Argentina and Ukraine and a number of other places would be more than happy to fill whatever needs they could, shipping soybeans to China. I think these things can be very devastating and let’s hope it doesn’t get to that point.”

The United States exported $10.5 billion in soybeans to China in 2015. That was more than half of the $20.3 billion in total U.S. farm exports to China.

Altogether, American farmers enjoyed a $16 billion farm trade surplus with China last year, with other major exports including sorghum ($2.1 billion), distiller’s dried grains with solubles ($1.6 billion), cotton ($860 million), forage products ($359 million), dairy products ($350 million), pork ($319 million), as well as wheat, corn, poultry and additional farm goods.