The famous lines of John Keats, “ A thing of beauty is a joy forever.” always make me to think about flowers. Many of us equate nature with beauty and forever joy. Can plants be the reason of any inconvenience? Some of them are; when they are distanced from their native regions. I remember coming across one such plant when I visited hills of Northern India for the first time. I was mesmerized by the yellow and red hues of beautiful flowers covering almost all the hills; until my friend belonging to the same region told me a different story. She said, locals call it “ Witch Shrub” as it supresses the growth native flora. That shrub is Lantana Camara; an invasive plant.
What are Invasive plants?
Some of the exotic plants become invasive when introduced into non-native environment for ornamental or agricultural purpose. They compete with native vegetation for space and resources as they have an edge over the local plants in terms of rapid growth and higher photosynthetic activity. Some invasive plants release inhibitory chemicals while others interfere with symbiotic relationship that native plants share with soil fungi. Invasive Alien plant species are among top five factors responsible for biodiversity loss.
How it reached India?
It was at the start of 19th century when multiple hybrid varieties of plant with vibrant flowers were brought to India as an ornamental plant which has now reached the forests of India. Over the time, more hybrid varieties have developed that grow as climbing woody vines or thick shrubs. International Union for Conservation of Nature has listed Lantana Camara among top 100 invasive plant species and top 10 weeds of the world. It has invaded around 40% of the Indian forests and Tiger reserves are worst hit.
The extent of invasion
Lantana Camara; a tropical American Shrub is found in various climatic conditions in India. As per the Global Ecology and Conservation report, it has invaded around 3,00,000 sq.km of forests in India including 1,54000 sq.km of Tiger ranges and most affected areas are South-western Ghats, Central deciduous forests, and Northern Shivalik hills. The sprawl of pretty flowers is serene but it is a big loss to regional biodiversity. A study reported fourfold increase in Lantana in Biligiri Ramaswamy Temple Wildlife Sanctuary from 1997-2008 with significant decrease in native species richness, diversity, and evenness.
How Lantana thrives?
Wastelands, forests recovering from fires, roadsides, and forests disturbed by anthropogenic activities are favourable for growth of Tick berry; another name for Lantana. It can survive in poor soils, altitudes up to 1800 metres above sea level, and is drought resistant. On contrary, it does not invade dense forest areas with taller tree canopies, intact forests and is unable to cope with the temperature below 50C. Human activities such as deforestation coupled with natural traits of the plant has provided the favourable conditions for this uncontrolled and unwanted expansion.
Impact on Environment
Research on plant-soil interactions has found that introduction of invasive species has altered the components of nutrient cycles of the ecosystem. Herbivores of the region struggle to find native forage plants. This creates ripples in food chain and food web which ultimately results in ecological instability. Herbivores attack crops for food, which sometimes, are followed by carnivores and this results in increased human-animal conflicts.
A study conducted at Bandipore Tiger Reserve, Madhya Pradesh has found that Lantana is also responsible for tree death by fires as it is known to increase the frequency of forest fires. Lantana develops into woody bushes; this bushy network is problematic for fast running animals such as tigers.
Impact on community
The livelihood of Indian tribals is intertwined with forest produce and it was reported in 2012 study that Lantana Invasion has direct impact on Soliga community in Southern states of India. Dense growth of Lantana has made it difficult for tribal to people to enter the forest and access the edible tubers that are part of their daily diet.
How to handle “The Lantana Menace”?
Lantana is a perennial plant with capability to revive through its root stock and nodes. It is an arduous task to mitigate the growth due to role of birds in pollination. Manual uprooting is the basic measure but it is neither successful nor economically feasible. Moreover, uprooting disturbs the neighbouring vegetation and makes the land more susceptible to soil erosion.
Biological control and use of herbicides can be employed but we need to assess how native flora and fauna reacts to these methods. Jim Corbett National Park has found a way of inverting the plant upside down after cutting and keeping it on the same spot for some time. This has resulted in checking the reproduction and reducing the density of Lantana growth.
Effective measures should be taken to protect Lantana infested forests from human activities such as hunting, illicit felling, and encroaching along with efforts to control the forest fires. This will make the forests moist in the long-run and modifications in species composition may arrest the growth of Lantana. Precautionary measures are the only way out till some research happens to control the invasion of Lantana in non-native regions.
Don’t fall for beauty of Lantana. You may plant one of it but in no time; it will hijack your garden.
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