Island tree canopy near national standard

Manatee County is just percentage points from meeting a national standard for forest coverage, according to a study released by the county.

The county worked with Keep Manatee Beautiful, ESciences and several other government agencies on its first study of its urban tree canopy.

The five-year analysis, funded with a $10,000 grant from the Florida Urban and Community Forestry Grant Program and another $10,000 grant from KMB, used software modeling and aerial photographs to evaluate the tree canopy in unincorporated Manatee and the six municipalities in the county.

KMB executive director Ingrid McClellan said the study provides local governments and organizations with “a precise percentage of benefits provided by every tree in Manatee County.”

American Forests, the nation’s oldest conservation group, set the standard for urban forest coverage at 40 percent of an area.

For Manatee County, the urban forestry canopy is 37 percent, just below American Forests’ standard but significantly higher than in other counties in Florida, according to the study.

The analysis found countywide an 11 percent increase in the tree canopy since 2004.

On Anna Maria Island, the analysis found an increase of 5 percent in the canopy in Holmes Beach, but a decrease of 4 percent or 14 acres in Bradenton Beach and a decrease of 2 percent or 8 acres in Anna Maria.

“Decreases in canopy may be the result of mature urban trees being lost to storms or bad maintenance practices, loss of trees to new development or the loss of mangrove forest to storms or development,” the study stated.

Longboat Key showed a 9 percent increase and the highest percentage of tree canopy among local municipalities — 46 percent of the town is wooded.

Palmetto had the lowest percentage — 25 percent — while the Island cities were in the middle. Anna Maria had 30 percent coverage, Bradenton Beach had 27 percent coverage and Holmes Beach had 35 percent coverage.

The percentages were used to determine the benefits of trees in different communities in terms of carbon storage and sequestration and air quality, according to KMB.

Trees take in carbon dioxide through their leaves. The carbon from the carbon dioxide is incorporated into the biomass of the tree and stored as wood. Thus, the preservation of mature trees is critical to the continued removal of carbon dioxide from the atmosphere.

The county’s study estimated that Anna Maria’s “forest” stores about 6,042 tons of carbon, which is a decrease of 329 tons from 2004. Bradenton Beach’s forest stores about 3,666 tons of carbon, a decrease of 577 tons. Holmes Beach’s trees store about 15,096 tons of carbon, an increase of 2,140 tons since 2004.

Trees remove pollutants from the atmosphere — the larger the canopy the more pollutants removed. The analysts measured pollutants in pounds and determined that, in 2009, trees removed 17,920 pounds of pollutants in Anna Maria, 10,861 pounds in Bradenton Beach and 44,720 pounds in Holmes Beach.

“Often, developers remove mature trees because they can create more lots or larger homes without them,” the report stated. “However, mature trees provide more environmental benefit than new trees. Because they have more leaves and more woody mass, mature trees sequester and store more carbon, filter more air pollutants and reduce more peak stormwater flow than new, smaller trees. Additionally, larger, mature trees provide shade for pedestrian walkways and for buildings, encouraging less usage of cars and reducing building costs.”