Just over one-third (37%) of the world’s 246 longest rivers remain free-flowing, according to a new study published in the scientific journal Nature. Dams and reservoirs are drastically reducing the diverse benefits that healthy rivers provide to people and nature across the globe.
A team of 34 international researchers from McGill University, World Wildlife Fund (WWF), and other institutions  assessed the connectivity status of 12 million kilometers (~7.5 million miles) of rivers worldwide, providing the first ever global assessment of the location and extent of the planet’s remaining free-flowing rivers. 
Among other findings, the researchers determined only 21 of the world’s 91 rivers longer than 1,000 km (~600 miles) that originally flowed to the ocean still retain a direct connection from source to sea. The planet’s remaining free-flowing rivers are largely restricted to remote regions of the Arctic, the Amazon Basin, and the Congo Basin.
“The world’s rivers form an intricate network with vital links to land, groundwater, and the atmosphere,’’ said lead author Günther Grill of McGill’s Department of Geography. ‘’Free-flowing rivers are important for humans and the environment alike, yet economic development around the world is making them increasingly rare. Using satellite imagery and other data, our study examines the extent of these rivers in more detail than ever before.”
Dams and reservoirs are the leading contributors to connectivity loss in global rivers. The study estimates there are around 60,000 large dams worldwide, and more than 3,700 hydropower dams are currently planned or under construction. They are often planned and built at the individual project level, making it difficult to assess their real impacts across an entire basin or region.
“Rivers are the lifeblood of our planet,” said Michele Thieme, lead freshwater scientist at WWF and global leader of WWF’s free-flowing rivers initiative. “They provide diverse benefits that are often overlooked and undervalued. This first-ever map of the world’s remaining free-flowing rivers will help decision makers prioritize and protect the full value rivers give to people and nature.”
Healthy rivers support freshwater fish stocks that improve food security for hundreds of millions of people, deliver sediment that keeps deltas above rising seas, mitigate the impact of extreme floods and droughts, prevent loss of infrastructure and fields to erosion, and support a wealth of biodiversity. Disrupting rivers’ connectivity often diminishes or even eliminates these critical ecosystem services.
Protecting remaining free-flowing rivers is also crucial to saving biodiversity in freshwater systems. Recent analysis of 16,704 populations of wildlife globally showed that populations of freshwater species experienced the most pronounced decline of all vertebrates over the past half-century, falling on average 83 percent since 1970.
The study also notes that climate change will further threaten the health of rivers worldwide. Rising temperatures are already impacting flow patterns, water quality, and biodiversity. Meanwhile, as countries around the world shift to low-carbon economies, hydropower planning and development is accelerating, adding urgency to the need to develop energy systems that minimize overall environmental and social impact.
“Renewable energy is like a recipe – you have to find the right mix of ingredients to have both a sustainable energy grid and a thriving natural world,” said Thieme. “While hydropower inevitably has a role to play in the renewable energy landscape, well-planned wind and solar energy can be more viable options for rivers and the communities, cities, and biodiversity that rely on them.”
The international community is committed to protect and restore rivers under Agenda 2030 for Sustainable Development, which requires countries to track the extent and condition of water-related ecosystems. This study delivers methods and data necessary for countries to maintain and restore free-flowing rivers around the world.
Visit freeflowingrivers.org for more information on free-flowing rivers and an interactive map of the world’s rivers.
 Contributing Institutions:
McGill University, WWF-US, WWF-NL, WWF-UK, WWF-Mediterranean, WWF-India, University of Basel, Joint Research Centre (JRC), WWF-China, WWF-Canada, WWF-Zambia, WWF Greater Mekong Programme, The Nature Conservancy, University of Nevada, WWF-Malaysia, IHE Delft, WWF- Germany and HTWG Konstanz, King’s College London, Umeå University, Swedish University of Agricultural Sciences, University of Washington, Harvard University, University of Wisconsin-Madison, Conservation International , WWF-Mexico, WWF International, Stanford University, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Freie Universität Berlin, WWF-Brazil, Eberhard Karls University of Tübingen.
 First ever science-based definition of a free-flowing river:
Rivers where ecosystem functions and services are largely unaffected by changes to fluvial connectivity allowing an unobstructed exchange of water, material, species, and energy within the river system and with surrounding landscapes.
Increasing Frequency of Cyclones and Flooding Portends Worse Problems
Sixteen years ago on August 29th, hurricane Katrina struck the Louisiana coast causing widespread damage that was estimated at $125 billion. This year, by a remarkable coincidence, hurricane Ida hit on the same date, again August 29th. The weather service holds the end of August though the beginning of September as the period with the highest likelihood of tropical cyclones hitting the Louisiana coast. In light of this, perhaps the coincidence is not quite as uncanny.
