Ryan Schuessler

Withering clouds: Climate change damaging biodiverse Costa Rica forest

Higher air temperatures mean rising clouds, altering the ecosystem by pushing flora and fauna toward higher ground

MONTEVERDE, Costa Rica — The cloud forests of Monteverde are known around the world for their biodiversity. But locals and scientists are warning the delicate ecosystem is increasingly without the clouds.

Increasing temperatures have caused the clouds in the mountain forests around Monteverde to rise, and scientists believe the warming climate is leading to the redistribution of species in the highlands, renowned for the striking biodiversity that draws in hundreds of thousands of tourists each year.

That is bad news. Monteverde’s cloudless cloud forests are a symptom of a regional change in climate with ecological and economic implications, since farming patterns change and the tourism industry could be hit. Data collected since the 1970s by bat biologist Richard LaVal show that the average minimum temperature of Monteverde increased nearly 3 degrees Celsius from 1990 to 2000 — which can expand the range of tropical lowland species 400 vertical meters into the cooler highlands. While the average temperature has decreased in recent years, the data continue to indicate a long-term trend of increasing temperatures, researchers say.

The increasing temperatures in the highlands have opened the door for lowland flora and fauna — which are adapted to warmer temperatures — to move into highland ecosystems where they were not usually found before.

a Toltec fruit-eating bat.
Daniel Neal

“We have at least 25 new bat species on the mountain from the tropical lowlands [that] are now here in Monteverde,” said Vino De Backer, a Belgian zoologist who has studied bats in Monteverde under Laval for the past eight years. His recent research has focused on upward elevation changes when increasing temperatures contribute to the vertical expansion of lowland species’ range.

As part of an ongoing data collection effort, De Backer found that highland species such as the Toltec fruit-eating bat have retreated to even higher altitudes as the temperature increases in its native range and lowland species move into the highlands.

“It’s almost half the percentage that it was before,” he said of the Toltec bat. “They are here, but they are retreating to higher elevation.”

LaVal and De Backer’s data show that in the early 1970s the Toltec bat accounted for 26.4 percent of bats collected in Monteverde. Last year it accounted for only 19.5 percent. From the 1970s to 1990s, another highland species, the highland yellow-shouldered bat, dropped from 43.2 percent to 22.4 percent.

Costa Rican coffee beans affected by a tree-killing fungus known as roya or coffee rust. The disease has become markedly worse in the past few years.
Juan Carlos Ulate / Reuters / Landov

Meanwhile, lowland bat species are moving higher into the native range of bats such as the Toltec. The Jamaican fruit bat — a lowland species — went from none in the 1970s to 12.6 percent of specimens caught last year.

“Now they are all over in Monteverde,” De Backer said.

Other lowland species of flora and fauna have moved into the highlands as well, causing problems for area farmers. Oldemar Salazar Picado grows coffee just below the famed Monteverde Cloud Forest Reserve. Over the past two years, the unprecedented number and abundance of fungi have destroyed approximately 80 percent of his crop. The roya fungus, also called coffee rust, has attacked his coffee plants at an unprecedented level, and he suspects the warmer temperatures and irregular weather patterns in recent years are to blame.

“I’ve been here 20 years, and it’s never been as strong as it has been the last two years,” he said. Salazar has had to plant more coffee to compensate for losses to the fungus.

Lelo Mata Leiton, who also runs a small farm in the same region, has also noticed changes. Over the past few years he has seen an increase in the number of birds around his farm, including the Montezuma oropendula, a species adapted to the warmer climates closer to the coast. He said that the birds decimated most of his orange crop this year.

He added, “And now you see more squirrels and raccoons from warmer climates than you used to.”

“Toucans are here now,” De Backer said. “Toucans were never here. They were in the lowlands.”

With at least 3,200 plant species (including more than 500 orchids), 161 species of amphibians and reptiles and more than 400 birds and 100 mammals, the Monteverde region is one of the most biodiverse places in the world and has become well known for its eco- and adventure-tourism industry. The region attracts some 200,000 tourists each year looking to catch a glimpse of rare, famed species such as quetzals.

A ringed centipede snake.
Ryan Schuessler

“We don’t escape the effects of climate change,” said Aníbal Torres, vice president of the Monteverde Institute, a regional education and resource center. “The whole ecology of the area has changed.”

And it’s not just in Monteverde. Christian Zuñiga Gutierrez, who works at the Parque Nacional Rincón de la Vieja — another tropical cloud forest, in nearby Guanacaste province — has noticed a similar change.

“We see ecosystems coming from the lowlands to higher places,” he said. “Sometimes we see birds that are not supposed to be here. That happens with insects. That also happens with plants.”

He specifically mentioned army ants moving higher up the slopes of the park’s volcano, which threaten other species not adapted to the ants’ predatory nature. There has also been an increase in lowland snake sightings in the cloud forests on the mountain, which prey on bird eggs. It took only a few minutes into a tour with a group of American students for Zuñiga to find a ringed centipede snake, once found only in the lowlands.

“The bad thing about living on top of the mountain is that there’s nowhere to go,” said biologist Dan Janzen of highland species that suddenly have to compete with those from the lowlands that have moved higher with the increasing temperature.

He cited one example, a species of wasp that spends the dry season dormant in the cloud forests of Rincón de la Vieja — a behavior adapted to an ecosystem without army ants. As the ants move higher on the volcano, they are attacking the dormant wasps and carrying them away to be eaten.

“You’ve created death valley for what lived above [the lowlands],” he said.

Janzen helped create the now-163,000-hectare Area de Conservación Guanacaste in 1985, which encompasses Rincón de la Vieja. He started doing research in Costa Rica in the early 1960s.

“What you see is the cloud layer, the real visible one, is sliding up the volcano,” he said. “As the warm and dry slides up the volcano, the things that live in the warm and the dry go with it.”

The lower temperatures in the Guanacaste and Monteverde highlands combine with trade wind patterns to create dense clouds that use to encompass vast stretches of forest. In a 1999 study, other scientists in Monteverde concluded that the abundance of mist in the cloud forests, which helped to keep the area cool, “has declined dramatically since the mid-1970s.”

An emerald toucanet (Aulacorhynchus prasinus).
FLPA / Alamy

In the past, visitors were lucky to catch a glimpse of the active crater of Rincón de la Vieja because the clouds were so dense. But that’s not always the case anymore, Zuñiga said, which is good for tourists, “but we know something is wrong.”

Janzen said, “The impact of climate change on biodiversity is much greater, and that’s empirically true.”

These days, Costa Rica’s famed cloud forests are becoming cloudless.

That’s not how it used to be, said local guide and researcher Victorino Molina Rojas. In 1930 his grandfather moved to Santa Elena, one of the communities near the Monteverde Cloud Forest. “At that time, Santa Elena was a cloud forest,” he said. “And here he said it was always misty. Cloudy and misty.”

He added, “Not anymore.”

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