Pink salmon—the smallest and most abundant of the Pacific salmon species, and a supper table mainstay in many parts of the world—may be swimming towards trouble.
And they are not the only dish likely to disappear from the menu. Mussels, oysters, clam and scallop could all become scarcer and more expensive as the seas become more acid. And as the world’s waters warm, fish will start to migrate away from their normal grounds at an ever-increasing rate.
Photo credit: Shutterstock
Previous studies have repeatedly and consistently explored potentially problematic consequences of change in the pH value of the world’s oceans. The higher the carbon dioxide concentrations in the air as a consequence of the burning of fossil fuels, the greater the change in oceanic acidity levels.
But researchers at the University of British Columbia, Vancouver, and colleagues looked at the special problems of freshwater fish.
Only about 0.8 percent of the world’s water is fresh—that is, found in lakes and rivers—but freshwater species represent 40 percent of all fishes. Salmon spawn and the young are reared in fresh water, before taking to the seas to mature, then returning to repeat the cycle.
The Vancouver scientists report in Nature Climate Change that they tested very young embryos in water at acidity levels expected at the end of this century, and observed them for 10 weeks.
They found that these laboratory-reared salmon were smaller, and their ability to smell was reduced, which could mean problems in returning to their spawning grounds or for scenting danger and responding to it.
At the age of seaward migration, they were less able to use oxygen in their muscles, which promised problems finding food, evading predators or making long journeys.
“The increase in carbon dioxide in water is actually quite small from a chemistry perspective, so we didn’t expect to see so many effects,” said Michelle Ou, lead author of the study. “The growth, physiology and behaviour of these developing pink salmon are very much influenced by these small changes.”
Salmon aren’t the only freshwater fish at risk from climate change. Research published in the journal Environmental Toxicology and Chemistry reveals that a rise in water temperatures of 5°C could make common pesticides and industrial contaminants ever more toxic.
Ronald Patra, an environmental scientist at the Department of Planning and Environment in New South Wales, Australia, and colleagues tested rainbow trout, silver perch, rainbowfish and western carp gudgeon at temperatures higher than optimum for the species and in the presence of endosulfan, chlorpyrifos and phenol—all of which wash into waterways from the land.
Results varied according to pollutant, species and temperature, but, overall, all three chemicals became increasingly toxic as water temperatures rose.
On the coast of Mangalore in southwest India, where mussel farming has become a growing industry, researchers decided to test future toxicity conditions for the green mussel.
The Society of Experimental Biology meeting in Prague learned that the bivalves were raised in high temperature and low salt conditions and exposed to toxic algae and bacteria of the kind that might be expected in a changing climate, which in turn affected the timing of the monsoon in ways that could lower seawater salinity.
“This is likely to increase the chance of outbreaks of toxic plankton blooms and make farming bivalves such as mussels increasingly challenging,” the meeting was told.
But changes to water chemistry—once again, the shift in pH values as yet more carbonic acid builds up in the seas—create problems enough for the commercial shellfisheries.
Wiley Evans, research associate at the Ocean Acidification Research Centre of the University of Alaska Fairbanks, and colleagues report in the Public Library of Science journal PLOS One that shellfish farmers off the Alaska coast might, at extra expense, have to start modifying the sea water in their hatcheries because, the researchers reported, they expect “significant effects” from acidification by 2040.
The scientists monitored for 10 months the effects of water chemistry changes on oyster, clam, scallop and other shellfish larvae.
But in general, as researchers have repeatedly found, increasingly corrosive waters would make it more difficult for shellfish to exploit the calcium carbonate minerals needed to make shells.
Shellfish spend their maturity in one spot, whereas fish can and do shift their grounds when the conditions become uncomfortable − with consequences for established commercial catches such as sardines and sea bass.
Likely to Migrate
But a 5°C average warming in global atmospheric temperatures—and climate scientists have repeatedly warned that this is possible before 2100—means that fish are likely to migrate away from their existing habitats considerably faster than they are doing now.