While not as large as Katrina, hurricane Ida was more powerful with winds in excess of 150 miles per hour. That is in line with climate scientists who now believe extreme weather events will tend to increase in both severity and frequency unless something is done about global warming.
Another example has been the heat wave last June in the Pacific Northwest in which hundreds of people died. Canada set an all-time-high temperature record of 49.6 degrees Celsius in the village of Lytton. The chance of all this happening without human-induced global warming is about 1 in a 1000. However, the warming makes the event 150 times more likely.
Following Ida was hurricane Larry. Also powerful, it formed in the Atlantic but luckily for the Atlantic coast chose a path straight north. These recurring extreme weather events have caught the attention of scientists. Thus Myhre from the Center for Climate Research in Norway and his coauthors find a strong increase in frequency and confirm previously established intensity. They collected data for Europe over a three-decade period (1951-1980) and repeated the process for 1984-2013. This historical data also allowed them to develop climate models for the future, and, as one might imagine, the future is not rosy.
Expanding their horizon, the authors note that historical and future changes in Europe follow a similar pattern. This does not hold when including the US, Japan and Australia which are likely to experience bigger changes. Given intensity and frequency going hand in hand and also that the study considered natural variability alone, we can only dread the inclusion of human forcing through climate drivers like greenhouse gases.
For coastal residents, sea level rise adds to the hazard. Worse, it is now a problem for people several miles inland. In South Florida, drainage canals are used to return water to the ocean after storm and flooding events; the difficulty now lies in rising sea levels that hinder the efficiency of the drainage canals.
Residents as far away as 20 miles inland have noticed water coming up their driveway, a new and frightening portend of the future. The South Florida Water Management District oversees the canals. It raises and lowers the gates controlling flow to the ocean or vice versa. Thus they can open the gates to release flood water from storms to the ocean.
The problem now is that the ocean level in the Atlantic during some storms is higher than the water level inland so they cannot open the gates — that would simply bring in more water.
All of these happenings are clearly not a happy future prospect … unless we take global warming seriously and act soon.
Human activity the common link between disasters around the world
Disasters such as cyclones, floods, and droughts are more connected than we might think, and human activity is the common thread, a UN report released on Wednesday reveals.
The study from the UN University, the academic and research arm of the UN, looks at 10 different disasters that occurred in 2020 and 2021, and finds that, even though they occurred in very different locations and do not initially appear to have much in common, they are, in fact, interconnected.
A consequence of human influence
The study builds on the ground-breaking Intergovernmental Panel on Climate Change (IPCC) assessment released on 9 August, and based on improved data on historic heating, which showed that human influence has warmed the climate at a rate that is unprecedented in at least the last 2,000 years. António Guterres, the UN Secretary-General described the IPCC assessment as a “code red for humanity”.
Over the 2020-2021 period covered by the UN University, several record-breaking disasters took place, including the COVID-19 pandemic, a cold wave which crippled the US state of Texas, wildfires which destroyed almost 5 million acres of Amazon rainforest, and 9 heavy storms in Viet Nam – in the span of only 7 weeks.
Whilst these disasters occurred thousands of miles apart, the study shows how they are related to one another, and can have consequences for people living in distant places.
An example of this is the recent heatwave in the Arctic and cold wave in Texas. In 2020, the Arctic experienced unusually high air temperatures, and the second-lowest amount of sea ice cover on record.
This warm air destabilized the polar vortex, a spinning mass of cold air above the North Pole, allowing colder air to move southward into North America, contributing to the sub-zero temperatures in Texas, during which the power grid froze up, and 210 people died.
COVID and the Cyclone
Another example of the connections between disasters included in the study and the pandemic, is Cyclone Amphan, which struck the border region of India and Bangladesh.
In an area where almost 50 per cent of the population is living under the poverty line, the COVID-19 pandemic and subsequent lockdowns left many people without any way to make a living, including migrant workers who were forced to return to their home areas and were housed in cyclone shelters while under quarantine.
When the region was hit by Cyclone Amphan, many people, concerned over social distancing, hygiene and privacy, avoided the shelters and decided to weather the storm in unsecure locations. In the aftermath, there was a spike in COVID-19 cases, compounding the 100 fatalities directly caused by Amphan, which also caused damage in excess of 13 billion USD and displaced 4.9 million people.
The new report identifies three root causes that affected most of the events in the analysis: human-induced greenhouse gas emissions, insufficient disaster risk management, and undervaluing environmental costs and benefits in decision-making.
The first of these, human induced greenhouse gas emissions, is identified as one of the reasons why Texas experienced freezing temperatures, but these emissions also contribute to the formation of super cyclones such as Cyclone Amphan, on the other side of the world.
Insufficient disaster risk management, notes the study, was one of the reasons why Texas experienced such high losses of life and excessive infrastructure damage during the cold snap, and also contributed to the high losses caused by the Central Viet Nam floods.
