The Yangtze is not an exception. Around the world, rivers<\/a> are no longer changing gradually.<\/p>\n Rather, they are being increasingly transformed by extreme climatic events such as floods, droughts and heatwaves. Our newly published global review<\/a> finds these events are pushing ecosystems beyond their limits<\/a> and eroding biodiversity and core functions.<\/p>\n In bringing together global evidence, our research sets out a roadmap for how science and management can respond to these mounting ecological pressures.<\/p>\n When impacts cascade<\/p>\n Because rivers are connected systems, impacts rarely remain localised. Extreme climatic events can send impacts cascading through entire river networks, affecting communities far from where they begin.<\/p>\n A drought in headwaters can disrupt downstream processes for months<\/a>, and when flows return, built-up material can trigger oxygen crashes<\/a> and fish kills far downstream.<\/p>\n Recovery is often uneven and incomplete, with some species lost and communities permanently changed, especially where rivers are fragmented and species cannot escape to refuges or are lured into traps<\/a>.<\/p>\n The consequences can be profound: extreme events can push ecosystems past tipping points<\/a>, after which full recovery is unlikely and systems may follow new paths instead of returning to their past states.<\/p>\n In some cases, even the most ambitious restoration efforts of recent decades may struggle to reverse biodiversity loss if the frequency of extremes continues to rise.<\/p>\n Our review also shows that when extreme events happen together or in sequence \u2013 known as compound events<\/a> \u2013 their impacts can be catastrophic for people and river biodiversity.<\/p>\n Whether that\u2019s a flood following a drought, a drought and heatwave operating in unison, or a flood falling on saturated ground, the impacts of these compound events can multiply.<\/p>\n The Yangtze drought and heatwave<\/a> collapsed plankton communities, while in New Mexico in 2011, wildfire followed by heavy rain damaged water quality<\/a> in the Rio Grande far downstream. Repeated extremes were shown to have altered invertebrate communities in Alaska\u2019s Wolf Point Creek for more than a decade<\/a>.<\/p>\n In Europe\u2019s Rh\u00f4ne River, a major heatwave in 2003 brought an increase in invasive species<\/a>, which was amplified by damaging floods that followed. In California\u2019s Klamath River, a wildfire and intense rain in 2022 led to widespread river failure<\/a> and a long fish kill zone.<\/p>\n These impacts are often made worse by existing pressures<\/a> such as pollution, land-use change and water withdrawals \u2013 as seen in the 2022 Oder River disaster<\/a> in Germany and recent repeated die-offs<\/a> in Australia\u2019s Murray-Darling Basin.<\/p>\n Importantly, the severity of ecological impacts aren\u2019t always proportional to that of the event that causes them. Instead, it is the order of events and existing stresses that often drive outsized impacts that are hard to predict and manage.<\/p>\n Dead fish lie in the Oder River during an environmental disaster in 2022, thought to have been caused by an algal bloom. Moving from reactive to proactive<\/p>\n While extreme events are stretching the resilience of river ecosystems, they are also exposing gaps in the science needed to design lasting ecological solutions.<\/p>\n Right now, studying the effects of these events is challenging for researchers because they tend to strike without warning. As a result, the evidence base remains limited and also unevenly spread around the world.<\/p>\n For water managers, this creates real uncertainty about how to prepare river biodiversity for extreme events.<\/p>\n One common idea is to protect safe havens<\/a>, such as cold streams, deep pools or shaded tributaries, which can offer species short-term relief from heat and drought.<\/p>\n Because of this, safeguarding these refuges is widely seen as a key part of river management. Nevertheless, questions are emerging about whether these refuges will persist or remain viable during extreme events.<\/p>\n Simply put, compounding extreme heatwaves and drought not only warm rivers, but also undermine the processes that create thermal refuges for freshwater species.<\/p>\n Engineered thermal refuges<\/a>, such as via groundwater pumping<\/a> or gravel trenches<\/a>, are starting to show promise<\/a> in early trials.<\/p>\n But better preparation for extreme events will require more proactive approaches, guided by adaptive frameworks such as the widely-used \u201cresist-accept-direct\u201d<\/a> strategy.<\/p>\n This can mean building river resilience through habitat restoration, better connectivity, giving rivers more room to move<\/a> and protecting or creating cold-water refuges<\/a> at a catchment scale.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/02\/file-20260223-56-brbeba.jpg\")
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\n Patrick Pleul\/Getty Images<\/a><\/p>\n