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 Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

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: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Simple processing technique could cut cost of organic PV and wearable electronics

06.12.2016 | Materials Sciences

3-D printed kidney phantoms aid nuclear medicine dosing calibration

06.12.2016 | Medical Engineering

Robot on demand: Mobile machining of aircraft components with high precision

06.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>