Forest ThreatNet

For some residents of the North Carolina coast, the 2014 Independence Day weekend will be remembered not for fireworks and family cookouts, but for damage assessment and cleanup following the high winds and heavy rain that downed trees when Hurricane Arthur came ashore on July 3. Eastern Threat Center researchers believe that Arthur did relatively little harm to the state’s coastal forests, but will continue to watch for delayed impacts using ForWarn—a satellite-based forest monitoring tool which provides maps that compare current and past levels of vegetation greenness. Of greater concern to the researchers and ForWarn users in NC are the lingering effects of another storm: Hurricane Irene.

Irene made landfall over eastern North Carolina on August 27, 2011, and significant flooding followed. A year later, Rob Trickel, head of the Forest Health branch of the North Carolina Forest Service, saw something peculiar in eastern North Carolina highlighted on a ForWarn map. “In September 2012, I was perusing ForWarn and the Forest Disturbance Monitor*. Since the Pains Bay Fire on the coastal plain the year before, I made it a point to periodically check out that part of the state on ForWarn maps to see how green up was progressing,” says Trickel. “On that day, I noticed an area of disturbance just east of the fire. I thought, ‘Did I miss that part of the fire?’ before realizing that this was not fire-related.”

Right: A recent ForWarn map image shows lingering impacts of Hurricane Irene. The red colors signify areas with the greatest loss of vegetation greenness. Click to enlarge.

Trickel continued his investigation by examining ForWarn’s map archives and discovered that the greenness of the vegetation appeared to have begun declining a year earlier, in September 2011. “When I realized this, I hypothesized that the disturbance was related to saltwater storm surge from Irene.”

While driving to a meeting on the coast soon after, Trickel observed the disturbance firsthand. “Many of the pines and hardwoods were dead and had already lost their leaves. Leaves on trees that were clinging to life were off-color,” he remembers. “After talking to some locals who said the area was inundated with water after Irene, there was no doubt that this was salt damage that could be traced back to the storm surge from the hurricane.” Today, most overstory trees in this area are dead, their leaves gone and bark sloughing off. These forests may eventually recover, but could require the assistance of land managers along the way.

Above: Some forested areas on the North Carolina coast are in decline due to storm surge impacts from Hurricane Irene. Photo by Jamie Dunbar, North Carolina Forest Service.

This example demonstrates not only the power of weather and climate in shaping forests, but also the power of online tools and relationships that make remote forest monitoring possible. Center research ecologist Steve Norman uses ForWarn to watch vegetation in areas hit by wildfire and hurricanes. “What I find remarkable is how well we can track the post-disturbance response from space, and how it differs from recent fires or other past hurricanes,” he says. “Sites like these coastal forests are particularly important to monitor over the long term because they are vulnerable to sea level rise, hurricanes, and wildfire. New technologies like ForWarn and information sharing through a network of users and land managers can help with that.”

*The Forest Disturbance Monitor is a complementary tool developed by Forest Service Forest Health Protection.