Local Case Study: Simpson Residence, 108 Lebanon Ave

Here we'll take a closer look at the “ecosystem benefits” of the trees right in one Mount Gretna yard — mine. Using data from TreePlotter, we can put real numbers on the services trees provide every single year. Spoiler: it’s a lot more than shade and autumn color.

In November 2023, Brandywine Urban Forest Consulting performed a Level II Site Assessment of the trees at my 0.47-acre property at 108 Lebanon Avenue. They inventoried and measured 98 trees, each 2 inches or more in diameter, and calculated their annual and long-term ecosystem benefits. 

What Are Ecosystem Benefits?

Ecosystem benefits are the measurable, monetary values that trees provide by doing natural work for us — like storing carbon, filtering air, and preventing stormwater from overwhelming drains. These benefits often go unnoticed, but without them, we’d be paying a lot more for engineered systems to replace what trees do for free.

How These Numbers Were Calculated
These figures come from a professional Level II Site Assessment conducted by Brandywine Urban Forest Consulting in November 2023. Their certified arborists inventoried and measured every tree on my property that was 2 inches or more in diameter — 98 trees in total on this 0.47-acre lot.

Using the TreePlotter™ Urban Forest software, Brandywine applied the U.S. Forest Service’s i-Tree Streets model to calculate both the environmental services and the economic value these trees provide. This professional analysis goes far beyond the estimates from the public National Tree Benefit Calculator, offering a precise, site-specific view of canopy benefits.

Learn more about the National Tree Benefit Calculator ›

Ecosystem Benefits: At a Glance

(Based on all trees at the Simpson residence)

Here’s what the trees on just under half an acre are doing every year:

• Avoided Runoff – 166,000 gallons/year
  Water that never becomes stormwater thanks to interception by tree leaves, branches, and roots.

• Stormwater Monetary Benefit – $1,480/year
  The dollar value of avoided treatment and infrastructure costs from that reduced runoff.

• Replacement Value – $1.34 million
  The estimated cost to replace these trees with ones of similar size and function. That’s not a number anyone would pay to replace one yard — it simply underscores how valuable mature trees are compared to saplings.

• Pollutants Removed – 598.3 lbs/year
  Airborne particles and gases filtered out by leaves, improving local air quality.

• Air Quality Monetary Benefit – $9,860/year
  The equivalent value of cleaner air (reduced health costs, improved well-being).

• Carbon Monetary Benefit – $101,470 total
  Long-term economic value of stored and sequestered carbon.

• Carbon Storage – 594.4 tons total
  The amount of carbon currently locked in the trees’ wood and roots.

• Carbon Sequestered – 10.4 tons/year
  The additional carbon captured from the atmosphere each year.

Why This Matters for the Whole Community

This is just one 0.47-acre lot in Mount Gretna. If a single yard contributes this much, imagine multiplying it across hundreds of private parcels and the roughly 25 acres of communal woodland. Together, the numbers become staggering: every tree — whether in a yard, along a street, or in the forest — works silently year-round to keep our water cleaner, our air fresher, and our climate more stable. Collectively, Mount Gretna’s forest is providing millions of dollars’ worth of ecological services every single year — for free.