Four Years After the Oder Disaster: Ecosystem Has Largely Recovered — But Large Mussels Are Still Missing

Causes of the 2022 Disaster

The Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) is the lead institution investigating the Oder. Federal Environment Minister Carsten Schneider (SPD) received the final report on the investigation program at the IGB site in Schwedt. „Der Umweltminister nahm in Schwedt den Abschlussbericht zu einem Untersuchungsprogramm am IGB zur Oder-Katastrophe entgegen, heißt es in der Mitteilung.

In his assessment, Schneider emphasized the importance of intact retreat habitats. „Das ist gerade angesichts des Klimawandels mit zunehmenden Hitzesommern und langen Trockenphasen wichtig", sagte er mit Blick auf Renaturierungsmaßnahmen entlang des Flusses. Schneider kündigte an, keine weiteren Ausbauten der Oder zu planen: „Das haben wir auch nicht vor. Wir machen Instandhaltungsmaßnahmen und Renaturierungsmaßnahmen.

Dispute Over Salt and Expansion

The salinity, which according to Schneider enters the Oder from mining areas on the Polish side, remains a central point of contention. He said the Federal Environment Minister was in exchange with Poland regarding the condition of the Oder and the salt discharges. Measures to reduce the discharges were being examined in Poland.

The expansion of the Oder with groynes has long been disputed between Poland and Germany. Against this backdrop, Schneider pointed to the German-Polish exchange on the condition of the border river. The Leibniz Institute also called for reducing the input of salt and nutrients into the river and creating more space for natural habitats.

Mussels as the Losers of the Recovery

From the perspective of IGB scientists, the assessment four years after the disaster is mixed. The consequences for the ecosystem would still be felt years later, the institute said. While fish populations had recovered comparatively well, the situation regarding large mussels was critical: „Das ist ökologisch besonders schwerwiegend, weil Großmuscheln große Mengen Wasser filtrieren und damit zur Reinigung des Flusses beitragen", sagte IGB-Direktorin Sonja Jähnig.

Fish ecologist Christian Wolter from the Leibniz Institute in Berlin explained the relatively good recovery of the fish with the presence of suitable retreat areas: „Wir sehen, dass zum Beispiel die relativ gute Erholung bei den Fischen darauf zurückzuführen ist, dass sie Rückzugsräume hatten, dass sie Refugien hatten, wo sie diese Krise abwarten konnten sozusagen und aus denen dann heraus die Wiederbesiedlung erfolgen konnte." Die Folgen für das Ökosystem wirkten noch Jahre nach, so das IGB.

Risk of Further Algal Blooms

For the future, the researchers continue to see a need for action. Wolter warned that the risk of a renewed algal bloom must be reduced at all costs. According to the research institute, the recovery of the large mussels will take many more years.

Overall, the scientists thus paint a picture of cautious hope: The Oder ecosystem has largely survived the 2022 crisis, but individual species groups, such as the large mussels that are central to water purification, will be missing for a long time to come.

The reports were broadcast on Deutschlandfunk on 15 June 2026.