English speakers tend to assume that all the important research is published in English.

More than half of the non-English papers observed in this study had no English title, abstract or keywords, making them all but invisible to most scientists doing database searches in English. […] This problem is a two-way street Not only does the larger scientific community miss out on research published in non-English languages. But the dominance of English as science’s lingua franca makes it more difficult for researchers and policy makers speaking non-English languages to take advantage of science that might help them. —Smithsonian