The UK Lakes Portal
Wastwater in the English Lake District. Image: Richard Walker | Flickr Creative Commons
Scientific data on over 40,000 UK lakes has been recently brought together into one open-access online portal. The UK Lakes Portal is the result of over 10 years work coordinated by the Centre for Hydrology & Ecology, and provides a comprehensive overview of the geography and ecology of UK lakes.
The portal contains physical, environmental, and water chemistry data compiled from an extensive set of sources over many years and is integrated with the National Biodiversity Network hub for biodiversity data. In addition, new data is constantly being added by citizen scientists using iRecord.
The portal gives information on geography of each lake (depth, surface area, location, altitude) which is linked to data on its biodiversity and information on the wider catchment that feeds it. The biodiversity data is part of a comprehensive new freshwater species list for the UK, which also includes information on non-native species.
In linking each lake to its wider catchment, the portal provides a valuable tool for scientists and policy makers advancing landscape approaches to freshwater research and management. In addition, by presenting the information in a clear and engaging form, the portal is likely to be of use to anyone interested in freshwaters: a comprehensive and interactive ‘wiki’ for UK lakes, if you like.
Professor Rosie Hails, Director of Biodiversity and Ecosystem Science at the Centre for Ecology & Hydrology, said:
“The UK Lakes Portal is a product of excellent collaboration between the Centre for Ecology & Hydrology, University College London and the UK conservation and environment agencies. This is one of many natural capital portals that we hope to develop in the future as an evidence base to support policy and decision making.”
Laurence Carvalho, Freshwater Ecologist at the Centre for Ecology & Hydrology (and a member of the MARS project) said:
“The UK Lakes Portal is a fantastic new resource for both scientists and the local citizen scientist interested in finding out more about their local lake and the biodiversity found within it. It has the potential to help us value the benefits we gain from UK lakes and answer questions such as how well connected is biodiversity across UK Lakes and how fast are invasive species spreading across UK freshwaters?”
Dipper from the Water of Leith
Dipper on the Water of Leith, Edinburgh. Image: Kris Kubik
The Water of Leith valley runs like a thread of blue and green from the Pentland Hills outside Edinburgh and through the city to the sea at Leith. It is a corridor of urban biodiversity: a place where brown trout, kingfishers and otters live within just a mile or two of the crowds and traffic of Princes Street.
One of the Water of Leith’s most charismatic residents is the dipper. This small brown and white bird – known for its ability to ‘dip’ and swim underwater – relies on fast-flowing and unpolluted rivers. Their presence on the Water of Leith is testament to years of conservation and restoration activity on the river following decades of industrial pollution.
Kris filming in the field.
The Water of Leith’s dippers have also caught the eye of an Edinburgh filmmaker and become the stars of a new BAFTA nominated film on the river. Kris Kubik, a film and TV student at Edinburgh University tracked dippers along the river over a number of months to capture stunning documents of their ecology and behaviour. Kris even built a hide at the waterside in order to film dippers in their natural habitats, and his film ‘Dipper from the Water of Leith‘ is currently being shown at film festivals ahead of a wider release.
We spoke to Kris to find out more about tracking and filming dippers along this diverse urban river.
Tell us about the background and inspiration for the film: why the Water of Leith, and why the dipper?
The idea to create a short film about the dipper appeared quite long time ago. When a few years ago I came to Edinburgh from Poland, the first thing I noticed in the city – and more generally in Scotland – were the large populations of dippers.
For me, it was something both amazing and really unique. In my country, this bird is not common and can be found only in some parts of the Tatra mountains, the Sudeten and Beskidy mountains. And then it occurred to me that someday I would like to be able to make a film with the dipper in the lead role.
How did you go about researching the dipper, its ecology and behaviour? And did this research influence how you approached shooting the film?
The dipper caught my attention, mainly because of the niche in which this unique and complex species live. Over the years, I recorded some facts about this bird. But it was general knowledge, so I felt that I need to explore its ecology in more depth. So I had to find researchers who studied the species for years. In this way I contacted, among others, ecologists Steve Ormerod and Peter Mawby.
The first step for research was to gather as much information in understanding the dipper’s behaviour and its habitat. The second step, importantly for me, was to try to look closer at my protagonist by spending all my spare time in the same habitat as the dipper: spending hours observing their lives and habits. Over the course of many months of research, I realised that I could film the dipper in a way that could tell a story.
