The phrase "this vast region" is correct and usable in written English.
You can use this phrase to refer to a large area, such as a region with a lot of land or a large geographical area. For example: "This vast region is home to a wide variety of plants and animals."
This vast region is often subdivided into the Palaearctic (Old World) and Nearctic (New World) subregions.
Now we are being urged to accept that even this vast region is just a minuscule fragment of the whole.
"Historically, elephants ranged right across the forests of this vast region of over 2m sq km, but they now cower in just a quarter of that area.
Both Thomas and Ms. Shaughnessy are part of economic and demographic developments rustling this vast region with its staggering vistas and lonely, cedar-studded mountains.
Heroin and H.I.V. have already penetrated virtually every corner of this vast region, a farrago of pristine forest and permafrost, dying company towns and smoky industrial cities.
Even more remarkably, she shows us the temperature anomaly charts – much of this vast region is presently 2-6C above normal temperatures for this time of year.
Many rebel groups and government troops have been vying for control in the vast region.
Who really knows a Corbières from a Faugères, to cite two appellations in the vast region?
All this in a vast region in which failed states are piling up, nations are disintegrating, terror insurgencies are spreading, humongous population upheavals are becoming the norm, and there are refugee flows of a sort not seen since significant parts of the planet were destroyed during World War II.
The main aim of the present work is to show the results of this process in Extremadura, a vast region situated in the south-west of Spain, which has been historically characterized by the preponderance of a type of open oak parkland, known as 'dehesa'.
There is a lack of information on this issue in Central Brazil, a vast region located in the innermost part of South America.
