Snags, stumps, and logs provide habitat

Three birds perched on a snag. A ball moss
(Tillandsia recurvata) also lives on this snag.

Dead standing trees are snags. If a snag is located so that it will not hurt people or damage property, leave it standing for its wildlife value. Snags are highly productive sources of habitat that work well in both natural areas and designed landscapes.

Tree basics

The vast majority of organisms on our planet depend upon the life-giving process of photosynthesis. Plants and other organisms with chlorophyll combine carbon dioxide from the air and water with energy from the sun to form sugars and oxygen gas. The plant can then combine the sugars to form starches, fats, enzymes, or whatever the plant needs. 

Photosynthesis: 6CO2 + 6H2O >> C6H12O6 + 6O2

Then most living organisms (plants, animals, fungi, bacteria) take in oxygen and digest the sugars in one form or another to gain energy for life through respiration, a process the equal and opposite of photosynthesis. 

Respiration: C6H12O6 + 6O2  >> 6CO2 + 6H2O 

Since trees normally live for many years, they sequester carbon in their wood and root tissues as long as they live, while the flowers, fruits and leaves store carbon only temporarily until they are eaten or decompose. Much of this decomposing plant matter ends up in the soil. But when a tree dies, the wood begins to break down as bacteria, fungi, insects, and other organisms begin to absorb the wood tissue so they can gain energy for life. As the wood deteriorates, then birds and other larger animals can consume the decomposers and so the carbon-based sugars stored in the wood moves up the food chain. The organisms store the sugars created during photosynthesis, but as they respire and when they die, the carbon is released into the atmosphere.

One note here on carbon sequestration: The soil sequesters 3 to 4 times as much carbon as all the terrestrial plants, including rain forests. Peat is especially important since it can sequester carbon for thousands of years. This is important because the more carbon sequestered means less carbon dioxide, our most abundant greenhouse gas, in the atmosphere and that is good for our only planet. (Read my article on peat moss.)