Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Island biodiversity: invaders out!

02.04.2007
Plant introductions onto the island of Réunion have really gathered speed over the past thirty years. A hundred or so introduced plants are now proving highly invasive and are threatening the natural environment.

Around half were introduced deliberately (ornamental, crop or forest species), and the other half accidentally, along with imported seeds. In addition to chemical, mechanical and more recently biological control measures, it is now crucial to intervene upstream of invasion to prevent the introduction of potentially invasive species or regulate the spread of plants that are already on the island.

Lake Gol is a particularly eloquent example. In early 2006, it was completely covered by a mixture of water hyacinths (Eichhornia crassipes) and water lettuces (Pistia stratiotes). In March 2006, cyclone Diwa cleared almost 99% of the lake by flushing it out and washing the plants into the sea, but eight months later, it was again totally covered, to the detriment of the aquatic ecosystem as a whole. These aquatic plants are estimated to produce some 250 tonnes of biomass per hectare per fortnight, a rate that rules out mechanical control and calls for biological measures, which have already proved their efficacy in many tropical countries.

Rational joint management of natural environments and rural areas

There are four main ways of intervening upstream of invasion. The first is to ban the introduction of risky plants. This means assessing the risks beforehand. To this end, analyses by CIRAD under the EU POSEIDOM* programme served to identify around fifty potentially invasive plants, most of them ornamental. A ban is due to be placed on introducing those plants in the French overseas regions. Of the ornamental species grown in the highlands of Reunion, 34 are highly invasive. Moreover, once plants are introduced, there is a latency period before they begin to multiply and spread. However, once they have spread over an area of 100 hectares, they are impossible to eradicate, which confirms the need for early intervention.

It is also vital to take account of the movement of species between the various elements of the landscape: forests, rangelands, crops and inhabited areas. This is the second line of intervention. For instance, grasslands, which contain a high proportion of species from outside (80%), can play a major role in plant movements on a landscape level, depending on how well they are managed. In sensitive areas such as the highlands, rearing herbivorous animals is one way of managing the environment. Recent work under a rangeland management project (PASTOFOR)**, showed that productive, well-kept grasslands help to maintain biodiversity in surrounding natural environments by limiting the spread of invasive species. On the other hand, grasslands in which weeds are not sufficiently controlled are a threat to neighbouring natural environments. The interfaces between different environments are key to the circulation and development of invasive species: rational joint management of natural environments and rural areas is the only way of controlling them.

Taking account of how plants spread

Classing invasive plants according to their ecological impact and ability to conquer new areas has meant that it is now possible to define the priorities more effectively. However, it is also necessary to determine how they spread depending on the ecological context and on how the environments concerned are managed. In fact, these plants may spread in different ways depending on the type of environment. For instance, the false pepper tree (Schinus terebenthifolius) grows from seed in humid environments and from suckers under dry conditions. Likewise, the giant bramble (Rubus alceifolius) bears fruit at low altitudes but only propagates vegetatively at heights of more than 1000 metres above sea level.

The results of these studies mean that it is now possible to take more effective action against the threat posed to the island's biodiversity by these invasive plants. Managing invasive species on an island means taking account of all the processes that lead to invasion and considering various levels of intervention, from preventing risky introductions, through early detection of the initial signs of invasions, to control and the subsequent restoration of environments. Lastly, over and above preventing invasion, the main priority is to make local populations aware of the problem.

* POSEIDOM: Programme of options specific to the remote and insular nature of the French overseas department.

** PASTOFOR: Management of pastoralism on the fringes of highly protected natural environments.

Helen Burford | alfa
Further information:
http://www.cirad.fr/en/actualite/communique.php?id=678

More articles from Ecology, The Environment and Conservation:

nachricht Dune ecosystem modelling
23.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Understanding animal social networks can aid wildlife conservation
23.06.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>