Jean-Pierre Gattuso, of the Oceanological Observatory in Villefranche, France, and colleagues looked at the evidence on a global scale and report in Science journal that, without attempts to mitigate global warming, the oceans and the creatures in them will be seriously affected by temperature changes and acidification.
This is very bad news for the millions of people in the communities that depend on the seas for a living.
“On a positive note, we still have options to substantially reduce these impacts now, but the longer we wait the fewer and fewer options we have,” warns co-author William Cheung, of the fisheries centre at Canada’s University of British Columbia.
Commenting on the research, Jason Hall-Spencer, a professor of marine biology at Plymouth University in the UK, said: “This review screams at me that the evidence is in, and it is not too late for society to benefit greatly from immediate reductions in CO2 emissions.”
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When hurricanes and other extreme storms unleash downpours like Tropical Storm Beta has been doing in the South, the floodwater doesn't always stay within the government's flood risk zones.
New research suggests that nearly twice as many properties are at risk from a 100-year flood today than the Federal Emergency Management Agency's flood maps indicate.
Flooding Outside the Zones<p>About <a href="https://furmancenter.org/files/Floodplain_PopulationBrief_12DEC2017.pdf" target="_blank">15 million</a> Americans live in FEMA's current 100-year flood zones. The designation warns them that their properties face a 1% risk of flooding in any given year. They must obtain flood insurance if they want a federally ensured loan – insurance that helps them recover from flooding.</p><p>In Greater Houston, however, <a href="https://doi.org/10.1111/j.1539-6924.2012.01840.x" target="_blank">47% of claims</a> made to FEMA across three decades before Hurricane Harvey were outside of the 100-year flood zones. Harris County, recognizing that FEMA flood maps don't capture the full risk, now <a href="https://www.hcfcd.org/floodinsurance" target="_blank" rel="noopener noreferrer">recommends that every household</a> in Houston and the rest of the county have flood insurance.</p><p>New risk models point to a similar conclusion: Flood risk in these areas outstrips expectations in the current FEMA flood maps.</p><p>One of those models, from the <a href="https://firststreet.org/flood-lab/research/2020-national-flood-risk-assessment-highlights/" target="_blank">First Street Foundation</a>, estimates that the number of properties at risk in a 100-year storm is 1.7 times higher than the FEMA maps suggest. Other <a href="https://doi.org/10.1088/1748-9326/aaac65" target="_blank" rel="noopener noreferrer">researchers</a> find an even higher margin, with 2.6 to 3.1 times more people exposed to serious flooding in a 100-year storm than FEMA estimates.</p>
What FEMA’s Flood Maps Miss<p>Understanding why areas outside the 100-year flood zones are flooding more often than the FEMA maps suggest involves larger social and environmental issues. Three reasons stand out.</p><p>First, some places rely on relatively old FEMA maps that don't account for recent urbanization.</p><p>Urbanization matters because impervious surfaces – think pavement and buildings – are not effective sponges like natural landscapes can be. Moreover, the process for updating floodplain maps is locally variable and can take years to complete. Famously, New York City was updating its maps when Hurricane Sandy hit in 2012 but hadn't finished, meaning flood maps in effect <a href="https://projects.propublica.org/nyc-flood/" target="_blank">were from 1983</a>. FEMA is required to assess whether updates are needed every five years, but the <a href="https://www.fema.gov/cis/nation.html" target="_blank" rel="noopener noreferrer">majority of maps</a> <a href="https://www.oig.dhs.gov/sites/default/files/assets/2017/OIG-17-110-Sep17.pdf" target="_blank" rel="noopener noreferrer">are older</a>.</p><p>Second, binary thinking can lead people to an underaccounting of risk, and that can mean communities fail to take steps that could protect a neighborhood from flooding. The logic goes: if I'm not in the 100-year floodplain, then I'm not at risk. Risk perception <a href="https://doi.org/10.1088/1748-9326/ab195a" target="_blank" rel="noopener noreferrer">research</a> backs this up. FEMA-delineated flood zones are the major factor shaping flood mitigation behaviors.