For those who worry that population growth and immigration stymies economic growth and reduces prosperity, events in Zimbabwe should be welcome. Robert Mugabe’s policies are driving millions of Zimbabweans into South Africa, Mozambique, and other African countries. See Tyler Cowen’s post  at Marginal Revolution, and this story in the just-released Economist  (subscription required).
No illegal immigrants in Zimbabwe; no "excess" or "uncontrolled" population growth; no worry that non-Zimbabweans are using scarce public resources.
According to the theory of many of those who fear immigration and population growth reduce wages, wages in Zimbabwe should rise, as should its people’s standard of living. According to those who fear that immigration and population growth damage the environment, the environment in Zimbabwe should become cleaner, safer, more sustainable, and more beautiful. According to those who fear that immigration and population growth put a too-heavy burden on government schools, roads, and other public goods, public goods in Zimbabwe should become models of efficient and uncongested use.