Why is the ground-air environment characterized by the greatest variety of forms of organisms?

The ground-air environment has the largest number of species of living organisms. All due to the fact that this environment occupies most of our planet. However, the environmental conditions are different everywhere. These differences have caused the emergence of new species of living organisms on our planet. In the aquatic environment, the living conditions are not so diverse, because there are much fewer species there than on land. There are fewer species in the organismic environment, since favorable conditions did not cause the rapid evolution of organisms.