Freshwater biodiversity - European Commission...Action Biodiversity, Water and Ecosystem Services (BIOMES) Global distribution of freshwater ecosystems Freshwater ecosystems may be

Freshwater biodiversity Status, trends, pressures and challenges

Joachim MaesJoint Research Centre – Institute of Environment and Sustainability

Rural Water and Ecosystem Resources Unit

Action Biodiversity, Water and Ecosystem Services (BIOMES)

Global distribution of freshwater ecosystems

Presenter

Presentation Notes

Freshwater ecosystems may be divided in rivers and streams, lakes and ponds and wetlands, areas of which the soil is saturated with water. This map shows the distribution of these freshwater ecosystems. Their combined surface area represents a bit less than 1% of the total land area.

Vertebrates Number Share in freshwater

Fishes 30.000 (41+1) %

Amphibians 5.700 >70 %

Reptiles 8.200 5 %

Birds 10.000 9 %

Mamals 5.400 6 %

"Pinocchio" Frog, recently discovered in New Zealand, National Geographic

• 1/3 of all vertebrates are ecologically dependent on fresh water• 6 % of all described species• There is a lack of global information for invertebrates and micro-organisms inhabiting fresh water

Freshwater ecosystem host a disproportionally rich species diversity

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Presentation Notes

The 1% is important to illustrate that freshwater ecosystems host a disproportionally rich diversity of species. From all fishes 41% are confined to fresh water while 1% is migratory moving between freshwater and oceans. Most amphibians are dependent on freshwater, especially for reproduction. Reptiles, especially turtles and crocodiles have many freshwater species. Waterfowl may represent 9% of all known birds and several mammals, like otters, beavers, dolphins, rat species inhabit lakes and streams. For some the numbers are rising as new species are being discovered and described. A recent discovery is this little frog that was found during a recent expedition in New Zealand. In summary, 1/3 of all vertebrates depends on freshwater habitats and there is an estimate that between 6 and 10% of all described species are dependent on freshwater. These are estimates because there is little global information on other taxa.

Total number of amphibian species per country per km2Source: World Resources Institute

High levels of endemism explain in part this rich freshwater biodiversity

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Why is there so much more biodiversity in fresh water. In part because many aquatic species are endemic: they occur exclusively in a particular place. Aquatic habitats are relatively isolated. Salt water and the borders between watersheds and river basins act as barriers for species. This limits gene flow and favours local radiation which results in high endemism. For amphibians, there is a positive relation between endemism and total species diversity. The most biodiverse regions are the regions with the highest levels of endemism. For amphibians this is globally clustered on a few hot spots. Globally, freshwater biodiversity is clustered and very high in areas where a lot of species are endemic. The danger of high levels of endemism is that local impacts result in the irreversible loss of species. Clearly, when talking about tipping points for biodiversity, the loss of endemic species is an issue.

Red: endemic fish species

The species flock of Cichlid fishes in the African great rift lakes:

A group of 500 closely related fish species that underwent rapid adaptive radiation during the last 100.000 years

Verheyen et al. Science 300.

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A remarkable example of endemism is the species flock of cichlid fishes in the great rift area. A species flock is a group of fishes in this case that underwent very rapid radiation. Rapid because it happened the last 100.000 years while some sources say that 14.600 years ago Lake Victoria was dry claiming therefore even faster rates of speciation. For these fishes, radiation into different species was strongly related to trophic and reproductive adaptations. So in general, these fishes segregated into different species as groups became adapted to special forms of feeding and reproducing. Especially the latter has led to remarkable behaviours. This is a picture of a male mimicking the eggs of female fishes which keep the eggs in their mouth for protection. When the female discovers that she has lost 2 eggs, she opens her mouth to capture the eggs, exactly when the male ejects his sperm to result in almost 100% fertilisation of the eggs.

Freshwater biodiversity in crisis

The LPI measures trends in vertebrate population abundance over time.

Sources: Burtchart et al. (2010) Science; Global population dynamics database, Imperial College London

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This remarkable freshwater biodiversity is, however, in crisis. This picture denotes the trend in the living planet index which measures the aggregate trend of the abundance of vertebrate populations. The dotted line summarizes the trend for freshwater vertebrates showing that the decline is stronger for freshwater species suggesting that we lost already 40% of the initial LSI value which was set to 1 for 1970.