Dipper from the Water of Leith uses underwater cameras to give a ‘dipper’s eye view of the river’ Image: Kris Kubik
The film is beautiful, and features a range of perspectives on/around/from the dipper. Tell us about the filming process and how you immersed yourself (quite literally) in the dipper’s world. What were some of the logistical challenges of shooting in the bird’s land (and water) scape?
It may sound quite humorous, but the main challenge for shooting footage of the dipper, wasn’t any wild animal or even the weather, but much simpler: avoiding walkers! It turned out that much of the land where I wanted to film and research the dipper was often busy with people and dogs.
I think that’s the nature of The Water of Leith: people love to walk there. And that’s fine, up to the point where you start to observe species through the lenses, and on a busy river, is impossible to reach dippers.
Therefore, it was important to find a location that would be well away from people. Fortunately, I managed to find a place near Edinburgh where I built a hide, so that I could blend in with nature, sit all day and not to be disturbed by anyone.
Dippers aren’t the only bird species on the Water of Leith… Image: Kris Kubik
Did making the film give you any new perspectives on the Water of Leith and its inhabitants? If so, how?
Making of film about nature gave me an amazing opportunity to dive into the world of wildlife. When you starting working on a project you have some rough idea and some basic knowledge about the whole subject. When you go deeper and deeper, beyond and above all of the surfaces,you start to see more details of the bird and its habitat.
It’s similar to the experience of seeing the bird in the distance: you know it’s shape and plumage. But when you start drawing the bird, you focusing on more details, and you discover a new dimension of the individual you are studying. It’s quite similar but obviously it’s not the same.
After many months spent in the wild under difficult weather conditions, you become a part of the landscape. You not only see the trees, you see a moss on them, single leaves, shapes, shadows, reflections, the way they are absorbing light and many other things. When you see the river, you don’t see just running water with rocks. You are see the river bed life, fishes, insects. Your senses become sharper. Your vision is more profound, and at some point you begin to identify yourself within nature.
A heron in the river margins. Image: Kris Kubik
The film has already been nominated for a Scottish BAFTA New Talent award – congratulations – will it be shown anywhere and will we be able to see it online?
Thank you so much, I’m so pleased by this nomination, this really means a lot to me. In my view, camera work is a really crucial part of wildlife filmmaking and it requires a lot of hard work and development.
At the moment, Dipper from the Water of Leith is showing in festival circles so for now, it isn’t available in full online (but see the trailer above). This project is really important for me, and my goal is to create a further length monograph film about the dipper.
Based on my short film, I will try to raise funds to create a more accomplished story about this species. I’m researching new locations, developing my camera skills and collaborating with some researchers. I finished a shot-list and most of the location hunting, and I’m in the process of filling up all the necessary documentation.
I will be honest with you, I can’t wait to get back to filming the dipper again: telling and sharing stories about the beauty of this unique species.
A ruffled dipper. Image: Kris Kubik
Lake Poopó, Bolivia with water in 2013 (left) and dry in 2016 (right). Image: Jesse Allen/NASA
Lakes across the world are drying up, largely due to water abstraction, according to new research.
Bolivia’s second largest lake, Lake Poopó has recently dried out to become a 2,700 km2 salt pan. This dramatic loss of an important freshwater ecosystem is due to a combination of silting and water abstraction in the Desaguadero River, which feeds Poopó, and ongoing climate change (temperature have risen 0.7 degrees in the Andes over the last 70 years).
A recent article in the New Scientist brings together evidence from across the world to suggest that Poopó’s vanishing act is not an outlier event. Instead, new research suggests that lakes across the world are shrinking or disappearing – particularly in arid regions – with significant effects on the biodiversity and human populations that they support.
Research by MARS scientist Meryem Beklioğlu from the Middle East Technical University in Ankara, Turkey indicates that lakes on the Central Anatolian Plateau shrunk in size by around half between 2003 and 2010. One Turkish lake, Lake Akşehir, has completely dried up, resulting in the extinction of the Central Anatolian Bleak. Two other endemic fish species, the Eber Gudgeon and a local dace (Leuciscus anatolicus) are now critically endangered.
