USA’s biggest palm collection faces future of sea level rise
It’s an iconic image of natural disaster in South Florida: a palm tree bent in half under the furious winds of a hurricane.
The threat of sea rise has given a new twist to that old symbol. Now, the rows of palms often poke out of pools of coastal flood waters, pushed inland by king tides or powerful storms.
That was exactly the scene at one of South Florida’s best-kept botanical secrets in the aftermath of Hurricane Irma. The storm swept six feet of Biscayne Bay water across the 120-acres that make up the Montgomery Botanical Center, drenching the nation’s largest collection of palm trees and cycads (a distant cousin of palms).
But the wrath of a single hurricane isn’t the biggest threat the garden faces. According to a scientific paper written by the center’s executive director, Patrick Griffith, the varied forces of climate change already have had impacts only likely to get worse.
Some effects are clear: the garden will likely lose a third of its acreage and more than a thousand plants to rising seas. Others, like how his other plants will react to more saltwater floods, hotter weather and higher groundwater levels, aren’t clear yet.
“We’re seeing that more palms appear to be more salt tolerant than we actually thought. We learned that in Hurricane Irma,” Griffith said. “Many of our palms were underwater for half a day. We thought we’d lose them but they’re still here.”
Rising bay waters and hotter daily temperatures are a threat to the coastal Coral Gables garden, a nerdier older sibling to the more famous Tropical Fairchild Botanic Garden just up Old Cutler Road. The center’s founders, Robert and Nell Montgomery, started their plant collection in 1932 and focused on scientific research, although the garden does allow visitors and host public workshops. A few years later they met David Fairchild and founded a new public garden named after the intrepid horticultural explorer.
At the time, gardeners loved South Florida because it was one of the few spots in the U.S. where plants could grow outdoors year round. In another century, if Griffith’s paper is correct, the region may not be the same hospitable destination.
Griffith has been the steward of the region’s oldest plant collection since 2005, but he’s focused on what his garden will look like in 2117 with three feet of sea level rise. In his paper, published in Curator: The Museum Journal, he analyzed sea rise models, the rate of plant replacement in the garden’s 86-year history and how the center fared after each of the dozen hurricanes it has weathered.
Montgomery has long seen the effects of flooding exacerbated by sea rise. Seasonal king tides, when the bay water rise the highest, already sweep over the banks of the center’s five lakes, washing over the road dividing them. Saltwater intrusion has made two of the property’s three wells too salty for irrigating the gardens. Only the westernmost well is still fresh enough.
But Griffith found that the Montgomery of 2117 will be a much different place. With an estimated three feet of sea rise — which Griffith’s model predicted by 2117 but the Southeast Florida Climate Compact predicts by around 2090 — one third of the garden would be underwater. That would soak more than 1,200 plants, about eight percent of the collection.
In a century, Griffith predicts, fewer than 120 of the plants in today’s garden of 14,000 will still be around, mostly due to the relatively short lifespan of palms and cycads and the garden’s quick rate of turnover.
In a collection stocked with some of the world’s rarest palms and cycads, that could represent a devastating loss. Botanical gardens are the last refuge of delicate and endangered plants that struggle to survive in the modern world. Griffith wrote in his paper, “Like other museums, botanic gardens are organized around collections: we stock, study and show heritage, history and handsomeness – thus, gardens are truly (horti)cultural institutions.”
Take the Attalea crassispatha, a thick-trunked feathery palm native to Haiti. There’s about a dozen growing at Montgomery, and more at next door neighbor Fairchild Gardens — a larger collection than all of Haiti.
Or the Tali palm, Corypha taliera. The 30-foot Indian palm is extinct in the wild. Only 20 exist in botanic gardens around the world, Griffith said. The Montgomery tree was one of nearly 400 trees that toppled during Irma, and the center got emergency funding from the National Science Foundation to right it.
The Tali palm is so rare, in part, because of its bizarre propagation habit. The tree only flowers once, when it’s about 60 years old. Then it dies. Montgomery’s specimen is only about 22 years old, Griffith said.
“Probably everybody working at Montgomery won’t be here when it flowers,” he said. “We’ll have to leave detailed instructions for what to do.”
The staff also travels the world discovering new palms and cycads in remote, exotic places. They traveled to Cuba seven years back, a trip that required intervention from Sen. Bill Nelson to proceed, and came back with some of the world’s rarest palms.
Griffith himself discovered a new palm on Curacao last year, the sabal antillensis. It only grows on two islands in the world. He discovered it by analyzing the “funny looking palm” in vacation pictures on social media.
“I think that’s how many new species are discovered these days,” he said.
Discoveries are also made inside the garden’s two greenhouses, where staffers run experiments. Griffith said he expects more of those experiments to be aimed toward discovering which palms and cycads can tolerate the most heat and saltwater. Those candidates, he said, will be the ones to survive the garden’s warmer, wetter future.
Griffith is optimistic that his garden will survive another century, because unlike a natural ecosystem like the Everglades, he and his team can select plants and prune the collection to respond to climate change. About half the collection gets replaced every 13 years, he said, which is a nimble enough time window to adapt to environmental changes.
There are still 73 plants around from the founding of the collection in 1932, he said, which gives him hope that with careful planning, he and his team can work to preserve the world’s rare palms and cycads for another hundred years.
“That’s why we keep them. We’re worried about them,” Griffith said. “We want to keep their lineages going.”