Invasive Weeds Undermining Farm Productivity, Biodiversity

By: Rakesh Lohumi, Sr. Advisor & Sr. Editor-ICN Group

SHIMLA: The Himalayas are a treasure house of medicinal and aromatic plants.With no effective strategy to thwart the march of invasive alien species, which pose a major threat to the indigenous flora, more and more area is being usurped by weeds like lantana, ageratum, parthenium (Congress grass) and eupatorium.

The appearance of large gregarious patches of these weeds from the Himalayan foothills in the north to the Tamil Nadu in the south is a matter of grave concern as they pose a serious threat to the biodiversity, particularly the valuable herbs and other medicinal plants.

These species have invaded large tracts of pastures and agriculture land and they also hampering proper regeneration of forests. Several lakh hectares of productive land and forest area has been covered by weeds across the country and their march is continuing unabated. Piecemeal efforts to arrest their spread are not yielding results as the scale of the problem is too large.

Weeds are estimated to cause around 30 percent loss in potential crop production. The alien species account for 42 percent of the weeds and their impact on farm production of the country in monetary works out to over $ 38 billion annually. One of the most obnoxious weeds Lantana Camara, which was introduced as an ornamental plant, has spread across the length and breadth of the country. Being poisonous it is not consumed by animals and thus all the more difficult to control.

Failure to check the spread of these invasive weeds will have long term implications as they severely affect the biodiversity and ecosystem. They overwhelm the indigenous flora which virtually putting livelihoods of local communities at stake.

The cost of controlling its spread comes to $ 70 per hectare which is prohibitive. Further, a coordinated effort involving several departments and agencies is required as the weed is not confined to forests or agriculture land; it has invaded orchards, village common land, parks, road sides and other public places.

In many areas farmers have stopped growing crops as large portion of their cultural land has come under weeds. The ongoing climate changes are only helping the weeds to spread and they are intruding into the flora-rich sub-temperate zone in the ecologically fragile Himalayan region.

The implications for the biodiversity will be enormous and far-reaching as large scale invasion of forests by poisonous weeds is taking a heavy toll on useful grasses and bushes which provided fodder for the cattle. Also the dominance of single species on the forest floor also increases the danger of wild fires which spread quickly due to thick undergrowth.

Some medicinal plants like viola (banafsha) have already been weeded out from the pine forests and as the weeds march further up in the hills more such important species will be wiped out. The Himalayas are a treasure house of medicinal and aromatic plants. The hill dwellers earn a large part of their meager income by collecting medicinal herbs from the forests. The spread of these undesirable species will, in the long run, endanger the livelihood

How grave the situation is can be judged from the fact that in Himachal Pradesh alone over 60% of the 2600 sq km of area under forest cover in the lower elevation (up to 1000m) is infested with Lantana Camara. It is rapidly spreading and it has been noticed in elevations up to 1500m.

In all invasive weeds have affected 1,85,201 hectare of forest land in the state with Lantana alone accounting for 156,284 hectare , followed by Ageratum (20,343 hectare), Parthenium (6,324 hectare) and Eupatorium (2,248 hectare). Rehabilitation of Lantana Infested Areas: Since 2009-10 approximately an area of 11,000 hectares of Lantana infested areas has been rehabilitated.

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