Many of Turkey’s lakes are shallow, which makes them vulnerable to increasing water abstraction for drinking and irrigation to meet the needs of growing populations in a warming climate. As lakes shrink, their salt levels rise and they become vulnerable to nutrient pollution and eutrophication, placing great stress onto freshwater biodiversity.
Beklioğlu uses computer models to predict how Turkish lakes will fare in the future, and suggests that at current rates of water abstraction, one of the largest lakes in the region, Lake Beysehir, will be completely dry by 2040.
Speaking to the New Scientist, she said “This water is critical for irrigation and for the local economy, but right now we are cutting off the branch we are sitting on.” To address these problems, Beklioğlu highlights the pressing need for sustainable approaches to water management in the region.
MARS scientists studying multiple stressors in Lake Beyeshir, Turkey. Image: METU Limnology Laboratory
MARS scientist Erik Jeppesen from Aarhus University in Denmark suggests that shrinking lakes across southern Europe, the Middle East and central Asia are the result of climate change and growing demand for water.
Speaking to the New Scientist, he said “This region is experiencing a drier climate now, which is also driving increased water extraction. Ultimately, the drying of the lakes along with the loss of groundwater and salinisation, will make the land less viable for agriculture in this region. This will put significant pressure on northern countries to produce more food, leading to deteriorating water quality in northern lakes due to increased fertiliser run-off entering lakes.”
Freshwater life under the microscope
Is there life in a drop of water? Using microscopes, freshwater scientists can help us see the often curious and beautiful array of microscopic life that lives – largely unnoticed – in almost every drop of water on Earth.
MARS scientists Steve Thackeray from the Centre for Ecology and Hydrology has created a new film collecting microscopic footage of the organisms collected in sampling in lakes across the North of England.
The film ‘Freshwater Wildlife Under the Microscope‘ reveals an array of organisms with fascinating forms and patterns. Short descriptions for each organism allow us to get to grips with the important roles they play in our freshwater ecosystems.
Accompanied by a minimal, ambient soundtrack, the film is an excellent introduction to the curious freshwater organisms that support our rivers and lakes, but are usually invisible to the naked eye.
Meet the MARS team: a selection of audio snapshots
Snowy mountain cabins above Fulda. Image: MARS Project
At the recent MARS meeting in Fulda we spoke to a number of project scientists to ask them about their work and their part in the project.
We recorded short audio ‘snapshots’ of each conversation to give a flavour of some of the themes of the week, and the people behind MARS. The results are embedded below to stream and download – enjoy.
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The science and policy of multiple stressors: four reflections from the MARS Mid-Term Meeting
Daniel Hering welcoming attendees at the MARS mid-term meeting in Fulda. Image: MARS
Last week, the MARS project held its mid-term meeting in Fulda, Germany. The meeting brought together project scientists, water managers and policy makers to discuss ongoing research into freshwater multiple stressors.
Below are four audio reflections on the meeting.
The first is from project leader Daniel Hering, who gives an overview of the progress MARS has made on the science and policy of multiple stressors.
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Next, Bas van der Wal of water management agency STOWA in the Netherlands tells us about his golden rules for translating freshwater science into policy and management using ‘ecological key factors’.
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We speak to Rolf Altenburger from the Helmholtz Centre for Enviromental Research (UFZ) in Leipzig, Germany about freshwater pollution and the SOLUTIONS project.
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Finally, Anne Lyche Solheim from NIVA in Norway tells us about the challenges of researching multiple stressors and creating dialogue with water managers and policy makers.
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Kathleen Carpenter: the mother of freshwater ecology
Cwmystwyth a metal mining area near Aberystwyth in Wales. The River Ystwyth to the left of the picture was heavily polluted by the mines. Image: W. L. Kovach
In this guest post for International Women’s Day, Dr. Catherine Duigan draws from her research on Dr. Kathleen Carpenter (1891-1970), the ‘mother’ of freshwater ecology, to suggest insights and wisdom that Carpenter might offer to new generations of freshwater scientists.
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Image of Kathleen Carpenter supplied by Piotr F Piesiewicz
I am an ecologist born in the late 1800s, and I wrote the first British freshwater ecology textbook, Life in Inland Waters (1928). Julian Huxley, the textbook series editor, recognised that the ‘Cinderella charms’ of freshwater biology were at the time being ‘eclipsed by those of her elder and more ample sister, Marine Biology’. My textbook was developed to support undergraduate education in the field and redress the balance.
