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New genetic bioassessment project for European freshwaters

December 7, 2016

Macroinvertebrates such as this green lacewing are commonly used in curremt bioassessments. Image: Wikicommons

European freshwaters are subject to multiple pressures which place increasing stress on the health and status of the aquatic ecosystems they support. In order to effectively design and monitor conservation and restoration strategies, bioassessments of aquatic ecosystems are required.

Bioassessments provide snapshots of the health and diversity of ecosystems, often focusing on sampling species which are particularly sensitive to pressures such as pollution. At present, bioassessments typically rely on morpho-taxonomy, where species are identified based on the morphology (or form and structure) of manually collected and sorted specimens. This approach is often time-consuming, limited in temporal and spatial resolution, and dependent on the taxonomic expertise of the analysts. As a result, bioassessments are currently of limited use in informing large-scale ecosystem management.

A new collaborative European research project aims to use cutting-edge genetic technology to improve the accuracy and scope of aquatic bioassessments. The DNAqua-Net project, funded under the European framework COST, is set to bring together a large international research community from across disciplines to develop best practice strategies for using novel genetic tools in the bioassessment and monitoring of aquatic ecosystems, both in Europe and beyond.

The project will develop genetic bioassessment techniques such as DNA barcoding, which allows for species to be identified from their DNA signature in tissue samples. DNA barcoding  uses short standardised gene fragments of organisms allowing an unequivocal assignment to species level based on sequence data. Standardised DNA-barcode libraries, generated by the international Barcode of Life project (iBOL), and its associated and validated databases, such as BOLD and R-Syst provide reference data, which make it possible to analyse multiple environmental samples within a few days.

DNAqua-Net will bring together researchers and institutions that were previously working independently to provide a collaborative focus for developing and applying novel genetic techniques for bioassessment. In particular, the team hope to utilise the potential of eDNA techniques, through which DNA does not have to be necessarily extracted from tissue, but can also be collected from sediments, biofilms, or the water itself.

eDNA techniques can provide information on more than a number of specifically targeted species: instead on the entire biodiversity of an aquatic environment. In addition to being less invasive than traditional sampling techniques, the combined eDNA approach could potentially detect invasive species and as such act as an early warning system for management.

The project team’s proposal is published in open-access Research Ideas and Outcomes journal. Reflecting on the potential of their forthcoming research, they state “Novel DNA-based approaches currently emerge, possibly acting as a “game-changer” in environmental diagnostics and bioassessments by providing high-resolution pictures of biodiversity from micro to macro scales.”

Lake ecosystems under ice

November 30, 2016

Frozen Lochan Urr in the Scottish Highlands. Image: John McSporran | Flickr Creative Commons

Around half of the world’s lakes (slightly more than 50 million) are periodically frozen and (partially or fully) covered in ice. However, ongoing climatic changes are causing reductions in ice coverage in lakes across the world. Despite this, there is comparatively little information on the ecology of under-ice conditions in lakes, and how changes to winter conditions are likely to affect their health and functioning all year round.

Recent research suggests that the timing and extent of winter ice cover can have ‘cascading‘ effects on spring and summer lake ecology, for example on algal growth. As such, winter ice cover may act as more than simply a seasonal ‘pause’ in lake productivity,  and instead play a significant role in shaping lake ecosystems all year round.

A large team of freshwater scientists from 42 research institutes across the northern hemisphere have recently collaborated to address the shortfall in knowledge of under-ice lake ecology. Writing in the journal Ecology Letters (open access), the team, led by Stephanie E Hampton at Washington State University, USA, carried out the first global synthesis of data on under-ice lake ecosystems, drawing on research from 101 lakes in Antarctica, Canada, Greenland, Europe and the USA.

The research team used the new global dataset to explore two key questions. First, they wanted to know about the ecological changes that happen in lakes between winter and summer. Second, they wanted to understand how winter and summer seasons were connected, and through which ecological variables these connections were made.

One major finding discussed in the paper is that whilst primary producers (algae) and consumers (zooplankton) are typically less abundant under ice than in summer, they maintain significant populations in many lakes through winter. This suggests that zooplankton actively feed and reproduce under ice. Light availability is likely to be an important limiting factor to winter algae and plankton populations, depending on variations in ice thickness and opacity and snow cover.

