There are many posited “global harms” of immigration, i.e., harms that accrue to the world at large and are not focused on the specific countries sending and receiving immigrants. These include:

• Increased footprint: Migration increases prosperity, which increases material consumption, exacerbating resource constraints, global warming, etc.
• Killing the goose that lays the golden eggs: If immigration hurts the immigration-receiving countries, this could boomerang on the world at large if there is a slowdown of the technological progress on which world growth depends.
• Cheap labor leading to a technological slowdown: The large supply of cheap labor under open borders may reduce the incentives for people in developed countries to develop labor-saving innovations.
• Animal welfare: Open borders can increase animal suffering worldwide through enhanced meat consumption and factory farming.