Trees are much more efficient in breaking down carbon dioxide than grass, as there is much more leaf area on a tree. As you stated, trees have many other benefits that grass does not provide, including pulling up ground water from lower depths, providing richer soil through the decomposition of leaves, sheltering many species of animals and shade-loving plants etc., so more trees is a no-brainer.

How about a compromise. Bamboo!

Its technically a fast growing grass but some varieties resemble trees & provide long lasting construction materiel that sequesters carbon in the buildings & furniture etc. made from it.

http://greencleanguide.com/2011/01/27/ca...

new bamboo shoots are also used as food in many parts of the world.

Common grass quickly degrades & releases the co2 it captured during its short growing cycle back into the biosphere..

Actually, on a small (1000 acre or so) plot, grass and a scattering of productive trees makes an excellent pasture and absorbs carbon and rainwater very well, and on a smller scale is reasonably profitable (and more pleasant than a feed lot )

Yes, but there aren't any grass huggers out there. Most of them just want to smoke it.

Trees At least a billion of them...get started

Grass is more efficient at converting carbon dioxide to oxygen, so more grass might help limit the global warming effect of carbon dioxide. But trees provide shade, and habitat to many creatures.

So would you like to have more trees on our world, or grass?