Another of the research team’s key findings is that dissolved nitrogen was consistently higher in winter ice conditions than in summer. This may be the result of winter nutrient mineralisation providing continued inputs of nitrogen into lakes through cold seasons.


Ice forms on the frozen Lake Michigan, USA. Image: Kamil Dziedzina

The research team found evidence for strong winter-summer linkages in some lakes, particularly those which had long historical datasets, such as the Laurentian Great Lakes, Wisonsin lakes, northern European lakes and Canadian lakes. Here, whilst the influence of winter conditions on the following summer differed among variables, winter and summer conditions were often negatively related.

This relationship means that high winter values (e.g. for zooplankton density or chlorophyll levels) resulted in low values in the following summer. In the case of chlorophyll, it is suggested that high winter levels may limit available nutrients for the following summer. For zooplankton, it may be the case that high abundances reduce the availability of readily ingestible phytoplankton at the beginning of the next season. However, given that previous studies have suggested that overwintering populations can boost summer populations and vice versa, there is clearly the need for further research on the seasonal dynamics of lake ecosystems.

“We are losing ice without a deep understanding of what ecological processes are at stake” is how the authors begin their conclusion. Whilst this synthesis has offered new insights into under-ice lake ecology, and how it may influence ecosystems year-round, there remains the need for significant further research. Studying long-term ecological data from sediment records may be one means of broadening our understanding of these dynamics.

The study suggests that lake conditions are not simply result of prevailing seasonal weather conditions but can also depend upon external and internal forces operating on the ecosystem in previous seasons. Predicting the ecological effects of shorter winters and longer summers, then, calls for an increased focus on winter lake ecosystem monitoring. As the authors wryly state, “In the future, we predict that there will be no more ‘off-seasons’ for freshwater ecologists.”


Conservation and restoration of riparian zones under multiple pressures

November 22, 2016

Riparian zone around Burns Run, Clinton County, Penn, USA. Image: Nicholas A. Tonelli | Flickr Creative Commons

Conservation efforts to maintain and restore riparian zones along many global rivers are often inadequate, according to a new study. Writing in the journal Biological Conservation, Eduardo González and colleagues draw on a body of emerging research on riparian zones to identify a range of ecological, socio-economic and policy pressures for their fragmented distributions.

Riparian zones are the ecosystems found along the banks of rivers and streams: narrow transitional zones between land and water, often with diverse ecosystems that play important roles in the ecological functioning of the wider landscape. Riparian zones – often dominated by tree and plant species which thrive in damp conditions – can help buffer diffuse pollution, mitigate flood risks, store carbon, reduce bank erosion, provide shaded and cool stream water, prevent livestock from trampling fish spawning grounds, and offer valuable biodiversity habitat.

However, riparian zones have been under pressure in many rivers across the world for decades, if not centuries. Floodplains have been widely built upon, river channels straightened and reinforced, hydrology patterns altered by dam building, and riparian woodland cleared in many landscapes. González and colleagues cite studies stating that up to 90% of North American and European floodplains are considered ‘ecologically dysfunctional’, and in Europe up to 88% of floodplain forests have disappeared, as a result of human activity.


Cheonggyecheon stream and new ‘riparian zone’ in Seoul, South Korea, daylighted from sewers in 2003. Image: Kaizer Rangwala, Flickr Creative Commons

Riparian zone restoration is an important part of many ongoing river basin management strategies, with some notable successes (see, for example the restoration of the Truckee River in Nevada, USA). However, González and colleagues identify three barriers to successful riparian zone management. The first barrier is ecological: some riparian ecosystems are so highly altered that they may not be able to respond positively to conservation initiatives (as this study outlines).