Source: EEA-ETC, Article 17 reports, 2009

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The article 17 reporting exercise confirms the loss of freshwater biodiversity. Article 17 data report on the status of habitats and species of community interest that are protected or listed under the Birds and Habitats directive. A first continental assessment was finished last year and it will serve also as input into the biodiversity baseline. For wetlands, 8% of the habitats and 14% of the species is in favourable condition. For rivers and lakes, these figures are 15% and 13% respectively. Note also that for 1/5 of the assessments, the status remains unknown.

Source: EEA-ETC, Article 17 reports, 2009

Amphibian population trends

from 1950 to 1997 using 936 populations.

Source: Houlahan et al. Nature 404

Geographical pattern of the dominant causes of rapid declineSource: Stuart et al. Science 306.

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Presentation Notes

Well known by now is the decline in amphibian species. I used two major publications in the field to illustrate this. On the right hand site you see a picture illustrating the trend of amphibian populations over time. The y axis measures the cumulative rate of change as the difference between the logarithm of the abundance of the previous year minus the logarithm of the abundance of the present year. Here the average is shown for almost 1000 populations. A total accumulated decline of 0.5 corresponds with a average population decrease of almost 70%. The geographical patterns of the major causes of decline of amphibians is depicted on the left hand side. Reduced habitat is a major cause of declines in the industrialized world and this is further emphasized by a recent publication as the number 1 cause of amphibian species declines. Over exploitation is the dominant cause of decline in the far east with frogs being used a food. Enigmatic declines are prevalent in the neotropics. Enigmatic declines are not fully understood but include climate change, disease and pollution to which amphibians with their sensitive skins may be more exposed.

Source: DAISIE European Invasive Alien Species Gateway (http://www.europe-aliens.org/)

FRESHWATER28%TERRESTRIAL

52%

MARINE35%

100 worst

FRESHWATER7%

TERRESTRIAL90%

MARINE7%

Alien species in European fresh water

11.000 aliens Sources: Burtchart et al. (2010) Science; Global population dynamics database, Imperial College London

Eriocheir sinensis, Chinese mitten crab

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Let’s have a more detailed look on the pressures on aquatic biodiversity. Maybe the most persistent pressure is the introduction of alien species which take the place of native species. It is a pressure which is hard to fight. Once settled, it seems virtually impossible to remove an invasive population without harming other species even worse. The problem is that many native species are not able to compete with invasive alien species for the same resources. As a result, they are literally outcompeted and their populations decline. In Europe, about 11.000 alien species have been described, the majortity inhabiting terrestrial habitats, mainly plants. Note that the numbers do not count up to 100% a some species may be found in both terrestrial and aquatic habitats. However, when considering only the worst species in terms of their impact on biodiversity, economy and health, 28 of them occur in freshwater, among which this Chinese crab species introduced by ships from the far east in the 1930s and causing huge damage to the fisheries. Clearly, international trade is a major cause of introductions to aquatic habitats with species present in the ballast water of large cargo ships. With increasing trade, the abundance of populations of alien species keeps on increasing almost every year as shown by the aggregate index on the right.

Habitat fragmentation is a major driverof biodiversity loss in freshwater ecosytems

Flow regulation structures in France

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Presentation Notes

A second major cause responsible for the decline of aquatic species is the fragmentation of freshwater habitat into little pieces. On the left data from a large study issued by the WWF showing the rate of damming of the largest rivers of the planet with large dams. A sharp increase in the 50s and continued damming in the following have reduced the number of free flowing rivers to less than 1/3. More detail for France is provided on the right. The black you see on the map are in fact dots with flow regulating structures such as barriers, locks and sluices. For most upstream parts of the major rivers in France, you can’t see the courses anymore. Dams, locks, sluices and to a larger extents also dikes subdivide the river into little fragments. Why is this so detrimental to biodiversity.

