Freshwater megafauna such as sturgeon, river dolphins and turtles could act as valuable ‘flagships’ for freshwater conservation, according to a new open-access study published in the journal BioScience.
In the last decade or so, it has become apparent that freshwater biodiversity is both highly threatened, and is decreasing at a higher rate than its terrestrial or marine counterparts. In part, this awareness can be mapped to an influential – and highly cited – 2006 paper by David Dudgeon and colleagues.
Despite the multiple threats and pressures faced by freshwater ecosystems across the world, they tend to receive less conservation attention, research and investment than their terrestrial and marine equivalents. In their new paper, lead author Dr. Savrina F. Carrizo (IUCN) and Dr. Sonja Jähnig (Leibniz-Institute of Freshwater Ecology and Inland Fisheries, IGB) together with other IGB researchers and a team of international co-authors, suggest that freshwater megafauna could provide a focus for conservation action by acting as flagships for overlooked aquatic ecosystems and biodiversity.
The flagship species concept in conservation is nothing new: rhinos, elephants, tigers and whales have been used for decades to gain public attention for environmental issues. Such charismatic, iconic, and popular animals can help attract media coverage and outside investment, and potentially help legitimise and communicate wider conservation messages.
The use of flagship species is sometimes linked to the ‘umbrella’ ecological model, where the conservation of flagship species – such as the giant panda in China, and jaguars in Central and South America – may benefit other flora and fauna in the protected ecosystems in which they live.
Given the limited time and funding available to many conservation organisations, and the often incomplete scientific knowledge of imperilled ecosystems, the flagship species concept provides a popular and promising tool for conservation planning across the world. But how might it help benefit freshwater ecosystems and biodiversity?
Freshwater megafauna status and threats
The authors of the new study – originally supported by the EU BioFresh project – argue that there are a number of freshwater ‘megafauna’ species, whose large size and spectacular appearance could help generate public interest for ‘hidden’ freshwater issues. Potential flagship candidates include the beluga sturgeon, American alligator, Yangtze finless porpoise, and the Caspian seal.
The research team assessed the conservation potential of such species in a three-part study. The first part of their study provided an assessment of the geographical distribution and conservation status of global freshwater megafauna. This required a definition of which animals could be called ‘megafauna’ – a term which could be interpreted to mean any ‘large animal’. The researchers decided that freshwater animals above 30kg in mass would qualify as ‘megafauna’.
The researchers then chose 132 megafauna species – 73 fishes, 36 reptiles and 23 mammals – which were seen as well-known or iconic. Over half (58%) of the 107 species assessed for the IUCN Red List were classified as threatened. Multiple pressures threatening their populations include overexploitation, habitat alteration, and pollution. The baiji and Chinese paddlefish have not been directly detected over the last decade, and are classified as Critically Endangered (Possibly Extinct). Six other species are Near Threatened, six more lack sufficient information to assess their conservation status, and twenty-five have not been evaluated for the Red List.
In short, despite their high visibility in many cases, freshwater megafauna species are widely threatened across the world, and their ecological status may be even worse than current assessments suggest.
Shortfalls in freshwater megafauna conservation
The researchers found that freshwater megafauna inhabit every continent except Antarctica, and mostly occur in large rivers and lakes. Southeast Asia and the Amazon Basin are particularly high in megafauna biodiversity. However, over three-quarters (84%) of global freshwater megafauna populations are found outside of protected areas. Only two – the Baikal seal and the Ungava seal – have more than half of their range in protected areas. Large rivers such as the Mekong and Ganges are particularly poorly protected.
The researchers suggest that this shortfall in existing protected area coverage presents a conservation opportunity. They argue that freshwater megafauna distributions can help guide the targets and boundaries of new protected areas or catchment management programmes. If successful, the research team state, such ‘megafauna-shaped’ protected areas have the potential to attract significant financial, public and political support for freshwater conservation.
Conservation potential of megafauna as ‘umbrella’ species
Would such new protected areas, or catchment management zones, benefit other non-megafauna freshwater biodiversity? This question guided the second part of the study, in which the researchers assessed the spatial overlap between the distributions of all freshwater biodiversity, and those of the selected 132 megafauna species.
They found that 93% of the distribution ranges for all assessed freshwater species co-occur with megafauna species, and 60% of the world’s threatened freshwater species are found within the collective megafauna range. Whether megafauna can act as ‘umbrella species’ for the protection of wider biodiversity is unclear, in part due to knowledge gaps about their often complex and dynamic lifecycles and uncertainty over their ecological roles.
Gaps in knowledge of freshwater megafauna
New scientific research is now required to generate baseline information on megafauna species, to help guide evidence-based conservation, in part through comprehensive Red List assessments. This is the focus of the third and final section of the new study, which provides a ‘horizon scan’ of the steps needed to promote freshwater megafauna flagships as a conservation tool.
The researchers suggest that in addition to new scientific data on the species, it is important to better understand their diverse (and often local) valuations by different social and cultural groups, including fishers, environmental managers, water resource users, local communities and indigenous people.
Linked to this, they suggest that the contribution of freshwater megafauna to the provision of ecosystem services – such as tourism, recreation and fishing – requires further investigation. A key challenge here is likely to be that many ecosystem services provided by freshwater megafauna are purely extractive, and can lead to overexploitation, as has been seen in beluga populations in the River Danube in Eastern Europe.
Freshwater megafauna and environmental policy
The authors of the new study suggest that the role of freshwater megafauna as ‘conservation flagships’ may help policy makers identify important areas for conservation and help them meet global environmental legislation and targets. 29 freshwater megafauna species are listed in the Convention on Migratory Species, and 74 in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Freshwater megafauna conservation also has the potential to help meet conservation goals in the Aichi Targets, restoration goals in the Ramsar Convention, and UN Sustainable Development Goals, they suggest.
Freshwater megafauna as flagships?
Of course, a key question is, if freshwater megafauna have such potential for conservation, then why haven’t they been deployed in the same way as tigers, pandas and whales, as yet? Do the physical characteristics of many freshwater ecosystems – variously turbulent, opaque, or otherwise off-limits to humans – restrict the potential of aquatic flagships?
The authors of this paper suggest that this might not be the case, and that freshwater megafauna offer an, as yet, overlooked conservation opportunity equivalent to the terrestrial megafauna. They propose that freshwater megafauna species might act as productive ‘flagships’, both to guide freshwater conservation planning, and to attract public, political and financial support for it.
Their study provides a number of important steps towards this goal, showing how freshwater megafauna are widely distributed globally, often have threatened populations, and have significant geographical overlaps with other freshwater biodiversity.
The data used in this study will be archived through the Freshwater Information Platform, and the metadata published through the Freshwater Metadata Journal.
View the freshwater megafauna maps from this article in the Global Freshwater Biodiversity Atlas online.