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Freshwater species populations fall by 81% between 1970 and 2012

October 27, 2016

Freshwater biodiversity is decreasing across the world. Image: Mike Goehler | Flickr Creative Commons

Freshwater species populations dropped by 81% globally between 1970 and 2012, according to a new World Wildlife Fund report released today. According to the Living Planet Report 2016, this freshwater species decline is more than double that observed in land (38%) and marine (36%) populations, and population declines are predicted to continue in years to come.

Habitat loss is the major cause of declining freshwater species populations, as lakes, rivers and wetlands across the world continue to be abstracted, fragmented, polluted and damaged. As ongoing research into multiple stressors tells us, freshwater habitat loss can be caused by numerous pressures caused by human activities throughout entire catchments and river basins. Over-exploitation is another key cause of species loss, as fish and bird populations are harvested for food, and reptiles and amphibians collected for the pet trade.


The new Living Planet Report findings continue the downward trend reported in the previous 2014 report (see our blog here). What is striking about the findings – in context, that the world’s freshwater species populations have dropped by around four-fifths since the year in which the Beatles split up and the first Earth Day was held – is that in many parts of the world, 1970 is likely to be an already heavily-altered biodiversity baseline from which to observe subsequent trends. In effect, the Living Planet Report is reporting an 81% decline in many freshwater populations already subject to extinctions and declines prior to 1970.

In a section focused on rivers, the Living Planet Report outlines that almost half of global river flows are subject to alterations (e.g. abstraction or channel modifications) or fragmentation (e.g. weirs and dams). As work by Christiane Zarfl and colleagues shows, such river modifications are likely to increase in the future, as around 3,700 major dam projects are proposed globally, many on previously lightly-altered river ecosystems.


The graph above shows a 41% decline in migratory fish species between 1970 and 2012. Migratory species are particularly affected by fragmentation of river courses, as their natural migration routes are likely to be blocked or impaired – which in turn affects their spawning success, and the ongoing health of their populations. The upturn in the population trend from the mid-2000s onwards may be interpreted hopefully: a result of environmental policy in regions such as Europe where water quality has improved, and fish passes have been widely installed (largely prompted by the Water Framework Directive).

However, it also highlights that the Living Planet Report is based on a reasonably small sample of global species (162 in total), and as such overall trends may be influenced by large increases in a small number of species (for example, the Atlantic salmon in UK rivers such as the Tyne), and may not adequately capture real-life global trends.

There is an inherent trade-off here, of course. Such biodiversity surveys and predictions are necessarily based on partial samples of the world’s wildlife. Despite its limitations, the Living Planet Report, gives the most comprehensive indication yet of global biodiversity trends.

According to the report, global populations of all fish, birds, mammals, amphibians and reptiles declined by around 58% between 1970 and 2012. This species loss across biomes is occurring at a rate of around 2% a year, and appears to show no signs of slowing down, despite global conservation efforts.

Marco Lambertini, Director General of WWF International stated:

“The richness and diversity of life on Earth is fundamental to the complex life systems that underpin it. Life supports life itself and we are part of the same equation. Lose biodiversity and the natural world and the life support systems, as we know them today, will collapse.”

The results of the new report were calculated using the Living Planet Index – a measure of the state of global biological diversity based on population trends of global vertebrate species. The index uses the Living Planet Database (LPD) which holds ongoing time-series data for over 18,000 global populations of more than 3,600 mammal, bird, fish, reptile and amphibian species, gathered from scientific journals, online databases and government reports. For the freshwater results, data from 3,324 populations of 881 freshwater species monitored across the globe between 1970 and 2012 was used.

Introducing the report, Johan Rockström from the Stockholm Resilience Centre frames the ongoing global species loss within recent debates over the designation of the Anthropocene – the proposed new geological epoch in which humans activity is a primary driver of Earth’s natural systems. Marco Lambertini suggests that the findings should be the catalyst for rapid and widespread cultural and behavioural shifts that work to “decouple human and economic development from environmental degradation.”

The report ends with a series of large-scale proposals for promoting sustainable development, including the transformation of economic, energy and food systems that promote unsustainable use of the environment.

