BY SARAH WILD

Even while drought is bringing many of Europe’s rivers to record lows and damaging biodiversity, the threat of catastrophic flooding following a dry spell lurks in the background.

Some of Europe’s most famous rivers such as the Rhine, Danube and Po, have been making headline news thanks to summer droughts. With water levels plummeting to record lows and the rivers drying out, many kinds of economic activities from shipping to farming have been disrupted.

But one little river in Europe that has avoided the media spotlight may offer valuable lessons about the worsening effects of global warming. It is the Albarine, located in south-eastern France and it is the focus of an EU-backed research project about the effects of drought on river ecosystems.

Worldwide, rivers are under stress from climate change. The research will help conservationists to understand the ways drought leads to the loss of biodiversity and respond appropriately.

Rising near the sleepy French town of Brénod near the Jura mountains, the Albarine flows almost 60 kilometres before its crystal-clear waters join the larger Ain River northeast of Lyon. However, there are a number of points during its course at which the Albarine river runs dry. This is something likely to happen to more waterways as global warming intensifies.

Extreme event

‘Drying is an event and drought is an extreme event,’ said Romain Sarremejane, a freshwater ecologist and Marie Skłodowska-Curie Actions (MSCA) post-doctoral research fellow at the French National Institute for Agriculture, Food, and Environment (INRAE).

‘You need to understand drying to understand drought. The issue might be in the future that, if you have big droughts, you will lose all the refuges where species might survive during a drying event.’

Sarremejane is part of the MetaDryNet research project, which is assessing how drying affects organisms in the Albarine and their ability to consume carbon-rich organic matter. At its lush headwaters near Brénod, many leaves fall into the Albarine – and this leaf litter provides food and nutrients along the river’s length.

Drying everywhere

Insects and other creatures nibble at them, and ‘little by little they decompose as you go downstream and then it’s very small particles that end up in the sea,’ Sarremejane said. ‘But when there is drying everywhere in the network, you have these leaves that accumulate in the dry riverbed and are not processed.’

This leaf build-up could result in creatures downstream going hungry and the river processing less carbon.

Sarremejane and his colleagues set out to investigate what happens in the Albarine’s dry patches. They sampled 20 sites, each about 100 metres long, to see how much organic matter passed through, how quickly it decomposed, how much carbon and methane each site emitted, and the diversity of invertebrates, bacteria and fungi present.

Half the sites were in areas where the river sometimes runs dry and the rest were in places where the river flows all year long.

As more places are dry for longer, this could also compromise the ability of creatures to move between parts of the river –– which could ultimately lead to a decrease in biodiversity as well as extinction.

About 60% of rivers worldwide are intermittent –– which means that they are dry for at least one day a year –– and that share is set to rise, according to Sarremejane. Many such waterways usually flow for six to eight months of the year and then dry during the summer.

Intermittency

‘This intermittency is becoming more and more common, and extending in time and space,’ he said.

If a river’s dry patches increase and expand for longer periods of time, these oases in the river where life weathers the drying may disappear too. ‘There is a big tipping point at which you might lose a lot of diversity,’ he said.

His future research will focus on how extreme weather events affect communities of creatures and their diversity in Europe’s rivers, and whether it is possible to quantify these tipping points.

Heavy rain

For all the difficulties triggered by droughts, rain itself poses challenges. When drought-hit areas eventually get rain, it tends to be heavier and harder to absorb, leading to floods which is one of the most catastrophic effects of climate change in European cities.

Benjamin Renard, principal investigator on the Hydrologic Extremes at the Global Scale (HEGS) project, is trying to understand what more precipitation means for river systems and whether it leads to more flooding.

River floods are among the most damaging extreme climate events in Europe, according to the European Environment Agency (EEA). If carbon emissions continue to increase, climate change could triple the direct damages from river floods.

In cities, more rain leads to flooding in the streets, but with rivers it’s not so simple.

‘You have river catchments, which act as a strong filter, so many things could happen,’ Renard said. ‘Flooding is not a direct translation of what’s happening in terms of precipitation.’

He and his collaborators created a statistical framework to assess the probability of rivers in an area flooding. Using data from about 2 000 rain-gauge and hydrometric stations, which measure river flow, their framework can determine the likelihood of a flood in a given region. The data, taken from stations around the world, spans the last hundred years.