</p><p>Third, the era of climate change scuttles conventional assumptions.</p><p>As the planet warms, extreme storms are becoming <a href="https://nca2018.globalchange.gov/" target="_blank">more common and severe</a>. If greenhouse gas emissions continue to increase at a high rate, computer models suggest that the chances of a severe storm dropping 20 inches of rain on Texas in any given year will increase from about 1% at the end of the last century to 18% at the end of this one, a chance of <a href="https://doi.org/10.1073/pnas.1716222114" target="_blank" rel="noopener noreferrer">once every 5.5 years</a>. So far, <a href="https://www.rstreet.org/wp-content/uploads/2020/02/195.pdf" target="_blank" rel="noopener noreferrer">FEMA hasn't taken into account the impact climate change is having</a> on extreme weather and sea level rise.</p>
Racial Disparities in Flooding Outside the Zones<p>So, who is at risk?</p><p>Years of research and evidence from storms have highlighted social inequalities in areas with a high risk of flooding. But most local governments have less understanding of the social and demographic composition of communities that experience flood impacts outside of flood zones.</p><p>In analyzing the damage from Hurricane Harvey in the Houston area, I found that <a href="https://doi.org/10.1088/1748-9326/aba0fe" target="_blank">Black and Hispanic residents disproportionately experienced flooding</a> in areas beyond FEMA's 100-year flood zones.</p><p>With the majority of flooding from Hurricane Harvey occurring outside of 100-year flood zones, this meant that the overall impact of Harvey was racially unequal too.</p><p>Research into where flooding occurs in Baltimore, Chicago and Phoenix points to some of the potential causes. <a href="https://www.nap.edu/read/25381/chapter/4#16" target="_blank" rel="noopener noreferrer">In Baltimore and Chicago</a>, for example, aging storm and sewer infrastructure, poor construction and insufficient efforts to mitigate flooding are part of the flooding problem in some predominantly Black neighborhoods.</p>
What Can Be Done About It<p>Better accounting for those three reasons could substantively improve risk assessments and help cities prioritize infrastructure improvements and flood mitigation projects in these at-risk neighborhoods.</p><p>For example, First Street Foundation's risk maps account for <a href="https://firststreet.org/flood-lab/research/flood-model-methodology_overview/" target="_blank">climate change</a> and present <a href="https://floodfactor.com/" target="_blank" rel="noopener noreferrer">ratings</a> on a scale from 1 to 10. FEMA, which works with communities to update flood maps, is <a href="https://www.fema.gov/media-library-data/1521054297905-ca85d066dddb84c975b165db653c9049/TMAC_2017_Annual_Report_Final508(v8)_03-12-2018.pdf" target="_blank" rel="noopener noreferrer">exploring rating systems</a>. And the National Academies of Sciences, Engineering and Medicine recently <a href="https://www.nationalacademies.org/news/2019/03/new-report-calls-for-different-approaches-to-predict-and-understand-urban-flooding" target="_blank" rel="noopener noreferrer">called for a new generation of flood maps</a> that takes climate change into account.</p><p>Including recent urbanization in those assessments will matter too, especially in fast-growing cities like Houston, where <a href="https://authors.elsevier.com/a/1boBRyDvMFW6W" target="_blank" rel="noopener noreferrer">386 new square miles</a> of impervious surfaces were created in the last 20 years. That's greater than the land area of New York City. New construction in one area can also <a href="https://scalawagmagazine.org/2018/01/city-in-a-swamp-as-houston-booms-its-flood-problems-are-only-getting-worse/" target="_blank" rel="noopener noreferrer">impact older neighborhoods downhill</a> during a flood, as some Houston communities discovered in Hurricane Harvey.</p><p>Improving risk assessments is needed not just to better prepare communities for major flood events, but also to prevent racial inequalities – in housing and beyond – from <a href="https://www.npr.org/2019/03/05/688786177/how-federal-disaster-money-favors-the-rich" target="_blank" rel="noopener noreferrer">growing</a> after the unequal impacts of disasters.</p>
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