Preliminary i-Tree Ecosystems Results

Casey Trees does more than just plant trees — we also undertake important research to determine the true value of a healthy urban forest. And to do so, we recruit individuals of all ages and abilities to serve as Volunteer Citizen Scientists.

Our latest research project — i-Tree Ecosystems Analysis — engaged almost 50 Volunteer Citizen Scientists who logged more than 250 donated hours of time in the field.

So what is the i-Tree Ecosystems Analysis? Good question. It’s a District-wide tree sample inventory that assesses the makeup of the tree canopy and helps determine the benefits that our trees provide.

From June to August 2015, Volunteer Citizen Scientists traveled to 201 randomly selected — and previously visited — plots scattered across the District. At each plot, Volunteer Citizen Science teams identified the present tree species, assessed their overall health and measured their height, width and trunk diameter. These sites, each 1/10 of an acre in circumference, represent a statistical sample of the total number of trees in D.C.

While we are still dissecting the results, we want to share with you two very interesting preliminary findings.

2009 2015
Number of Trees 2.58 Million 2.43 Million
Most Common species American beech, Callery pear, Tulip tree American beech, Boxelder, Tulip tree
Structural values 3.99 Billion 4.28 Billion

Most notably, the total number of trees in D.C. has decreased over the past six years from 2.58 million (2009) to 2.43 million (2015). That said, the structural value, or the dollar amount trees provide by cleaning our air and water, has increased from $3.99 billion to $4.28 billion.

How is this possible?  Because even though the number of trees has decreased, the size of our remaining trees has increased. Bigger trees provide significantly more benefits than smaller trees!

Overall, the preliminary findings make one thing clear — D.C. and its partners need to strategically plan and plant trees to ensure the long-term health of our tree canopy. Doing so will ensure that D.C. residents and visitors will be able to enjoy the benefits of trees for generations to come.

We look forward to sharing with you the full results in the coming months — along with making new Volunteer Citizen Scientist opportunities available.