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Some Effects of Irma on the Fakahatchee’s Ecosystem

FOF November 29, 2017 Armchair Interpretive Walks

by Patrick Higgins

Irma

John Kaiser, Francine Stevens and Tom Maish on Sunday, October 15. Amazingly, debris from Irma had already been cleared up to gate 12 except for this pile. Photo by Patrick Higgins.

After devastating the Florida Keys on the morning of September 10th and wreaking havoc on Everglades City and the Fakahatchee as it moved north, Hurricane Irma’s eye made a second U.S. landfall on Marco Island around 3:30 PM as a category 4 storm with sustained winds of 130 mph. Irma had been swirling at hurricane strength since August 31st and had been a major category 3 or above for nearly all of that time. It battered both coasts of southern Florida, swept up the peninsula and produced high seas and storm surges as far north as South Carolina.

We don’t have a recording for Irma’s wind strength in the park because the anemometer failed and even an accurate rain gauge reading was not possible because much of the rain was horizontal. Although the park recorded some 12 inches of rain it probably received closer to 20. The tremendous destructive force of the hurricane was obvious to all from the downed trees, ruined powerlines, damaged roofs, collapsed structures, and flooding and debris everywhere. At one stage water was even flowing over Highway 41 and State Road 29. But there are many more subtle effects on the natural world which may not be as immediately apparent.

For instance, Hurricane Irma will have affected birds in the eastern flyway on their autumn migration from northern breeding grounds to their winter homes in the tropics. Not only will many have been blown perhaps hundreds of miles off course, and some even drowned at sea, but the landscape they traversed would have been substantially altered and in many cases denuded. Food sources like berries and insects may have been eliminated and flooding would have reduced foraging opportunities on the ground. Certainly in the storm’s immediate aftermath in my own yard I saw the few butterflies that had survived desperately searching for nectar sources. All the blooms had been blown away.

But there will be some winners too. Driving down San Marco Road to Goodland a few days after the storm, our vultures had clearly benefited. Hundreds lined the causeway feasting on the fish that had been trapped on the road when the tidal surge receded.

Irma’s path across Cuba may have transported a fresh infusion of orchid and bromeliad seeds to the Fakahatchee. Tropical storm winds are how many of our epiphytes originally arrived. Who knows, maybe some lost species could even reappear?

Toppled trees in our swamp will have created more horizontal habitat suitable for skinks and reptile sunning. Snapped tree trunks may have opened-up cavities in which small animals can make homes. Uprooted trees will also have left depressions which may later become ephemeral ponds which will be safe from predatory fish and available for tree frogs to spawn. The same uprooted trees will have exposed bare earth making it easier for seeds to sprout. Ground birds will benefit from increased shelter, and highly adaptable raccoons will find new food sources by scavenging Irma’s debris.

When the water subsides, the dead material littering the forest floor will decay and the newly abundant sunlight streaming through gaps in the canopy will promote lush new growth in which small herbaceous seedlings will compete – ultimately probably unsuccessfully – with fresh vertical shoots from now horizontal trees. In this race vigorous vines may smother some of the defoliated trees before they have fully recovered, producing a dense secondary jungle-like habitat.

Openings in the canopy will allow formerly shaded saplings to make a dash for the Sun. Unfortunately some of these opportunists may be invasive species. A week after Irma, I already noted Brazilian pepper rushing into bloom.

Some trees in exposed locations would have had their bark entirely stripped off and will die standing up, turning them into snags ripe for colonization by fungi and invertebrates. However, the many downed trees, broken branches and stripped leaves will increase the fuel load and the future risk of wildfire.

Wounded trees may also be more susceptible to future insect infestation and disease as happened in Everglades National Park following Hurricane Andrew. A few months after Andrew many pines began to yellow and die as they succumbed in their weakened condition to pine bark beetles and weevils.

Endangered species with small residual populations nearly always fare badly from catastrophic events like hurricanes. A huge number of epiphytes will have been torn from their perches. Some of the rarer species may take years to recover or disappear.

Generally however, our native plant species are better adapted to hurricanes than non-natives. For instance it was very rare to see a toppled royal palm in Naples despite their huge numbers and exposed street plantings. They just shed their fronds as the wind load increased, leaving their growing tip intact. This was very evident going up Janes Scenic Drive last week. Where everything else was reduced to a tangled mass, royal palms protruded upright and only slightly frazzled all along the road north of gate 7. Most were already in flower or even fruiting in reaction to the stress. Gumbo limbos pursue a different hurricane strategy. Their limbs are very brittle and easily shed to reduce wind load and then readily root where they land.

Our southern slash pine, Pinus elliottii densa, is also adapted to the higher frequency of hurricanes in south Florida. Unlike its cousins north of Interstate 70, it doesn’t grow quite as tall and has a deeper tap root making it more resistant to extreme winds. My house is near Naples Airport where they clocked 142 mph gusts. I feared the 60+ ft pines behind my house would come crashing through the roof, but they stood firm just shedding a few limbs and masses of needles.

In the southern reaches of the park, Irma’s wind and waves will have rearranged coastal sands and inundated sea turtle nests, wiping out the last 6 weeks of our hatching season. Further out, Gulf surface waters will have been re-oxygenated by the storm’s wave action, but this could also have churned up dormant red tide cysts which may haunt us later. Meanwhile, Irma may have temporarily broken up algal blooms, but the release of extra nutrient-laden floodwater from Lake Okeechobee is quickly countering this further up the coast.

The same forces will have driven salt water into our coastal marshes leaving salt concentrations that may persist for years. Conversely, subsequent floodwater discharge through the Faka Union Canal and East River will have reduced salinity in our bays, disrupting some estuarine life cycles.

Our tidal mangrove swamps, where many of our wading birds would have sheltered in the storm, acted as a natural buffer by absorbing its energy, but may suffer delayed damage as they did from Hurricane Donna. This was as the result of extra depositions of mud as the mangroves slowed the storm’s water flow. In Donna’s case the extra layer of mud interfered with the oxygen supply to the mangroves’ roots, killing vast tracts months later where accumulations were the greatest.

But the speed of the natural world’s recovery in a tropical-like environment is remarkable. The live oaks, West Indian mahogany and gumbo limbo in my yard were almost completely defoliated, yet 10 days later were leafing out again. Fresh blooms are everywhere as plants compete to produce seeds to exploit Irma’s disturbance.

Sadly the economic loss and human recovery from the devastation takes much longer. I think we are all still a little shell shocked. The only saving grace from the prolonged loss of electrical power and a blacked-out Naples was that for the first time, I could see the Milky Way right in the city center – a reminder of the fragility of our civilization.