Such solutions have an inherent tension – how to address rapid, ongoing biodiversity loss through national and global political systems that are often slow-moving and which  continue to promote economic development alongside (or sometimes, instead of) environmental protection. The UN’s Sustainable Development Goals are highlighted as a framework for positive global political and economic change, and the upcoming Convention on Biological Diversity COP in Mexico in December potentially provides a global platform for political leaders to respond to ongoing biodiversity loss.

Reflecting on the report, Mike Barrett, Director of Science and Policy at WWF-UK said:

“For the first time since the demise of the dinosaurs 65 million years ago, we face a global mass extinction of wildlife. We ignore the decline of other species at our peril – for they are the barometer that reveals our impact on the world that sustains us.

“Humanity’s misuse of natural resources is threatening habitats, pushing irreplaceable species to the brink and threatening the stability of our climate. We know how to stop this. It requires governments, businesses and citizens to rethink how we produce, consume, measure success and value the natural environment.

A snapshot of the world’s water quality: water pollution increases in Africa, Asia and Latin America

October 19, 2016

A polluted river near Suide, China. Image: Adam Cohn | Flickr Creative Commons

Water pollution has worsened since the 1990s in many rivers in Africa, Asia and Latin America, according to a new report ‘A Snapshot of the World’s Water Quality: Towards a Global Assessment‘ by the United Nations Environment Programme (UNEP). High levels of pathogens such as cholera and typhoid are present in around a third of all rivers in the three regions, creating a health risk for millions of people who rely on freshwaters for drinking, bathing and cleaning.

Severe organic pollution (primarily from untreated sewage in wastewater and agricultural fertilisers) impacts around 15% of rivers in Africa, Asia and Latin America, which is reported to place stress of the health and status of fish populations (e.g. through harmful algal blooms and reductions in dissolved oxygen in the water), with knock-on effects for food security of communities who rely on fishing. Both organic and pathogen pollution worsened between 1990 and 2010 in more than half of rivers in the three regions.

Moderate-to-high salinity levels were detected in around 10% of rivers surveyed across the three regions. As with the other two types of water stresses, salinity is reported to have increased in around a third of rivers in the study regions between 1990 and 2010, as a result of many rivers receiving flows of salt-laden irrigation wastewater, domestic wastewater from urban areas and mine runoff, and where water level are reduced by climate changes and/or abstraction.

Freshwater organisms often only tolerate a fixed range of levels of dissolved salts in their habitats, and increased salinity can therefore place significant stress on their health (as reported in this 2013 journal paper). Water with high salinity levels is likely to also require treatment before it is safe for humans to drink.

The UNEP undertook their study as a means of assessing progress towards improving global water security, linked to their set of 17 Sustainable Development Goals. The report highlights the central role that freshwater quality plays in water security, but notes that global assessments of water quality are still patchy and incomplete, particularly in the developing world. As such, the new report is a precursor to an intended global assesment of water quality.

The report highlights that global trends in freshwater quality are uneven, and that whilst broad improvements are being made in some – often more developed – regions (e.g. through the Water Framework Directive in Europe, and the Clean Water Act in the USA), water quality is falling in large parts of the world. Such decreases in water quality often have a range of negative impacts on human and non-human lives which are inextricably tied to freshwater ecosystems.

These impacts can be unevenly spread amongst society, too. The report suggests that women and children are particularly at risk from pathogen pollution, as in many developing countries they may be the members of society who have most contact with water through cleaning, washing and cooking.

The key driver of decreasing water quality in Asia, Africa and Latin America is the growth in non- or poorly-treated wastewater discharges into freshwaters. The report advocates improvements to wastewater treatment infrastructure where pollution from urban populations and industry is high. However, this is far from a straightforward process, dependent on appropriate finance and political will, and often more locally-specific in terms of small-scale society-environment interactions and development trends than this broad-scale assessment can cover in a detailed way.

Despite the negative trends, the report ends on a hopeful note: whilst water pollution is getting worse in Asia, Africa and Latin America, the majority of rivers in the three regions are still in ‘good’ condition, with some barely affected by pollution. Moreover, it is suggested that there is significant potential for their ongoing conservation and restoration in response to well-documented ongoing threats.

