Reuters AlertNet 22 Oct 10;
TOKYO, Oct 22 (Reuters) - Damage to rivers, wetlands and lakes threatens to destabilise the diversity of freshwater fish species, posing risks for food security, incomes and nutrition, a U.N.-backed report said on Friday.
Rivers and lakes are the source of 13 million tonnes of fish annually, which in turn provide employment to 60 million people, the study by the United Nations Environment Programme (UNEP) and the World Fish Centre showed.
Fish from inland waters is also important for nutrition, especially in Africa and parts of Asia, by supplying micronutrients such as vitamin A, calcium, iron and zinc, the report added.
It said such factors highlighted the risks to humans from the destruction of freshwater ecosystems and the urgency to protect them from pollution, climate change, overfishing and construction of dams.
The report was released on the sidelines of an Oct 18-29 U.N. meeting in Nagoya, Japan, aimed at pushing governments and businesses to do more to fight accelerating losses in animal and plant species. [ID:nTOE69L09O]
While fish production had grown in Asia and Africa over the past 40 years, catch in other regions had levelled off and in some cases, fallen, with environmental damage cited as a factor, the report said.
Fisheries in the Volga River in Europe have declined because of dams, while fisheries in Lake Malawi and Lake Malombe in Africa have fallen from overfishing and environmental degradation.
"It takes a concerted effort to protect and maintain these so-to-speak 'free' ecosystem services around the world," Yumiko Kura of the World Fish Center told a news conference on the sidelines of the Nagoya meeting.
"It is important to maintain these natural ecosystem services from human destruction because it is very costly to replace these ecosystem services once they are lost." (Reporting by Chisa Fujioka; Editing by Sugita Katyal)
Warming 'destabilises aquatic ecosystems'
Mark Kinver BBC News 23 Oct 10;
Future warming could have "profound implications" for the stability of freshwater ecosystems, a study warns.
Researchers said warmer water affected the distribution and size of plankton - tiny organisms that form the basis of food chains in aquatic systems.
The team warmed plankton-containing vessels by 4C (7F) - the temperature by which some of the world's rivers and lakes could warm over the next century.
The findings appear in the journal Global Change Biology.
"Our study provides almost the first direct experimental evidence that - in the short-term - if a [freshwater] ecosystem warms up, it has profound implications for the size structure of plankton communities," said lead author Gabriel Yvon-Durocher from Queen Mary, University of London.
"Essentially, what we observed within the phytoplankton (microscopic plants) community was that it switched from a system that was dominated by larger autotrophs (plants that photosynthesise) to a system that was dominated by smaller autotrophs with a lower standing biomass."
Dr Yvon-Durocher added that a greater abundance, but lower overall biomass, of smaller phytoplankton had "very important implications for the stability of plankton food webs".
"This meant that the distribution of biomass between plants and animals changed from a... situation where you had a large amount of plants and a smaller amount of animal consumers to an 'inverted pyramid' where you have a smaller quantity of plant biomass and a larger amount of animal biomass," he told BBC News.
"Systems that tend to have larger consumer biomass relative to the resource biomass tend to be less stable over time."
Dr Yvon-Durocher explained that phytoplankton played a key role in the food webs of oceans, rivers and lakes.
"An inordinate amount of the primary productivity and carbon draw-down in ocean and freshwater ecosystems are carried out by microscopic planktonic organisms."
Because the tiny plants are able to produce their own food by using energy from sunlight, they are an important food source for zooplankton - microscopic animals that are not able to synthesise their own food.
The zooplankton are also a vital food for other creatures higher up the the food chain.
"Understanding the dynamics of these communities is going to be crucial in understanding how marine and freshwater ecosystems will respond to changes in temperature."
Fresh insight
For their experiment, the team of UK and Spanish researchers used 20 mesocosms, which are containers that allow scientists to study freshwater ecosystems in a controlled environment.
"We were able to, in a relatively small plot of land, have 20 replicated ecosystems - half of which we warmed, and the other half we kept at an ambient year-round temperature," explained Dr Yvon-Durocher.
