LOS ANGELES—Low birth rates, uncertainty over immigration and long-term impacts from COVID-19 will result in a year-over-year population decline in Southern California for the first time ever, researchers said in the first of a two-part demographic conference sponsored by the Southern California Association of Governments (SCAG) and the University of Southern California. The 32nd annual Demographic Workshop, held virtually this year, is built around the theme, “The Post-Pandemic City.” Participants are taking a close look at several intersecting developments that could significantly change life in the six-county SCAG region, including the pandemic and post-pandemic recovery, heightened awareness of racial equity and inclusion, and results of the 2020 Census. The latter already will result in California losing a Congressional seat. Part two of the workshop will be held June 15. For decades, Southern California has ranked among the most vibrant population centers in the United States, climbing above 19 million. However, …