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More than one million barriers fragment Europe’s rivers

December 18, 2020
Vidrau hydroelectric dam on the Argeș River, Romania. Image: Jarom Irkavan | AMBER

European rivers are fragmented by at least 1.2 million barriers, which can significantly alter their flow and habitat provision, according to an ambitious new study published this week. The results, issued in Nature, suggest that Europe has some of the most fragmented river systems in the world, with an estimated 0.74 barriers per kilometre of river.

River fragmentation is not only the result of large dam and hydropower constructions. Instead, the research team, coordinated by the Horizon 2020 AMBER project, mapped thousands of smaller structures such as weirs, culverts, fords, sluices and ramps in rivers across the European river network.

These structures fragment river systems in different ways, often affecting their flow, course and links with wider floodplains. This variety in impacts extends to ecosystem processes, too: some structures may affect the movement of fish and insect species but barely impact nutrient and sediment flows, or vice versa. Just to add to this complex picture, these barrier impacts can often be highly variable in scale across time and space.

These are key issues for European river managers seeking to conserve and restore their catchments after decades of modifications for energy production, industry, agriculture, urban growth and flood protection. As the authors of the new paper outline, there is a shortfall in knowledge about where river barriers are located in European rivers, and the variable impacts they have on fluvial dynamics and aquatic biodiversity.

“The extent of river fragmentation in Europe is much higher than anyone had anticipated,” says Barbara Belletti, a river geomorphologist who led the study at Politecnico di Milano and is now at CNRS, the French National Centre for Scientific Research.

European river basins mapped by colour. Image: AMBER from ECRINS data, EEA, Copenhagen, 2012

Belletti and colleagues carried out the mammoth task of mapping European river barriers in three steps. First, they compiled barrier records across the 1.65 million km long European river network from 120 local, regional and national databases. Second, they ‘ground truthed’ this data by walking around 2,700km of the river network in 26 countries during low-flow conditions. This allowed them to record the location and characteristics of river barriers, and to address errors or omissions in the existing data. They found that not one of the 147 rivers they surveyed in person was free of obstructions. Third, the research team extrapolated their data to estimate barrier densities in regions with poor and patchy datasets.

Their study maps around 630,000 river barriers across Europe – largely ramps, bed sills, weirs and culverts. As you might expect, the highest barrier densities are found in the heavily modified river systems of Central Europe, and the lowest densities in more remote and sparsely populated regions. This work is illustrated in the AMBER Barrier Atlas, the first comprehensive river barrier map of Europe.

“Over 100,000 of these barriers are obsolete and negatively impacting freshwater biodiversity and contributing to the poor ecological status of rivers. The AMBER Barrier Atlas provides the push we need to take action, and make the removal of obsolete barriers happen everywhere,” says Herman Wanningen, managing director of the World Fish Migration Foundation.

A large dam on the Soča River, in the Slovenian Alps. The Balkan region is home to some of Europe’s last unfragmented river systems. Image: Jan Pirnat | AMBER

The research team state that there are still relatively unfragmented river systems to be found in the Balkans, the Baltic states, and parts of Scandinavia and southern Europe. However, many of these systems are threatened by proposed dam developments. The authors suggest that their results can inform the implementation of the EU Biodiversity Strategy, which aims to restore fragmented river systems across Europe.

“Many barriers are obsolete and removing them provides unprecedented opportunities for restoration,” says Carlos de Garcia de Leaniz, AMBER coordinator and Chair in Aquatic Biosciences at Swansea University. “Our results feed directly into the new EU Biodiversity Strategy and will help to reconnect at least 25,000 km of Europe’s rivers by 2030.”

The new AMBER barrier atlas is a highly valuable resource for environmental managers and policy makers in Europe seeking to underpin their conservation and restoration work with accurate data. An important next step may be to extend and join up this study’s approach to global river systems, particularly where datasets on river barriers are currently restricted.


Belletti, B., Garcia de Leaniz, C., Jones, J. et al. (2020) More than one million barriers fragment Europe’s rivers. Nature 588, 436–441.

Experts urge action to protect and restore small English freshwater habitats

December 3, 2020
Whitchurch Pond. Scientists are increasingly showing the importance of such small water bodies to landscape biodiversity and ecosystem services. Image: Freshwater Habitats Trust

A group of freshwater experts have written to the UK government to call for urgent action to protect England’s small aquatic habitats. They state that the country’s network of ponds, streams, ditches and headwaters – which make up around 80% of England’s freshwaters, and support over 70% of freshwater species – are vital biodiversity hotspots, often providing crucial refuges for rare plants and animals.

However, small freshwater sites are largely ignored by biodiversity monitoring programmes, such as those guided by the EU Water Framework Directive. Linked to this, funding for their protection and restoration is scarce. In short, the authors of the new letter – coordinated by the Freshwater Habitats Trust – argue that there is a critical lack of attention afforded to small freshwaters, and an urgent need to address this blindspot in environmental management and policy.

The open letter is addressed to Dieter Helm, the Independent Chair of the UK government’s Natural Capital Committee, which recently published its final response to the government’s 25 Year Environment Plan. The report explores how the government could address declines in ‘natural assets’ – atmosphere, freshwater, minerals and resources, marine, soils, biota and land – in England over the next quarter century.

The freshwater section of the report identifies small water bodies as a focus of urgent attention. It states that, “The government should develop a baseline and metrics for the condition and extent of smaller waterbodies comparable to those for WFD water bodies. Such an assessment should look to incorporate citizen science to engage communities, and the use of other developing monitoring approaches.”