"The great advantage of using the mescosm set-up is that it allows the manipulation of an entire ecosystem.
"There is an absolute wealth of literature on the effects of warming and climate change on single species, but we understand very little about what happens at a community level."
Commenting on their results, the team said: "These findings could provide some novel insights into how future warming might change the distribution of organism size and biomass in freshwater ecosystems.
"The size structure of plankton communities is a key driver of rates of carbon sequestration and nutrient cycling."
They added that warming waters could have an impact on a global scale.
However, Dr Yvon-Durocher said that it did not mean that the future for aquatic ecosystems was looking bleak.
"What it means is that the make-up of ecological communities are likely to profoundly change as a result of warming," he suggested.
"It may mean that the species' composition might change, but what we don't understand is how those changes are going to affect the functions of the ecosystems.
"That is the next step."
River and lake fish 'neglected but essential'
Richard Black BBC News 22 Oct 10;
Inland fisheries provide employment for more people than their marine equivalents, as well as being a vital source of nutrients, a study concludes.
The UN-backed Blue Harvest study says that in Africa alone, fish from rivers and lakes are a key source of protein and minerals for 100 million people.
However, dams and other kinds of water management have drastically reduced yields, particularly in Europe.
Properly valuing these fisheries could lead to better forms of management.
The study was launched at the UN Convention on Biological Diversity meeting here.
It puts the yield of fish from these predominantly freshwater sources at 13-30 million tonnes per year.
In terms of quantity, that is dwarfed by the amount coming from the oceans and aquaculture, which produce in the region of 50 million tonnes annually.
But because inland fishers generally deploy low-tech methods and use the fish for local consumption, the employment benefit is somewhat higher.
The UN Environment Programme (Unep) says this is the first study to bring together inland fisheries data from across the world.
"This fascinating report has brought to the fore the often neglected subject of inland fisheries," said Unep's executive director Achim Steiner.
"While marine fisheries are under increasing scrutiny, those based on river and lake systems rarely engage the international community - an oversight of potentially profound implications."
End of the line
That scrunity is one of the factors that have led to governments, and fishing communities themselves, to take action to conserve marine fish stocks.
But in inland fisheries, the situation can be more complex.
Dams and other modifications of waterways can have big and unintended consequences for these fisheries, while communities and industries alongside can also disturb them with pollution.
"If you look at Japan, or countries around Europe that used to have commercial inland fisheries, they now don't exist," said Yumiko Kura of the WorldFish Center, a UN-supported research institute based in Malaysia.
"The level of modification done to freshwater lakes and rivers has a lot to do with the productivity of those systems - many freshwater species are migratory, and connectivity between river systems and betwen rivers and the sea is very important."
Where inland fishing is possible in industrialised countries, she noted, it is usually for recreation rather than staple food, and often supported by the regular release of juvenile fish.
Basin cut
To illustrate the point, Blue Harvest compares the health of the salmon populations in two of North America's largest river systems, the Fraser and Columbia, which both supported major fisheries until the early 1900s.
Since then, nearly 150 dams have been built on the the Columbia and its tributaries; the Fraser has just a handful.
The Fraser is recognised as the biggest salmon-producing river basin in the world, while on the Columbia, most populations are under government protection, and have to be supported by hatcheries, the addition of measures such as fish ladders, and the regular transportation of fish between different parts of the basin.
The report warns that unless modifications in major developing world rivers such as the Mekong are carried out in ways that allow fish to flourish, there will be a decline in catches essential for millions of people.
This does not mean that dams and other infrastructure should not be built, it concludes - but that development must be appropriate, and decisions made only after properly assessing the economic, nutritional and social benefits of the fisheries.
A related concern, said Ms Kura, was preserving the diversity of inland water systems such as the Mekong, where fishers catch on the order of 500 different species.
"When you look at the fisherman's net, there are countless species in it - they don't rely on any particular one, but on all of them," she said at the launch here.
"In some years, certain species might not be available but other ones are, because different species have different ways of responding to environmental changes - so biodiversity is key to sustaining the vitality of the fishing industry."
