<
https://www.bbc.com/future/article/20240229-why-europe-is-removing-its-dams>
'Three years ago, when construction workers started demolishing a series of
dams on the Hiitolanjoki River in Finland, they were greatly surprised to spot
a run of salmon. Part of the country's last wild and landlocked population, the
fish were returning to the river after years of absence. For Pauliina Louhi, it
was a sign that the ecosystem's recovery had begun.
"It was not only adults – there were many salmon juveniles," Louhi, an
ecologist at Natural Resources Institute Finland, a Finnish research
organisation, recounts enthusiastically. "They had already been spawning on the
lowermost part of the river. When I saw how the site looked after the dam
removal, I actually had tears in my eyes."
The river used to be a key migration route for the endangered freshwater salmon
from Lake Ladoga, in nearby Russia, to Finland. But between 1911 and 1925 the
introduction of three dams supplying hydroelectric energy created barriers
between the salmon and their spawning grounds. The salmon and other fish, like
brown trout, were trapped on the Finnish side of the river, which remained
fragmented for 100 years.
Today, however, with the dams removed, the water runs freely once again through
newly built rapids surrounded by tall trees. Every time a dam was removed,
salmon "embraced" the new part of the river, says Hanna Ollikainen, executive
director of the South Karelian Recreation Area Foundation, a civil society
organisation, which acquired the dams and is responsible for the environmental
and touristic development of the area. In 2021, after the first removal, five
spawning nests were spotted; in autumn 2022, one year on, baby salmon reached a
record-breaking number of 200 fish per acre (0.4 hectares). When the removal of
the upmost dam, Ritakoski, was completed in December 2023, they found a free
passage to the upper parts of the river and its tributaries.
The removal of the three dams was the result of decades of work, which took
into consideration not only the health of the river, but also the economic
context, says Ollikainen. Evaluations concluded that their electricity
production had become unprofitable for the power plant owners – especially when
the costs of maintenance and mandatory environmental protections, such as
fish-ladder introductions, were taken into account, Ollikainen says. So the
dams were sold and dismantled.'
Via
Positive.News
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
