Grass above the ground sustains humans bodily, feeding the world whether by direct consumption or via the animals who themselves eat grass. As Chapman writes in ‘An Introduction to the Grasses’: 
…in a hungry world grasses are the centrepiece of agriculture and when we look at one damaged environment after another, grasses offer us some of the best hopes for rehabilitation. 

Grasses can also sustain the human soul, giving us the greenness we need to soothe our minds and reconnect us to nature wherever we are. Grass grows between the cracks in pavements, along the roadside, in our gardens, parks and meadows, it is accessible. It also has the potential to sustain our future, our continued existence. 

Species-rich grasslands are valuable carbon stores, locking away carbon in roots and soil. Living soil, aerated by earthworms, is nutrient rich, fed by the grassroots. That depth of storage makes it a stable carbon sink. Trees store the majority of their carbon above ground, grasslands store theirs mostly below. The deep down storage protects it from wildfire and disease and subsequent carbon release. We need woodlands and peatlands and we need grasslands.