A number of recent studies have shown that the conservation and restoration of small water bodies can bring about significant environmental benefits. A study by Penny Williams and colleagues published earlier this year found that creating ‘clean water’ pond habitats in farmland can significantly improve landscape biodiversity over relatively short time periods.

A 2018 review by William Riley and colleagues found that small water bodies provide a range of important ecosystem services, such as natural flood control, but are inherently vulnerable to human pressures. A 2016 study by Matthew Hill and colleagues showed that ponds are important ‘stepping stone’ habitats for biodiversity across wide landscapes. And more studies are being published each year, representing a shift in contemporary ecological thought from ‘big is better’ to ‘small is beautiful’ in understanding how freshwater habitats support biodiversity and provide ecosystem services.

In this context, the open letter – signed by 21 prominent UK freshwater researchers – argues that post-Brexit policy change provides an opportunity for the government to address historic shortcomings in the monitoring and protection of small water bodies.

Signatory Dr Jeremy Biggs says, “This could be a win-win solution – for a fraction of what the government and water industry is spending now, we can reverse the inexorable decline of UK freshwater wildlife by focusing on small waters. And post-Brexit changes in legislation give an opportunity to set our own rules to protect freshwater by properly including small waters.”

The letter outlines three key steps for the UK Office for Environmental Protection and other government agencies to address. First, it calls for the implementation of a national monitoring programme for small water bodies which connects with the current river and lake monitoring programmes. Second, it asks policy makers to set specific targets for small waterbody quality and numbers, and integrate these into existing planning and agri-environment policies, such as the Environment Act. Third, it urges the adoption of the Wildlife and Countryside Link recommendations for a funded programme of small water conservation, restoration and creation as part of the next government Spending Review.

In short, the open letter asks the UK government to follow the recommendations of current freshwater research on small water bodies synthesised in the 25 Year Environment Plan report. In doing so, the letter authors argue we can grasp an important opportunity to better monitor, protect and restore vital English ponds, streams, ditches and headwaters in the future.

Pet flea treatments cause toxic chemical pollution in English rivers

November 17, 2020
Image: Nathan Rupert | Flickr Creative Commons

Toxic pesticides found in veterinary flea treatments used on domestic cats and dogs have been detected at potentially harmful levels in English rivers. Researchers have found widespread contamination of two neurotoxic chemicals – fipronil and the neonicotinoid imidacloprid – in 20 sampled rivers, from the Test on the south coast to the Eden in Cumbria. Fipronil was found in 98% of samples, and the average level of its highly toxic breakdown product fipronil sulfone was 38 times above the recommended environmental safety limit.

Both fipronil and imidacloprid are banned for agricultural use due to their harmful environmental effects, including significant reductions in populations of both aquatic and pollinating insects and disruptions to the food webs that depend on them. However, there has been little attention given to the environmental impacts of their use in veterinary flea treatments for cats and dogs. The researchers behind the new study, published in the journal Science of the Total Environment, aimed to address this shortfall by analysing river water samples collected by the Environment Agency between 2016 and 2018.

“The use of pet parasite products has increased over the years, with millions of dogs and cats now being routinely treated multiple times per year,” said lead author Rosemary Perkins, a PhD researcher at the University of Sussex, and a qualified vet. “Fipronil is one of the most commonly used flea products, and recent studies have shown that it degrades to compounds that are more persistent in the environment, and more toxic to most insects, than fipronil itself. Our results, showing that fipronil and its toxic breakdown products are present in nearly all of the freshwater samples tested, are extremely concerning.”

There are 66 licensed veterinary flea treatment products containing fipronil and 21 containing imidacloprid available in the UK. There are around 10 million dogs and 11 million cats in the UK, and the new study suggests that the widespread use of routine flea treatment products has the potential to significantly affect the health of aquatic life in English freshwaters.

“Fipronil and imidacloprid are both highly toxic to all insects and other aquatic invertebrates,” said co-author Professor Dave Goulson from the University of Sussex. “Studies have shown both pesticides to be associated with declines in the abundance of aquatic invertebrate communities. The finding that our rivers are routinely and chronically contaminated with both of these chemicals and mixtures of their toxic breakdown products is deeply troubling.” Speaking to The Guardian, Professor Goulson added that one imidacloprid-based flea treatment for a medium-sized dog contains enough pesticide to kill 60 million bees.

The researchers found that the highest levels of pollution were found immediately downstream of wastewater treatment works. They suggest that this supports the hypothesis that significant quantities of environmentally-harmful pesticides are entering rivers via the washing of treated pets, their bedding, and other surfaces they come into contact with. It is also possible that swimming and rainfall wash-off from treated pets could be additional pathways for the flea treatment pesticides to reach waterways.

“We’ve identified a number of steps that can be taken to minimise or avoid environmental harm from pet flea and / or tick treatments,” outlined Rosemary Perkins. “These range from introducing stricter prescription-only regulations, to considering a more judicious and risk-based approach to the control of parasites in pets, for example by moving away from blanket year-round prophylactic use. We’d recommend a re-evaluation of the environmental risks posed by pet parasite products, and a reappraisal of the risk assessments that these products undergo prior to regulatory approval.”


Perkins R, et al (2020), “Potential role of veterinary flea products in widespread pesticide contamination of English rivers”, Science of The Total Environment,

A global digital observatory of Earth: exploring the potential of culturomics and iEcology for aquatic conservation

November 10, 2020
Online images, videos and audio of the natural world are being used by conservationists to track changes in global ecosystems. Image: Cindy Shelbey | Flickr Creative Commons

The natural world has never been more closely documented than it is today, not only in scientific studies but also in the public use of digital technologies to capture and share their daily lives. Photographs, videos and audio recordings of nature shared on social media and other online platforms could provide valuable ‘big data’ resources for aquatic conservation, according to the authors of a new journal article.

