Measurements of global forest cover can vary widely — by as much as 6 percent of the planet’s land area, a swath equal in size
to China, according to research from the University of Maryland. The reason behind the discrepancy actually lies in how different researchers and organizations define forest cover, the researchers note. Geographers have long called for the definition to be standardized, but until now, no one had quantified the scope of the variance. The largest ambiguities in forest calculations are driven by uncertainties near savannas, shrublands, mountain ridge forests, and other areas with intermediate tree cover. “It’s not technology’s fault” that forest maps are inconsistent, said lead author Joseph Sexton. But until the definitions are standardized, he said, it will be difficult to properly assess land cover or conservation measures related to climate change and biodiversity.