The second barrier is socio-economic: where societies prioritise floodplain development and flood defences over the potential (perhaps sometime poorly communicated) ecosystem services and benefits that riparian zones may generate. The third barrier is the structure of policy systems in which environmental goals may be marginalised by economic or social imperatives. The complexity of such policy barriers are clearly outlined in the following passage from the study:

One of the problems associated with the lack of formal recognition of riparian zones is that the application of individual policies can have antagonistic effects. For example, in Europe, young cohorts of poplar and willow trees are frequently removed under the Flood Risk Directive to avoid vegetation encroachment and increase stream conveyance capacity (Geerling et al., 2008), while these same species are being promoted by the Habitats Directive to preserve alluvial forests (Hughes and Rood, 2003) and create ecological networks along river corridors (Jongman et al., 2004). The creation and maintenance of alluvial forests are also supported by the European Agricultural Funds for Rural Development and enforced by the cross-compliance regulation as one strategy to achieve vegetated buffer zones along rivers (Gumiero et al., 2016).

In common with every modern-day environmental issue, we might add in climate change as a fourth key barrier to riparian zone conservation. Hydrology alterations, increased droughts in some regions, and floods in others, changes to species habitat niches and biological invasions and extinctions are all projected to occur under global climatic change over coming decades (see this analysis of climate change and riparian zone vegetation for more information).


A diverse riparian zone along a river in the Rif region of Morocco. Image: Nuria Bonada

In order to navigate this complicated landscape, the authors argue that riparian zone management is in need of integrated approaches that promote and restore the value of these unique ecosystems. González and colleagues sketch a model for such integrative riparian zone management, based on five themes: education, inventory, protection, sustainable management, and restoration.

Expanded and effective education schemes about the value and aesthetics of well-functioning riparian ecosystems are advocated by the authors, whether through NGO outreach, citizen science initiatives or national education policies. In many urbanised and agricultural landscapes, there may be a ‘shifted baseline‘ in environmental perception which means that many people may be unaware of historical riparian zones in their local landscapes. Such education work may thus form the groundwork for generating popular support for riparian conservation and restoration.

Whilst it may sometimes seem like humans have mapped and measured every inch of the world, there are still ecosystems in even highly populated areas that are still only partially understood and monitored by scientists. Riparian zones are one such ecosystem type: they cover vast distances, cross political and environmental boundaries, and can be highly dynamic over seasons. As such, developing long-term environmental inventory and monitoring schemes can help inform and prioritise riparian conservation and restoration, and provide a stronger scientific base for influencing policy decisions.


Room for biodiversity, heritage and art along the Water of Leith riparian corridor in urban Edinburgh, Scotland. Image: Saskia Heijltjes | Flickr Creative Commons

The final three themes of González and colleagues’ management proposal are linked aspects of conservation: protection, sustainable management, and restoration. In some areas, protection through restricting activities such as livestock grazing or agricultural production is highly effective in promoting riparian regrowth.

In others, engaging local communities with the sustainable shared use of riparian zones is key, for example through  ‘green corridor’ riparian zones along urban rivers (such as on the Water of Leith in Edinburgh). In some areas, this may involve the use policy incentives such as payments for ecosystem services or agri-environmental schemes to promote riparian zone conservation and compensate for the loss of potentially valuable land. The authors advocate that all economic activities in riparian zones should be run on sustainable management principles.

Riparian restoration is a core element of many river basin management plans across the world. González and colleagues highlight a key challenge for such restoration: many riparian zones have been so highly modified that it is difficult to return ecological conditions and processes to a pre-modification ‘reference’ state. Where riparian zones have been lost as the result of the construction of a small dam or flood walls, the subsequent removal of such structures may allow for “room for the river” to be restored. In many cases, though, the active transformation of riparian land through alterations to river hydrology and environmental flows, tree-planting, control of grazing, or ceasing of agricultural production is necessary. For the authors, such restoration processes require clear, realistic, multi-scale and evaluable goals.

Riparian zones are valuable land to many individuals, both human and non-human. To humans, they provide the space to access, use and enjoy waterways, and fertile and often aesthetically pleasing land for development and production. For plants and animals, riparian zones are often diverse and valuable habitats, which in turn can generate a broad range of ecosystem services.

As such, they are always likely to be contentious spaces for management, planning and policy, particularly when the uncertainties of flooding and climate change (and their subsequent management and mitigation) are brought into decision-making processes. Whilst González and colleagues’ paper doesn’t necessarily offer any new information, it provides a valuable and clear-headed review and synthesis of the existing research in the field, which will likely help extend and develop current debates in riparian zone management and policy.