‘The data sets we use for both precipitation and floods are from every single continent except Antarctica,’ he said.

The framework links climate variables – such as temperature, atmospheric pressure and wind speed – to the probability of extreme weather events including heavy rainfall or flooding.

Heavier precipitation

‘We confirmed, indeed, that precipitation was getting heavier worldwide, but for floods the signal is much more complicated,’ Renard said. ‘You have some geographic areas where you don’t see much change, some areas where you see increasing floods, and some where you see decreasing floods.’

Renard plans to use the framework for seasonal forecasting or even for different extreme weather events.

‘There is nothing in the framework that is specific to flooding,’ he said. Researchers could configure the framework to other events such as heat waves, droughts and wildfires.

In any case, deploying it for seasonal forecasting would form part of a useful early-warning system. This would allow people to prepare, for example, for nearby river floods and help prevent the loss of life and destruction of property.

The research in this article was funded by the EU. This article was originally published in Horizon, the EU Research and Innovation Magazine. 

Today, a major wildfire in France has destroyed thousands of hectares of forest and forced many people to flee their homes. Meanwhile, dry weather, extreme heat and strong winds have combined to fan wildfires across Europe, the United States and other parts of the world over the last few weeks.                                                                      

Extreme wildfires are devastating to people, biodiversity and ecosystems. They also exacerbate climate change by contributing significantly to greenhouse gas emissions.

While Europe and North America are in the crosshairs now, earlier this year, large parts of Chile and Argentina were engulfed in flames. That includes vast tracts of peatlands, key stores of carbon which, when released, feed planetary warming.

We asked Jacqueline Alvarez, head of the United Nations Environment Programme (UNEP) Office for Latin America and the Caribbean, to tell us more about the drivers of peatland wildfires and what can be done to limit their spread next year.

A recent report, Spreading like Wildfire: The Rising Threat of Extraordinary Landscape Fires, by UNEP and GRID-Arendal, finds that climate change and land-use changes, like deforestation, are making wildfires worse. Are those problems contributing to fires in Argentina and Chile?

Jacqueline Alvarez (JA): Yes. The changing climate has created a troubling reality, yet we shouldn’t undervalue the fact that people cause most wildfires. Beyond natural causes, there is evidence that the fires are being intentionally set to deforest and clear land for speculative businesses. In Argentina, the National Fire Management Service shows in its daily reports that since August 2021, 95 per cent of fires have been due to human intervention.

However, climate change is certainly increasing the vulnerability of peatlands to fire, which is problematic as when peatlands burn, they release more carbon dioxide than many other ecosystems and can be extremely difficult to extinguish. Land use changes due to human activity also have profound impacts on peatlands, which can greatly increase their vulnerability to more frequent and intense wildfires.

Which areas are most at risk in Chile?

JA: The areas where human populations and plant ecosystems coexist are those with the highest risk of wildfires. About 60 per cent of wildfires are in these areas, mainly in central Chile around Valparaíso and La Araucanía, which comprise about 5 per cent of national territory but accommodate around 80 per cent of the population. For this reason, these are priority areas when establishing strategies for the management and design of less risky landscapes. From 2010 to 2020, the central-southern zone of Chile, home to much of Chile’s peatland area, experienced a mega-drought that has had a strong impact on the wildfire regime by drying out biomass and peat soils.

Earlier this year, peatland wildfires in Chilean Tierra del Fuego burned for over a month and destroyed 1,200 hectares of native forest. The blazes killed plants and animals, and spewed carbon into the air. It has been suggested that faster action at the central level could have prevented the fire from reaching such a scale. What do you think Latin America and the Caribbean can do as a region to foster coordinated and rapid responses to wildfires?

JA: A coordinated approach requires planned, permanent, systematic and joint work, with special focus on communities directly exposed to this threat. In this context, the prevention of wildfires should be aimed at the population that lives in risk areas. However, appropriate funding is needed for such efforts. Effective fire response also requires an understanding of the ecosystem in question, its vulnerability or adaptation to fire, the amount of available fuel, the assets, infrastructure and lives at risk, and the likelihood of a fire outbreak developing  into a wildfire. It’s important to promote regional networks for collaboration, especially among countries with similar ecosystems and threats.

