The blue fly : not a fly on the wall
The invasive bramble Rubus alceifolius is not called a "plant pest" for nothing. Originally from South-East Asia and accidentally introduced to Reunion in the 19th century, its development at the expense of local species is comparable to that of an infection spreading in an organism. In the absence of a predator, its progression knows no limit. Until now, the control methods put in place, mainly mechanical or chemical, have been expensive and inefficient ...
Finally, a little bee from Sumatra has proved to be the right remedy. Cibdela janthina, known as "the blue fly", has, after a whole battery of tests conducted by CIRAD since 1997, been declared able to restore the biodiversity of Reunion. This little hymenopter has the peculiarity of exclusively attacking the genus Rubus, to which the invasive bramble belongs. Following its introduction on the island in 2007, the results were not long coming; 700 hectares formerly colonized have now been returned to nature! The invasive bramble now only thrives above 1200m above sea level in areas the bluefly finds difficult to reach.
Larvae of Cibdela janthina / Adult Cibdela janthina - © Antoine Franck – CIRAD
Biological control of an invasive population is similar to testing a new treatment. It must be studied, adapted and specific. Sometimes it's a success, as was the case for the invasive bramble with the blue fly. In other cases, the treatment acts in the desired way but has disastrous side effects.
Being able to restore biodiversity without playing the mad scientist is one of the ambitions of the project COREIDS, developed at CESAB and led by ecological researchers François Massol and Patrice David. They analysed the functioning of ecosystems in detail; what are the different species that contribute to their balance? How do they interact? What could be the effects of a disruptor as was the case with the invasive bramble? All of these elements will ultimately help to better understand and anticipate threats to biodiversity ... prevention is better than cure!
On a wing and a prayer: the journey of the wandering albatross across the globe
Lying on a mattress of moss, feet dangling over a 200 m high cliff, under a grey and windy sub-Antarctic sky, one can hear the footsteps of the wandering albatross (Diomedea exulans) as it prepares to take off for its long journey. The wind catches the 3 m long wingspan and lifts the gigantic bird into the air propelling it onto another journey into the stormy Southern Ocean.
Its voyage will be remarkable, lasting many months and circumnavigating the globe. For us the Southern Ocean can be a forbidding, even dangerous, place but for the albatross the stormy conditions are a boon. Their streamlined bodies and their long, narrow wings give them the ability to ride the wind, extracting energy as it rushes over the waves to keep them airborne. So efficient is this that the birds can travel for thousands of kilometers without flapping their wings once!
Much of the bird’s life while on this long journey is a mystery to us. How does it navigate its way around the world? How does it find its food?
This bird is carrying a small satellite linked data logger, which will help answer some of these important questions. The device provides very accurate locations several times a day. Combined with data from an army of other instrumented albatross, seals and penguins, the track from this bird will help researchers from the analyse and synthesis group « RAATD » identify what areas in the vast Southern Ocean are of particular importance to Southern Ocean predators, and guide us in designing new management strategies to protect the bird and its children. for many generations to come.
See the future through the bromeliads
What if biodiversity allowed us to read our future? This is the observation of the team of Régis CEREGHINO, a researcher at the University of Toulouse who studies the bromeliads with a magnifying glass. Many of these flowering plants shelter small reservoirs of rainwater that contain algae, bacteria, fungi, invertebrate larvae and small frogs. True miniature versions of lakes, bromeliads, among other characteristics, respond quickly to change. While it takes tens or even hundreds of years for a large lake to respond to a mutation, bromeliads respond within a few weeks.
(c) Jean-François Carrias
AWe can manipulate their environment to simulate deforestation or climate change. From their response, researchers can draw ecological rules. When climate change is simulated where rains are scarce, bromeliads dry up. The first species to be affected are small predators that then release pressure on their prey. The consequences are many, including for man. In these stagnant systems are larvae of mosquitoes which, in the absence of predators, are likely to swarm and potentially transmit viruses. The moral of the story ? Biodiversity is a set of interacting species. The elimination of species in a context of global change can have cascading consequences and a (very) high cost to society.
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