The Stream, May 22, 2024: Global Freshwater Migratory Fish Populations Plummet in Past 50 Years, Study Finds

Much of the Au Sable’s trout population has fled to the northern Michigan river’s tributaries, instinctively searching for oxygen-richer waters. © J. Carl Ganter / Circle of Blue


  • The rapid melting of thousands of glaciers in Pakistan is already affecting farming, energy generation, and the water security of hundreds of thousands of people.
  • Over the last half-century, migratory freshwater fish populations have endured a “catastrophic” global population decline.
  • In the Philippines, a small group of farmers is working to protect and promote Indigenous seeds and growing practices that require less water.
  • As heat waves bake southern Europe, Germany, Belgium, France, and Italy contend with heavy rainstorms and flooding that have triggered emergencies and evacuations.

As much as 50 percent of the world’s natural pastures have been deteriorated by overuse and the effects of climate change, including drought, soil erosion, and wildfire.

“When we cut down a forest, when we see a 100-year-old tree fall, it rightly evokes an emotional response in many of us. The conversion of ancient rangelands, on the other hand, happens in ‘silence’ and generates little public reaction.” — Ibrahim Thiaw, executive secretary of the United Nations Convention to Combat Desertification. 

Covering 54 percent of all land on earth, rangelands — which include wetlands, tundras, and savannas — support the lives and economies of two billion people globally. 

But a new UN report suggests that the health of these vast land areas is in danger, with at least 25 percent — and up to 50 percent — showing signs of significant degradation due to extremely hot, dry weather and overexploitation. As a result, one-sixth of the world’s food supply and one-third of Earth’s carbon reservoir are at risk of being lost. 

These effects are particularly acute in West Africa and Central Asia, where livestock production accounts for as much as 80 percent of all jobs, and as much as 60 percent of all land is used for grazing. 

It isn’t just dollars and jobs that may be lost; rangelands are also home to a third of the world’s biodiversity hotspots, and a quarter of the world’s languages.

— Christian Thorsberg, Interim Stream Editor

Recent WaterNews from Circle of Blue

The Lead

A new update to the Living Planet Index details a grim assessment of the past 50 years for the health of migratory freshwater fish. Since 1970, their collective global populations have fallen by more than 80 percent, the Guardian reports

The team of researchers analyzed population trends of 284 migratory freshwater fish species, such as sturgeon and shad. They found that, on average, 65 percent of species saw their populations decrease, while 31 percent increased. 

Where they’ve happened, the declines have been drastic. Nearly 80 freshwater migratory fish species saw their populations fall between 80 percent and 100 percent since 1970; more than 40 other species experienced drops between 60 percent and 80 percent. 

Latin America and the Caribbean have been most affected — there, the abundance of these species have declined by 91 percent. 

“Migratory fish are central to the cultures of many Indigenous peoples, nourish millions of people across the globe, and sustain a vast web of species and ecosystems,” Herman Wanningen, founder of the World Fish Migration Foundation, told the Guardian. “We cannot continue to let them slip silently away.”

According to the report, habitat loss and degradation accounted for about half of all threats to these fish, with a third of losses due to overfishing. To help restore their populations, the report recommends strengthening monitoring efforts in some of the most crucial waterways — including the Congo, Mekong, Yangtze, Irrawaddy, and Salween rivers — and removing barriers to fish passage, including dams and poorly designed culverts.

This Week’s Top Water Stories, Told In Numbers


Percent of European residents, one in eight, who live in an area prone to flooding, according to a study published by the European Environment Agency and reported on by EuroNews. And this week, heavy rain fell in Germany’s southwestern state of Saarland, submerging streets, breaching a dike, and temporarily shuttering a power station. It is the region’s worst flooding in three decades, DW reports. Rising floodwaters similarly halted transportation in parts of neighboring Netherlands, while residents in Belgium were forced onto their roofs to escape the rising waters. Deluges totalling more than 4.5 inches of rain fell in France’s Alsace region, in a span of just 24 hours; more than 5 inches of rain fell in Milan in that same duration, according to a different EuroNews report.



Registered members in the Benguet Association of Seed Savers (BASS), a group of farmers in the northern Philippines dedicated to conserving the seeds of regional Indigenous communities, Mongabay reports. These seeds, cultivated over countless generations, require less water and fewer pesticides than newer, commercially available seeds — making them all the more precious in the country’s north, where drought and heat have hit farmers hard. 

On the Radar

More than 7,000 glaciers rest within Pakistan’s Karakoram mountain range, the wellspring of a life-supporting alpine ecosystem. Glacial melt feeds rivers, supports agriculture, and powers energy generators for the 200,000 residents of Skardu, and other nearby communities, Al Jazeera reports. But, like nearly all glaciers worldwide, they are melting faster than before, disrupting reservoirs and flooding waterways. It is an overabundance of water in the short term, and a looming insecurity for years to come. Some areas, where seasonal melting is disrupted or skewed, are already feeling the squeeze — last summer, water levels in Satpara Dam hit significant lows for the first time in many locals’ lifetimes.

More Water News

Great Salt Lake: Two consecutive wet winters have raised the Utah lake’s water level by six feet, though it still remains below healthy levels, the New York Times reports. The water level is expected to drop another three feet by summer’s end, and experts worry that the brief good news will lead to complacency over the water crisis. 

Southern African Drought: Zambia, Zimbabwe, and Malawi have each declared a state of emergency in recent months, as ongoing drought has decimated crop production and ignited a regional hunger crisis, Yale Environment 360 reports. With farming no longer profitable in drought-ridden areas, some families have been forced to enter the lumber business: cutting down trees, an act they know drives climate change, in order to make an income and purchase increasingly expensive food. Prices have increased by 82 percent in some regions.

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