Eduardo González, María R. Felipe-Lucia, Bérenger Bourgeois, Bruno Boz, Christer Nilsson, Grant Palmer, Anna A. Sher (2016) Integrative conservation of riparian zones, Biological Conservation, Online 9 November 2016

Multiple stressors in Science of the Total Environment

November 16, 2016

MARS scientists studying multiple stressors in Lake Beyeshir, Turkey. Image: METU Limnology Laboratory

The MARS Project has been undertaking scientific research into the effects of multiple stressors on aquatic environments for nearly three years now, and project scientists are beginning to widely publish their findings.

Six new papers involving MARS research have recently been published online in the journal Science of the Total Environment, some of which are currently available for free through open-access publishing.


Analysing the impact of multiple stressors in aquatic biomonitoring data: A ‘cookbook’ with applications in R

The health and status of Europe’s freshwaters has been closely monitored since 2000, creating detailed environmental and biological datasets covering over 120,000 water bodies. However, this data has – until now – been rarely used to analyse multiple stressor interactions and impacts. This is partly because of the various scales at which stressors are monitored and reported. A MARS team led by Christian Feld has designed an analytical framework that allows for multiple stressor effects to be analysed through this rich biomonitoring dataset, which is outlined in this paper (link).

Effects of hydro- and thermopeaking on benthic macroinvertebrate drift

Hydropower plants – often located on mountain streams and rivers – are commonly designed to operate in response to electricity demand. This means that the timing and flow of the water they release during and after electricity production can be highly variable. This process is known as ‘hydropeaking’, and can have a range of detrimental ecological effects on downstream ecosystems. Working at the HyTEC facility in Austria, a team led by Lisa Schülting used experimental flumes to observe the ‘drift’ (or movement down and across the simulated stream bed) of macroinvertebrate (or aquatic insect) species.

Overall, the team found that hydropeaking significantly increased the rates of macroinvertebrate drift from their original position on the stream bed. However, this pattern was influenced by water temperature: when hydropeaks of water were cold, total drift rates were reduced, although with strong taxon-specific response patterns. The results were also influenced by the time of day that hydropeaks occurred: increased water flows during the night led to significantly higher drift rates than those during daytime (link).


A golden morning on the Danube River in Budapest. Image: Miroslav Petrasko | Flickr Creative Commons

Relative influence of chemical and non-chemical stressors on invertebrate communities: a case study in the Danube River

Understanding the influence of chemical pollution on the health, diversity and status of biological communities in aquatic ecosystems is a key challenge for ecological risk assessments. However, there are a vast number of different chemicals (and new ones developed each year) which can form complex ‘cocktails’ in freshwaters, and can trigger a number of multiple stress effects. In many cases, the toxic effects of chemical pollution on aquatic life is poorly understood.

A collaborative team from the SOLUTIONS and MARS projects led by Andreu Rico used data from a comprehensive ecological survey of the Danube River – from its source in Germany to its mouth at the Black Sea – to analyse the influence of chemical and non-chemical stressors on invertebrates. They found that variations in invertebrate communities along the Danube are influenced more by varying habitat conditions and physico-chemical parameters (e.g. suspended solids, nutrients and dissolved oxygen) than by chemical pollution (link).

Potamodromous fish movements under multiple stressors: Connectivity reduction and oxygen depletion

Potamodromous fish are those which migrate, but only within freshwater environments, such as from a river to a lake for spawning. In Mediterranean rivers, two key stressors are water abstraction – which can reduce the connectivity between ecosystems needed for migration – and diffuse pollution – which can have harmful ecological impacts such as oxygen depletion.

A team led by Paulo Branco studied the impacts of these two stressors on a Mediterranean potamodromous fish species, the Iberian barbel (Luciobarbus bocagei) using experimental flumes. They found that when connectivity was reduced, fish movement was similarly reduced, regardless of oxygen depletion levels. When connectivity was high, fish movements were reduced in response to increasing oxygen depletion. The results suggest that oxygen depletion as a result of diffuse pollution may prove a barrier to fish migration, even when physical connectivity between different parts of a river basin is high (link).