“These are kinds of data that are produced as a by-product of our daily lives. Someone’s online snorkelling video could help ecologists understand which reef species are present, or the behaviour of recreational users relative to particularly sensitive species,” explains Professor Kate Sherren, a co-author of the study from Dalhousie University, Canada.

Culturomics and iEcology: emerging areas of digital research for conservation

As Professor Sherren suggests, analysing everyday public documentation of the environment could provide researchers with insights into both biodiversity patterns and trends, and human-nature-interactions. This idea has already begun to gain traction in terrestrial conservation, centred around two key emerging research areas: culturomics and iEcology.

“Both research areas emerge from the novel opportunities afforded by the ever-increasing reach of the internet – more than half of the human population has access to the internet these days – and widespread participation in digital platforms like social media,” says co-author Dr. Ricardo Correia from the University of Helsinki, Finland. “They share similar approaches and methods but culturomics focuses on exploring human-nature interactions whereas iEcology focuses on extracting information about nature.”

“Conservation culturomics is focused on human interactions with nature, especially related to conservation issues – for example, societal perceptions, attitudes, values and support for conservation measures, and topics such cultural ecosystem services, tourism, wildlife trade and recreational fishing. iEcology is focused on ecological questions, including distribution of species, population dynamics, behavioural studies and ecosystem processes,” explains lead author Dr. Ivan Jarić, from the Biology Centre of the Czech Academy of Sciences. “The main advantage of these approaches is that they are based on a huge amount of available data that are already out there, available for research, and allow conducting both local and global studies with very low research costs.”

Reflecting on increased volumes of social media posts from friends and colleagues documenting urban nature during the recent COVID-19 pandemic, Dr. Correia highlights the potential of culturomics and iEcology approaches for conservation. “The novelty here is that this trend would have probably passed unnoticed were it not for our ability to connect to others across using social media and other digital platforms. This is simple example of a way that such information can be used for the benefit of conservation but the truth is that many of the potential applications still remain to be explored – which is one of the reasons why we are so excited about the future of these research areas.”

Culturomics and iEcology approaches could benefit fisheries management (1); social impact assessments (2); detection, mapping, and monitoring of threatened, rare, and alien species (3); ecosystem status and anthropogenic impacts (4); and the identification of aquatic flagship and umbrella species (5). Image: Jarić et al (2020)

Using digital research methods to support aquatic conservation

In their open-access paper in the PLoS Biology journal, the authors argue that there is untapped potential in applying these concepts to aquatic research, monitoring and conservation planning. They state that whilst marine and freshwater ecosystems cover around 72% of the Earth’s surface, and are disproportionately threatened compared to their terrestrial counterparts, they are widely under-researched and monitored. Could culturomics and iEcology approaches to delving through the masses of online media generated each day offer researchers a valuable new lens on aquatic ecosystems and their dynamics?

The authors highlight six potentially promising areas for the application of these concepts in aquatic environments. First, the detection, mapping, and monitoring of threatened, rare, and alien aquatic species could be supported by analysing online photographs, videos and audio recordings. The authors highlight that these techniques are already being applied to monitor populations of cetaceans in the Mediterranean Sea, Hawaiian monk seals, and Eurasian otters in South Korea.

Second, digital research techniques can help conservationists detect and monitor changes in ecosystems, particularly in response to pressures such as climate change. The authors describe how analyses of Google Images revealed a climate-driven shift in breeding periods of Japanese dace, and documented a parasite-induced coloration phenomenon in Caribbean reef fish. They suggest that whilst such techniques cannot replace traditional field studies, they provide valuable tools for preliminary studies which can help identify priority areas for more intensive research.

Third, culturomics and iEcology techniques could help wildlife and fisheries managers monitor the dynamics and sustainability of fishing and hunting practices and the wildlife trade. For example, digital analyses of photographs and news articles have been used to document trends in fish catch size and composition over time. These analyses can be extended to cover historical data such as digitised texts, images and ship logs to give a longer-term picture of wildlife harvesting over time, often for periods when scientific sampling data are limited.

Fourth, the authors suggest that these digital research techniques could help identify flagship and umbrella species for aquatic conservation, and monitor their potential public reception and interactions. Here, the two approaches could work in tandem: with culturomics identifying flagship species based on societal interest; and iEcology identifying umbrella species by mapping their distributions and overlaps with key habitats and species.

Fifth, the rise of social media as an integral part of global tourism practices has created masses of digital data detailing how people interact with protected areas and landscapes. There is already a growing body of culturomics research using this data, for example on tourist practices and movements in Ramsar wetlands in South Korea and India, and in marine protected areas such as Costa dos Corais in Brazil and the Great Barrier Reef in Australia.

Finally, the authors identify potential in the using these digital research techniques to assess the social impacts of construction and infrastructure development such as hydroelectric projects, wind farms and oil rigs in aquatic environments. Reflecting on her collaboration with Yan Chen using culturomics techniques to assess the social impacts of hydrolectric dam development, Prof. Sherren says, “We were surprised by the nuance that emerged, particularly from the thematic rather than spatial analysis. These were rich stories of how Instagram users currently lived in places facing big change, in one case a dam removal and in another a dam construction, that could easily be used to anticipate impact. The potential use of such methods was clear to update the practice of legislated social impact assessment for large developments, as well as monitoring.”

