Chelsea Harvey The Washington Post 16 Sep 17;
As residents of the Southeast are returning home and assessing the damage left by Hurricane Irma, Florida scientists are anxiously waiting to evaluate the storm’s impact on one of the state’s most valuable — and vulnerable — ecosystems: the Everglades.
Already threatened by the continuous progression of sea-level rise — which pumps damaging salt water into the habitat, jeopardizing groundwater resources, contributing to erosion and threatening wildlife and vegetation — some scientists worry that the weakened Everglades are becoming less resilient to disruptive events like hurricanes. The issue is a prime example of the way climate change can render ecosystems more vulnerable to even natural disturbances.
Indeed, it’s an issue that President Barack Obama chose to highlight two years ago during his last term. On a visit to Everglades National Park in April 2015, timed to coincide with Earth Day, Obama emphasized the growing threat of climate change and pointed to the impact of the rising seas in Florida as an example.
“Climate change is threatening this treasure and the communities that depend on it, which includes almost all of South Florida,” he said in a speech delivered at the entrance of Everglades National Park. “And if we don’t act, there may not be an Everglades as we know it.”
Everglades National Park consists of about 1.5 million acres, or more than 2,300 square miles, of wetland area, containing pine woodlands, saw grass marshes and extensive mangrove forests, which help to naturally build up the land and buffer the coast against the rising seas. It’s home to a diverse variety of wildlife — including crocodiles and alligators, as Obama pointed out in his speech — and it’s part of the freshwater system that feeds South Florida’s Biscayne Aquifer, a source of drinking water for millions of people.
Hurricanes, in and of themselves, are not necessarily devastating events for the Everglades, according to Harold Wanless, an expert on coastal geology at the University of Miami. They have long been a natural and common occurrence in South Florida. They can even sometimes benefit the landscape by throwing mud onto the coast and helping to build up the land.
“From my point of view, they’re part of the system,” Wanless told The Washington Post.
Over the last century, however, sea-level rise — accelerated by human-induced global warming — has begun to degrade the Everglades by allowing salt water to seep into the system. This is bad news for the freshwater plants and animals that live there, but it’s also a major threat to South Florida’s drinking water supplies. And some scientists believe that salt water intrusion may be contributing to the erosion and collapse of certain parts of the landscape.
“Plants are not as productive as they have been, and soils in places are disappearing,” said Evelyn Gaiser, an Everglades expert and executive director of the School of Environment, Arts and Society at Florida International University. Particularly concerning is a process known by scientists as “peat collapse,” in which the rich, organic soil beneath the marshes is starting to collapse and be overtaken by open water.
“We’re trying to understand through a lot of ongoing science why that’s happening, but what we do know is it is occurring in areas that are receiving more salt than they have in the past, as a result of chronic salt water encroachment,” Gaiser said.
These soil losses are also making it increasingly difficult for the mangrove forests — some of the Everglades’ greatest natural defenses against sea level rise — to maintain themselves at the edges of the ecosystem, Wanless noted.
Now, scientists are growing increasingly concerned that the impact of hurricanes could exacerbate some of the climate-related challenges already facing the Everglades, by driving more salty water into the system or destroying more mangroves.
Researchers are awaiting clearance to enter the national park and begin assessing the impact of Hurricane Irma, but there are a few disturbances they’ll be looking out for, according to Len Berry, former head of the Florida Center for Environmental Studies at Florida Atlantic University and now a professor emeritus and independent consultant. A major priority will be “looking for the extent inland that the surge went, bringing salt water,” he told The Post.
“What’s expected to happen is that you get short-term contamination of the aquifer, but what’s more important perhaps is you get a longer-term degradation of the vegetation,” he added. While there’s some hope that the mangrove forests may continue to gradually shift inland in advance of the rising seas, a violent storm surge can overwhelm them, he said.
Indeed, previous hurricanes have destroyed thousands of mangrove trees as they passed through — Hurricane Wilma in 2005 was one of them. That said, Gaiser noted that the destroyed mangroves were regrowing within a matter of months, and had reached their previous levels of productivity within a few years.
The question now, she said, is how 12 more years of sea-level rise and degradation have affected the Everglades’ resiliency.
“Is this kind of recovery that we saw 12 years ago still possible?” she asked. “Because we know that we are on a different trajectory in this ecosystem than even we knew about 12 years ago at the timing of Hurricane Wilma.”
For now, scientists are continuing to collect data and improve the models they use to make long-term forecasts for the future of the Everglades, Gaiser said.
Scientists say there are still important improvements that could made to the region’s ongoing recovery efforts. Wanless has suggested more resources devoted to the recovery of mangroves, especially after large disturbances like hurricanes, and to the recycling and storage of much-needed fresh water to bolster the Everglades’ water levels.
That said, the greatest ongoing challenge for the Everglades remains the progression of climate change and the relentless rising of the seas. The Everglades’ response to Hurricane Irma may hold important clues about how the ecosystem is continuing to change, at a time when the its future remains deeply uncertain.
“When things are changing outside the range of anything that you’ve seen in the past it’s very hard to be very sure about what might happen in the future,” Gaiser said.
Chris Mooney contributed to this report.
