Yellow mastic tree thrives in Grand Cayman’s inland forest

The trek to see one of Grand Cayman’s most notable trees will take you over a harsh and unforgiving forest floor strewn with hardened rock and gnarled tree roots. Here, the plants have no soil to give them nutrients, and the trees have endured repeated battering by storms over the centuries.

The Mastic Trail, named for the native yellow mastic tree, provides a glimpse to a part of Cayman that has existed in its present form for millions of years. And in the middle of the trail, there’s a majestic specimen of yellow mastic that has likely been standing since the days of Christopher Columbus.

The path to the yellow mastic begins at the northern trailhead, and the walk commences in a small field that was previously used as a cow pasture. As you make your way deeper on the trail and further from the main road, you progress into older forests and walk into a more alien environment.

For the first residents of Cayman, the Mastic Trail would look much as it did today. There are some non-native trees planted by people in the northern area of the trail, but the southern stages are pretty much unaltered, said Stuart Mailer, the environmental programs manager for the National Trust for the Cayman Islands.

“They might have been interested in doing a bit of logging, but it was such a distance to carry out any trees that they’d cut. So it was pretty much left alone,” said Mr. Mailer of the old-growth forest. “It’s in about the same state it would’ve been when Christopher Columbus arrived at the island.”

The National Trust has been trying to acquire much of the Mastic Trail land for preservation, and to date, it has been able to purchase about 840 acres out of 1,200 in its intended target area. The trail is barely wide enough for one person to walk in most areas, and it’s framed by lush vegetation.

Stuart Mailer, environmental programs manager for the National Trust, leads relaxed and educational Mastic Trail tours. – Photos: Alvaro Serey

Mr. Mailer warns people on his tour groups to be wary of Maiden Plum, a shrub that carries a toxin similar to poison ivy. He points out fruit trees on both sides of the trail as you march forward, and he shares a simple secret: Almost none of the plants bearing fruit in Cayman belong here.

“If you were to make a list of all the tropical fruit you can think of,” said Mr. Mailer at one point of the journey, “I’d be surprised if you had a single Cayman native plant.”

That includes Caribbean staples such as bananas, breadfruit, pineapple and coconuts, all of which were introduced to Cayman by human settlers at some point in the last few hundred years.

Interestingly, the Mastic Trail has one native tree specimen that was only identified within the last 20 years. The tree – Casearia staffordiae – is named after the naturalist, Ann Stafford, who discovered it and pressed the flower samples that ultimately confirmed it as a unique species.

A tour of the Mastic Trail provides a look into Cayman’s natural history.

There’s a point on the trail where the narrow forest trail becomes rougher, where the sure grass-and-dirt footing gives way to a rocky outcropping and every step becomes perilous. That is not just a milestone for the average hiker, said Mr. Mailer, as much as it is a signpost of a totally different world.

“You’ll notice that on either side of the trail, there’s a rock wall. And behind me, the ground rises up to a higher level,” he said. “This is actually an ancient coastline. If you had been standing here 125,000 years ago, you’d have wet feet. This is where sea level was. And it would’ve been a very shallow sea at this point, so probably a mangrove swamp. This island is very low-lying, less than 20 feet above sea level. The vast majority of Grand Cayman would’ve been underwater 125,000 years ago. That may sound like a long time in human terms, but it’s not a very long time in evolutionary or geological terms.”

In practical terms, Mr. Mailer said, everything beyond that point has been evolving for millions of years. All of Cayman’s native flora and fauna would have developed above the water line. And they would have had to evolve in a region that is struck by heavy storms several times per century.

One such tree, the red birch, has developed a unique survival strategy. Its roots have burrowed down around solid rock, and its limbs have evolved to grow in a hurricane-rich environment.

The holes in this tree were made by a yellow-bellied sapsucker, a migratory woodpecker that feeds on tree sap and insects.

“Birch is a rather soft wood and it has an interesting strategy for living in a major hurricane zone. It sheds its branches,” Mr. Mailer said. “When the winds get to tropical force, the trees start shedding branches. If we have a big storm or even a big squall, I’ll quite often have to pick up branches from the red birch. By losing all those branches, it cuts down its wind resistance and it manages to stay standing when stronger trees around it are broken off and blown over. If they still are alive, they have to start their life from the forest floor. The birch is still standing and puts out new branches.”

The inner section of the Mastic Trail is prone to much of the same weather as the rest of the island, and the local plants can go about six months without really seeing much in the form of precipitation.

In several junctures along the side of the trail, you can see dense groupings of mushrooms growing rampantly, and they help provide the trees with the nutrients they need to grow.

“The fungus acts like a giant net,” Mr. Mailer said. “They have microscopic filaments that penetrate through tiny hairline cracks in the rock and act like a net, sucking in water and nutrients and feeding them to the trees. The trees, in turn, provide the fungus with sugar. It’s a symbiotic relationship, and it allows the trees to survive and thrive in what appears to be a completely uninhabitable environment.”

The mushrooms on the Mastic Trail forest floor help provide the nutrients the trees need in a soil-free environment.

Finally, after hiking for an hour or more, you can come to find the best surviving specimen of the tree the trail is named after. It’s a tall and solidly built tree with an expansive canopy, and Mr. Mailer said that when he arrived at the National Trust, it was estimated to be around 700 years old.

“This particular mastic tree was big and old when humans first came across it,” he said. “Hell, it was probably a big tree when Christopher Columbus sailed into the Caribbean.”

This prickly ash tree, Zanthoxylum caribaeum, grows in much of the region and can be found along the Mastic Trail.

The tree is hollow and it eventually stood at the corner of three parcels of land, which may have encouraged early residents of Cayman to leave it right where it was. But even so, it had to survive centuries worth of horrible storms to remain as one of the oldest trees on the Mastic Trail.

Two or three times a century, Mr. Mailer said, Cayman will be struck by a storm that is at least a Category 4. That is strong enough to knock down even the most significant trees, or at least to knock off their tops and rip off their branches. But the yellow mastic has somehow survived and adapted to those conditions, and it has been shaped by countless storms that have battered its position.

Early in his tenure at the National Trust, Mr. Mailer said, there was a bit of a controversy surrounding the tree. It was being strangled by a huge sprawling vine that threatened to overwhelm it, and volunteers debated whether they should let nature run its course or attempt to salvage the tree.

“Nothing happened. I don’t know if that’s because they made the decision to let nature take its course. My guess is, being a big committee, they didn’t make a decision,” said Mr. Mailer of the trail’s signature yellow mastic. “Eventually, in 2004, we had Hurricane Ivan, and after the storm, people came to inspect the damage on the trail. They noticed that this tree had a bare trunk, a couple branches and nothing else. It was still alive, and the vine had ended up in a huge pile of rotting vegetation.

“Nature took its course and left the mastic tree for another 700 years of life.”

This majestic yellow mastic was threatened by strangulation by a vine at one point, but it was saved by Hurricane Ivan in 2004. – Photos: Alvaro Serey

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