The collaborative work in the new study led from discussions at two events. The first was a meeting on the topic at the 5th European Congress of Conservation Biology in 2018 in Jyvaskyla, Finland, which led to the formation of an informal research network, which is currently in process of becoming an official working group of the Society of Conservation Biology. The second was at ALTER-Net & EKLIPSE Conference in 2019 in Ghent, Belgium, where Dr. Jarić gave a presentation on the topic at a workshop organised by the Alliance for Freshwater Life.

Challenges and concerns for the uptake of culturomics and iEcology. Image: Jarić et al (2020)

Challenges and outlook for ‘a global digital observatory of Earth’

The research team identify a number of logistical and ethical challenges facing researchers seeking to use culturomics and iEcology techniques. “Digital data can be affected by various cultural, political, and socioeconomic factors, and they may be biased towards more active users and specific social groups,” says co-author Dr. Andrea Soriano-Redondo, from CIBIO/InBio in Portugal. “Also, the uneven spatial coverage of the internet and its users is even more pronounced in the aquatic realms. Generally, our data coverage decreases with distance from shore and water depth, and centres mainly around urban and recreational areas.”

Another key step towards adopting these techniques is the use of new technologies to aid data analysis. “The increasingly diverse applications for aquatic ecosystems will be further enhanced by emerging technologies such as automated web crawling and data processing, machine learning, automatic species identification, apps, and ecoacoustics,” says co-author Dr. Uri Roll from the Ben-Gurion University of the Negev in Israel. “We ultimately envision a global digital observatory of Earth, an online platform established for continuous collection and processing of key digital data from a wide variety of sources, with a near real-time information provided on ecosystem changes and human–nature interactions.”

So, perhaps in a not-too-distant future, every time you snap a picture of a trip to the beach, a video of a river adventure, or a sound recording of water birds you might well be inadvertently helping researchers figure out how aquatic ecosystems are faring. Dr. Jarić suggests that culturomics and iEcology “are rapidly emerging fields – with most of the related papers published over the last 2-3 years – and they are likely to become established as major areas of research within conservation science and ecology in the future.”


Jarić I, Roll U, Arlinghaus R, Belmaker J, Chen Y, China V, et al. (2020) Expanding conservation culturomics and iEcology from terrestrial to aquatic realms. PLoS Biol 18(10): e3000935.

There is no green hydropower: European NGOs call for end to construction

November 5, 2020
Nant y Moch hydroelectic dam, Wales. Image: Statkraft | Flickr Creative Commons

A group of 150 European environmental organisations have released a manifesto calling for EU institutions to stop supporting the construction of new hydropower plants. The coalition of NGOs released the document following the recent World Fish Migration Day, which highlighted the significant barriers – particularly from hydropower constructions – faced by migratory species in European and global rivers.

The coalition, which includes the WWF, BirdLife and Climate Action Network Europe, state that new hydropower plants make only a small contribution towards green energy transition compared to the significant environmental impacts they have on river ecosystems. As such, in the context of ongoing freshwater biodiversity loss, they argue that the construction of new hydropower schemes contradicts the biodiversity goals of the European Green Deal policy. Put bluntly, they state, “There is no green hydropower.”

There are over 21,000 existing hydropower plants in Europe, with around another 8,700 additional plants planned or under construction. The manifesto calls for an end to EU subsidies and European Investment Bank and European Bank for Reconstruction and Development financing for all new hydropower plants. It states that public finance for new hydropower plants should be reallocated to ecological restoration, dam removal projects and towards less ecologically harmful renewable energies such as wind and solar power.

“The European Commission and the European financial institutions’ continued financing of new hydropower projects completely contradicts the ambitions of the EU Biodiversity Strategy and its goal of restoring 25,000km of free-flowing rivers,” said Andreas Baumüller, Head of Natural Resources at the WWF European Policy Office. “Removing financing tools and incentives to new hydropower projects is an increasingly urgent step towards reversing biodiversity loss in the EU, meeting the targets set by the Water Framework Directive, and supporting the European Green Deal.”

Responding to the manifesto, a spokesperson from the International Hydropower Association said, “Climate change is widely recognized as one of, if not the most, significant threat to biodiversity. Hydropower is by far the largest source of renewable electricity globally and will play a crucial role if we are to meet the Paris Agreement target of keeping the global temperature increase below 1.5 degrees C. An outright moratorium on hydropower  in Europe  would be inappropriate and stop many important projects going ahead, which are urgently required to ensure  the success of the clean energy transition.”

It is undeniable that hydropower is a valuable source of renewable energy in Europe. The big issue is the negative impacts hydropower constructions have on river ecosystems. Large hydropower plants can completely transform the course and character of a river, significantly altering flows of water, nutrients, sediments and migratory species along its length. Even small and ‘run-of-the-river’ plants can cause significant habitat alterations and act as barriers to migratory species.

“We urgently need to move to a 100% renewable energy system,” stated Alex Mason, Senior Policy Officer, Climate & Energy, WWF European Policy Office. “But the contribution new hydropower could make is trivial compared to the massive ecological damage it would cause. We should be investing in wind and solar instead, combined with demand flexibility and storage.” 


Read No More Hydropower in Europe: A Manifesto

World Fish Migration Day 2020

October 23, 2020
The World Fish Migration Day 2020 takes place on October 24th with online events around the world. Image: WFMF

Communities around the world will join together tomorrow to celebrate World Fish Migration Day. The event – started in 2014 – aims to raise awareness of the importance of migratory fish populations, and the threats they face. This year World Fish Migration Day will feature over 300 events across 66 countries – many of which are available to join online.

