Flash flood in Palapye, Central District, Botswana. Heavy rain caused a small dam to burst on the Lotsane River, which flows through the village. The mud walls of traditionally built houses dissolved like icing sugar, leaving just the roofs: the breeze-block buildings in the background survived intact. A young goat has become entangled in a wire fence and drowned, but it’s believed no human lives were lost. Taken 1995 on film. Author: JackyR, CC BY-SA 3.0.
“We need to drastically reduce greenhouse gas emissions and adapt to a new reality where floods and heatwaves are more intense and damaging,” said a co-author of the study.
“If we do not reduce emissions and keep global temperatures below 1.5°C, many extreme weather events will become increasingly destructive.”
Intense rainfall that led to deadly flooding and landslides in South Africa last month was made twice as likely by the human-caused climate crisis, a team of scientists revealed Friday, pointing to the findings as proof of the need to swiftly and significantly curb planet-heating emissions.
Experts at the World Weather Attribution (WWA) initiative found that heavy rainfall episodes like the one in April that left at least 435 people dead can be expected about once every 20 years versus the once every 40 years it would be without humanity warming the planet.
WWA climatologists warn that without successful efforts to dramatically reduce emissions, the frequency and intensity of such extreme events will increase as the global temperature does.
“If we do not reduce emissions and keep global temperatures below 1.5°C, many extreme weather events will become increasingly destructive,” said study co-author Izidine Pinto of the Climate System Analysis Group at the University of Cape Town. “We need to drastically reduce greenhouse gas emissions and adapt to a new reality where floods and heatwaves are more intense and damaging.”
During an April speech announcing a disaster declaration, South African President Cyril Ramaphosa said that communities in the eastern part of the country were “devastated by catastrophic flooding,” noting that it “caused extensive damage to houses, businesses, roads, bridges and water, electricity, rail, and telecommunications infrastructure.”
Ramaphosa also highlighted the death toll, sharing that when he and other officials visited affected families, “they told us heart-breaking stories about children, mothers, fathers, sisters, brothers, grandparents, and neighbors being swept away as their homes crumbled under the pressure of the flood waters.”
The city of Durban was hit particularly hard and its port—the largest in Africa—had to suspend operations because of the extreme weather.
Friederike Otto from Imperial College London, who leads WWA and co-authored the new study, pointed out that “most people who died in the floods lived in informal settlements, so again we are seeing how climate change disproportionately impacts the most vulnerable people.”
“However, the flooding of the Port of Durban, where African minerals and crops are shipped worldwide, is also a reminder that there are no borders for climate impacts,” she added. “What happens in one place can have substantial consequences elsewhere.
Structural vulnerability, a legacy from apartheid, rapid urban growth & climate change turned heavy April rains into a disaster for Durban and surrounding areas – new @wxrisk study https://t.co/6C4grKwWtm pic.twitter.com/7WbaKz9COk
— Dr Friederike Otto (@FrediOtto) May 13, 2022
In addition to the chances of an event such as the mid-April rain disaster doubling due to human-induced climate change, the WWA team found that “the intensity of the current event has increased by 4-8%.”
The New York Times noted that “the work has yet to be peer-reviewed or published, but it uses methods that have been reviewed previously” and “the finding that the likelihood of such an extreme rain event has increased with global warming is consistent with many other studies of individual events and broader trends.”
WWA’s previous work includes a review of last year’s fatal heatwave in the Pacific Northwest, which the scientists concluded would have been “virtually impossible” in a world without the climate emergency.
“Our results provide a strong warning,” that WWA analysis said. “Our rapidly warming climate is bringing us into uncharted territory that has significant consequences for health, well-being, and livelihoods.”
Reducing air pollution from fossil fuels could save more than a million U.S. lives over the next 20 years.
Photo by Andreas Gücklhorn on Unsplash
A transition from fossil fuels to clean, renewable energy is essential for reducing global warming. And it rapidly improves public health.
“Within the moment, essentially, we act, within that same year, we start to see cleaner air,” says Drew Shindell, a distinguished professor of Earth sciences at Duke University.
He says that burning fossil fuels produces both climate-warming gases and tiny particles that are harmful to breathe.
“They can get down into the tiny little blood vessels that line the lung wall, and therefore get deep into the body and cause respiratory and cardiovascular illness,” Shindell says.
So he says reducing the use of fossil fuels is not only important to the long-term health of the planet. It can also save people’s lives in the near-term.