The river continuum and flood pulse concepts describe the longitudinal and transversal interactions in river systems. These

interactions are essential to maintain biodiversity

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For that, we need to understand how biodiversity is organised along the two major dimensions of rivers: the longitudinal and the vertical. Two concepts explain the interactions that take place along these dimensions and that are important to support biodiversity. The River Continuum Concept draws attention to the close dependence of the structure and function of biological communities In mountain streams (I-III order) aquatic biological communities are supported by large amounts of organic debris (leaves and branches) provided by riparian vegetation, while the shading of the latter reduces the development of photosynthetic producers (eg . seaweeds). The river metabolism is therefore heterotrophic (supported by contributions from terrestrial organic) and community structure of invertebrates is dominated by shredders and collectors, while the pastures are under-represented, reflecting the limited availability of food resources they need (algae, mosses, hydrophytes vascular) (see figure). Proceeding downstream, the rivers of medium size (Order IV-VI) reduction of the surface shaded and the rise of photosynthesis lead the transition to a river autotrophic metabolism (supported by aquatic organic production), making the aquatic communities energy self-sufficient with respect to terrestrial inputs, however, remain an important resource, increasing the pastures at the expense of shredders, and collectors continue to abound, taking advantage of the organic fine particles produced by shredding the mountain branches. In large rivers (of order greater than 6 °) shadowing becomes negligible, but photosynthesis is generally limited by the turbidity of the water: the return conditions heterotrophic and community-supported by large amounts of organic matter articulated end, coming largely traits-becomes much more dominated by collectors. These processes are synchronized throughout the year so interrupting this model by inserting dams has negative consequences for biodiversity downstream. In addition to that, many species are adapted to the natural cycle of floods depected on the right. Many fish species use flooded vegetation to hide eggs or make nests, making flooded grasslands for instance essential habitats for fish. By constraining rivers into their channel, much of this interaction is lost and populations depending on that decline.

Logistic reponse of diadromous fish to DO

Dissolved oxygen (mg O2 L-1)

0 1 2 3 4 5 6 7 8 9 10 11

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3-spinedsticklebacképinoche

eel anguille

flounder flet

smeltéperlan

twaite shadalose feinte

Poor water quality blocks fish migration.

Too much nutrients and organic pollution creates hypoxic zones in the river which cannot be passed by fishes moving upstream or downstreamSource: Maes et al. 2008 ECSA

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It is not necessarily dams that cause habitat fragmentation; also pollution does. Here is an example of how a dead virtually anoxic zone in the river Scheldt blocks the upstream movement of migratory fish. Such species called anadromous if they move upstream to reproduce in freshwater and catadromous if they travel to sea for reproducing are true indicators of the health of entire rivers. Examples of the former group are salmon or depicted here shad; examples of the latter group are eels or depicted here flounder. These species need the entire river gradient to complete their life cycle. The map shows the part of the basin that is free of flow regulating structures. When I was at the university we sampled these fishes using these particular nets placed at low tide. We related the catch statistics to dissolved oxygen concentration showing strong positive reponses to DO. However, large loadings of waste water containing too much nitrogen components, mainly from Brussels arrived in the river creating an anoxic zone through which fish were incapable to pass.

Nutrient loading CLEAR TURBID

CLEA

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TU

RBID

CLEA

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RBID

Nutrient loading

Chlo

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In shallow pond and lakes, increasing nutrient loading shifts the ecosystem from a stable clear state dominated by macrophytes to a stable but turbid state dominated by small phytoplankton species.

Pictures taken from STOWA, Van helder naar troebel en weer terug.Scheffer et al. TREE 8

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Too much nutrients negatively affect the biodiversity in shallow ponds and lakes. This conceptual model by Maarten Scheffer illustrates this. Under low nutrient loading, small ponds and lakes have clear water dominated by waterplants and rich invertebrate and fish communities. This is a stable state. After a disturbance, energy input from outside pushing the marble up, the stable clear state returns, the marble rolls back. Under increasing nutrient loading, a disturbance may result in another state, a turbid state, dominated by small plankton and poor fish communities dominated by 1 or 2 species. If you push the marble too far, it cannot return without investing energy from outside for instance via biomanipulation – changing the structure of the foodweb by removing fish that benefit from the turbid state. On the right hand side the same shift from clear to turbid under increasing nutrient loading is shown. The damage to biodiversity is not irreversible but a different path needs to be followed. Nutrient loading has to decrease much more than the critical threshold.

<0.5 mg L-1

0.5 – 1.5 mg L-1

>1.5 mg L-1

Ecological status of European lakes according to the harmonized methodology of the Water Framework Directive Intercalibration Group.