This year’s event – the fourth of its kind – takes place in the wake of the latest Living Planet Index for Migratory Freshwater Fish report, which found an average 76% global decline in monitored migratory fish populations since 1970. The picture is particularly bad in Europe, where declines of 93% were observed. These declines are attributed to a combination of habitat loss, dam and hydropower construction, climate change and over-exploitation of populations.

Despite these startling trends, the World Fish Migration Foundation say that migratory fish do not receive the public attention they deserve. The aim of their Day is to raise public awareness of the importance of migratory fish populations in our lives, and to encourage citizen action in asking NGOs and policy makers to conserve and restore ‘global swimways’.

The ‘Love Flows’ documentary profiles some of the events from 2018 World Fish Migration Day, showcasing local celebrations, community knowledge, and shared visions for global rivers.

This year’s World Fish Migration Day is centred around a series of online webinars starting this evening (European time, 23rd October), which will discuss events and issues from around the world. You can explore hundreds of other global events through an interactive map here.

The Day will culminate with the Eurofishion song contest, where ten finalists will perform their migratory fish-themed songs for judges. The shortlisted videos include children singing about salmon at a Slovakian zoo, a coordinated dance party about urban trout populations in Finland, a South African children’s choir singing a new piece written by an 11-year old choir member, and a Kenyan hip-hop track about water pollution in rivers.


Explore the World Fish Migration Day events here.

Safeguarding freshwater life beyond 2020: 14 recommendations for environmental policy

October 15, 2020
A headwater stream in the Austrian Alps. Image: Theo Crazzolara | Flickr Creative Commons

Freshwater biodiversity is in a critical state of decline across the world, as startlingly shown in the most recent WWF Living Planet report. This year, updates to two international policy frameworks which could have significant influence on the future of freshwater life – the Convention on Biological Diversity (CBD) and the European Union (EU) Biodiversity Strategy – are being prepared. How can we ensure that global freshwater biodiversity is properly valued and protected by these frameworks over coming decades?

An international research team led by Dr. Sonja Jähnig at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) in Germany have published a journal paper containing 14 key recommendations for the global protection of freshwater biodiversity. Their aim is to encourage decision makers to ensure that both the post-2020 CBD Global Biodiversity Framework and the post-2020 EU Biodiversity Strategy better account for freshwater ecosystems.

“This is an important moment to bring scientific knowledge into the process,” says Dr. Jähnig. “Political strategies and decisions must emphasise the unique ecology of freshwater life and the many threats to it. In previous regulations, the protection of freshwaters has often been treated in an inferior manner. Inland waters have been included within land regulations – because they are not marine – or with seas and oceans – because they are aquatic. It is time that freshwater biodiversity is recognised in its own right – the latest Living Planet Report shows that the loss of freshwater populations is the most dramatic – a loss of 84 percent between 1970 and 2016,” Dr. Jähnig states.

The new open-access paper – published in Conservation Letters – draws on the expertise and experience of its 21 authors, many of whom have been involved in major freshwater research projects such as MARS and BioFresh in recent years. Their collaboration was initiated at the ALTER-Net / Eklipse conference in Ghent in July 2019, which was hosted to discuss EU biodiversity strategy post-2020.

As co-author Dr. Astrid Schmidt-Kloiber explains, this is a crucial time for environmental policy and conservation, “The year 2020 marks the end of the UN biodiversity decade. In the last 10 years major efforts have been undertaken to save the world’s biodiversity, but none of the Aichi Targets has been met so far. Now the Convention on Biological Diversity and the EU Biodiversity Strategy need to be prepared and adapted for the next 10 years and we wanted to make a contribution that exclusively deals with the biodiversity of freshwaters, which are among the most threatened ecosystems on earth.”

The authors’ 14 recommendations are split into four categories which encompass visioning, planning, monitoring and practice for freshwater conservation.

The 14 recommendations for freshwaters in the post-2020 Global Biodiversity Framework. Image: van Rees et al (2020)

Visions and targets for freshwater conservation

The article’s first recommendation is also its most radical and urgent: that freshwaters should be considered a true ecological ‘third realm’ that deserves legal and scientific prominence in biodiversity frameworks and strategies. Freshwaters can sometimes ‘slip between the gaps’ of terrestrial and marine policies, which means that their unique threats, valuable ecosystem services and distinctive ecology are not properly accounted for and protected.

Lead author Dr. Charles van Rees explains, “We want to communicate the uniqueness of freshwater ecosystems and biodiversity, how they cannot be managed similarly to terrestrial or marine systems, how they are intertwined with human health and societal water security, and how they are more intensely threatened than other realms of biodiversity.” 

As Dr. van Rees notes, the authors recommend that freshwater ecosystems should be recognised and framed as life-supporting systems that provide vital functions to humans and non-humans alike. The processes that shape freshwater systems – and the services they provide – often take place across wide geographical scales and long timescales, and ensuring that these systems retain connectivity through policy and management is another of the authors’ recommendations. This has implications for how different environmental policies are implemented, as co-author Dr. Gregor Kalinkat outlines, “Better integration of water-related regulations like the Water Framework Directive and the EU Biodiversity Strategy is a key goal that needs to be achieved.”

A history of global environmental policies which influence freshwater conservation. Image: van Rees et al (2020)

Creating the conditions for effective freshwater conservation

Linked to their previous recommendation, the authors state that freshwater ecosystems should be managed across their whole catchment, regardless of political boundaries. Freshwaters don’t function in isolation from land, air and sea, but instead are in a constant state of environmental exchange and dynamism, which can lead to complex sets of human pressures. Managing freshwaters at ‘the catchment scale’ is widely agreed to be the most effective way to address these dynamics. This links to another of the author’s recommendations: to incorporate insights from cutting-edge ecological systems theory around complexity, non-linearity and feedback loops.