In a recent study, his team found that by cutting carbon pollution in line with the goals of the Paris climate agreement, the U.S. alone could avoid more than a million premature deaths over the next 20 years.
Shindell says he hopes the research will help people understand that switching to clean, renewable energy is not only an investment in the long-term future of the planet but in people’s health today.
Deep in the San Francisco Bay, two rivers splinter into a vague triangle, creating one of the richest watersheds in California. This estuary – the Sacramento-San Joaquin River Delta – is an important source of freshwater for the 4 million folks who live in the region. Local agricultural, fishing, and recreation industries bring in billions of dollars a year, and the area also provides a rich habitat for local wildlife.
Over the past few decades, this watershed has seen a dramatic change in its climate. Years-long droughts and record-high temperatures have transformed the region – a shift that’s told no better, perhaps, than through the story of the Delta smelt.
The Delta smelt is an iridescent fish about the size of a finger. The fish is a bioindicator, often noted for its distinct smell of fresh cucumbers. Though small in size, it has an impact reaching beyond the Delta, all the way to Capitol Hill. The smelt’s role in Northern California’s decades-long “water wars” have made it a key player in shaping the region’s water policy.
A harbinger of threats to other species
As a bioindicator, its presence in the Delta signifies a healthy ecosystem – one that can support a diverse range of life. However, not since the 1980s have the fish been abundant in the wild.
To Tien-Chieh Hung, PhD, director of the Fish Conservation and Culture Laboratory (FCCL) at UC Davis, it’s simple: “If these fish are going extinct, then there are other species that are going to be listed as threatened or endangered, too.”
There was a time when these fish swam through the Delta in the thousands. Trawling surveys would pull up nets full of their thin, shimmering bodies. It’s now rare for these surveys to catch even one.
In fact, the largest known population of Delta smelt doesn’t live in the Delta at all. They live, instead, just south of the watershed, in large white circular lab tanks Hung oversees at the FCCL, now rearing a captive population in the tens of thousands.
This decades-long effort has been meticulous. The smelt was listed as threatened in 1993 but the project to culture the fish was established only a decade later, in 2004. Since then, FCCL scientists each year scour the estuary in search of wild smelt. Each such specimen found is then transported into the lab to be tagged and genetically cataloged.
The careful genetic classification of each wild Delta smelt has been key to preserving the genetic diversity of the captive population to keep it as similar to the wild stock as possible. For years, when breeding season comes along, this genetic catalog is carefully consulted to pair-up smelt for mating new generations in the lab. But keeping this cultured population diverse has become harder over the past decade as finding wild smelt has become rarer in the estuary.
The hard reality: In 2021, California’s Department of Fish and Wildlife’s Fall Midwater Trawl Survey found none at all, prompting scientists to do something they have been putting off for years – begin preparing for the first release of cultivated smelt into the wild.
A long troubling history, and now comes climate change
The Delta smelt raised in captivity do not smell much like cucumbers. Hung mentions that this trait seems to be connected to stress. The smelt at the FCCL have no predators, perfectly saline water, and plenty of food piped into their tanks. Their lives in the Delta are much less comfy.
Importantly, the Delta smelt evolved specifically in, and is named after, the ecosystem of the San Francisco Bay Delta, for thousands of years having an estuary with cool, freshwater running through its many channels. The watershed in modern times feels very different: According to scientist Peter Moyle, associate director of the Center for Watershed Sciences at UC Davis, “that [original] habitat just isn’t there.”
Irrevocable changes in the smelt’s ecosystem began in the 1800s. Non-native species – like the bluegill and largemouth bass – were introduced to the watershed for sportfishing. Fish very similar to the Delta smelt, like the silverside and wakasagi, were introduced soon after as supplemental food for these new game fish. The former meant more predation for the Delta smelt, the latter meant more competition.
In addition to these new fish in the Delta, regional water programs like the Central Valley Project and the State Water Project began operating in the 1960s. These projects diverted water flows in the estuary to serve communities in Northern California and, consequently, turned the watershed more saline than brackish.
All of this, coupled with rising temperatures and consistently historic droughts in the region, have created a deadly Delta for the smelt; though this is also a realityformanyestuaries, worldwide. “Climate change,” said Moyle, “has just accelerated things.”
The Delta smelt has a lifespan of only one year, and its population was initially devastated by a prolonged drought in the 80s. This time, however, recovery proved particularly difficult because conditions continued to worsen and some non-native species adapted to these changes better than the smelt. In past droughts, smelt populations have diminished even as populations of introduced silversides increased.
