The recovery of European freshwater biodiversity has come to a halt
Authors: Haase Peter , Bowler Diana E. , Baker Nathan J. , Bonada Núria , Domisch Sami , Garcia Marquez Jaime R. , Heino Jani , Hering Daniel , Jähnig Sonja C. , Schmidt-Kloiber Astrid , Stubbington Rachel , Altermatt Florian , Álvarez-Cabria Mario , Amatulli Giuseppe , Angeler David G. , Archambaud-Suard Gaït , Jorrín Iñaki Arrate , Aspin Thomas , Azpiroz Iker , Bañares Iñaki , Ortiz José Barquín , Bodin Christian L. , Bonacina Luca , Bottarin Roberta , Cañedo-Argüelles Miguel , Csabai Zoltán , Datry Thibault , de Eyto Elvira , Dohet Alain , Dörflinger Gerald , Drohan Emma , Eikland Knut A. , England Judy , Eriksen Tor E. , Evtimova Vesela , Feio Maria J. , Ferréol Martial , Floury Mathieu , Forcellini Maxence , Forio Marie Anne Eurie , Fornaroli Riccardo , Friberg Nikolai , Fruget Jean-François , Georgieva Galia , Goethals Peter , Graça Manuel A. S. , Graf Wolfram , House Andy , Huttunen Kaisa-Leena , Jensen Thomas C. , Johnson Richard K. , Jones J. Iwan , Kiesel Jens , Kuglerová Lenka , Larrañaga Aitor , Leitner Patrick , L’Hoste Lionel , Lizée Marie-Helène , Lorenz Armin W. , Maire Anthony , Arnaiz Jesús Alberto Manzanos , McKie Brendan G. , Millán Andrés , Monteith Don , Muotka Timo , Murphy John F. , Ozolins Davis , Paavola Riku , Paril Petr , Peñas Francisco J. , Pilotto Francesca , Polášek Marek , Rasmussen Jes Jessen , Rubio Manu , Sánchez-Fernández David , Sandin Leonard , Schäfer Ralf B. , Scotti Alberto , Shen Longzhu Q. , Skuja Agnija , Stoll Stefan , Straka Michal , Timm Henn , Tyufekchieva Violeta G. , Tziortzis Iakovos , Uzunov Yordan , van der Lee Gea H. , Vannevel Rudy , Varadinova Emilia , Várbíró Gábor , Velle Gaute , Verdonschot Piet F. M. , Verdonschot Ralf C. M. , Vidinova Yanka , Wiberg-Larsen Peter , Welti Ellen A. R. 
Published: August 2023

Owing to a long history of anthropogenic pressures, freshwater ecosystems are among the most vulnerable to biodiversity loss1. Mitigation measures, including wastewater treatment and hydromorphological restoration, have aimed to improve environmental quality and foster the recovery of freshwater biodiversity2. Here, using 1,816 time series of freshwater invertebrate communities collected across 22 European countries between 1968 and 2020, we quantified temporal trends in taxonomic and functional diversity and their responses to environmental pressures and gradients. We observed overall increases in taxon richness (0.73% per year), functional richness (2.4% per year) and abundance (1.17% per year). However, these increases primarily occurred before the 2010s, and have since plateaued. Freshwater communities downstream of dams, urban areas and cropland were less likely to experience recovery. Communities at sites with faster rates of warming had fewer gains in taxon richness, functional richness and abundance. Although biodiversity gains in the 1990s and 2000s probably reflect the effectiveness of water-quality improvements and restoration projects, the decelerating trajectory in the 2010s suggests that the current measures offer diminishing returns. Given new and persistent pressures on freshwater ecosystems, including emerging pollutants, climate change and the spread of invasive species, we call for additional mitigation to revive the recovery of freshwater biodiversity.