Fortunately, I was also born at a time when the rights of women were starting to be acknowledged. I attended and worked at universities in Europe and the US which pioneered the education of women, including the University of London, University College of Wales at Aberystwyth and Radcliffe College in Massachusetts.
When I arrived at Aberystwyth in 1911, some of the local river systems were devoid of life. My research linked the lack of invertebrates in these rivers to metal mining activity and demonstrated the way that fish gills were damaged by pollution, which often led to suffocation. My textbook described the different natural zones in rivers and lakes, and recognised the adaptations of different biota in aquatic ecosystems. I also recorded glacial relict species in British streams. Students at Aberystwyth to this day continue to discover my papers as part of literature reviews and the river research continues.
What would be my advice to the next generation of female freshwater ecologists?
Do something you love and be passionate about it
Passion helps to inspire the next generation. I gained a huge amount of aesthetic and scientific pleasure in describing and observing the organisms in rivers and lakes. In the preface to my textbook I talk about “a world of infinite beauty, infinite variety, infinite charm”. Showing passion makes people take notice and realise that some things are special.
Work hard at communicating your research
I was a communicator from the early days of my career as an assistant lecturer at Aberystwyth University. The textbook provided a story which lasted several decades and was supplemented by a series of scientific papers in a range of journals. I was also a regular contributor to conferences in Britain and abroad. It was amusing to generate newspaper headlines about ‘cannibal salmon’ after presenting a dietary study and referring to a spent male which had potentially consumed his own offspring. Today I would be using social media! #freshwaters #pollution #Faberystwyth!
Play a part in your professional learned societies
I was a member of several scientific societies, including the British Association for the Advancement in Science, Sigma Xi and the British Ecological Society. Scientific meetings provide incentives to produce high quality work and opportunities to travel and develop a professional network. Build your confidence by talking to the leaders in your field.
Travel and gain experience
In the early part of the 1900s freshwater science was developing in Europe and North America. I sailed across the Atlantic several times, travelling alone with up to $100 dollars in my pocket. One particularly memorable voyage to a scientific conference in Toronto had many eminent male scientists on board. I lived, taught and undertook research in British and American academic communities.
Take time to encourage other women.
I would be delighted to be considered a role model for young women scientists. In the US I was a member of the Delta Epsilon Sigma Society which was founded to provide women with an environment where they could network and interact with peers in informal and powerful ways that male scientists could. I still remember the tea party at Illinois State University before the meeting of the American Association of University Women in October 1928 where I contributed as a guest of honour to the discussion on British Universities.
Be generous to your students (and staff), they will reward you too.
A good relationship between teacher and student cultivates a common understanding and stimulates learning. One of my recorded awards was to have been elected to the Honor Society by the undergraduates of Washington College. The production of a textbook early in my career was a gift to future students. Take the time to talk and share knowledge.
Interdisciplinary research is vital for advancing our understanding of the world
In Life in Inland Waters I made the case for interdisciplinary research combining approaches from chemistry and biology to assess water quality. I would like to be contributing to current research into the links between the natural environment and human well-being, because I believed time spent by city workers on the riverbank was good for health and a quiet mind.
Speak more than one language
In the early decades of the 1900s freshwater science was dominated by continental European studies. Fortunately I was well placed to interpret them and present them to a wider audience because my father was German, and I had a working knowledge of French. Knowing more than one language increases your accessibility to information, especially indigenous knowledge, and can open up collaborative opportunities. Sign up for that class in Spanish or Welsh!
Demonstrate the practical relevance of your work
Nature is important in its own right – there to be enjoyed and protected – but today I appreciate that the final chapter in Life in Inland Waters reads like an early attempt to form the concept of ecosystem services. I thought it important to demonstrate the wider socio-economic context of my work: from the financial value of salmon sold at Billingsgate market in London to the human health risks of dirty water. My research informed the remedial efforts of a local River Pollution Committee. Perhaps this can be considered an early example of research having science-policy impact.
Wear sensible clothes when you do fieldwork and be safe
Can you contemplate the prospect of sampling a river whilst wearing a long skirt?! Fortunately for me, following the First World War women were able to adopt more practical, working clothes, including trousers. I can endorse research in the history of science which suggests that the development of sports clothing helped to make fieldwork socially acceptable for women ecologists. Working in an aquatic environment comes with risks, and you need to embrace health and safety requirements. Be sensible.