Such freshwater conservation attempts across the three regions could be strengthened by four actions, according to the UNEP authors: better monitoring of water quality; comprehensive assessments of national and global water quality to allow for locally targeted conservation; the transfer of knowledge on new approaches for water management (e.g. nature-based solutions and new treatment technologies) to developing countries; and the promotion of good governance and effective institutions to support these initiatives.

The report authors emphasise that protecting and improving water quality should be considered an integral part of environmental sustainability, as outlined by the UNEP Sustainable Development Goals. This highlights the interdependence of freshwater ecosystem health and status and human livelihoods, and the potentially wide-ranging effects that changes to water quality can have on all our lives.

Read the full UNEP report online here

Microplastics in transitional waters

October 14, 2016

75% of flounder sampled in the Thames Estuary were found to have ingested microplastics. Image: Hans Hillewaert | Flickr Creative Commons

Estuarine – or ‘transitional’ – waters are often unique and fascinating ecosystems – dynamic, liminal landscapes of brackish water between freshwater and the sea, through which adapted species such as salmon and flounder frequently migrate and move. Transitional ecosystems are often highly influenced by the tide, which can alter the amount, speed and salinity of water flows numerous times each day.

The term ‘transitional waters’ first came to prominence through the publication of the EU Water Framework Directive in 2000, which required European member states to improve the ecological status of fjords, estuaries, lagoons, deltas and rias alongside fresh and groundwaters through their river basin management plans. As Steve Ormerod and G Carleton Ray recently argued, such interconnected freshwater-marine management may have a range of positive aquatic conservation outcomes.

Transitional waters are impacted by a range of distinctive pressures and stresses. Estuaries are frequently dredged and deepened in order to allow for shipping, whilst coastal land may be reclaimed and reinforced in order to provide building land to support tourism and flood defences. Such morphological stressors can significantly alter the amount and quality of habitat available to aquatic species in transitional ecosystems.

Transitional waters are often impacted by a range of chemical stressors, too. River estuaries often accumulate nutrients and pollutants brought downstream from their catchments from agricultural, industrial and urban emissions. High nutrient levels coupled with reduced water flows in estuary waters may cause algal blooms and eutrophication, whilst high levels of deposition may cause the buildup of harmful chemicals and toxins in estuary sediments.

Microplastic pollution is an emerging aquatic stressor (we’ve previously covered it here), which is increasingly common in transitional waters. Microplastics are – as the name suggests – tiny pieces of plastic (less than 5mm in diameter) which are often used in domestic cleaning products, toothpastes and facial washes. As this blog by Winnie Courtene-Jones outlines, microbeads are so small they typically pass through water filtration systems, are incredibly prevalent (a single tube of body scrub can contain up to 360,000 microbeads), and are often hard-wearing, potentially taking decades to break down.

Microplastics pose an environmental threat largely through their accumulation: they are increasingly found in the bodies of aquatic mammals, birds, fish and crustaceans, and can increase the uptake of pollutants, be sources of toxins, and alter reproduction and feeding behaviours.

A newly published paper in the journal Environmental Pollution provides evidence on the increasing impact of microplastics on fish species in transitional habitats. A team of researchers from Royal Holloway and the Natural History in London led by Alex McGoran investigated the ingestion of microplastics by two fish species – flounder and smelt – in the Thames Estuary in south-east England.

The researchers found that 75% of flounders sampled at two different sites in the estuary had microplastic fibres in their gut. The most frequent microplastics found were red or black polyamides, with others including acrylic, nylon, polyethylene and polyethylene terephthalate.

The impact of microplastic stress on fish species depended on their feeding strategies. Where the bottom-feeding (or benthic) flounder had extremely high levels of microplastic ingestion, only around 20% of the open-water feeding (or pelagic) smelt sampled were affected.

The new study provides the first scientific evidence of microplastic ingestion in Thames Estuary fish species. It complements recent research by the Thames21 charity, which has documented widespread plastic pollution in the Thames in London, through a series of citizen science initiatives. The plastics documented in the Thames21 surveys were most frequently derived from the breakdown of food packaging discarded as litter.

In the USA, the use of plastic microbeads in cosmetic products has been banned, and there are increasing calls in the UK and Europe to do the same. Increasing evidence on the incidences and impacts of microplastics in aquatic ecosystems – such as in the new study – can only help support ongoing campaigns for their regulation.

Read the full article (open-access) in Environmental Pollution here.

