Pollution, deforestation, urbanisation
If you are referring to the countries surrounding the Mediterranean sea, the answer would be Egypt with a population of about 82,079,636, give or take a few. The second most populated country on the Mediterranean would be Turkey, with a population of 78,785,548.
The Great Plains have the least population of the regions listed above.
The Northern European Plain has a maritime climate in some parts with rain all seasons which make it favorable for farming.Some parts of the plain are characteristic of delta plains.Delta plains are very rich in fertile soils and the flat terrain adds to the advantage.