What kinds of legal protection do peatlands have in Argentina, Chile and Peru?

JA: There is no specific legal protection for peatlands in these countries. In the case of Peru, which has extensive peatlands, an important advance has been made within a recent decree on the protection of wetlands, where special mention is made of peatlands, prohibiting the extraction of peat for commercial purposes. In Chile there is a draft law on peatlands prohibiting the extraction of pompón, the Chilean name for sphagnum moss, currently in the final phase of approval. In July 2021, lawmakers in Argentina began debating the creation of a law to regulate human interventions in wetlands. In South America, there is an urgent need for countries to enact strong, dedicated environmental protection laws for wetlands.  

What are the key knowledge gaps that need to be filled to inform policymaking better?

JA: One of the problems is that many policymakers are unaware of the significant socioeconomic benefits that peatlands offer. They are a habitat for many unique and threatened species, they regulate water cycles, they control pollution and sediments, they serve as a source of water and locally harvested products, and they are an inspiration for art, religion and cultural values. A lack of information means that political decisions on land use are leading to the degradation and conversion of these high-carbon ecosystems. Peatlands need to be recognized across levels of governance as a high-priority ecosystem for urgent action by policymakers given that they benefit the climate, people and biodiversity.

UNEP

Two of the largest reservoirs in America, which provide water and electricity to millions, are in danger of reaching ‘dead pool status.’ A result of the climate crisis and overconsumption of water, experts say.

Lake Mead, in Nevada and Arizona, and Lake Powell, in Utah and Arizona, are currently at their lowest levels ever. ‘Dead pool’ status would mean the water level in the dams was so low it could no longer flow downstream and power the hydroelectric power stations.

The Lake Mead reservoir, which is the largest artificial body of water in America, was created in the 1930s by the construction of the Hoover Dam, an engineering masterpiece. Lake Powell, the second largest, was created in the 1960s, with the construction of the Glen Canyon Dam.

“The conditions in the American west, which we’re seeing around the Colorado River basin, have been so dry for more than 20 years that we’re no longer speaking of a drought,” said Lis Mullin Bernhardt, an ecosystems expert at the United Nations Environment Programme (UNEP), “We refer to it as “aridification” – a new very dry normal.”

Lake Mead and Lake Powell, which is created by the Glen Canyon Dam, not only provide water and electricity to tens of millions in Nevada, Arizona, California, Wyoming, Colorado, New Mexico and Mexico, but they also provide irrigation water for agriculture. Experts warn that as the crisis deepens, water cuts will need to be introduced, but this may not be enough.

“While regulating and managing water supply and demand are essential in both the short and long term, climate change is at the heart of this issue,” said Maria Morgado, UNEP’s Ecosystems Officer in North America. “In the long term we need to address the root causes of climate change as well as water demands.”

Over the last 20 years, 90 per cent of major disasters were caused by floods, droughts and other water-related events. With more frequent droughts, people in water-scarce areas will increasingly depend on groundwater because of its buffer capacity and resilience to climate variability.

Increases in water demand due to growing populations and irrigation for agriculture have been compounded by climate change impacts such as reductions in precipitation and temperature rises. A rise in temperature leads to increased evaporation of surface water and baking of the earth, decreasing soil moisture.

“These conditions are alarming, and particularly in the Lake Powell and Lake Mead region, it is the perfect storm.”

This is part of a wider trend affecting hundreds of millions of people across the planet. As climate change wreaks havoc on the Earth’s interconnected natural systems, drought and desertification are swiftly becoming the new normal, everywhere from the United States to Europe and Africa.

Drought in Numbers, a 2022 report from the UN Convention to Combat Desertification, found that since 1970 weather, climate and water hazards have accounted for 50 per cent of all disasters and impact 55 million people globally every year. The report also found that 2.3 billion people face water stress annually.

Drought is also one of several factors that impacts land degradation, with between 20 and 40 per cent of the world’s land being classed as degraded, affecting half the world’s population and impacting croplands, drylands, wetlands, forests and grasslands.

The UN Decade on Ecosystem Restoration, of which UNEP is one of the leading members, was set up to halt and restore ecosystems around the world. The Decade runs until 2030, the same timeline as the Sustainable Development Goals, and aims to counteract climate change and halt biodiversity collapse through restoring ecosystems.

UNEP