Managing multiple stressors in European water bodies: reporting on MARS progress

October 6, 2016
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The MARS Work Package 6 Team at the Centre for Hydrology and Ecology in Edinburgh. Image: Christian Feld

Work in the EU MARS Project (which supports this blog) is currently gaining pace, as results from experiments and catchment modelling on the impacts of multiple stressors in European water bodies are increasingly available. Last week, a team of MARS scientists working on potential scenarios for multiple stressor management in Europe met at the Centre for Hydrology and Ecology in Edinburgh, Scotland.

Following the meeting, the team report that they now have sufficient evidence on the effects of multiple stressors in freshwater systems in Europe to provide new insights into these previously partially understood water management challenges. The next step is to synthesise the knowledge in a digestible way, to come up with practical guidance for water managers.

Such guidance would particularly focus on stressors interactions and stressors hierarchies, to support water managers attempting to mitigate the effects of multiple stresses and seeking to understand the potential effectiveness of different strategies. For example a management question might be: “in a fragmented, nutrient-rich stream ecosystem, what happens to aquatic life and ecosystem services when we remove barriers such as dams and weirs?” There are tools in MARS being developed that help detect both stressor interactions and hierarchies.

Reporting back on the meeting, MARS and CEH scientist Stephen Thackeray said, “My major feeling from the meeting was that there was a great deal of enthusiasm amongst the members of the team to not only develop our scientific understanding of the impacts of multiple stressors on water bodies, but also to translate this understanding into tools and messages that are useful and relevant for water body managers, and the wider community. We are planning some publications to outline what we feel are important next steps in this field of research.”

Another meeting participant, MARS scientist Christian Feld suggested some positive news, “Interestingly, the recently published deliverable 4.1 on the multiple-stressor analysis within the 16 MARS basin leads to the assumption that multiple stressors have a much less complicated role than expected, which may be a good message for European water managers.”

Find out more about the MARS project here.

Taking stock and looking forward in aquatic conservation

September 29, 2016

A restored section of the Rappahannock River Valley NWR, VA, USA. Image: Chesapeake Bay Program | Flickr Creative Commons

Last week we covered a new opinion piece by Steve Ormerod and G Carleton Ray which outlined emerging topics and approaches for aquatic science-policy dialogue. This week, the piece has been published as part of a new 25th anniversary special issue of the journal Aquatic Conservation: Marine and Freshwater Ecosystems, which features a range of articles taking stock of the current and emerging themes and trends in aquatic conservation.

As the issue editors Philip J. Boon and John M. Baxter outline, the pressures faced by aquatic ecosystems have largely intensified since the journal’s founding in 1991, and policy and management responses have developed in tandem. Pressures from urban development, hydropower, agriculture and industry have worsened across Europe in that time, whilst emerging topics such as climate change and ocean acidification, river basin management, ‘people and nature‘ conservation, ecosystem services and economics, conservation genetics and invasive alien species have become common aquatic research themes, often through new multidisciplinary approaches. A set of overarching European policies addressing aquatic environments have been set in the same period, including the Habitats Directive, Floods Directive, Water Framework Directive, Marine Strategy Framework Directive, and the EU Regulation on Invasive Alien Species.

So, what is the current state of play in aquatic conservation, and how might things change in coming years? The articles in the special issue address a range of topics in response to these questions.

Fish populations – both in freshwaters and in the sea – are chiefly threatened by habitat loss and degradation, invasive species, pollution and over-exploitation, as Angela Arthington and colleagues report, pressures which are all potentially intensified by climate change. Size matters, too: smaller fish are generally threatened by their habitats becoming increasingly isolated and fragmented; whereas larger species are most often threatened by over-fishing. The authors suggest that expanded conservation measures (such as protected areas) which ideally encompass both freshwater and marine environments and reduce human pressures on fish populations – particularly at migratory ‘bottlenecks’ such as estuaries – are needed to mitigate ongoing ecological damage.

