By Amy LeGaux
Published July 2015 Grassroots Mapping Forum #8.
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On August 29, 2005 Hurricane Katrina’s winds and microbursts destroyed 70 to 80% of Audubon Louisiana Nature Center’s (a facility of Audubon Nature Institute) 86 acre mature closed canopy bottomland hardwood forest. Storm surge overtopping and compromising the levees at Lake Borgne brought 6-8 feet of storm surge through the center. This surge was ~15PPT salinity and sat for nearly 3 weeks. Salt water intrusion contributed to another 10-20% of tree loss leaving only 10% of the forested wetland. The storm surge also brought with it millions of Chinese Tallow tree seeds from the surrounding community. The Nature Center sits in a low spot with elevations as low as -12 feet below sea level. This set up the optimum conditions for a complete invasion of Chinese Tallow; seed settlement, disturbed ground and open canopy.
Prior to Hurricane Katrina aerial photos taken by the United States Department of Agriculture Natural Resource Conservation Service showed 3 smalls stands of Chinese Tallow at the Center. Public Lab aerial and infrared photography taken subsequent to Katrina shows the current density of Chinese Tallow compared to areas that have been reforested from 2008-date. Volunteers from many organizations including Common Ground Wetlands, AmeriCorps NCCC teams, Operation Nehemiah, and Camp Restore began removing tallow. Collaboration with the USDA NRCS, National Park Service Exotic Plant Management Team and LSU Ag Center determined that cutting down the young tallow or girdling more mature trees and direct spray with Garlon would be the most effective way to eliminate the tallow. The herbicide however only manages tallow to 70% so volunteers were also needed to keep the reforested areas free from tallow.
In 2008 the Coalition to Restore Coastal Louisiana awarded funding to the Nature Center to restore urban canopy through a grant from Entergy Corporation; 10 acres were cleared of tallow leaving any healthy bottomland hardwoods and reforested with 600 trees. The following year 4 acres of the previous planting were supplemented and an additional 3 acres cleared and reforested with trees from Restore the Earth Foundation. After this initial planting REF committed to donating 10,000 trees total. To date 25-26 acres have been cleared and replanted. Another 14 -18 acres has been funded for clearing and replanting in the fall and winter of this year bringing the total acres to more than half of the total acreage.
Public lab photos have been an invaluable asset in teaching the thousands of volunteers about coastal wetland loss in Louisiana. You can clearly see on the photos where the restorations have taken place based on varying colors and crown size when compared to the monochromatic uniform crown size of mature Chinese Tallow.