Untangling the effects of multiple human stressors and their impacts on fish assemblages in European running waters

Understanding the impacts and interactions of multiple stresses on aquatic environments is a key research challenge for scientists, both in Europe and across the world. This study, led by Rafaela Schinegger, used data from over 3,000 sampling sites to map the effects of multiple stressor combinations on fish assemblages in European rivers (read an earlier blog post relating to the work here).

Across the sampling sites, 15 different stressor combinations were observed. Rivers were affected by single stressors only at 30% of sites, whilst 42% of sites were affected by multiple stressor combinations, and 28% were un-impacted. The multiple stressor interaction types varied in character: 40% were additive (where the total stress effect is the sum of each stressor), 30% were synergistic (where the total stress effect exceeds the sum of each stressor) and 30% were antagonistic (where total stress effect is less than the sum of each stressor) (read more about multiple stressor interactions here).

Stressor interactions varied with habitat type: antagonistic effects were only observed in headwaters and medium-gradient rivers, whilst synergistic effects increased from headwaters through medium gradient rivers and Mediterranean streams to large lowland rivers. The study is an important step forward in understanding multiple stressor interactions and impacts in European rivers, and will most likely provide valuable information for guiding conservation and restoration management (open-access link).


The Otra River, Norway. Image: Baard Skaaden

Effects of multiple stresses hydropower, acid deposition and climate change on water chemistry and salmon populations in the River Otra, Norway

The Otra River in Southern Norway is impacted by acid deposition, hydropower development (around 40% of the river has been modified for electricity production) and, increasingly, by climate change. The Otra supports populations of both land-locked and migratory (anadromous, moving between rivers and the sea) salmon which have been severely impacted by acidification in the latter part of the 20th century.

Environmental policy and conservation initiatives have prompted a reduction in acid deposition into the Otra since the 1980s, which has caused a partial recovery of both populations of salmon. However, in order to predict and manage the long-term health and status of the Otra’s salmon populations, it is important to consider acidification as part of a multiple stress combination affecting the river alongside hydropower and climate change.

A MARS team led by Richard F Wright used a set of linked process-oriented models to provide estimates of future water discharge and chemistry and their effects on fish populations in the Otra River. The models were run to 2100 using two Representative Concentration Pathway climate scenarios: RCP4.5, in which global carbon emissions peak at 2040 then decline; and RCP8.5 in which global carbon emissions continue to rise through the 21st century.

The projected changes in climate produced only small – but ecologically positive – changes in the water chemistry of the Otra River. Run-off was predicted to increase by around 30%, largely during winter (as a result of increased precipitation and snowmelt), which, when coupled with projected decreases in acid deposition through the 21st century reduces the possibility of acidification. And, linked to this, the likelihood of river water pH dropping below levels where fish are significantly stressed (5.8 for parr and 6.2 for smolt) is reduced.

The study suggests that future climate change may cause slight improvements the water chemistry conditions for salmon populations in the Otra River through the 21st century. However – as the authors acknowledge – this result addresses only one aspect of climate change and not others such as increased water temperatures, river basin vegetation growth and soil mineralisation. Future river run-off levels will be affected by the continuation of hydropower projects on the river.

As such, the multiple stressor combination of acidification, hydropower and climate change on the Otra River are fundamentally linked, and whilst this study sheds new light on their interactions, their complex, interconnected nature provides ongoing challenges for environmental modelling and management (link).

Invasion of the Swamp Monster

November 9, 2016

Crassula helmsii – an invasive aquatic plant. Image: eyeweed | Flickr Creative Commons

In August, we heard from Dr Claire Wordley from the Conservation Evidence Group at the University of Cambridge about the publication of What Works in Conservation, an evidence-based manual reporting the effectiveness of different conservation approaches on a range of ecosystems and species.

Since then, the group has published a new set of findings on the control of freshwater invasive species, based on reviews of recent scientific studies.

Today, we hear from Dr Wordley again, as she writes about the ecological impacts of Crassula – an invasive aquatic plant originally from Australia which is popular with gardeners in Europe – and the effectiveness of different control methods to halt its spread.