Invertebrates are some of the most important, but under-studied and protected, organisms in aquatic ecosystems, according to Kevin Collier and colleagues. The authors report that global assessments of 7857 freshwater invertebrates and 2864 marine invertebrate species (of which a third were reported as lacking suitable data), the most threatened taxa were those with poor dispersal abilities and  local endemism, for example many gastropods, crayfish and mussels. Invertebrate populations are richest in freshwater springs and subterranean hydrological systems, and in marine coral reefs and lagoons; but increasingly impacted by pollution, over-exploitation, habitat degradation and  invasive species. The authors argue that to increase political and conservation engagement with aquatic invertebrates, work needs to be done on better understanding their global diversity and extinction threats.

Michael Gangloff and colleagues review a set of emerging threats to aquatic ecosystems – as in the previous papers, these are habitat loss and fragmentation, pollution, over-exploitation and invasive species and diseases – and suggest a range of potential mitigation strategies, ranging from more traditional legislation to newer nature-based solutions such as green infrastructure in cities for buffering pollutants. The global spread of one of these key threats –  invasive species – is investigated by Elena Tricarico and colleagues, who examine data from three regions with different climates and ecological histories – temperate Europe, tropical Asian Hong Kong, and Neotropical Brazil. They find that freshwaters are more susceptible to invasion than marine habitats, but that (as for invertebrates in the Collier et al study) detailed and up-to-date national and regional inventories of invasive species presence and impact are lacking in many areas.

As Gangloff and colleagues outline, there are a range of  management approaches used in mitigating stresses on aquatic ecosystems. One key approach is habitat restoration. In their paper, Juergen Geist and Stephen Hawkins demonstrate how restoration approaches are increasingly incorporating concepts from advancing ecological theory, such as the importance of (re)building ecosystem processes, connectivity and resilience. They suggest that a key balance to be struck in restoration is incorporating such concepts into adaptive management, whilst at the same time setting clear goals for the restored ecosystem’s trajectory, which are important for leveraging political and public support.

Wetlands are often a focus for restoration management as they are often hotspots for biodiversity, valuable natural filtration systems for pollutants, carbon sinks and flood buffers. However, the contribution by Richard Kingsford and colleagues suggests that wetlands remain ‘conservation’s poor cousins’ as whilst they cover between 5–10% of the world’s land surface, around 70% of wetland areas are highly damaged and degraded. As with reports on other aquatic ecosystems and species in this collection, Kingsford and colleagues report that the distribution and health of global wetland ecosystems is poorly mapped. As such, they suggest that wetland research should be prioritised by conservationists as many wetland ecosystems face increase pressures from water abstraction, draining and conversion into agricultural land across the world.

Three more papers consider the importance of human value systems in guiding aquatic conservation efforts. Kenneth Irvine and colleagues outline the challenges of conserving tropical aquatic ecosystems which are often highly biodiverse, yet data poor. They highlight the potential of applying the ecosystem service framework through local and national institutions to aim for sustainable human use of aquatic ecosystems, based on ongoing monitoring, reporting and accountability of management.

Andrew Boulton and colleagues that the ecosystem service framework should be used to complement – rather than replace – existing conservation and restoration goals for biodiversity and ecosystem health. They outline four recommendations for setting ecosystem service-based goals for conservation:

  • explicitly listing and evaluating the sets of ecosystem services to be conserved;
  • identifying potential trade-offs arising from their conservation;
  • specifying time frames for ecosystem service conservation (or enhancement); and
  • forecasting how conservation strategies might benefit ecosystem function, service flow and public benefit.

Stefan Gelcich and Jay O’Keeffe draw from emerging research on social perception of conservation initiatives as a means of illuminating the tangled interconnections between people and the environment, and the importance of public and policy perceptions of the natural world in designing, framing and legitimating conservation and restoration work. And finally, Steve Ormerod and G Carleton Ray conclude the special issue with their piece, arguing for increased attention to ecological resilience and linked freshwater-marine systems in aquatic conservation and restoration policy.

Your can read the full 25th anniversary issue here.

Connecting the shifting currents of aquatic science and policy

September 23, 2016

Bridging science and policy: the River Taff in Cardiff, Wales, which has been restored in recent decades. Image: Andrew Rees | Flickr Creative Commons

Dialogues between environmental scientists and policy makers form key cogs in modern conservation and restoration practices. Scientific research can inform and support ‘evidence-based’ policy making, whilst policy makers will often prioritise and fund socially and environmentally pertinent research topics.

