New research has confirmed that over the past 25 years, at least a third of rivers and streams in the United States have become saltier. Without action, by 2100 more than half of these waterways will contain 50 percent more salt than they do now.
Experts warn that such extreme levels of salt pollution will pose a serious threat to fresh water resources, urban infrastructure and natural ecosystems across the country. Moreover, it will also affect the agricultural sector, doubling the number of too salty, and therefore unsuitable for irrigation, streams from three to six percent.
Nor was it a surprise that the study pointed to the culpability of certain human activities: the use of fertilizers and deicing salts, land clearing, fossil fuel extraction, irrigation, and even climate change.
“Most of the reasons are related to the increase in the share of land that people use, and climate change accounts for only 12 percent of the total. Today, the saltiest streams are found in the northern Great Plains. Salt levels are high there for natural reasons, but mining, oil and gas are releasing more and more salt, discovering new rocks and pumping out salty groundwater,”said the authors of an article published in Royal Society B.
A study earlier this year also showed that acid rain caused by human air pollution can dissolve salt-containing substances, which also exacerbates the problem.
Directly or indirectly, salt increases in the United States are not regulated by federal law, and therefore government control may be inconsistent. In parts of the country where salinity is particularly high, it has been found that salt levels in freshwater streams are nearly half that of the ocean.
The negative effects of salinity are often underestimated. When salts such as sodium bicarbonate and magnesium chloride enter waterways, it causes a domino effect, releasing toxic metals from the soil into the stream itself. These changes may seem small, but they can be devastating to delicate freshwater ecosystems, leading to the death of several species, including insects.
The impact of this process on humans is also felt: in Australia and Europe, freshwater reservoirs are becoming saltier, causing serious economic and health problems. For the United States, for example, this water pollution costs billions of dollars. So, the damage from the salinization of the Colorado River Basin alone is estimated at $ 300 million.
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Such forecasts of increasing salinity in streams and rivers underline the need for effective measures to ensure the protection of water resources and freshwater ecosystems, the researchers emphasize.
Dmitry Mazalevsky