New theory: why mountain regions are unusually biodiverse
The world’s mountain regions are extraordinarily biodiverse. Research with Danish participation advances a theory explaining why.
Researchers have long known that mountain regions are unusually biodiverse.
More species live in mountain regions than in rainforests, and new species evolve more rapidly at high elevations than under the tree canopy.
Now a research group led by Danes has created a theory explaining why. The theory can also be useful in protecting plant and animal species globally.
“The theory can explain why mountains are so biodiverse. One thing that supports biodiversity in mountain regions is a diversity of rocks and thus minerals that are not present in large rainforests,” explains Minik Rosing, Professor, Natural History Museum of Denmark, University of Copenhagen.
The research, led by Carsten Rahbek, Professor, University of Copenhagen, was recently published in Science.
Mountains are similar to Darwin’s finch islands
In the research, zoologists, botanists and geologists investigated why mountain regions are unusually biodiverse.
However, some of this is not entirely new territory.
Mountains can be considered small topographical islands. If a plant or animal species is on one mountain peak, it cannot easily reach another pinnacle and is therefore isolated as if it were on an island.
Charles Darwin observed more than 150 years ago that, when finches of the same species are isolated on different islands and experience different conditions, they develop distinctive features adapted to the special conditions of their particular island. This boosts evolution and ends up developing new species.
“This also happens in mountain regions, contributing to greater biodiversity than if the landscape were completely flat,” says Minik Rosing.
Variation in the abundance of minerals increases biodiversity
In addition to dividing habitats into islands, mountain regions can stimulate evolution through variation in the abundance of minerals.
This brings us to the new theory.
All life requires minerals, and these are part of a cycle like everything else.
Plants primarily absorb the minerals, which are then transported over time into the seas, where they sink to the bottom and become part of the sedimentary layer of the seabed.
Over millions of years, tectonic forces raise the seabed, and the minerals turn into mountains again over geological time. Each geological environment thus acquires its very own mineral composition, present in the layers of a mountain.
“Different species thrive differently precisely because the mineral composition varies between rock layers. Some species thrive better on one mineral composition, and others thrive better on another. The result is rich biodiversity,” explains Minik Rosing.
The Amazon does not support biodiversity as well as mountain regions
In contrast, the areas below the mountains, such as the Amazon basin at the foot of the Andes, become the final destination for all the minerals eroded from the mountains over time and through wind, weather and biology. The mineral composition in these basins is therefore much more homogeneous than in the mountains and thus does not support biodiversity as well.
“The great variation in the mineral bedrock supports greater biological diversity in mountain regions. In addition to the geographical islands, geochemical islands emerge in which many animals, plants and insects can live,” says Minik Rosing.
Linking biological variation and geological variation
The new theory was developed by comprehensively reviewing the scientific literature in this field. The researchers collected data from hundreds of scientific studies of either the geology or the biology of the world’s mountain regions. Jon Fjeldså, Professor, University of Copenhagen performed many of these studies.
Many of the results came from the Andes and eastern Africa since researchers from the University of Copenhagen have conducted much research in these places.
By comparing the biological diversity of mountain regions with their geochemical diversity, the researchers established that greater variation in geology is linked to greater variation in biology – thus confirming the theory.
The Amazon is being felled to fertilize farmland with minerals
This research work is not just a theoretical exercise. The link between geology and biodiversity can also have serious implications.
Minik Rosing focuses on what is on everyone’s mind now: the Amazon is burning.
The main reason is that people have set fire to the forest to clear land and to release the nutrients, especially minerals, stored in the trees into the soil.
When these nutrients get into the soil, farmers can grow crops, but unfortunately, the soil lacks minerals in the Amazon, so after a few years, farmers have to cut more trees and clear new land to access new fertile soil.
“By understanding the link between biology – including crops – and minerals, we can better understand which nutrients the farmland lacks. We can then apply these to existing farmland so that farmers do not have to keep cutting down the Amazon,” says Minik Rosing.
Climate change is a major threat to biodiversity in mountain regions
The research work also affects the approach to protecting global biodiversity in general.
In this context, knowing where the great hotspots of biodiversity are and what supports this great biodiversity are important.
This is the only way to protect biodiversity.
Climate change is strongly threatening biodiversity in mountain regions.
As the climate gets warmer, the habitats of many animals and plants move higher up the mountains, which may not be optimal environments.
Nearby mountains may have the exact climatic conditions that some animals or plants need to survive, but since the animals and plants are marooned as if they were on remote islands, they cannot get to these mountains.
“They will potentially be threatened by climate change, but if we do not understand the process, we will not be able to do anything about it. Mountain regions that are unusually biodiverse may be crucial for overall global biodiversity,” says Minik Rosing.
“Building mountain biodiversity: geological and evolutionary processes” has been published in Science. The Novo Nordisk Foundation awarded a research grant in 2016–2018 to Minik Rosing, a co-author.