30 Sep Battling the Invaders: Top 5 Worst Invasive Plants in Mauritius

30 September 2023

 

You would be mistaken for thinking that Mauritius is covered in lush tropical native forest as nearly a quarter of the island is forested. Yet less than 2% of the original high quality native forest remains. And, it’s under attack from invasive plant species. A daily challenge for Ebony Forest’s restoration teams based in Chamarel, Vallée De L’Est and Montagne Longue is to remove and keep exotic vegetation at bay. Without action, we risk forests of single species and the extinction of unique plant species, as well as the fauna that depend on them.

 

More than 1,675 plant species have been introduced in Mauritius, of which 20 have been identified as particularly aggressive invaders (UNDP). That’s more than double the number of native Mauritian flowering plants! We’ve chosen five species which we consider the worst invasive plants in Mauritius – Hiptage benghalensis, Psidium cattleianum, Mikania micrantha, Falcataria moluccana, and Ravenala madagascariensis – due to their invasiveness, impact on native biodiversity and difficulty to control.

 

Hiptage benghalensis

Common name: liane cerf

Hiptage benghalensis, known locally as “liane cerf” or in Reunion as “liane de papillon” (butterfly vine), originates from India, Southeast Asia and the Philippines. Although its creamy white to pale yellow flowers are beautiful, this invader is deadly. It rapidly establishes itself, giving rise to dense thickets that smoother native vegetation. Its remarkable growth rate, prolific seed production and ability to disperse long distances due to its unique three-winged helicopter-like fruit make it a considerable challenge to manage. If left unchecked, this invasive species suffocates and strangles endemic trees, depriving them of vital sunlight, burdening their structures, and ultimately leading to their demise.

Liane cerf strangling a native plant.

Mature liane cerf fruits are carried for miles in the wind.

 

Psidium cattleianum

Common name: Strawberry Guava or goyave de Chine

Originally hailing from Brazil, not China as its local name, “goyave de Chine”, implies, Psidium cattleianum was introduced to Mauritius as an ornamental plant. Aided by invasive pigs and birds, that spread its seeds, guava forms dense thickets that shade out native plants, preventing natural regeneration. Without control, guava replaces native flora, limiting the food sources and habitats of endemic animals and ultimately reducing biodiversity. While both guava and Hiptage, are among the World’s worst invasive plants, they can be controlled by cutting the trunk with a machete or chainsaw near the base and applying a herbicide to the cut stump to prevent regrowth.

Cutting guava is a key part of the Ebony Forest restoration teams activities. Photo source Christine Griffiths

 

Mikania micrantha

Common name: Mile-a-Minute Weed

Mikania micrantha, also known as the Mile-a-Minute Weed, has its origins in Central and South America. Its rapid growth, which can exceed 30 centimetres per day, has earned it its nickname. This creeper forms thick mats that smother native vegetation, climbing over planted saplings, trees and shrubs, denying them of sunlight. It regenerates readily and its wind-dispersed seeds spread easily making it a particular challenge for our restoration teams to control. Fortunately, once a native canopy forms, this light-loving weed is shaded out. 

Mikania rapidly forms dense blankets, killing vegetation. Photo source

 

Falcataria moluccana

Common name: Albizia

Origin: Southeast Asia and the Pacific

Albizia, scientifically known as Falcataria moluccana, was introduced to Mauritius for its fast growth. This nitrogen-fixing tree, which can grow up to 7 metres in its first year and reach 40 metres in height, outcompetes native plants for light and nutrients, forming dense stands that alter water availability and soil composition. Its attractiveness as an ornamental tree conceals the danger it presents to infrastructure and people. Unlike endemic canopy trees that are adapted to cyclones, Albizia’s branches readily break or the tree is uprooted during strong winds. To avoid damaging endemic or planted trees, our restoration team ring-bark or girdle them, by stripping the bark of the tree’s trunk. This disrupts the flow of nutrients and water between the roots and the canopy, slowly killing the tree.

Beautiful, yet dangerous. Left unchecked, Falcataria moluccana take over natural areas.

 

Ravenala madagascariensis

Common name: Traveller’s Palm

The Traveller’s Palm, Ravenala madagascariensis, hailing from Madagascar, forms dense monocultures, excluding native vegetation. Despite its palm-like appearance, it is not a palm, but a relative of the bird of paradise plant (Strelitiziaceae). While endemic geckos are easily spotted in Ravenala, if uncontrolled, this invasive, which can grow up to 10 metres in height, takes over and displaces native vegetation, reducing biodiversity. Favouring moist areas, our restoration teams at Ebony Forest and Vallée de L’Est remove Ravenala by cutting the trees or injecting poison to slowly kill the plants.

Dense patch of Ravenale in Mauritius. Photo by Adisha Sewydal.

 

Besides its attractive fan-shaped arrangement of leaves, Ravenale produces blue seeds which are unusual in nature. Photo source

 

Conclusion

Mauritius is facing a biodiversity crisis and invasive species, plants or animals, are a major driving force in ecosystem degradation. Most invasive species were introduced to Mauritius by humans, so next time you are considering planting an exotic plant in your garden, think twice. Habitat restoration requires long-term commitment and investment and it is thanks to the Mauritius Forestry Service and our partners that we are able to maintain this battle. Just to name a few. Fondation Franklinia, whose mission is to conserve some of the world’s most threatened trees, has been co-funding our forest restoration activities at all three restoration sites since 2020. The Critical Ecosystem Partnership Fund has supported our forest restoration activities since 2016. The Mauritius Commercial Bank, Currimjee Foundation, Mr Bricolage, Bioculture Ltd, and Livestock Feed Ltd as well as all those that have visited Ebony Forest, are supporting saving our native biodiversity.