In praise of big old trees

Nothing is more beautiful than a tall, stately tree. But sometimes they get in the way of progress. Well-meaning people think that planting a couple of smaller trees will make up for the loss of the elder statesman. Not so.

Trees provide many important services to the environment, and larger ones do so more effectively and efficiently. Trees take carbon dioxide out of the atmosphere, which is why the preservation of old forests is an important component to any attempt to mitigate climate change. When trees are cut, unless their wood is used in long-lived products like housing or furniture, the carbon dioxide they stored returns to the atmosphere.

Anyone who has walked into a forest on a hot summer day knows about the cooling quality of trees. This is not just due to shading. Trees take up water from the soil, and most of it is evaporated from the leaves, a sort of natural air conditioner. Smaller trees with fewer leaves won’t have the same effect, even if they are planted at higher densities.

Trees also remove pollutants like ozone and nitric oxide from the atmosphere; the amount taken up depends on leaf area. So taller trees are more effective at scrubbing away these pollutants.

In some ecosystems, large old trees provide nesting or sheltering cavities for up to 30% of the nearby bird, mammal, and insect species.

Keep these services in mind the next time you encounter a big, old tree—especially one someone wants to cut down.

Produced in collaboration with WAMC Northeast Public Radio, this podcast originally aired on May 13, 2013. To access a full archive of Earth Wise podcasts, visit: www.earthwiseradio.org.