Answer:
A feature of the reduction in death rates has been the increased excess mortality of males. There have also been big and rapid reductions in death rates in many developing countries, even in the absence of important improvements in living standards. Antibiotics and insecticides have made a major contribution to this movement in the last twenty years. It is unlikely that death rates will fall as rapidly in the next few decades as in the recent past in either developed or developing countries.
The soil is eroded and worn
destroying one part of the ecosystem affects every other part of it .
River valley trade made them key economic areas.
Hope this helped. :)
