Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The South East Asian snail disaster

31.03.2004


A promising enterprise became an economical and ecological disaster. The golden apple snail (Pomacea canaliculata) that was brought to Asia in 1980 to be cultured in ponds for human consumption instead spread through rice fields, irrigation channels and wetlands. It had a voracious appetite for rice seedlings and soon became a dreaded pest in the rice fields. In the Philippines alone, accumulative crop losses since the snail introduction is estimated to 1 billion US dollars. The snail is still spreading in South East Asia and it has recently invaded North Australia, Hawaii and southern USA. Recent research, however, shows that the invasive snail is a serious threat to natural environments as well.



This is because the snail consumes the aquatic plants in natural wetlands. These wetlands harbor great biodiversity, and many of the animals depend on aquatic plants for their survival at some life stage. These wetlands are also an important resource in the “unofficial economy” since the rural poor harvest plants, catch fish and collect drinking water in the wetlands.

– The ongoing invasion is nothing but an ecological disaster says Nils O L Carlsson at Lund University, who has quantified the effects of the invasive snail on natural wetlands in Laos and Thailand.


Entrepreneurs brought this South American snail to Taiwan in 1980. The intention was to grow these large snails (may grow to the size of a medium apple) in ponds to sell them at local food markets and export them to Europe. The project backfired. The Asian markets turned cold to the taste of the snail and all export to Europe was banned when it was found that the snail may be an intermediate host for a parasite that destroy the central nervous system in man.

At this time, however, the explosive invasion had already started. The snail is originally from Southern Brazil and Argentina and there is no feeding, growth or reproduction in the winter. At the higher mean temperatures in South East Asia growth and reproduction is greatly enhanced.

- The female snails lay around 300 eggs weekly and year around and flooded bushes in the wetlands often contain up to 100 000 eggs, says Nils Carlsson and he continues:

- When the snails attacked rice seedlings the invasion received a lot of attention. The farmers panicked and used both registered and non-registered pesticides. The invasion has therefore led to unsustainable use of chemicals and large negative non-target effects on many organisms, including man. Ironically, the snails effect on natural systems has been almost totally neglected, as the measurable economical damage from the snail was thought to be smaller in these systems.

- The wetlands are crucial for the diversity of both in-water, amphibious and land organisms, and rural people harvest plants, catch fish and collect drinking water in these systems. When the invasive snails consume all the plants, these productive systems turn into stagnant ponds with alga blooms.

Nils Carlsson is the first to quantify the effects of the snail in natural wetlands. He found that snail densities in these are as high as in infested rice fields and that the snails consume almost all plants. When the plants are consumed, the snails recycle large amounts of nutrients and these nutrients enhance phytoplankton growth instead. This is therefore a great threat to all organisms that depend on aquatic plants as food, refuge or spawning substrate. The values of the ecosystem services the wetlands provide rural people also drop dramatically after a snail invasion.
This snail invasion is thus not only a threat to rice production but also a serious ecological threat to all invaded wetlands.

- In both rice fields and wetlands you see a lot of people with cut and wounded feet says Nils. There are broken and sharp snail shells everywhere.

Besides higher mean temperatures, a popular explanation to the snails enormous success in South East Asia has been release from natural enemies, but Nils does not agree. Hunting and fishing pressures are very high in rural Asia. In Laos for instance, you can drive through rice fields and wetlands for an entire day without seeing a single bird. Nils has conducted experiments in Laos where he found that at least four native fish species, one native freshwater turtle and one native freshwater crab could consume the snail.
- More studies may confirm that the “immune system” of these environments have been fished and hunted away and that there are strong economical reasons to conserve biodiversity in this part of the world.

Göran Frankel | alfa

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>