My first comment, without reading, is that it look like an excessively long paragraph. Pargraphs of great length don't make for comfortable reading- one idea/point (and development) per paragraph helps the reader.
Now after reading:
because of the rivers in both areas provided- because the rivers...
specialization but these - comma before but
the Tigris and the Euphrates River- rivers?? or nothing??
these silts- you've jumped from singular to plural-
the Nile River flooded annually and it also carried silt that was deposited into the river banks.- why the past tense here? It still does
enabled superb agriculture fields- hmm, how about created superb agricultural land?
With these fields men- no women involved?
Both lands have regions around the river that differed from the other region- the repetition of region makes it hard to follow
invading emigrants- invaders?
pressures and treats - threats
were constantly been- being
civilizations that wants- singular/plural problem
surrounded by lands-unclear phrase
inland trades occurred- does trade 'occur'? Competitions also occurred- repetition of verb
unique difference- differences (and maybe not unique)