That statement is false
Water indeed travel through layers of rocks and soil but they're permeable.It will get straight to the soil so it can be absorbed by the plants to create oxygen
The main sources are humans which is why it is stated that the global warming is man made. The levels have increased beyond all measure, increasing since the 1950s by a 100 CO2 parts per million, and it keeps increasing by 2ppm on a yearly basis. The statistics from the industrial revolution era are not much different and show how much we've increased the CO2 in modern times.
In a time before railroads and highways, the Great Lakes and St. Lawrence River served as the primary transportation system. Many of North America's largest cities were established along the waterway as commerce flourished between their ports. Today, Great Lakes-Seaway shipping is equally important.
