BEIJING—Chinese birth control policies could cut between 2.6 million and 4.5 million births of the Uyghur and other ethnic minorities in southern Xinjiang within 20 years, up to a third of the region’s projected minority population, according to a new analysis by a German researcher. The report, shared exclusively with Reuters ahead of publication, also includes a previously unreported cache of research produced by Chinese academics and officials on Beijing’s intent behind the birth control policies in Xinjiang, where official data shows birth rates already dropped by 48.7 percent between 2017 and 2019. Adrian Zenz’s research comes amid growing calls among some western countries for an investigation into whether China’s actions in Xinjiang amount to genocide, a charge Beijing vehemently denies. The research by Zenz is the first such peer-reviewed analysis of the long-term population impact of Beijing’s multi-year crackdown in the western region. Rights groups, researchers and some residents …