“We use the term regime shift,” said Brian Schreier, a scientist with the Department of Water Resources (DWR) in West Sacramento, about the smelt’s decline. And this regime shift was not so easy to reverse. Even as the conditions in the estuary worsened, millions of people still relied on these water projects to survive.
Steps leading to boosting number of smelt in the wild
In 2008, the US Fish & Wildlife Service (USFWS) issued a Biological Opinion (BiOp) that expanding the export of water from the Delta would severely impact the smelt population. That action mandated that measures, like reduced pumping, be taken to prevent such a future for the fish. That 2008 BiOp was reversed in 2019, however, when the Trump administration issued a new statement claiming that the smelt population would be fine given that the FCCL has spent decades rearing a robust captive population to supplement the wild fish.
Even though the FCCL’s plan has always been to eventually release these fish into the wild, scientists have resisted doing so for nearly 20 years. They expressed concerns that the captive population might not be fit for conditions in the wild, or that they would adversely impact the wild smelt population that is surviving.
Water and Power Law Group’s Natural Resource Counsel, Paul Kibel, recalls the way hatcheries failed at replacing salmon populations in a 2020 article “Salmon Lessons for the Delta Smelt.” “The replacement assumption has proven faulty,” Kibel wrote, “as the total abundance of salmon declined at the same time the propagation and release of hatchery salmon has expanded.” In the case of the salmon, the replacement population not only increased competition for their wild counterparts, but they had also been domesticated in the hatchery and were unfit to survive in the wild.
These were real concerns also for scientists working with the smelt. And though the 2019 BiOp placed excessive and perhaps unreasonable emphasis on the hatchery fish solution, it may have also – temporarily, at least – saved the Delta smelt.
“That was the first regulatory document that actually had legal backing,” said Schreier, “and effectively mandated that supplementation would occur.” And, late last year, for the first time ever, supplementation finally did.
‘A roller coaster’ as 12,000 hatchery smelts were reintroduced
December 15, 2021, marked the first release of hatchery Delta smelt into the wild. More than 12,000 of these fish were transported from their cool, roomy tanks in the FCCL and placed into several barrels in the back of a pick-up truck. They were then driven to Rio Vista where the barrels were transported to a boat and sailed into the channels of the Delta, where the fish were finally released together.
The road to this release was “a roller coaster,” according to Schreier: It involved many months of experimental trial releases where select populations of hatchery fish were exposed to conditions of the Delta in aluminum cages specially designed to prevent their escaping even as food and fresh water flowed through.
“We started under what we thought would be the best conditions,” said Melinda Baerwald, an ecologist at the DWR, about the caged trials. “To be perfectly honest, we didn’t have high hopes.” But she says she was pleasantly surprised when this first trial had a nearly 100% survival rate of the captive smelt.
The research team then tried exposing the hatchery population to progressively worsening conditions to see how they would fare, another step that proved reassuring. Baerwald recalls one of the last caged trials they did last summer. “It was fairly shocking,” she said.
The team took the smelt out to the Yolo Bypass in the middle of a heat wave. They weren’t expecting the smelt to stay alive for about a week. “But the fish kept surviving,” she said.
74 wild smelt is more than zero … but ‘a desperation measure’?
Since the first release in December, four more releases have occurred in two additional locations. And, since these releases have taken place, local trawling surveys have picked up 74 smelt, compared to the previous number of consistently zero.
Baerwald and Schreier wanted these releases to take place in the wintertime to ensure the best chances of survival in the increasingly warming Delta. They also mentioned that doing the releases during cooler months allows the captive Delta smelt to spawn the next generation directly in the rivers so they can begin their lives in the watershed.
The scientists are hopeful, but Moyle says it’s also “a desperation measure.” The factors that caused the wild smelt’s original decline have still not been properly addressed and the smelt are facing increasingly dire conditions. California and much of the U.S. West, has also been in a drought since February 2020 and the beginning of 2022 continues to be historically dry.
One may wonder what hope there is, really, for such a little fish as the Delta smelt. Human combustion and emissions of fossil fuels continue to cause unprecedented warming around the world. And these hotter temperatures have also been noted to increase drought severity. So long as temperatures continue to rise as predicted, the Delta of today – plagued with unrelenting droughts and contested water projects and chemical runoff – will never be the Delta of the smelt’s past.
And eventually, without a proper habitat to enter into, those hatchery fish will have nowhere to go to.
Hanisha Harjani is a reporter, artist, and student, currently attending UC Berkeley Graduate School of Journalism.