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Dr. Catherine Duigan was educated at University College Dublin where she did a Ph.D on zooplankton in Irish lakes. Her international research background has included working in the USA, France, and Africa. She did post-doctoral research at Aberystwyth University and was the only woman to take part in two expeditions to the High Atlas Mountains in Morocco.
Catherine then went on to follow in the footsteps of Kathleen Carpenter with a professional interest in freshwater ecology in Wales, including writing and co-editing The Rivers of Wales book. She is currently leading a group of technical specialists covering aquatic and terrestrial environments at Natural Resources Wales in Bangor. As an honorary lecturer at Bangor University she contributes to teaching modules on freshwater ecology. She is also a STEM Ambassador.
Catherine considers bringing attention to Kathleen Carpenter’s history a very welcome obligation. Women scientists need to tell each other’s stories.
River Torridge in Devon, a sample site for mayflies in the study. Image: alexwhite | Flickr
Polluted rivers with low oxygen levels are more susceptible to the harmful effects of climate change, according to a new study co-authored by MARS scientist Professor Steve Ormerod.
Researchers from Cardiff University and Radboud University in the Netherlands led by Wilco Verberk used laboratory studies and over 42,000 samples from UK rivers to show that two common mayfly species are less able to tolerate rising water temperatures in polluted rivers with low oxygen levels. The breakdown of organic pollutants such as sewage and farm run-off uses oxygen, meaning that polluted waterways often suffer severe drops in dissolved oxygen levels.
The study, published in Global Change Biology (open access), adds to the growing evidence on the influence of multiple stressors in shaping how freshwater ecosystems are likely to respond to climate change. Specifically, it suggests that reductions in water pollution may help increase the resilience of freshwater biodiversity to the effects of future climate change.
“Cool water insects like many mayflies are in triple jeopardy in warmer, polluted waters,” explains Professor Ormerod. “First, at higher temperatures, water can hold less oxygen. Secondly, insects need more oxygen to keep pace with their needs as temperatures increase. Thirdly, oxygen is used in the breakdown of organic pollution, with this effect occurring most rapidly in warmer waters. These three effects mean that warm polluted waters are the worst combination.”
Blue-winged olive (Serratella ignita) Image: Wikipedia
In laboratory studies, the team found that mayflies such as the green drake (Ephemera danica) and the blue-winged olive (Serratella ignita) were able to survive temperatures 3-5 °C higher where oxygen levels were high, compared to where they were depleted. Hypoxia – or severe oxygen depletion – lowered lethal water temperature limits by roughly 5.5 °C and 8.2 °C for the green drake and blue-winged olive respectively. Mayflies were used as bioindicators in the study as they are common and ecologically important features of many river and stream ecosystems.
Analysis of long-term field study data provided support for these laboratory findings, showing that mayfly populations were significantly reduced in poorly oxygenated stream sites, and that these reductions were particularly pronounced under warm water conditions. In short, low oxygen levels reduced the optimum stream temperature for mayfly populations, and threatened their abundance. The team used data provided by the Environment Agency and Natural Resources Wales collected using kick samples from 2632 sites across England and Wales between 1989 and 2008.
Green drake (Ephemera danica). Image: Wikipedia
In bringing together field and laboratory studies as a means of assessing how reductions in pollution may help to adapt river ecosystems to climate change, the study is highly innovative. The broad similarities in findings between the field and laboratory studies suggests that low oxygen levels not only impair mayfly survival at extremes of temperature, but can also restrict their abundance at temperatures well below lethal limits.
Improving water oxygenation through management of pollution could thus provide a key element in strategies to adapt Britain’s rivers and streams to climate change, potentially increasing ecosystem resilience to rising water temperatures in the future.
Co-author Dr Isabelle Durance, Director of Cardiff University’s new Water Research Institute states, “Our work presents real hope in the fight against climate change. We need to find ways to reduce the future effects of warming, and our data show how regulating and reducing pollution offers real benefit.”
Remote alpine lakes affected by nitrogen from agriculture transported across vast distances in the atmosphere
White Miller Lake in the Uinta Mountains. Image: Pierce Martin | Flickr
Remote mountain lakes in Utah, USA receive significant amounts of nutrients transported in the atmosphere from human activities many miles away, according to a new study. High alpine lakes are generally nutrient poor, and so this atmospheric arrival of nutrients – largely originating from nitrate and ammonium based fertilisers used in agriculture – has the potential to significantly alter the health and functioning of their ecosystems.