The multiple ways in which aquatic ecosystems support and shape human lives makes productive science-policy dialogues about their management and protection particularly important. As Prof Emily Stanley articulated in a recent interview, aquatic ecosystems across the world are increasingly impacted by human pressures, which are causing ever more complex and uncertain ecological impacts (such as state shifts or multiple stressor interactions, for example), and which may be described under the broad umbrella term of the ‘Anthropocene’.

As such, there is a pressing need for science-policy dialogues to help form adaptive policy and management responses to such new ‘natures’, to try to build in ecosystem resilience to emerging treats to climate change and to conserve highly-pressurised biodiversity.

In this context, a new opinion piece by  Steve Ormerod from Cardiff University and G. Carleton Ray from the University of Virginia argues that aquatic scientists can play a pivotal role in identifying gaps, failings and emerging trends for policy and regulatory practices. Writing in Aquatic Conservation Marine and Freshwater Ecosystems, the authors identify the concept of resilience as an organising principle for science-policy responses to emerging human pressures. Promoting environmental resilience provides a means of bringing new ecological concepts, the importance of an ‘ecosystem approach’, and the value of ecosystem services and natural capital further into policy making.

Two major pieces of aquatic legislation, the US Clean Water Act (1972), and the EU Water Framework Directive (2000) were significantly shaped by scientific evidence, both in their design and in ongoing monitoring and enforcement. However, Ormerod and Carleton Ray argue that there is still untapped potential for aquatic scientists to help improve and develop environmental decision-making in an ever-changing world.

New and novel science-policy practices are emerging from one of Europe’s smallest countries. In 2015, the Wellbeing of Future Generations Act was passed by the Welsh government, making the promotion of environmental resilience a key aspect of public body sustainability strategies. Through the Act, targets for environmental resilience – promoted through reduced greenhouse gas emissions, soil and water body restoration and biodiversity conservation amongst others – are set alongside social, economic and cultural goals. Another Welsh policy, the Environment (Wales) Act of 2016 has set the ecosystem approach – i.e. a focus on the health, structure, function, condition and service provision of ecosystems in all decision-making – directly into national legislation.

Ormerod and Carleton Ray highlight that effective environmental management and conservation action often requires long-term measures, which in turn require political commitments beyond the fixed-term cycles of government. Here, they suggest the importance of analysing and communicating the results of long-term data sets on freshwater ecosystems, as a means of demonstrating the value of long-term perspectives and large-scale policy interventions.

The authors suggest that aquatic science is not only important in shaping the form of environmental policy, but also in evaluating its ongoing implementation. For example, Britain’s urban rivers have largely become cleaner and healthier since the implementation of the EU Wastewater Treatment Directive in 1991; changes which have been tracked to by ongoing scientific monitoring programmes, which now indicate that there may be associated benefits in how the river ecosystems adapt to future climate change.

Aquatic scientists should engage more fully in policy arenas, in order to identify and fill gaps in existing environmental policy and regulation through good evidence and communication, argue Ormerod and Carleton Ray. An example of such engagement is in the MARS project, which identified the lack of consideration given to aquatic multiple stressor impacts in the EU Water Framework Directive, and is now midway through a large research project to provide policy-relevant results to address this deficit.

However, the authors argue that there remains significant potential in acknowledging concepts of environmental dynamism and complexity in policy and management globally, particularly the connectivity between land and water systems and between transitional waters where fresh and marine waters interact.

Ormerod and Carleton Ray’s concluding points are far-reaching and perceptive:

In sum, we are proposing that freshwater and marine conservation biologists work together towards an expanded, systemic approach to aquatic ecosystems to incorporate interaction across the whole land-freshwater-ocean nexus – both in scientific terms and onward into policy… expanding the role of science in aquatic policy and legislation requires fuller recognition of where aquatic conservation now stands in a changing world. It is not our intention to offer a prescriptive approach to any aspect of the science-policy interface, but rather to point out the nature of the present-day challenge.  The 21st century is much different from preceding centuries. Aquatic issues are converging, requiring a systems approach and an improved understanding of how physical and biological processes interact under an accelerating pace of environmental change.

A key challenge, then, for aquatic science-policy dialogue is not only to scientifically understand the emergent properties of a changing world, but also to provide convincing arguments for the importance of nature-based solutions for entwined social, economic and environmental issues through policy-making.

