Final answer:
The increased population in Region IV-A of the Philippines is due to its high food-producing capacity and the economic development that creates job opportunities, driving rural-to-urban migration.
Step-by-step explanation:
The population growth in the Calabarzon region, also known as Region IV-A in the Philippines, can be attributed to several factors. This region boasts a high food-producing capacity, including deltas, river valleys, and fertile plains, which not only support the local population but also attract people from other areas seeking food security. Additionally, the economic development and related job opportunities in urban areas of the Philippines have encouraged a rural-to-urban migration trend. This trend is not only observed in the Philippines but also in other newly industrialized countries and regions experiencing growth in trades such as Southeast Asia and sub-Saharan Africa. Climate change has also contributed to migration patterns regionally, though it is not a primary driver specifically mentioned for Calabarzon's population increase.