Question:  Over the winter, a lot of downed branches accumulated on my property.  In the past I’ve burned them. It’s the cheap solution, and my neighbors haven’t yet complained about the smoke.  But now with all the news about global warming I’m wondering whether instead I should just let the branches decompose.  Or have them chipped and spread in wooded areas. What do you think?

Answer:  You’ve identified several basic choices.

Choice #1 – Cut & rot:  

From an environmental perspective, it might be best to move the branches to a wooded area of your property (if not already there), cut them so they’re in contact with the ground, and let them rot.  A USDA Forest Service publication notes that “dying and dead wood provides one of the two or three greatest resources for animal species in a natural forest, and if fallen timber and slightly decayed trees are removed the whole system is gravely impoverished….”  

A significant portion of animal species – birds and mammals – rely on dying and dead wood as habitat for themselves or for their food sources.  Small sticks begin decomposing almost immediately, especially if they are in contact with damp ground. Larger branches in your brush pile will ultimately turn into compost after a few years, and in the interim can provide habitat for small wildlife and birds.  

Choice #2 – Chip & rot:

Chipping the branches is a reasonable second choice if cutting them and then allowing them to rot in place is unacceptable because of the very large volume of wood involved.  Turning the branches into wood chips accelerates rotting, and aged chips can be used as mulch. A combination of chipping some branches and allowing others to rot might be the right approach on some lots.  Bear in mind, however, that chippers use power – typically from gasoline – and present their own environmental issues.

Choice #3 – Burning:  

Burning is the least environmentally sensitive approach, since burning releases carbon dioxide and other pollutants into the atmosphere.  Yes, it’s a small amount compared to our cars and homes, but in this age of climate change every little bit helps.

But doesn’t rotting wood emit bad stuff?  Yes. The methane produced by rotting wood is, on a pound-for-pound basis, much worse than carbon dioxide in global warming potential.  But the small amount of methane released during rotting can’t compare to the huge amounts of carbon dioxide released during burning. In addition, that small amount of methane is released slowly over several years as the wood rots.  Burning releases carbon dioxide and other hazardous pollutants all at once. So allowing downed branches to rot is the better choice.

Choice #4 – Composting :

Here’s an alternative that might be the best yet: on-site composting.  But it’s a bit more work.

Pile the branches on the ground or in a shallow trench with as few air gaps as possible.  Include logs, too. The piles can be anywhere from a few inches to a few feet high. Toss on leaves, grass clipping and other organic-rich matter.  Cover with a few inches of soil. Add some nitrogen, such as bone meal. Then on top of the piles plant native flowers, grasses, bushes, even small saplings.  

The covered wood rots even faster than if left on the ground surface, so the height of the piles diminishes rather quickly.  The rotting wood produces carbon and heat, which stimulates the roots of the surface plants. It also enriches the soil. Another benefit:  since rotting wood holds moisture, large compost piles may act like sponges to take up water that would otherwise remain on the ground surface.  As you can tell, composting entails more work. But some people are devoted to this approach for extracting the most benefit from downed branches and limbs.

Nature’s way.  You might wonder how these approaches compare with what has happened naturally in woodlands over the eons.  Left alone, wood rotted on the forest floor. It also burned periodically in fires caused by lightening and by our ancestors.  Natural fires were an important part of forest management. The fires recycled nutrients tied up in old plant growth, controlled weed growth, and stimulated new plant growth.  Today, “controlled burns” are a way to simulate natural fires. Controlled burns are usually conducted over large expanses of property for best effect in rejuvenating a property.  Burn piles, however, typically occupy a very small, isolated area. That difference means that a burn pile is incapable of accomplishing the benefits of a geographically large controlled burn.

To sum it up.  The best approach from an environmental perspective is to leave the downed branches in place, or to cut them and disperse them on the ground.  Next best is to supplement that practice with chipping and spreading the excess on the ground. You might try composting if you’re up for some experimentation and exercise.  A burn pile is generally the last choice for managing downed branches and limbs. Thanks for asking!