The authors highlight that whilst the designation of new protected areas can be politically and economically challenging, initiatives such as wetland restoration have the potential to provide simultaneous climate and conservation benefits. They also discuss how large and ‘charismatic’ freshwater species have the potential to act as valuable ‘flagships’ in raising public awareness of conservation initiatives. The environmental impacts of invasive freshwater species continues to grow as an issue, and the authors recommend that regulatory frameworks should better account for their monitoring, assessment and management.

Monitoring and planning for the future

In planning for how freshwaters are best studied in support of environmental policy, the authors make three recommendations around biodiversity monitoring and data. First, they state that freshwater monitoring programmes should be better coordinated and funded at national and global scales. Second, they advocate for making large freshwater datasets open-access and widely available – as is already happening through the Freshwater Information Platform – as a means of supporting collaborative research across large geographical areas.

Third, they suggest that future biodiversity monitoring schemes should take advantage of novel research methods and data sources in order to better account for underrepresented – but ecologically crucial – groups like parasites, fungi, and bacteria. They highlight an emerging toolkit of monitoring methods, including environmental DNA, remotely sensed earth observations, culturomics and citizen science as valuable avenues for research.

Dr Astrid Schmidt-Kloiber says, “I think that we need Europe-wide specific harmonised freshwater monitoring programmes to create a reliable baseline about the current state of freshwater biodiversity and to help the Red Listing process. Though the Water Framework Directive has already created a lot of valuable data, it has to be emphasised that WFD monitoring captures only a subset of the freshwater biota, as it is not specifically meant to record, for example, the total species diversity. This is directly related to better access to existing and mobilisation of new biodiversity data, which also still would need major improvements.”

In using this data to shape conservation practice, the authors recommend that future freshwater policies should encourage catchment management which balances both human and wildlife water needs. Freshwater ecosystems are often subject to numerous competing demands on the resources they provide, and the authors highlight the range of new decision-support tools which can help policy makers navigate their complexity.

Synergies between the 14 recommendations and the 6 ‘bending the curve of freshwater decline’ priority actions outlined by David Tickner and colleagues (2020). Filled circles indicate parallel coverage; open circles denote where recommendations provide a means of implementation for priority actions. Image: van Rees et al (2020)

Cross-cutting issues for freshwater conservation

The final two recommendations in the paper relate to cross-cutting issues for freshwater management. First, the authors state that freshwater biodiversity species extinction risk listing and protections should be better informed by global assessments. They highlight how a relatively small proportion of freshwater species classified as threatened by the IUCN Red List are adequately protected by EU biodiversity policies.

Second, they suggest that future environmental policies should support the use of Integrated Water Resources Management as a means of sustainably managing freshwater systems, particularly across administrative and political boundaries. They describe how key contemporary issues surrounding multiple stressors and environmental flows are being managed through IWRM approaches.

Summing up and looking forward

The paper provides a succinct and powerful statement in support of better freshwater conservation and management, and is informed by cutting-edge research and theory in the field. “We hope that this paper will highlight under-recognised research on freshwater ecology and conservation and bring the freshwater biodiversity crisis to the forefront,” says Dr. Charles van Rees. “More than raising the alarm, though, we hope to provide more actionable, practicable guidelines and suggestions for how governments can support the research and management needed to address this crisis. This is a major step toward what David Tickner and colleagues recently called ‘bending the curve’ for freshwater biodiversity,” Dr. van Rees explains. 

“Through the joint effects of climate change, overexploitation, pollution, species introduction, and many other factors, we are losing biodiversity at an alarming rate, and at a global scale,” adds co-author Dr. Stephen Thackeray. “These losses are especially pronounced in freshwater habitats, and yet the plight of freshwater species specifically does not always get the public and policy attention that it deserves. It is clear that we need to take action to protect our freshwater wildlife, and it is our hope that our recommendations can help guide decision making and conservation for these imperilled ecosystems,” Dr. Thackeray suggests.

“Even if results of international conservation efforts have been very sobering so far – we scientists will continue to contribute our expertise to highlight the dramatic loss of freshwater biodiversity and help to mitigate and stop it. The recommendations formulated can help to improve the political framework for the protection of aquatic biodiversity,” Dr. Sonja Jähnig concludes.


van Rees, CB, Waylen, KA, Schmidt‐Kloiber, A, et al. Safeguarding freshwater life beyond 2020: Recommendations for the new global biodiversity framework from the European experience. Conservation Letters. 2020; e12771.

‘Lost’ Brazilian frogs rediscovered with environmental DNA

October 9, 2020
Phasmahyla guttata – the spotted leaf frog – which had not been documented in the Parque Nacional da Serra dos Órgãos, Brazil since 1977 and was ‘rediscovered’ using eDNA in the new study. Image: Leo Malagoli | Cornell University Press Office

Scientists have used cutting-edge DNA techniques to identify the presence of a Brazilian frog species not seen since 1968, and thought to be extinct.

Organisms leave DNA traces in soil, water and air in their habitats, and this ‘environmental DNA’ (or eDNA) can increasingly be sampled and matched to reference databases. So, even if researchers don’t see or hear a particular species, they can identify the eDNA ‘footprint’ it leaves behind in an environment.

The ‘lost’ frog, Megaelosia bocainensis, was one of seven frog species – including four other declining species, and two that had disappeared locally – that were detected by the new study, published in Molecular Ecology.

The research team collected and analysed frog eDNA from stream and pond water at five sites in the biodiverse Atlantic Coastal Forest and Cerrado grasslands in southeastern Brazil. They were looking for 13 frog species that are presumed extinct; 12 species that have disappeared locally; and five species that were once abundant but are now scarce.

