There are various reasons for population migration, which have certain impacts on society, economy, ecology, and culture. Answer questions 6-11. In the following population migration matters

① The resettlement in the Three Gorges Reservoir area is first of all needed for project construction and does not belong to ecological migration, so it does not meet the meaning of the question;

② The migration of farmers in western Ningxia is mainly due to the dry climate and belongs to ecological migration. Immigration, so it is correct;

③The migration of educated youth from the east to the western border is due to political factors, so it does not meet the meaning of the question;

④Farmers in southern Shaanxi moved out of disaster-prone mountainous areas, and due to ecological problems It belongs to ecological migration, so it is correct.

So choose: D.