The study, led by Beth Hundey from The University of Western Ontario and recently published in Nature Communications (open access), suggests that for alpine lake ecosystems, “even modest increases in nitrogen deposition can have significant effects including eutrophication, acidification and the reduction of biodiversity.”
In order to protect these remote ecosystems, which often provide water resources for nearby lowlands and hotspots for rare and endemic biodiversity, it is important to identify the sources of nitrogen that reach them.
Reactive nitrogen (given the chemical symbol Nr) is the name given to all forms of biologically available nitrogen, including inorganic forms such as ammonia, ammonium, nitrogen oxide and nitrates; and organic compounds such as urea and nucleic acids. Reactive nitrogen is added to the environment naturally by lightning strikes and nitrogen fixation.
However, human activities such as synthetic fertiliser production and fossil fuel contributions have doubled levels of reactive nitrogen in the Earth’s nitrogen cycle. The emissions from such nitrogen-producing activities may be transported and deposited hundreds, even thousands, of miles from their source.
Mirror Lake in the Uinta Mountains. Image: Bryant Olsen | Flickr
The team analysed three stable isotopes (Δ17O, δ18O and δ15N) sampled in water from lakes in the Uinta Mountains in northeastern Utah, USA. This analysis allowed the team to determine where the nitrates found in the lakes – which are remote, with little direct human impact – originate from and how they were transported. For example, the isotope samples allowed the team to differentiate between nitrates originating from fossil fuel burning, biomass burning and lightning that is oxidised in the atmosphere; and those which are oxidised in land and water ecosystems.
Their results show that at least 70% of the total nitrate inputs into the Uinta Mountain lakes originate from the atmosphere. The majority of the nitrates arriving into the lakes are the result of agricultural activities, specifically the use of nitrate and ammonium fertilisers. The research team suggest that, “similarities in nitrate isotope compositions between Uinta Mountain lakes and lakes throughout the US Rocky Mountains suggest that these findings apply to other mountain regions in western North America.”
These findings are significant because they highlight how nitrate-caused ecological stress in mountain lakes may be the result of from multiple sources of nitrogen located many miles from the affected ecosystems. In short, human activities such as intensive agriculture have the potential to negatively impact even the most seemingly remote or ‘wild’ places.
For environmental managers and policy makers seeking to conserve these ecosystems, the study suggests that the geographical range of potential nitrate sources must be widened if nitrate levels are to be managed and their effects mitigated. Here, local ecological stresses are inextricably tied to wider-scale human activities. As such managing the emission and transportation of nitrates across vast distance is likely to pose ever more complex challenges for environmental policy and conservation.
Functional redundancy and how river ecosystems respond to stress
A well preserved section of the Segura River in Murcia, Spain, showing a riparian area dominated by black poplar, ashes and willows.
This week we have a guest post written by Daniel Bruno and Cayetano Gutiérrez-Cánovas on their new Journal of Applied Ecology paper which examines the potential of using the functional redundancy concept to assess how river ecosystems respond to stress.
Daniel is a researcher at the University of Murcia in Spain. His work explores river conservation and restoration, riparian ecology and the use of indicators to assess ecological status. Tano is a research associate at the University of Cardiff in Wales, whose work in the MARS project analyses how aquatic ecosystems respond to multiple stressor interactions at different spatial and temporal scales.
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The world’s ecosystems are experiencing an unprecedented increase in the number and variety of impacts that alter their ecological functioning. Such ecosystem alterations include changes to primary production, pollination, nutrient cycling and organic matter decomposition, among others.
Traditionally, ecologists have used species composition and other taxonomical approaches as indicators for ecosystem health. For example, some species are more likely to be abundant in disturbed sites, while others are very sensitive to human-caused stress. However, these techniques are not able to tell us how ecosystem functions might change after the disturbance, which would be far more useful for environmental managers in predicting and reacting to such impacts.
In a new study recently published in the Journal of Applied Ecology, we tested the potential of new functional indicators for assessing how river ecosystems respond to stress. We found that some of these indicators were able to detect single and combined effect of stressors, which may allow a better understanding of how freshwater ecosystem functioning responds to human pressures. Among them, functional redundancy is the most promising indicator as it relates positively to stability, resistance and resilience in ecosystems with a high sensitivity to stress.
