By Tim Clancy, for Let’s Talk Plants! November 2024.
Pines In Oakcrest Park
Sometime in the last approximately 35 years some Torrey pines, Pinus torreyana, were planted at Oakcrest Park in Encinitas. At the time of planting, the trees were much admired and mostly planted for aesthetic purposes or to provide some function such as a screen. In the case of Oakcrest Park the trees are amenity trees planted for the enjoyment of park users, and so it has been for several decades. The trees grew and also provided the more recently much touted eco-services. These are benefits that were generally not considered when they were originally installed. One of the oft cited benefits is the ability of trees to sequester carbon.
Mature trees have been shown to sequester in the range of 48lbs. of carbon per year. This, of course, is great news. We need all the carbon sequestration help we can get and if an added benefit of planting trees is locking away carbon we’ll take it. Unfortunately for us, the time it takes for a tree to become carbon neutral is between 25 and 33 years according to research by the U.S Forest Service. They considered all the components of a tree’s carbon footprint from the time the seed sprouts to its arrival at its planting site and all the work involved in planting and maintaining the tree. The eight-year difference between 25 and 33 is based on maintenance intensity. More pruning increases the length of time to carbon neutral status.
The Torrey pines at Oakcrest Park are declining and have been doing so for a few years now. As you can see in the photographs they have lost a great amount of vitality in the last 30 months. It appears that they have been compromised by a fungal disease. Some sort of needle blight has taken hold and is slowly killing the trees. Dead needles on pine trees are nothing new. In San Diego most of the pines that we grow have a needle life of about four years. So, the evergreen continues to grow and create new needles to replace the older ones. This can be seen when you look at pine branches and observe new growth at the tips and the older needles just a few inches from the tip are brown and dead.
Sometime in the next two years the Oakcrest Park trees will need to be removed as they slowly die due to a reduced ability to photosynthesize and replace the affected foliage. This will result in a “carbon release” of much of the sequestered carbon just a few short years after they became carbon neutral. It is likely that some of the sequestered carbon will remain that way in the form of benches and stools as the trees are “repurposed” upon removal.
When we look at the data that we have available, it turns out that trees as carbon sequestration devices is definitely not a good idea in the short term and probably not a good idea for long term carbon sequestration since the end result is a carbon release.
It will be a sad time when these trees come down and Oakcrest Park will change forever.
Tim Clancy & Associates LLC
P.O. Box 1180 – Cardiff-by-the-Sea, CA 92007
International Society of Arboriculture Certified Arborist No. WE-0806A
International Society of Arboriculture - Tree Risk Assessment Qualified
He can be reached at treemanagers@gmail.com
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