America is seeing more and more of its most fertile land snapped up by China and other foreign buyers, yet problems with how the US tracks such data means it’s difficult to know just how much.

Foreign ownership and investment in US farmland, pastures and forests jumped to about 40 million acres in 2021, up 40% from 2016, according to Department of Agriculture data. But an analysis conducted by the US Government Accountability Office —

a non-partisan watchdog that reports to Congress — found mistakes in the data, including the largest land holding linked with China being counted twice. Other challenges include the USDA’s reliance on foreigners self-reporting their activity.

Outside ownership of US cropland is drawing attention from Washington as concern rises about possible threats to food supply chains and other national security risks. Lawmakers have called for a crackdown on sales of farmland to China and other nations.

“Without improving its internal processes, USDA cannot report reliable information to Congress or the public about where and how much US agricultural land is held by foreign persons,” the report said.