“Little bits of DNA in the environment don’t tell us about how many individuals there are or whether those individuals are healthy, but it does tell us that the species is still present,” said senior author Kelly Zamudio, the Goldwin Smith Professor of Ecology and Evolutionary Biology in the College of Arts and Sciences at Cornell University.

“This is one more kind of survey data, and for species that are declining or locally disappeared, it not only means they are there, but there’s now the potential to study them in more detail,” Zamudio added.

A museum specimen of Megaelosia bocainensis, collected in 1968. The species disappeared from Parque Nacional da Serra da Bocaina, Brazil, and was detected by eDNA surveys. Image: Délio Baêta | Cornell University Press Office

The researchers then extracted the eDNA from their water samples and genetically sequenced it. This allowed them to isolate frog eDNA from that of humans, pigs, chickens and other organisms which share the environment.

“Now you’ve got a subset of genetic sequences that we know only belong to frogs, and then it’s step by step, going finer and finer, until you get to the genus and species you are looking for,” Zamudio said.

Because Megaelosia bocainensis has not been seen for over 50 years, the research team didn’t have tissue samples to extract DNA from for comparison with their eDNA samples. However, they did have the genetic sequences for the frog’s sister species in the genus Megaelosia.

“We know there’s a Megaelosia there,” Zamudio said, “we just don’t know which one it is, but the only one that has ever been reported there historically is the one that went missing. Do we believe it? That’s how far the analysis can take us.”

Using eDNA techniques allows scientists to search for traces of such elusive species at low population densities. It offers rich potential in characterising species geographic ranges, population fluctuations and conservation status. It is already being used to track the spread of invasive species through freshwater ecosystems, such as Asian carp in the USA.

The discovery of the Megaelosia eDNA in the water samples clearly signals the need for more targeted amphibian research and conservation efforts in the region. How many more ‘lost’ freshwater species are still out there, quietly persisting in tiny numbers, despite multiple human pressures and threats? Could eDNA techniques help conservationists better identify and protect these species in the future?


Lopes, CM, Baêta, D, Valentini, A, et al. Lost and found: Frogs in a biodiversity hotspot rediscovered with environmental DNA. Mol Ecol. 2020; 00: 1– 10.

84% of global freshwater species populations lost since 1970: can we ‘bend the curve’ of this trend?

September 25, 2020
The Yangtze River in China – home of the Chinese sturgeon, populations of which have declined by 97% since 1982 due to habitat degradation. Image: Boris Kasamov | Flickr Creative Commons

Global populations of mammals, birds, amphibians, reptiles and fish have, on average, declined by two-thirds since 1970, according to the latest WWF Living Planet Report, released earlier this month. Continuing the trends shown in past reports, freshwaters are particularly imperilled: with 84% of global freshwater species populations lost between 1970 and 2016.

The bi-annual Living Planet Report tracks trends in global wildlife abundance, based on data from 21,000 populations of more than 4,000 vertebrate species. Population declines in freshwater ecosystems – which equate to an average annual loss of 4% globally – were higher than those in terrestrial and oceanic environments.

Significant declines in global freshwater species populations

WWF have published a Deep Dive into Freshwater’ document looking at the stark findings of the Living Planet Report, and outlining ways to support global freshwater conservation in their wake. The publication states that population declines are particularly acute among freshwater amphibians, reptiles and fishes. Whilst freshwater population declines have been observed globally, they are most severe in Latin America and the Caribbean.

The drivers of these declines include habitat degradation, pollution, over-exploitation, invasive species and sand mining. These pressures are not always adequately managed in a large-scale, cross-boundary way by conservation schemes. The report suggests that large ‘megafauna’ species are particularly threatened, as their populations are less resilient to environmental pressures. One stark example is the spawning population of the Chinese sturgeon in China’s Yangtze river, which declined by 97% between 1982 and 2015 due to dam construction.

Global freshwater species populations declined by 84% on average between 1970–2016. Image: WWF Living Planet Report 2020
Global wetlands are being lost at a rate of around 1.6% each year – three times faster than rainforests. Image: WWF Living Planet Report 2020

Lost wetlands and fragmented rivers

The ‘Deep Dive’ publication identifies two key trends in freshwater ecosystem change which are likely to be contributing to freshwater population declines. First, it states that nearly 70% of global wetlands have been lost since 1900, and they are still being destroyed at a rate (around 1.6% per year) three-times faster than rainforests. Wetlands are crucial ecosystems for many endangered and endemic species, and provide many benefits such as natural flood prevention to human communities. However, they are being widely drained, dammed and dyked across the world, often to support crop and livestock production.

Second, a 2019 mapping of millions of kilometres of global rivers revealed that only one-third of the world’s 242 longest rivers (more than 1000km in length) remain free-flowing. The majority of the remaining free-flowing rivers are found in remote areas of the Arctic, Congo and Amazon basins. The construction of dam and hydropower infrastructure can significantly alter the flows of water, sediment and nutrients through a river catchment, and inhibit the movement of migratory species. Despite increasing global attention to the issue, proposals for new dam constructions continue apace on many large river systems across the world.

Bending the curve of freshwater biodiversity loss?

In a blog posted earlier this week, Dean Muruven, WWF Global Freshwater Policy Lead, urges everyone working in freshwater conservation to pause and reflect on the results of the Living Planet Report. He writes, “If you have been an academic championing freshwater conservation throughout your career, you may have to finally accept that all those important (and they are critically important) science papers and commentary pieces in top academic journals have not had the expected impact. Instead of helping to save species, they have largely catalogued their decline. Maybe it’s time to start focusing on policies as well as papers — and perhaps even protests.”