Map of potential risk for eutrophication for surface freshwater based on estimated total nitrogen concentrations

Source: Grizzetti et al. In press. Nitrogen as a threat to European water quality. In "The European Nitrogen Assessment"

Presenter

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Many of the European waters run the risk of eutrophication. These maps were made by Bruna Grizzetti who was at the JRC for many years. She modelled the flow of nitrogen in Europe and one of the applications is this risk map using conservative values for the eutrophication risk from nitrogen contribution. Data on ecological status as defined by the Water framework directive are becoming available and our unit and action have devoted large efforts in the intercalibration exercise. One of the outcomes is this map for European lakes showing the division of lakes in three classes: poor good and high ecological status.

Recovery of freshwater biodiversity

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I already referred to biomanipulation as a way of recovery for shallow lakes and ponds which indicates that it is possible to rehabilitate freshwater habitats and biodiversity. Several successful efforts have been done to recover migratory fish populations for instance in the Rhine where many of the migratory fishes such as twaite shad and allis shad, trout, salmon and lampreys seek up their historical spawning grounds again. I am impressed by the different programs in France, for the Loire and the Gironde, to restore populations and allow the upstream migrations. The Logrami website counts the passage of salmon on their way up. I could experience myself the return of fishes to the Scheldt estuary after decades of heavy organic and chemical pollution.


Improving water quality is an effective method for rehabilitating fish populations in streams where natural colonization is possible.

Source: Data from INBO, Belgium

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The latter is more detailed on this slide. We have been monitoring this recovery of fish populations in the River Scheldt since 1995 and the figure depicts the gradual increase in fish abundance and species along with the increase in oxygen concentration. It shows that omproving water quality is an effective method for rehabilitating fish populations in streams where natural colonization is possible.

“Recovery of the Hudson River population of Shortnose sturgeon suggests the combination of species and habitat protection with patience can yield successful species recovery, even near one of the world’s largest human population centers”.

Source: Bain et al. (2007) Plos ONE.


Presenter

Presentation Notes

Crossing the Atlantic the data on top of the slide show the recovery of the shortnose sturgeon population. Sturgeon species are often threatened species because there particular habitat needs, their dependence on free flowing rivers and overexploitation. The graph plots the catch per unit effort (bars)and the estimated population size (dots) showing that the population has tripled in a decade. I cite the conclusion that …

Low High

Freshwater biodiversity supports the provisionof key ecosystem services by aquatic ecosystems

Provisioning servicesAvailability of fresh water

(% inland waters)Source: CLC2000

Regulating servicesPurifying water

(nutrient retention capacity)Source: Grizzetti et al. GREEN model, JRC

Cultural servicesRecreation

(number of compliant bathingwaters Source: EEA)

Presenter

Presentation Notes

At the JRC, we are interested in mapping ecosystem services at Eu scale. Currently, we are preparing a set of maps to show how the supply of these services in distributed over Europe, also for water related services. Freshwater ecosystems provide and regulate water quantity and quality and there is tremendous value in the provision of recreation by freshwater lakes and rivers. Globally, freshwater sytems sustain the livelihood of millions providing people with food and drinking water.

• Freshwater ecosystems support 6% of all described species and 1/3 of all vertebrates.

• Freshwater ecosystems provide key ecosystem services to sustain human livelihoods.

• Fresh waters experience greater than average declines in biodiversity. The high level of endemism makes freshwater ecosystems particularly vulnerable.

• Biodiversity assessments remain difficult; the present knowlegde base is insufficient. – BIOFRESH project: to improve capacity to protect and manage freshwater biodiversity in the face of ongoing

changes to global climate and socioeconomics. www.freshwaterbiodiversity.eu

– Coordinator is Prof. Dr. Klement Tockner (Leibniz-Institute of Freshwater Ecology and Inland Fisheries)

• The most important threats are flow modification/habitat destruction, pollution and invasion by exotic species.

• Recovery, sometimes rapid (decade), is possible but requires a combination of policy, persisted efforts and, importantly, patience.

Summary and conclusions

http://www.freshwaterbiodiversity.eu/

• Bruna Grizzetti, JRC

• Faycal Bouraoui , JRC

• Ana-Cristina Cardoso , JRC

• Jochen Vandekerkhove , JRC

• Alberto Aloe , JRC

• Jan Breine, INBO, Belgium

Acknowledgements

Freshwater biodiversity - European Commission...Action Biodiversity, Water and Ecosystem Services (BIOMES) Global distribution of freshwater ecosystems Freshwater ecosystems may be

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