Trees are throwing less shade on Manatee County, according to study

Trees canopies are seen on Thursday afternoon in downtown Bradenton. A recent report from Keep Manatee Beautiful has shown a general decline in tree canopy coverage in Manatee County.
Trees canopies are seen on Thursday afternoon in downtown Bradenton. A recent report from Keep Manatee Beautiful has shown a general decline in tree canopy coverage in Manatee County. zwittman@bradenton.com

While Manatee County’s tree canopy coverage is more than it was 10 years ago, the results of a recent analysis give worry that the acreage is on a general decline, Keep Manatee Beautiful has found.

In time for Arbor Day on Friday, the nonprofit announced that as of 2014 (the most recent data available), tree canopy covered 155,378 acres of the county’s 489,013 total acres, or about 32 percent. That’s about a 7 percent decrease from the last data collection period in 2009.

In 2015, Keep Manatee Beautiful was awarded a $7,322 Urban and Community Forestry grant from the U.S. Forest Service to continue its tree canopy analysis started in 2004. The process includes using aerial photographs taken by the Southwest Florida Water Management District that are snapped every five years. They are then analyzed by scientists using software designed by the U.S. Forest Service to denote the canopy’s economic and environmental worth — things like carbon storage, air quality and stormwater runoff reduction.

This analysis compared data from study years of 2004, 2009 and 2014, which showed the percentage of tree canopy wavering over the years. The first study in 2004 showed 26 percent of the county was covered by tree canopy; that number grew to 39 percent, then sank to 32 percent in 2014.

Until earlier this year, the ideal canopy coverage was targeted at 40 percent, which was a standard set by conservation organization American Forests and used by forest management groups nationally. Now the organization has loosened the reins on the tree canopy benchmark.

The tree canopy cover denotes the amount of land under and around trees. Florida Forest Service urban forestry coordinator Lou Shepherd calls it “the footprint of the urban forest.”

Not only does a tree’s cover help cool microclimates underneath its shade, it helps with stormwater retention, air quality and carbon storage. But as the science evolves, American Forest decided that more parameters should be included to show progress in addition to tree canopy coverage, and that specific targets should vary with each city. For desert cities, a 15 percent canopy will do; in the grasslands, a 20 percent canopy is a sufficient goal. But for forested areas like Florida, Shepherd said the goal varies from 40 to 60 percent.

“It’s still a good goal,” Shepherd said of the 40 percent level for Manatee, adding that it will still be measured for historical data. But it’s not the only thing to be measured; factors like leaf area, biodiversity, invasive species and tree health are things to be considered.

But the major reason for our decline? Development and invasive species, said Keep Manatee Beautiful’s executive director Ingrid McClellan.

It’s noticeable in the water district’s county overview how the development boom in East Manatee has affected tree cover. On the map, the pink designation for development slowly eats up the green tree canopy.

“Trees equate to economy,” she said. When people see green, so will the county.

Also, while intentions are good with removing invasive species like Australian pines and Brazilian peppers, it in turn affects the total canopy coverage.

Although impacted trees can be removed in exchange for a fee that goes into the county’s Tree Trust Fund, McClellan identified suggestions to the government to curb the downfall of the county’s canopy: filling two new urban forest manager positions — which had recently been eliminated — to oversee all tree management projects in the county; requiring the incorporation of native landscape vegetation and preserving tree communities in new developments; deeming public and private trees protected under the landscape standards; and planting new trees on streets with little to no trees.

She identified some counties that are managing their tree canopies well: Sarasota, Lee and Alachua. Shepherd said Gainesville is a model city with its sustainability approach.

“We manage sand on the beach. Nobody’s managing the tree canopy,” McClellan said.

Hannah Morse: 941-745-7055, @mannahhorse

How much tree canopies covered Manatee County from 2004 to 2014

2004: 26 percent

2009: 39 percent

2014: 32 percent

Source: Keep Manatee Beautiful