Muruven argues that it is time for freshwater conservationists to radically improve how they communicate their work to wider audiences. He suggests that this involves “stepping out of the freshwater conservation bubble and having those difficult conversations with those that share a different a world view from us — to pave the way for learning and partnerships.”

The six priorities in the WWF Emergency Recovery Plan for Freshwater Biodiversity. Image: WWF

The WWF’s current approach to fostering widespread dialogue and action on tackling the freshwater biodiversity crisis centres on their Emergency Recovery Plan for Freshwater Biodiversity. The plan, discussed in a blog back in February, is based on six key themes.

They are: letting rivers flow more naturally; reducing pollution; protecting critical wetland habitats; ending overfishing and unsustainable sand mining in rivers and lakes; controlling invasive species; and safeguarding and restoring river connectivity through better planning of dams and hydropower.

The authors of the Emergency Recovery Plan suggest that unless significant collective action is taken to ‘bend the curve’ of freshwater biodiversity loss globally then the downward trends of species loss and ecosystem degradation will continue apace. The time to tackle this crucial issue is now: the key question, as Muruven puts it, is, “are we capable as a freshwater community of coalescing around the Emergency Recovery Plan for the next five years and collectively have a go at bending the curve?”


Read the WWF Living Planet Report 2020

Chemical pollution limits the ecological status of European freshwaters

September 11, 2020
Grand Canal Dock in Dublin: the legacy of heavy industry poses chemical pollution issues in many urban waters in Europe. Image: William Murphy | Flickr Creative Commons

Chemical pollution poses a significant threat to the health of freshwater ecosystems, both in Europe and across the world. A major 2014 study suggested that chemical pollution has acute, potentially lethal, impacts on freshwater organisms at more than one in ten monitored sites across Europe; and long-term negative impacts at almost half of these sites.

The challenge is an unenviable one for water managers: how to monitor and manage more than 140,000 different toxic substances, each with unique properties and impacts? And in addition, how to understand and mitigate the interactions and impacts of chemical ‘cocktail’ mixtures on the aquatic environment?

Disciplinary differences in monitoring chemical pollution

At present, aquatic chemical pollution is monitored in two main ways. Applied ecologists generally carry out field observations in a process of ‘gradual assessment’, which allows them to assess ecological impacts on a five-point scale ranging from major to minor. On the other hand, ecotoxicologists base their assessments on laboratory experiments, and provide a binary diagnosis of water quality: either a toxic chemical (or mixture) is present at an acceptable level; or it is too high, and should be managed.

These two approaches present a dilemma for water managers: how to combine and act on the different diagnoses they receive? A new study published this week outlines how applied ecologists and ecotoxicologists can better synthesise their results to provide practical information for water managers seeking to mitigate the effects of chemical pollution.

Synthesising applied ecology and ecotoxicology approaches

The study, a collaboration by an interdisciplinary group of European researchers, proposes five ecotoxicological classes that can be linked to the five degrees of ecological impacts. Lead author Leo Posthuma from the Dutch National Institute for Public Health and the Environment explains,

“In this study, we bridged disciplinary differences by building an integrative data set for European surface waters, and analysing whether and in how far chemical pollution (from the applied ecotoxicologists) acts as a limiting factor to ecological status (from the applied ecologists). We found that mixtures matter: increased exposure to mixtures of 24 priority substances of Europe-wide concern implies increased limitations to maintain or reach good ecological status.”

“Applied ecologists and applied ecotoxicologists usually give separate information to water quality managers,” Posthuma outlines. “This is because applied ecology is built on field observations, whereas applied ecotoxicology is based on laboratory toxicity tests, as making chemical exposure gradients for over 350,000 substances in trade across the globe would be impracticable and unethical. Water quality managers are thus often confronted with two independent types of management advice: views from ecologists, and views from ecotoxicologists. That is not an optimal situation, especially since the ‘indicator systems’ of each discipline are vastly dissimilar,” he says.

The relationship between ecological status and mixtures of chemical pollutants. Image: Posthuma et al (2020)

Providing comprehensive and practial advice to water managers

Writing in Nature: Scientific Reports, the research team, drawn from RIVM, WEnR, Deltares and other European partners, outline how current water quality assessments might show the presence of a chemical pollution problem, but don’t diagnose its magnitude. They outline ways of evaluating the dynamics, geographies and impacts of chemical mixtures in the aquatic environment to help identify ‘hot spots’ of chemical pollution requiring management.

Crucially, they describe the relationships between chemical pollution and the ecological status of water bodies. This provides important information for water management, as Posthuma explains, “Our collaboration is important because – if successful – we can for the first time provide water quality protection, assessment and management experts with unified and comprehensive types of management information.

“Our findings are important in two ways,” Posthuma continues. “First, the outcomes show that chemical mixture exposures should not be neglected as key cause of reduced ecological status. That is: forgetting mixtures in diagnosing reduced water quality may result in ‘ill-defined measures’ which will not succeed, as chemical pollution is the hidden weakest link, limiting recovery.

“Second, the outcomes show that it is feasible to bridge the classical gap between applied ecology and ecotoxicology in such a way that the assessment of chemical pollution is now aligned with the ‘thinking’ of applied ecologists,” Posthuma says. “The approach we describe has the potential to be used worldwide.”


Posthuma, L., Zijp, M.C., De Zwart, D. et al. Chemical pollution imposes limitations to the ecological status of European surface waters. Sci Rep 10, 14825 (2020). (open access)