The report also shows how the record rate of deforestation in the Amazon is linked to the high global demand for meat: this demand has led to an increase in the need for soy, which is used as animal feed for poultry. As a result, tracts of forest are being cut down.
“What we can learn from this report is that disasters we see happening around the world are much more interconnected than we may realize, and they are also connected to individual behaviour”, says one of the report’s authors, UNU scientist Jack O’Connor. “Our actions have consequences, for all of us,”
Solutions also linked
However, Mr. O’Connor is adamant that, just as the problems are interlinked, so are the solutions.
The report shows that cutting harmful greenhouse gas emissions can positively affect the outcome of many different types of disasters, prevent a further increase in the frequency and severity of hazards, and protect biodiversity and ecosystems.
Blue sky thinking: 5 things to know about air pollution
Around 90 per cent of people go through their daily lives breathing harmful polluted air, which has been described by the United Nations as the most important health issue of our time. To mark the first International Day of Clean Air for blue skies, on 7 September, UN News explains how bad it is and what is being done to tackle it.
1) Air pollution kills millions and harms the environment
It may have dropped from the top of news headlines in recent months, but air pollution remains a lethal danger to many: it precipitates conditions including heart disease, lung disease, lung cancer and strokes, and is estimated to cause one in nine of all premature deaths, around seven million every year.
Air pollution is also harming also harms our natural environment. It decreases the oxygen supply in our oceans, makes it harder for plants to grow, and contributes to climate change.
Yet, despite the damage it causes, there are worrying signs that air pollution is not seen as a priority in many countries: in the first ever assessment of air quality laws, released on 2 September by the UN Environment Programme (UNEP), it was revealed that around 43 per cent of countries lack a legal definition for air pollution, and almost a third of them have yet to adopt legally mandated outdoor air quality standards.
2) The main causes
Five types of human activity are responsible for most air pollution: agriculture, transport, industry, waste and households.
Agricultural processes and livestock produce methane, an extremely powerful greenhouse gas, and a cause of asthma and other respiratory illnesses. Methane is also a by-product of waste burning, which emits other polluting toxins, which end up entering the food chain. Meanwhile industries release large amounts of carbon monoxide, hydrocarbons, particulate matter and chemicals.
Transport continues to be responsible for the premature deaths of hundreds of thousands of people, despite the global phase out of dangerous leaded fuel at the end of August. This milestone was lauded by senior UN officials, including the Secretary-General, who said that it would prevent around one million premature deaths each year. However, vehicles continue to spew fine particulate matter, ozone, black carbon and nitrogen dioxide into the atmosphere; it’s estimated that treating health conditions caused by air pollution costs approximately $1 trillion per year globally.
Whilst it may not come as a great shock to learn that these activities are harmful to health and the environment, some people may be surprised to hear that households are responsible for around 4.3 million deaths each year. This is because many households burn open fires and use inefficient stoves inside homes, belching out toxic particulate matter, carbon monoxide, lead and mercury.
3) This is an urgent issue
The reason that the UN is ringing alarm bells about this issue now, is that the evidence of the effects of air pollution on humans is mounting. In recent years exposure to air pollution has been found to contribute to an increased risk of diabetes, dementia, impaired cognitive development and lower intelligence levels.
On top of this, we have known for years that it is linked to cardiovascular and respiratory disease.
Concern about this type of pollution dovetails with increased global action to tackle the climate crisis: this is an environmental issue as well as a health issue, and actions to clean up the skies would go a long way to reducing global warming. Other harmful environmental effects include depleted soil and waterways, endangered freshwater sources and lower crop yields.
4) Improving air quality is a responsibility of government and private sector
On International Day of Clean Air for blue skies, the UN is calling on governments to do more to cut air pollution and improve air quality.
Specific actions they could take include implementing integrated air quality and climate change policies; phasing out petrol and diesel cars; and committing to reduce emissions from the waste sector.
Businesses can also make a difference, by pledging to reduce and eventually eliminate waste; switching to low-emission or electric vehicles for their transport fleets; and find ways to cut emissions of air pollutants from their facilities and supply chains.
5)…and it is our responsibility, as well
At an individual level, as the harmful cost of household activities shows, a lot can be achieved if we change our behaviour.
Simple actions can include using public transportation, cycling or walking; reducing household waste and composting; eating less meat by switching to a plant-based diet; and conserving energy.
The Website for the International Day contains more ideas of actions that we can take, and how we can encourage our communities and cities to make changes that would contribute to cleaner skies: these include organizing tree-planting activities, raising awareness with events and exhibitions, and committing to expanding green open spaces.
How clean is your air?
You may well be wondering exactly how clean or dirty the air around you is right now. If so, take a look at a UNEP website which shows how exposed we are to air pollution, wherever we live.
The site indicates that more than five billion people, or around 70 per cent of the global population, are breathing air that is above the pollution limits recommended by the World Health Organization.
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