Crassula: A ‘Superweed’ from the South

The Australian Swamp Stonecrop is a small, unassuming looking plant with incredible superpowers. It can survive both baking heat and freezing cold; it can live underwater, on the water’s surface and on land; it can survive being dried out, bleached and sprayed with hot foam; and it can regenerate from tiny fragments. Unfortunately, in the UK it is an invasive species, choking the oxygen from ponds and shading out other plants with knock on effects for entire freshwater ecosystems.

Australian Swamp Stonecrop, also known as New Zealand Pigmyweed (or to give it its Latin name, Crassula helmsii), was first introduced to the UK from Tasmania in 1911 and sold in garden centres from 1927 as an ornamental pond oxygenator. Shockingly, despite being documented as an invasive plant in New Forest ponds as early as 1976, its sale in the UK was only banned in 2014. Crassula appears to be spread mostly by people, whether deliberately or accidentally; it appears to be concentrated around car parks, residential areas and areas where equipment such as fishing gear is likely to have come from an infected site.

Nearly 20% of 700 UK waterbodies surveyed contained the weed. Since every 10% increase in Crassula corresponds with a 5% decrease in native vegetation, and negative effects of Crassula invasion have been documented for zooplankton, macro-invertebrates and fish, with possible negative impacts on amphibians as well, control and ideally eradication is clearly needed. But what works to destroy this ‘superweed’?


Crassula blanketing a small pond. Image: Benjamin Blondel | Creative Commons

Killing the hydra

Like the seven headed hydra of legend, Crassula helmsii seems able to regenerate after incredibly harsh treatment and being shattered into tiny pieces. Documenting clearly what works to control this beast – and what does not – is critical. This work has recently been completed by Conservation Evidence at the University of Cambridge, as part of an ongoing series on controlling freshwater invasives. The team has worked to collect together all the evidence on different ways of killing Crassula, and experts have scored these for their effectiveness (or otherwise).

One of the most effective ways to knock back Crassula appears to be applying herbicides, particularly glyphosate and diquat or diquat alginate. While each of these performed well to reduce Crassula in many trials – and the use of glyphosate and diquat together led to a 98% reduction in one trial – there are concerns that the medicine may cure the disease, but kill the patient. One study in the New Forest noted that native plant cover fell in the treatment sites at a greater rate than in the control sites, and glyphosate appears to be toxic to amphibians. There may also be adverse effects on some bird species, although this may be due more to habitat level changes than direct toxicity as other birds appeared to benefit from wetlands being sprayed with glyphosate.

Covering the invasive plant with black sheeting or carpet strips, may, where feasible, provide an alternate approach. While the evidence for the effectiveness of keeping Crassula in the dark is not as strong as the evidence for spraying it, five studies showed very promising results that lightproof barriers can eradicate or severely reduce the coverage of the weed. Sadly, on two sites Crassula recolonised after it was eradicated – indicating that controlling the spread of this plant is likely to be an uphill battle for some time to come. Flooding contaminated ponds with salt water also appears effective at killing Crassula, but salt levels need to be high, as it can survive in brackish water. The lethal effects of salt water are likely to be experienced by native flora – and in some cases fauna.

Since Crassula appears to be mostly spread by people, often on equipment such as nets and rods, effective biosecurity measures to stop the spread will be critical to maintaining areas free from this relentless invasive. Crassula survives drying well, but a 15 minute immersion in 45 °C water led to mortality in 90 % of the plants by one hour after treatment. Experimenting with hotter temperatures and longer immersion times may improve this further.


Crassula growing from an urban storm drain in Australia. Image: eyeweed | Flickr Creative Commons

Treatments to forget

Unfortunately, not all the methods that have been trialled to get rid of Crassula have proven effective. Since Crassula, like other aquatic plants, needs light to grow, aquatic dyes that reduce the light available to submerged plants seemed like a good idea. Unfortunately, in a trial in the New Forest, this proved to be a non-starter, with Crassula cover increasing slightly in dyed pools. Hot foam was another inventive idea – foam stays in contact with the plant for longer than hot water, rupturing the cells of the leaves. Sadly, this was totally ineffective in one trial, and pretty ineffective in another, meaning that this treatment won’t be rolled out to a pond near you any time soon.

