A Caribbean island gets everyone involved in protecting beloved species

Excellent article on environmental protection in Saba. [Many thanks to Peter Jordens for bringing this link to our attention.] Anna Gibbs (Science News, Vol. 202, No. 6) explores the wealth of varied species in need of support on Saba.

The coral reef, once bustling with more than 5,000 long-spined sea urchins, became a ghost town in a matter of days. White skeletons with dangling spines dotted the reef near the Dutch Caribbean island of Saba, the water cloudy from the disintegrating corpses. In just a week last April, half of the urchins, Diadema antillarum, in a section of reef called “Diadema City” had died. In June, only 100 remained. The mysterious die-off started sweeping across the Caribbean in February. It’s eerily similar to a mass mortality event in 1983 that wiped out as much as 99 percent of the Caribbean Diadema population — a huge blow to not only the urchins, which have not fully recovered four decades later, but also the reefs. Without urchins grazing, algae can overwhelm a reef, damaging adult coral and leaving nowhere for new coral to settle.

Before the die-off, Saba’s coral cover — the part of a reef that consists of live hard coral rather than sponges, algae or other organisms — hovered around 50 percent. Today, that number is down to 3 percent. “It’s just downhill, downhill, downhill,” says Alwin Hylkema, a marine ecologist at Van Hall Larenstein University of Applied Sciences and Wageningen University in the Netherlands who is based in Saba (pronounced “say-bah”).

I learned about Saba’s sea urchin problem only shortly after I learned that the island existed. Saba is a blip in the Caribbean; at 13 square kilometers, it’s about a quarter the size of Manhattan, with the towering Mount Scenery volcano at its center. Its reefs attract scuba divers, but a lack of beaches shields it from regular Caribbean tourist traffic — hence its nickname, “the unspoiled queen.” What the island lacks in size and sand it makes up for with its great variety of species, its biodiversity. Steep cliffs support several micro­climates. In just a few hours, a visitor can hike from volcanic rock to grassy field to misty cloud forest.

This diversity makes Saba the perfect spot for Sea & Learn, an annual educational program that brings scientists from around the world to the island. Former dive shop owner Lynn Costenaro launched the program in 2003 to encourage more divers to visit Saba during the off-season. But the event has grown to play an important role in educating the island’s 2,000 residents about their home’s unique wildlife and ecosystems.

[. . .] Some island species occupy only one island; others are spread out in small populations across several islands. Species within small populations can develop a very narrow, island-specific set of adaptations, which spells trouble when humans and invasive species arrive. Today, any given plant or animal on an island is 12 times as likely to go extinct as species on the mainland, [Severin] Irl and an international group of researchers reported in the November 2021 Global Ecology and Conservation. And the decline is speeding up at an unprecedented rate. As biodiversity decreases, islands lose the complexity that helps keep the ecosystem stable and less vulnerable to disruptions, such as climate change. “We’re in the midst of a biodiversity crisis … and islands are really bearing the brunt of that global change,” says arachnologist Lauren Esposito of the California Academy of Sciences, who has presented research on spiders and scorpions at Sea & Learn.

The features that put island inhabitants at risk — their small size and isolation — also make them wonderful laboratories. Like the famous Galápagos Islands that turned Charles Darwin on to natural selection, islands present opportunities to study individual species as well as ecosystem dynamics, in a relatively small microcosm. In 2021, the California Academy of Sciences launched Islands 2030, co-led by Esposito, in five tropical archipelagos, including the Lesser Antilles where Saba is located. The aim is to conduct biodiversity research as well as train local communities to become guardians of their environments. The program took its inaugural trip to Saba’s Sea & Learn last October. I attended that Sea & Learn and tagged along on field trips to see what progress and pitfalls researchers had experienced while working on Saba to protect a tiny orchid, a bright-billed bird and those dying urchins.

Counting orchids

[. . .] After defining an orchid as a flowering plant with three petals and a laundry list of unusual attributes, [Mike] Bechtold described the disorganized history of orchid research on Saba, including a series of miscommunications that has resulted in count discrepancies. A recently published book identifies 22 species, while Bechtold counts 32.

“To know what we have to preserve, well, we at least have to know what is there,” says Michiel Boeken, a former secondary school teacher from the Netherlands who studied orchids on Saba during his 2010 to 2012 tenure as principal of the island’s only secondary school.

The morning after his presentation, Bechtold led a hike to Spring Bay to look for orchids. We walked along the island’s only major road — aptly named The Road. At the trailhead, we descended into a swath of trees laden with mosses and other plants. We’d only walked for about 10 minutes when Bechtold pointed out an Epidendrum ciliare, the most common orchid on Saba, perched on a tree.

Stepping carefully over hermit crabs, we looked for the pile of rocks that marked where to leave the trail to find another species, Brassavola cucullata. Bechtold, Boeken and colleagues had surveyed the Spring Bay population from 2011 to 2014 to see if Saba’s numbers were declining. As we lowered ourselves down the steep hillside, we eventually spied the tiny white and yellow flowers of B. cucullata atop a tall tree with a metal tag glued beneath it; it was #582 of 834 B. cucullata plants that Bechtold helped tag a decade earlier. [. . .] Plants close to the ground were often munched on by wild goats.

The orchid is found from Mexico to northern South America. But here, the B. cucullata population was indeed declining, with small plants dying and not many new plants starting to grow, the researchers reported in 2020 in the International Journal of Plant Sciences. Without counting flowers for many more years, if not decades, it will be hard to know if the decline reflects natural population dynamics or if it’s a troublesome trend. [. . .]

Tracking red-billed tropicbirds

[. . .] Overhead, red-billed tropicbirds, with long white tails and bright crimson beaks, swooped out across the sea.

About 1,500 breeding pairs of Phaethon aethereus mesonauta, one of the three subspecies of red-billed tropicbirds, breed on Saba, as much as a quarter of the subspecies’s global population. Tropic­birds spend most of their lives at sea, only coming to land for a few months each year to breed and raise a single chick. Their cliffside nesting spot makes the birds hard to study even when they’re on land. [. . .] For full article, see https://www.sciencenews.org/article/saba-caribbean-island-species-conservation

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