Shrouded in mist, dripping with water and boasting an extraordinary richness of plant and animal life, the cloud forests of Monteverde in north-western Costa Rica offer a glimpse into what seems like another world.
With vines curling down from the trees, and orchids and ferns in abundance, it is no surprise that the forests are home to well over 2,000 species of plants.
Animal life is also plentiful, and tourists often hope to catch a glimpse of the resplendent quetzal, a bird famed for its iridescent green and red plumage and the male's elaborately long tail feathers.
Climate change is, however, putting in doubt the future of cloud forests in Costa Rica and elsewhere in Latin America.
Tour guides in the cloud forests, which are easily reachable on foot from the main town in Monteverde, tell visitors that these habitats are migrating to higher altitudes as the climate changes.
The threat posed by climate change was identified at least 25 years ago, and in recent years the impact has become increasingly apparent.
“It’s very likely that the overall area of cloud forests will be reduced, because the conditions that create them are changing. The clouds are moving up,” said Gerardo Avalos, a professor of ecology at the University of Costa Rica.
“Cloud forests depend on water, on a lot of water, not only in the atmosphere but in the soil, on the ground. And the flora has been adapted to these high levels of humidity.
“What we see now: the dry season is getting drier, the wet season is getting more intense. We have these fluctuations.”
Up in the clouds
A 2025 study by researchers based in Mexico and the United States found that cloud forests in the region have migrated upwards by between 1.8 metres and 2.7 metres per year since 1979 because of climate change. The research, published in Science, warned that cloud forests were “among the most threatened ecosystems” in the area.
“Our results highlight the vulnerability of cloud forests under global change and the urgency to increase monitoring of species’ responses,” the researchers wrote.
“Neotropical cloud forests are especially vulnerable, as their distribution is tightly linked to cloud formation, temperature, relative humidity and vegetation cover.”
In Monteverde, as clouds form at higher elevations, the growth rate of some plant species is falling, said Prof Avalos. This reduces the extent to which the forests capture or sequester carbon.
“What happens in the lowlands is something similar and what happens in the highlands, way above the cloud forests, is also something similar: conditions are getting more erratic, the ecosystems are getting more stressed out and the forests are growing less. They are releasing more carbon into the atmosphere,” he said.
Plant and animal species characteristic of lowland forests are moving up and invading the cloud forests, while some cloud forest species are, in turn, migrating to higher altitudes. Fast-growing weedy species are becoming more prominent in some areas.
Invasive forces
“Even the rainbow-billed toucan is invading the cloud forest,” Prof Avalos said. “And toucans eat chicks, eat eggs and also eat fruits from other plants, with unforeseen consequences in the fauna and flora of cloud forests.
“We are in a time of change. Ecosystem changes are happening in a human life. Before that we have seen centuries in order to see changes.”
As upward migration continues, slow-growing tree species may suffer the “summit trap” in the Monteverde area, because the limited elevation of the peaks means that flora and fauna looking to escape warmer areas cannot go any higher.
With habitats changing fast, the quetzal – a bird so celebrated in Costa Rica that volumes dedicated to it are displayed prominently in local bookshops – faces an uncertain future.
Already it is classified as “near threatened” by the International Union for Conservation of Nature (IUCN) as its habitat shrinks from deforestation and other damage.
The birds, which eat wild avocados, lizards and small invertebrates, need to nest in cavities they make in dead trees, or in hollows created by woodpeckers.
The availability of suitable sites in old-growth cloud forests may fall, Prof Avalos said, although this may be partially mitigated by the installation of nesting boxes.
“I believe the quetzal will show some degree of adaptation, but it will rely on having large tracts of cloud forest and oak forest in which wild avocados should be very abundant. It’s very likely the population densities are going to change,” he said.
Need for protection
Ensuring that existing habitats are protected is regarded as essential if the country’s natural environment is to have the best chance of coping with climate change.
The recent study in Science noted that species can sometimes adapt to rapidly changing climates, but this is more difficult if there are land use changes, for example deforestation.
The way that Costa Rica's natural environment attracts tourists has ensured that many areas are preserved, and is likely to be vital to the continued protection of cloud forests and other at-risk ecosystems.
Michael Mooring, a professor in the Department of Biology at Point Loma Nazarene University in San Diego, US, has carried out field research in Costa Rica for more than 15 years. He said the Central American nation is “well known as having one of the best environmental protection programmes on the planet”.
“About 26 per cent of Costa Rica’s land area is under protected status of various kinds – national parks, biological reserves, indigenous reserves [and] private wildlife refuges,” Prof Mooring said.
“Back in the 1970s and 1980s, Costa Rica had one of the highest rates of deforestation in the world, but they have succeeded in making a remarkable reversal in forest and biological diversity loss through wise public policy. They have even succeeded in increasing forest area due to restoration projects.”
Indeed, while it may look ancient and pristine to the casual visitor, some cloud forest in Monteverde is on former farmland turned over to nature.
Prof Mooring said that, as well as the economic value of tourism, other factors that have contributed to reversing deforestation include a government scheme in which landowners are paid to protect their forest areas.
“There is a wonderful conservation vibe in Costa Rica,” he added. “It is a remarkable social sense of pride in the beauty of their wildlife and natural environment.
“And compared with their Central American neighbours, Costa Rica far exceeds them in protected areas, forest cover, renewable energy, and eco-tourism development.”
Preserving the natural environment and maintaining connections between lowlands, middle elevations and highlands so that plants can move up and down is essential in a country where 70 per cent of the continental area is dominated by mountains, Prof Avalos said.
“If you have fragmentation and isolated reserves, animals and plants will have a hard time using the gradient. So large reserves, higher interconnection between reserves, these are our best defence against climate change,” he said.