Bleach was another failed treatment – adding hydrogen peroxide to tanks containing Crassula did not have sufficient controlling effects to merit field testing, where other plants and native wildlife may be damaged by the chemical. Grazing was also rated as likely to be ineffective or harmful – trials showed varying results, but Crassula cover actually increased significantly in grazed plots in one trial, and did not vary significantly between grazed and ungrazed plots in the other trial.


Crassula covering the shoreline of a lake. Image: Benjamin Blondel | Flickr Creative Commons

Go forth and test

As ever, there are treatments out there that have not yet been tested sufficiently (or at all) – some of which may later prove to be effective. It is up to conservation practitioners who use these methods to test them experimentally and publish the results where they can be accessed by others, enabling the whole community to learn from each manager’s experience.

Combining treatments such as spraying and covering plants with light proof barriers is one method that needs more testing. Other suggestions range from using liquid nitrogen or flame throwers to using fungal-based herbicides and educating the public about the need to decontaminate clothes and equipment between ponds.

Whatever methods people are using to get rid of this plant, it is clear that rigorous collection of more data is needed; on what works to kill Crassula, on what methods lead to an increase in native plant cover, and on what the effects of treatment are on freshwater fauna from zooplankton to fish, frogs and birds. Trials don’t need to be huge to help build our knowledge base, so long as they are well designed – in conservation science, truly every little counts.


What next?

Conservation Evidence will continue to add species to the freshwater invasives synopsis, which already contains 139 actions on American bullfrog, Asian clams, brown and black bullheads, floating pennywort, Ponto-Caspian gammarids, Ponto-Caspian gobies, Procambarus crayfish, red-eared terrapin, skunk cabbage, water primrose and now Crassula helmsii.

The synopsis will hopefully stimulate action to fill in the knowledge gaps, making invasive species control more effective; and when the synopsis is updated in a few years’ time, it is hoped that the evidence base will be much stronger. If not, we could see more freshwater ecosystems irreversibly altered.

Tools for managing multiple pressures: workshop collaborations between MARS and ECOSTAT

November 3, 2016

Attendees at the Den Helder workshop in October 2016. Image: MARS

At the end of October, MARS, a European Union FP7 project, and ECOSTAT, an European Commission Working Group for the implementation of the Water Framework Directive, held a collaborative workshop to discuss the challenges of aquatic multiple pressures in Den Helder, Netherlands. Around 50 ECOSTAT members and 10 international stakeholders attended the workshop.

In their invited presentation, Wouter van de Bund and Sandra Poikane from ECOSTAT outlined the challenges of linking multiple pressures and ecological classification, whilst Jo Halvard Halleraker used examples from water management in Norway to suggest the management tools needed to conserve and restore aquatic ecosystems under multiple pressures.

Four central aspects of the developing MARS toolbox for multiple pressure management were presented as prototypes. Clara Chrzanowski outlined the new Information System, Christian Feld presented the Diagnosis Tool, Gerben van Geest introduced the Model Selection Tool, and Markus Venohr discussed the Scenario Analysis Tool.


Discussions at the Den Helder workshop. Image: MARS

The aim is that each of these MARS tools will soon provide comprehensive and accessible resources for managing and mitigating multiple pressures in Europe. Attendee feedback highlighted the potential role of such tools in guiding both local and transboundary water management.

Similarly, workshop feedback from stakeholders (such as water managers) highlighted current difficulties in locating and accessing appropriate scientific research to guide management plans. It is intended that the MARS Information System will address this shortfall, by presenting up-to-date scientific research on multiple pressure interactions and impacts in a clear and accessible format.


The evocative location for the workshop. Image: MARS

Reflecting on the discussions at the workshop, Markus Venohr said: “We received valuable feedback in this early phase of the toolbox development, helping us to develop most appropriate functionalities of the individual tools. In particular the reflection of national management options on EU scale and our attempts to further close the knowledge-gap between stressors and biological responses received special interest.”

Further engagements with European water management stakeholders are planned in the future to test the developing toolbox and discuss their results and outcomes.

MARS website

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.

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