‘Cloud forests move water between trees, mountains and sky — they become a Goldilocks zone for life’

Dirk Karger is a senior researcher at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL). Speaking to Times Evoke, he explains wondrous places where clouds and life on Earth meet:
The saying ‘under a cloud’ normally denotes a touch of suspicion or distrust between humans. However, in the realm of nature, being under a cloud is not a matter of worry — it can be a blessing. Dirk Karger, a senior researcher exploring the interface between macroecology, bio diversity and climatology, explains why. ‘I look at the relationships between bio diversity and climate, mainly in complex ecosystems like mountains,’ Karger tells TE from Zurich. We often think of climate and biodiversity as distinct — one seems sky-bound, the other lives on terra firma — but Karger emphasises, there are indelible links joining them.

Earth’s atmosphere itself was created by biodiversity, he explains. ‘The first plants on Earth made oxygen and put it in the atmosphere. This allowed animal life to evolve. Climate is also determined by species themselves — think of a forest which provides moisture to the atmosphere as it evapotranspirates water from the ground. This causes the formation of clouds. There are other links as well — darker plants reflect less radiation back out into the atmosphere while lighter plants reflect more. These dynamics have a direct influence on the climate system.’ As species shape climate, the opposite also holds true. Karger says, ‘The distribution of species is mainly determined by climate — species have a specific range where they can tolerate certain temperatures. There are thus warmth-loving species and cold-loving ones — climate determines where a species is found.’
Clouds play an incredibly important role in this mega-picture of climate and life. ‘Clouds carry water which is the essence of all life,’ Karger points out. ‘As soon as clouds hit a mountain, they start to interact very powerfully with vegetation there. In mountainous locations, the forests on hills act as filters — they sieve the clouds and get the rain or water back from these atmospheric formations into the land’s water cycle. These very direct interactions between atmosphere and ecosystems result in this water which is extremely important for biodiversity — this is why cloud forests have such a high richness of species,’ says Karger. ‘In fact, these have the highest biodiversity per square meter worldwide across terrestrial ecosystems because there is this constant supply of water from the clouds.’

Cloud forests are usually found at mid-elevations in tropical areas — spread mostly across South America, with some in Africa and parts of southeast Asia too, they do not normally occur where there is harsh winter. Life inside these forests is so abundant, it often thrives on life itself — ‘A main component of cloud forests are epiphytes,’ says Karger. ‘These are plants which have grown on other plants. Imagine these forests as full of mosses hanging off the branches of trees, lush canopies with ferns and orchids laced onto other vegetation. This ecosystem is very stratified from the ground up, with different layers going to the canopy where we also find a very large number of species. Within this ecosystem, a microclimate stays constantly moist and at a moderate temperature. This is like a Goldilocks zone for life where conditions are absolutely perfect,’ Karger smiles, perhaps recollecting seeing such a magical place, ‘This is why we have such an abundance of species thriving there.’

Researchers are now studying the impacts of climate change on these ecosystems. Signs of change — even distress — are already visible as the world warms. ‘With mountain ecosystems, species have to follow their optimal niche — so, if the climate warms by, say, two degrees, the species will have to move 200 metres up to follow their optimal temperature. In cloud forests though, it’s not just temperature which determines species but the clouds themselves,’ Karger outlines. ‘As the climate warms, moisture in the atmosphere is changing. There is more water in some areas and less in others. Clouds too are growing variable in the amount of water they offer — receiving less water means worsened conditions for life, particularly in such ecosystems,’ Karger says.

Other human-caused factors are also threatening the magical cloud forest. ‘In lowland cloud forests, the trees which provided water for clouds to form don’t exist anymore, being lost to deforestation, so the atmosphere is growing dryer — less water then hits the mountains, which means less water gets filtered out of the atmosphere. The entire landscape becomes dryer with reduced water for all the species. Negative feedback loops begin — with less water in the entire system, the whole cloud forest gets severely impacted.’

It took thousands of years for these cloud forests to form. It took amazing intricacies of science — with trees releasing just enough water to make clouds which then returned the gift to the trees — to generate and boost their bursts of life, making these the extraordinary sites they are, perhaps even an inspiration for South America’s fabulous ‘magic realism’ literature, where dark jaguars speak and jewel-like butterflies sing as they carry messages of hate and love to human beings. Today, these wondrous places and all their cast of characters, from clouds to carnivorous plants, face severe threats — remember them the next time you place your carbon footprint with a heavy tread.