Anand Pendharkar: Alien invaders

Invasive species can choke ecosystems and kill economies

The news of Dr Rauf Ali's death circulated among friends and fellow wildlifers on April 1. Known for his jovial nature, everybody wondered whether it was an April Fool's Day prank. Sadly, it wasn't. His passing away was a blow to the scientific community. As the founder of the Foundation for Ecological Research, Advocacy and Learning (FERAL), and having been a faculty in almost all top conservation related courses, he was the towering dogma-breaker.

His professional demeanour would have his students and colleagues in splits, yet making them ponder upon conservation questions. There is no doubt that he had stepped out of the shadows of his world-famous uncle, Dr Salim Ali, and earned a wide-spread following of his own. After the tragic tsunami on December 26, 2004, that ravaged the Bay Islands and South India, Rauf toiled for the economic rehabilitation of the tribals, especially of the Nicobar Islands.

The pretty but harmful flowers of Eupatorium
The pretty but harmful flowers of Eupatorium

His research work, mainly centred in the Andaman Islands, was about the impact of invasive species on indigenous and endemic flora and fauna. Threats to conservation of local and range-restricted species, due to introduction and colonolisation of exotic plants and animals, are colossal.

And Mumbai's biodiverse islands are no exception. The Western Ghats are rich in every type of life-form (taxon), be it terrestrial, fossorial, aquatic, aerial or marine. Over the years, visitors, invaders, colonial rulers and passionate horticulturists have introduced hundreds of types of exotic plants into our forests and urban neighbourhoods. Funnily, now many of these introduced species even have regional names, along with suitable mythological references.

On April 4, SPROUTS celebrated its 21st anniversary with a nature trail at the Sanjay Gandhi National Park (SGNP). The trail focused on the forest flora and we came across many indigenous plants, such as Bhedha, Ukshi, Tendu, Sagwan, Kusum and Semal. We sighted exotic species, such as the Copperpod, Gulmohar, Raintree, Gliricidia and the ubiquitous lantana.

Late Dr Rauf Ali
Late Dr Rauf Ali

Native Indigenous species have their life cycles intertwined with local fauna. Animals spend millions of years co-evolving with plants, and don't change their diets on individual whims. Thus, our exotic species are creatures introduced from dissimilar ecological regions and many show a great capacity to spread on their own, turning into invasive weeds.

Introduced for their ornamental value, some creatures spread to a degree that causes damage to the local environment, economy or human health. However, others remain limited to their introduced habitats. Some islands also lack large grazers or predators and these non-native species put the indigenous species at risk.

Introduced in India by the British as a hedge plant, Lantana is among the top 10 invasive aliens across the world. These butterfly magnets can choke forests. They don't allow other plants to grow, they turn into climbers and spread up to 30 – 35 feet. Their spines injure graziers and the leaves mildly poison cattle who consume them. Mumbai's forests, gardens and lakes are choked by invasive weeds, viz. Eupatorium, Cassia tora, Ivy-leaved Morning Glory, Congress-grass and Water Hyacinth. Some affect human health and others threaten our entire ecosystems.

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