WATERING EARTH
SEA LEVEL CANALS CRIS-CROSS DESERTS TO FILL EARTH'S DEPRESSIONS TO VAST INLAND SEAS - SUN EVAPORATES WATER, CREATING RAIN & CHANGING CLIMATE TO GREEN THE DESERT - SOLAR POWERED PUMPS RAISE WATER UP MOUNTAINS WHERE SUN FLASHES WATER TO STEAM DESALINATING I

Solution

Earth's depressions are in arid areas - bringing water to them changes climate - greening desert and making it habitable - 

Canals are 3000feet (one kilometer) wide and 120 feet deep to accommodate largest ships. Digging canals is profit making enterprise for world's displaced people - since everything taken out of the ground is useful - making worthless desert land waterfront without political baloney increases value exponentially - sustaining the societies that settle along the shores.
Huge solar engine of the desert is harnessed to raise water up sides of canals where some is flashed into steam desalinating it to run down the hillside and gain minerals to be potable so as to nourish plants animals humans and industry.
Natural revisions to political boundaries along ecological lines reduces tension between tribes and other people; enormous productivity of virgin waterfront with fresh water and energy in abundance creates substantial wealth for all habitants - wealthy people do not wage war.   
Canals connections open up interior lands to the worlds waterways promoting peaceful commerce and more wealth.
Natural reduction in densities in other parts of the planet promotes well being.