By Alex Kirby / Climate News Network

Signs of receding ice appear in the Bernese Alps, Switzerland. (Heitere Fahne / Flickr)

LONDON – The rising temperatures caused by climate change are having a marked effect on mountains worldwide. Science has already established that increased warming is affecting distinct mountain features such as glaciers and high-altitude species, and there is now evidence that the entire ecosystem is undergoing change.

An international research team has found that the growing heat is changing the vegetation and even the soil in the world’s mountains. They report their findings on this wider disruption in Nature journal.

Scientists from 10 universities studied the area around the treeline in seven different regions (Europe, Japan, Australia, New Zealand, Canada, the US and South America). They predict that in mountainous regions the heat will grow fast by the end of the century, so that the temperature at a given altitude now will by 2100 have reached 300 metres higher, with far-reaching consequences.

Balance of nutrients

Across the world, climate change is altering the concentrations of nutrients in plants and soils. Higher temperatures mean that the concentration of nitrogen, for example, is rising significantly, but not that of phosphorus.

“This effect is disrupting the balance between these and other nutrients, which is making the ecosystem more vulnerable,” says Ellen Cieraad, a plant ecologist at the Institute of Environmental Sciences of Leiden University in the Netherlands, and a lead author of the study.

If the composition of the vegetation changes, and on top of that the treeline is not able to migrate fast enough, the nitrogen and phosphorous cycles will no longer coincide.

It is not only the heat that is scaling the mountainsides. Inevitably, many plants are also migrating up the slopes, and in some areas the treeline is following suit as well. The higher temperatures are causing changes in soil nutrients, organic matter and the composition of bacteria.

To some extent, that is happening to all types of vegetation involved, Dr Cieraad says. And that is worrying: “If the composition of the vegetation changes, and on top of that the treeline is not able to migrate fast enough, the nitrogen and phosphorous cycles will no longer coincide.” More research could establish how far these changes are affecting the treeline.

Migration of the treeline goes hand in hand with changes in the water cycle, snowfall and temperature, the researchers say. The water supply becomes unreliable, for example, not only in the mountains themselves but also in areas downstream that depend on water from the higher altitudes to feed major rivers. And many mountainous regions will no longer be suitable for winter sports.

Changes in mountains

Knowledge about the effects of climate change on mountain ecosystems is quite limited, the study says, because the data can only be gained through years of research. So rather than conducting short experiments, the researchers studied the composition of ecosystems and the processes taking place in them at different altitudes in different mountain ranges.

Dr Cieraad says: “The temperature differences at what are called elevation gradients in the mountains constitute a powerful natural experiment in which you can observe the effects of climate change on plant communities and ecosystems [an elevation gradient is a measurement, for example, of species richness].

“Studying elevation gradients at different places throughout the world means we are able to map changes more quickly and can predict future developments better.”

Alex Kirby is a former BBC journalist and environment correspondent. He now works with universities, charities and international agencies to improve their media skills, and with journalists in the developing world keen to specialise in environmental reporting.

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