Invasive plants spreading faster & wider, say experts

Pune: Invasive plant species are affecting native species of biodiversity more adversely now, ecologists said.

Sachin Punekar, an ecologist and founder-president of Biospheres, said, “ Invasive species can sweep away local biodiversity and are the second biggest threat, after habitat destruction and alteration.”

Punekar has been actively involved in weed eradication programmes that he started in 2016. The commonest invasive plant species was cosmos bipinnatus or the Mexican weed and eupatorium odoratum.

The post-monsoon invasion of cosmos bipinnatus can wreak havoc on local flora. They grow along the roadside and the hill slopes.

Cosmos can be seen growing in clumps at Katraj Ghat, Sinhagad and Shivneri forts. “The species is growing near the forts, ghat regions and along the roadside. Earlier, it was in some pockets of Taljai hill. It has spread everywhere,” he said.

Their growth hampers native grasses which are fodder species that herbivores and livestock feed on. Invasive species is are allelopathic and as such poisonous to native crops, Punekar added.

Eupatorium odoratum is commonly seen in the outskirts of deciduous as well as moist deciduous forests throughout the Western Ghats. “Both the species form dense clumps, hardly allowing other native species to grow,” Punekar added.

Amateur botanist Shrikant Ingalhalikar said there was a problem of incorrect interpretation of native and invasive species. Many native trees have disappeared from Pune out of sheer negligence and people are fighting to save the invasive plants, he added.

“The problem lies in the interpretation of native and invasive varieties. Considering examples of native and exotic species, it is important to understand that all exotic species are not invasive. As a blanket, when everyone talks about exotic, they think every exotic species is invasive. There has to be focus on eradication of invasive species like cosmos or water hyacinth,” he said.

The area under cosmos species is doubling each year, he said. “Cosmos is a harmful species and has to be nipped before it flowers. I have been observing it for about 40 years and each year it is doubling. Now, it is beyond control,” he added.


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