Mangroves near Everglades City. They’re responding to climate change by extending their territory north and reproducing more rapidly. Credit: Wikimedia Commons
The speakers at last week’s Republican National Convention used a lot of words — nearly 78,000 of them, according to a report in Forbes. Some words we heard over and over: “socialism,” “radical,” “law and order.”
Two rather important ones, though, were noticeable by their absence: “climate change.”
You would think seeing meek little Tropical Storm Laura rapidly morph into a roaring Category 4 hurricane thanks to the overly warm waters of the Gulf of Mexico would have alerted them that those two words are important.
But I guess the conventioneers were using their coronavirus strategy on this: Ignore it. Take no precautions. Pretend it doesn’t exist. Maybe if we wish hard enough, it will go away on its own!
Here in Florida, we don’t have the luxury of ignoring how the climate’s changing. We can’t.
For one thing, we are more frequently the target of hurricanes than any other state. For another, our geography makes us more vulnerable to rising seas.
Most of the state is a flat peninsula with water on three sides and houses built as close to the shoreline as possible. As the high tides inch higher and higher, they’re bound to swamp us like a johnboat with a leaky bottom and no bucket for bailing.
Then consider the fact that we’re already sweltering in the summer, and now it’s getting warmer and warmer, to the point where we don’t even cool down at night.
There are other signals of what’s going on — increases in mosquito-borne diseases like dengue fever, for instance, and a boom in toxic algae blooms. Both were predicted by the federal government’s Third National Climate Assessment in 2014, and six years later both predictions have proven accurate.
A lot of the news stories about climate change and Florida originate from Miami Beach, where sunny day flooding has become such a big problem. To counteract it, the city is installing expensive pumps and raising the roadways. Think of it as the modern equivalent of the Dutch boy with his finger in the dike, except we’re going to need both hands.
But there are subtler signs of what’s going on, too. One of them popped up on social media last week even as the Republican convention was pretending climate change didn’t exist.
Good news? Maybe not
The staff of the Apalachicola National Estuarine Research Reserve in the Panhandle posted pictures on their Facebook page that were described as “good news from the field.” Their good news: “Mangroves are spreading further into the panhandle, becoming a thriving new component of coastal habitats.”
The Facebook post said that over the past month the staff had “visited 20 transects spanning the coastlines of Franklin County, and they collected data on growth, reproduction, and spatial data on over 120 red and black mangroves.”
In response, a coastal biologist named Blair Witherington, author of “Florida’s Living Beaches: A Guide for the Curious Beachcomber,” posted a comment taking issue with this characterization as “good news.”
The mangroves weren’t spreading into virgin territory, he pointed out. They were invading areas that had been classified as saltmarsh, where the landscape was dominated by cordgrass.
A Florida saltmarsh is open and sunny. The mangroves, on the other hand, tend to grow closer together than the trees in a pine forest. Their roots spread out like a man stretching his legs, and their leaves grow thick, casting everything beneath them into shadow.
If you’ve ever paddled a kayak inside a mangrove thicket, you know how its boughs can suddenly block out the sunlight as if someone threw a switch. In other words, saltmarsh and mangrove create very different habitats that attract a very different set of animals.
“When one community replaces the other, this diversity is lost,” Witherington wrote. “I would not call this change good news. But it certainly is ‘news.’”
I called Witherington to ask him about this. “Some of these animals fit into their communities in unique ways,” he explained. “Everything is connected to everything else.”
That’s especially true for the smaller critters that are down at the bottom of the food chain, such as crabs and snails, he said. Alter their habitat and that has the potential to alter the whole food chain, creating a widespread change.
My next call was to Samantha Chapman, a biology professor at Villanova University who’s been studying how Florida’s mangroves have been migrating up the state’s Atlantic coast for the past eight years.
When she started, she worked with mangroves around the Titusville area near Cape Canaveral. Now she’s found them up near the St. Mary’s River, which forms the border between Florida and Georgia — about 170 miles north of where her studies began. At this rate they’ll soon be marching through Georgia like Gen. Sherman.
“It’s crazy, right?” she asked. “Our main study site now is near St. Augustine.”
I asked what was driving this: Rising seas turning the marshes saltier? Rising temperatures making the water warmer? Combination of the two? Nope, she said, it’s something even stranger: Reduced freeze events.
Mangroves can survive a short freeze, she explained, but not a prolonged, hard freeze. By combing through the weather records kept by the state’s orange juice industry, she said, biologists have been able to document that Florida is having fewer prolonged hard freezes than it used to. As those have diminished, the mangroves have adapted by expanding their range.
They’ve adapted in another way, too. Not only are the mangroves spreading into areas that once were hostile to them, she said, but they have also altered their life cycle to speed things up.
“Normally it takes them about 15 years of growth before they start making seeds,” she said. “Now, as they get into these marshes, they’re producing seeds when they’re only a couple of years old.”
Watching the mangroves marching, observing them speeding up their seed-production, “it’s something with climate change that you can see,” she said. “It’s a very, very visible representation of what’s going on.”
Don’t get me wrong. Mangroves are, in general, good. They’re a native species, not an invasive one like Brazilian peppers (which have been moving north too, unfortunately). They soak up carbon like crazy, which helps us combat climate change. Seeing mangroves sprouting along a coastline is usually a good thing — except when it leads to a loss of different kinds of natural habitat.
The other problem with having too many mangroves is that climate change may overwhelm them, too. They’re considered resilient, to a point.
But a study by the U.S. Geological Survey published last year said sea level rise could wipe out mangroves all along the Florida coast — even the new, more aggressive ones that Chapman’s been studying. Unless of course nature finds a way to adapt to that too.
So, here’s the question we humans have to consider: Nature is finding ways to adapt to how we’ve changed the climate. What are we doing to adapt to it? Or at least slow it down?
We know what’s causing climate change: excessive emissions of greenhouse gases. We know where most of those come from: coal- and oil-burning power plant smokestacks and the tailpipes of our gas-powered cars.
We know how to cut those emissions: Stop relying on fossil fuels and switch to solar and wind. Drive less. Don’t waste electric power. Build houses that are designed to conserve energy.
Yet we keep electing leaders who won’t take those steps, who act as if saving our own lives will cost too much money and thus is not worth doing.
Although he didn’t say anything about climate change at the convention, our current president has repeatedly claimed it’s a hoax. He’s pledged his loyalty to reviving the dying coal industry, allowing oil companies to drill anywhere they want, rolling back rules calling for cleaner cars even when the automakers don’t want him to.
Our current governor paid lip service to doing something about climate by appointing a “chief resilience officer” last year — but she had no qualifications for the job and quit in February after just six months. So far, he hasn’t bothered to name a replacement.
Honestly, the way things are going, if an army of those aggressive mangroves suddenly showed up on the lawn of the Governor’s Mansion or even the White House and knocked down all the security fences so they could move in, I wouldn’t blame them one bit.
Maybe we’d even be better off. At least they’re doing something about the problem.
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