Climate Change's Effects on Mountain Regions: Insights from FAO/IAEA Scientific Expeditions to the Andes

What are the key findings of the surveys, so far?

In Chile, Bolivia and Peru, scientists have helped to better understand the impact of climate change on land and water resources in the high Andes. Through three major field campaigns in the three countries, with participation of local and international scientists, more than 800 soil, sediment and ice samples were collected.

Nuclear techniques helped trace the origins and pathways of sediments and calculate the sedimentation rate of lakes, reservoirs and wetlands. New sediments become exposed after the ice of the glacier retreats. When these are transported by rainwater, they can invade waterways and pollute rivers and fish with heavy metals. They can also settle in and dry out wetlands, which may then become less suitable for capturing and buffering water, and at the same time they can become a source of greenhouse gas emissions. Downstream, when the ice melts, at first the water availability increases. The water then reduces as the stock of ice available decreases, reducing the amount of water discharged into the river. Reduced water quality and availability impact local populations, crop production, livestock and tourism.

Studies carried out by Brazilian scientists linked to the project have also made it possible to better understand the impact of Amazonian forest fires on the melting of glaciers in the Andes. As smoke plumes from forest fires reach the glacier, they darken its surface causing it to then absorb more of the sun's energy, and therefore amplify the melting. Modelling combined with in situ measurements showed that this phenomenon may contribute to approximately five per cent of the surface melting of the Zongo glacier in Bolivia.

Further, the surveys in field and laboratory using isotope techniques helped to identify types of soils, land use and cover being most critical for emitting greenhouse gases when temperature further increases.

How are nuclear and isotopic techniques used and what makes them unique in assessing the impact of climate change in mountainous regions?

Conventional techniques and methods, such as sediment redistribution measurement, are no longer sufficient to assess, at a fine level of detail, the impacts of climate change on soil and water resources in mountainous regions. Thus, the application of isotopic and nuclear techniques – highly reliable and precise tools – open a new window of possibilities to decipher subtle changes in the ecosystems we are studying.

Nuclear techniques based on the measurement of carbon-13, carbon-14 and nitrogen-15 isotopes were used to determine the age of soil’s organic carbon content and its stability. When organic carbon is not stable, the soil can release CO₂ more easily. Various experiments were conducted in laboratories, using soil samples from the different study sites with varying climates, land use and soils. By changing temperature and soil moisture regimes in the laboratory, the scientists aimed to find out how changing climate conditions would lead to an increase in greenhouse gas emissions and as well as whether the old or just young carbon would be a source for greenhouse gases.

Climate change also has an impact on sediment distribution. Scientists measured sedimentation rates in natural and artificial water bodies, to find out how large the impact of climate change, such as retreating of glaciers, was on this process. Nuclear techniques included various radionuclides present in the soil and sediments, which are used to assess soil degradation and sediment redistribution in different time scales.

Nuclear techniques were also used – along with conventional techniques – to date sediments and understand past and current changes in climate and the landscape. Understanding the past allows to better predict future trends.

How can the kind of information gathered on the expeditions support the development of climate change adaptation strategies for ecosystems and local populations?

We expect to offer new, accurate science-based evidence for decision makers to establish tailor-made regional policies for climate change adaptation and mitigation. The United Nations Environment Programme and FAO support the science–policy dialogue resulting from the findings. Decision makers are involved and local populations also expressed clear support to our work, which is encouraging for us.

Our data are useful for developing water resource management plans and managing watersheds. For example, controlling erosion in hydrographic basins – the areas of streams where precipitation drains off into rivers or other bodies of water – will reduce the production of sediments that can compromise the storage capacity of reservoirs supplying water for human consumption and hydropower production.

Also, comparing “signatures” between the current and the accumulated sediment in proglacial lakes, which are freshwater lakes formed behind ice dams or the soil and rock material left behind by a moving glacier, offers a perspective over time of the changes that have occurred during the glacial retreat stages. This helps in developing possible future scenarios, for which watershed management plans can be established.

David Choquehuanca, the Vice-President of Bolivia, and Bernardo Gurarachi, the first Bolivian to reach the top of Mount Everest, both expressed their full support for our project, as it responds to the need to generate scientific evidence on the impacts of climate change on water resources. The results obtained will be used by government institutions such as the Ministry of the Environment and Water and the Authority of Mother Earth in Bolivia to develop policies for adaptation to climate change.

How can scientists globally use the results of this work and what are the next steps?

A sharing platform on the IAEA’s Cyber Learning Platform for Network Education and Training makes data available to experts for evidence-based decision making. It enables researchers and laboratories from different countries to have organized and systematized data to carry out their studies on a global scale.

The current FAO/IAEA project running until 2023 involves more regional participants from research institutes and universities, more decision makers and more members of the local population.

We expect now to gain a better understanding of the role played by high altitude wetlands as regulators of water flow, thanks to the use of Cosmic Ray Neutron Sensors, a new technology that can measure the moisture content of the soil in a wide area continuously. We will also strengthen and extend the interregional network of laboratories and competent institutions for the evaluation and prediction of climate change impacts.