River flow is changing completely in all countries of the northern hemisphere

Global warming not only has consequences on temperatures, precipitation and the melting of glaciers. The flow of rivers also changes, according to a new study published in the journal Science. The difference in flow between winter and spring is increasingly smaller, which risks affecting the entire ecosystem.

A team of English hydrologists has analyzed river flow at around 10,000 stations around the world over the last 35 years. They found that all regions of the northern hemisphere were affected by a change in SpeedSpeed Rivers and streams. In fact, the flows show a decreasing trend in spring and an increasing trend in winter, a situation completely reversed compared to the natural cycle in:

  • 40% of North American stations;
  • 32% of southern Siberian stations;
  • 19% of the tourist complexes in northern Europe.

These measurements take into account natural flows and exclude flows modified by dams or other developments that would distort the results. The southern hemisphere appears much less affected by these changes in flow, with the exception of southeastern Brazil, which shows even sharper extremes between winter and spring.

The cause is early melting of snow and early growth of plants.

Where does this surprising development in the northern hemisphere come from? Mainly due to the melting of ice in the Arctic, the researchers say, and due to the meltingmelting earlier snowfall at the end of winter, which increases winter flows. The change in the growing season of plants also plays a role: rising temperatures allow plants to grow earlier in the season and absorb more precipitationprecipitation, which contributes to the reduction of the river flow. Therefore, what is altered is the natural variation of rivers during the seasons. The consequences on the biodiversitybiodiversity that depend on these rivers have not yet been evaluated and this will be the subject of future studies.

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