For Ormerod and Carleton Ray, this is a collaborative process, concluding that, “Together, science and policy must spur each other onwards.”

Stream Ecosystems in a Changing Environment: an interview with Emily Stanley

September 13, 2016
An upland stream in the English Lake District. Image: oatsy40 | Flickr Creative Commons

An upland stream in the English Lake District. Image: oatsy40 | Flickr Creative Commons

Stream ecosystems form important parts of many landscapes; slim threads of moving water often high in biodiversity (sometimes in the most surprisingly developed places), nutrient and carbon cycling processes and recreational and aesthetic appeal. However, streams across the world are increasingly threatened by pressures including pollution, climate change, abstraction, the spread of invasive species, fragmentation and channel alterations.

A new book ‘Stream Ecosystems in a Changing Environment‘, co-edited by Jeremy B Jones of University of Alaska Fairbanks and Emily H Stanley of the Center for Limnology at the University of Wisconsin provides a timely, cutting-edge perspective on the response of stream ecosystems to environmental change.  We spoke to Professor Stanley to find out more.

screen-shot-2016-09-13-at-15-34-20Freshwater Blog: Could you tell us a little about ‘Stream Ecosystems in a Changing Environment’, its aims, contents and contributors?

Emily Stanley: The book was inspired by the 2000 book ‘Streams and Ground Waters edited by Jay Jones and Pat Mulholland. Jay and I wanted to provide an up-to-date resource for stream ecologists, and we also very much wanted to honor the memory of Pat Mulholland. Pat was such an influential scientist in the field, but more importantly, a friend, mentor, and truly exceptional and kind human being. We all miss him very much.

As the title indicates, the ‘Streams and Ground Water‘ book had emphasized groundwater and how it affected/interacted with streams and rivers. In this book, we wanted to broaden the scope and consider a range of topics from hydrology, geomorphology, and ecosystem ecology. And in particular, we wanted to bring things into the 21st century and recognize the interactions between humans and the environment. That included presenting new concepts and understanding that have been gained by studying human-dominated streams, and conversely how basic scientific concepts have been used to study these environments.

We wanted the book to be useful for both researchers and managers, and we had learned from the ‘Streams and Ground Waters‘ experience that many of our colleagues found the book to be particularly useful for graduate students. So providing a strong and updated resource for early career scientists was also a major goal.

The contributing authors are a great bunch – and include a mixture of ecological, geomorphological, and hydrological experts. Jay and I invited people to contribute chapters because of their leadership in the field and their creative approaches to their science. Some of these authors come at ecological questions from physical/earth science backgrounds, and bring a perspective that may be new for many stream ecologists. We view this as one of the strengths of the book.

A seasonally dry stream in a forest in Missouri, USA. Image: Kyle Spradley

A seasonally dry stream in a forest in Missouri, USA. Image: Kyle Spradley

What are the big themes and challenges in stream ecology?  What are some of the most recent advances in our understandings of stream ecosystems, and where are there still gaps to be addressed?

I think some of the challenges and opportunities that have been unfolding over the past 10-15 years involve understanding streams and rivers at larger spatial scales, learning how to take advantage of new technologies such as automated sensors for measuring water chemistry, and providing information needed to understand and managing streams in rivers in the context of long-term changes in climate, land use, and water use and regulation.

Not surprisingly, there have been lots of major advances in stream and river research over the past decade – often in direct response to these broad challenges. We’ve seen substantial growth in the breadth and capacity of models and statistical methods, more studies of streams and rivers at continental and global scales, new insights from research that takes advantage of the automated sensors as well as from new tools for investigating organic matter composition – as just a few examples.

Overall, we have become far more quantitative in our science. Many of the chapters provide a perspective on the state of the art for new approaches and accompanying insights provided by new tools and models (many of which were developed by the chapter authors themselves). These include, for example: providing a thorough overview of models used to quantify metabolism that make use of data from automated sensors and what new insights we’ve gained from these new approaches, a new quantitative framework for nutrient spiraling that integrates nitrogen and phosphorus cycles, or a detailed consideration of the challenges associated with understanding streams and larger scales – accompanied by the introduction of a new analytical strategy for scaling up results generated from small, reach-scale studies to drainage systems distributed across landscapes.