The functional indicators used here account for the variability of the biological attributes of riparian vegetation (plants growing on land along river banks) that relate with ecosystem functioning, such as size, growth rate or leaf surface.
These measures have several advantages when compared to species-based tools. They have broader spatial utility (species composition varies more spatially than their biological attributes); better comparison among taxonomic groups (biological attributes as size are shared among all kind of organisms) and can be linked directly with ecosystem processes. There are many such links: leaf nutrient content affects in-stream processes like decomposition; larger trees cause more shadow which can alter river temperature and production and contribute to significant habitat modifications like natural, woody dams.
Riparian vegetation beside an intermittent river (Corneros River in Murcia, Spain), affected by drought in the Segura Basin study area.
Our study was conducted in a Mediterranean climate river basin (the Segura River) located in the southeast of Spain, where agricultural intensification, dams and natural droughts are the main causes of ecosystem stress. We produced different metrics to account for the multiple functional traits and aspects of the riparian plants. Then, we compared how those metrics responded to the single and combined stressors impacting on the ecosystem.
There were two main groups of functional indicators. First, measures of functional diversity which described the variability of biological attributes driving ecosystem functions. To measure functional diversity we calculated functional richness (community functional variability), functional evenness (how individuals or species are distributed among functional types) and functional dispersion (mean functional similarity among species);
Second, we used measures of functional redundancy, which can be defined as the number of species performing similar roles in an ecosystem, for example nutrient cycling, sediment fixation or climate regulation. Higher values of redundancy can mean increased long-term stability of related ecosystem functioning. This means that in functionally redundant ecosystems it may be possible for populations of some species to highly stressed or even made locally extinct, with little or no impact on ecosystem functioning.
One of the ways to estimate functional redundancy classifies species into functional groups which make similar contributions to ecosystem functioning. In our study, we classified riparian plants in five major functional groups: large highly water demanding trees; water demanding shrubs; evergreen shrubs; climbing plants; and drought-adapted vegetation.
Reach of the Mundo river in Albacete, Spain, which is disturbed by agricultural intensification. Note the scarcity of woody riparian vegetation in the left margin being dominated by evergreen shrubs and invasive species (e.g. Arundo donax).
Our results showed that stressors, when considered individually, caused general marked declines in functional indicators, with a variety in the size of decline. Generally, agricultural intensification was the most influential stressor for riparian functionality, followed by natural droughts. Hydrological regulation weakly affected functional indicators.
Functional redundancy was the most sensitive indicator in response to single and combined environmental filters. Combined effects on functional redundancy resulted from the interaction between agricultural impacts and droughts; and agricultural impacts and flow regulation. This suggests that such stressors should be considered together for the most accurate understanding of their effects on ecosystem health.
The most significant implication of these results is that functional redundancy can be used to identify which ecosystem functions are at the highest risk when an ecosystem is stressed. When we lose species from the same functional group (species playing a similar ecosystem function), this causes a decrease in functional redundancy. As such, using this functional index provides a valuable early warning system before ecosystem function begin to decline. Therefore, incorporating functional redundancy into river evaluation and management planning may help us to anticipate the effects caused by the ongoing global change.
Predicted functional redundancy for riparian communities in the Segura Basin study area.
An important advantage of the functional redundancy approach is its accurate response to combined stressors (best model explained near to 60% of its variability). We predicted the functional redundancy values for the entire river network (see figure above). For this forecast, we used a large dataset of sites from which agricultural intensification, flow regulation and natural drought were estimated, constituting a potential basis for biomonitoring and environmental management at the basin scale. This map is useful to detect the most impacted river reaches, to plan restoration measures, as well as to conserve the reaches with the best ecological functioning.
The predictors used here are low-cost, coarse-grain variables that are easy to obtain from digital maps and environmental databases. We also provide an open statistical method (R-scripts) to estimate the functional features and run the models showed in the study, allowing administrations and ecologists to extend this method to their study areas. Therefore, although the sensitiveness of functional redundancy to human impact must be specifically compared with other traditional biomonitoring tools and river types, it can be considered as an ecologically-sound measure able to detect ecological responses to single and multiple stressors.
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