As these tools/models/frameworks emerge, I suspect that over the next decade we’ll continue to see more tool and model development, but we’ll also see these new strategies put to work. While we’ve made great strides in understanding riverine processes at large scales, I think there are still substantial opportunities in this realm. And clearly much of this work includes the science for dealing with complicated management problems. Gaps and emerging challenges in these areas are particularly well laid out the final three contributed chapters.

A forest stream in the Czech Republic Image: Dominique Cappronnier | Flickr Creative Commons

A forest stream in the Czech Republic Image: Dominique Cappronnier | Flickr Creative Commons

In your synthesis, you note that the world has entered a new geological era, the ‘Anthropocene’ where human activities take on the magnitude of natural, geological and climatic processes in affecting Earth systems.  Interestingly, you state that “Nowhere is this truer than in aquatic ecosystems”.  How is the Anthropocene era evident in aquatic ecosystems?  And does the naming of the Anthropocene era change anything in how we study, understand and manage freshwaters?

The simple reality is that freshwaters have always been a focal point for human development, and as the world population continues to grow, we continue to make demands on these distinctly finite resources. In blunt terms, humans have been very successful plumbers. We continuously try to compensate for the fact that fresh water is unevenly distributed in space and time, and one of the emerging hallmarks of the Anthropocene is the human alteration of the global hydrologic cycle. And accompanying these movements and delays of freshwater flows via dam construction, irrigation, groundwater withdrawals, inter-basin transfers, substituting in ditches or drainage systems for natural channels, and so on are distinct changes in water quality and in ecosystem processes.

Because fresh water is a relatively limited global resource, the conflicting challenge of providing sufficient water of sufficient quality for human needs while maintaining freshwater ecosystems has sharpened. Trying to manage this conflict in a sustainable fashion has clearly been inspiring research over the past 1-2 decades, and we hoped to capture some of this work in the book.  I think by putting a label on it – the Anthropocene – underscores the value and urgency for data and research needed to sustain freshwaters.

While many people have reflected on this point before – and more elegantly than me! – I’m struck by the transition that has occurred over my scientific career, and even over just the last 10 years. As a graduate student, research on topics such as nutrient cycling or surface-groundwater interactions were purely academic in nature and most researchers worked in relatively protected places to minimize confounding and annoying effects of human influence. I can’t even remember hearing talks on, for example, urban streams. Now, several years later, this basic research continues – and must, because we need to understand the fundamental workings of ecosystems.

But there has also been a huge shift to working in human-dominated ecosystems and to ask questions about the nature of this human influence. This includes incorporating a forward-looking perspective in science and management – how do we manage freshwater ecosystems and meet human needs for water now, a decade for now, or a century from now? In short, as researchers and managers, we are rising to the challenge of the Anthropocene.

An urban stream in Colorado. Image: Mick Chester | Flickr Creative Commons

An urban stream in Colorado. Image: Mick Chester | Flickr Creative Commons

Following on from the last question, I see an underlying theme of the book as being how stream ecology can have intellectual and practical interchanges with environmental policy and management in an era of increasing uncertainty.  How can these interchanges be most productive, do you think? What can aquatic ecology offer in terms of addressing social needs and environmental problems?

This is a great question, and one that is tough for me to answer! As I mentioned above, there has been a lot of growth in the field over the past decade in terms of developing new tools, models, etc. that are providing us with new power and new opportunities to ask questions about how streams and rivers work, and how best to manage these ecosystems. And as we tune in to the challenge of freshwater sustainability, I think it’s safe to say that most researchers are interacting with managers and policy-makers far more often than in the past.

Again thinking back on my own history, interactions with these groups was almost completely absent until the last 15 years. Now it is a fundamental part of my work, and we routinely include agency researchers and managers in our projects. That said, I think we are all still learning how to produce good science and useful science, and how to be most effective at informing decision-making with scientific understanding.

It’s great to see some emerging behaviors and practices becoming routing that should help facilitate these interactions. These including things such as data sharing and open data access, training opportunities for scientists to improve our communication skills with non-scientific audiences (journalists, policy makers, local stakeholders, etc.), and research initiatives that explicitly embrace integrated social-ecological approaches and questions.

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