It’s hard to imagine how much of the Bandipur Tiger Reserve is covered in lantana until you see it. As Range Forest Officer Srinivasea RD rode in a government jeep along an entry road in mid-April, it seemed to be everywhere on both sides of the asphalt. When it’s dry and brown, lantana camara -- once a decorative shrub brought to India in colonial times, now an invasive weed known simply as lantana -- looks like giant cobwebs thread across the ground or thousands upon thousands of tumbleweeds looped together amid scattered trees, waiting on a good gust of wind.
Lantana has evolved from nuisance to threat because of its ability to take over large swaths of land. It’s grown so much in the woodland savannas of south India’s tiger reserves and national parks that a small spark can use lantana to explode into a broiling fire, a problem that seems likely to worsen as the region’s temperature rises and monsoon rains become more erratic, leading to longer dry periods. The plant has also crowded animals and other plants out of huge swaths of space in which they used to roam and grow.
“These reserves in Karnataka and Tamil Nadu, they have been practically overpowered by lantana,” said BK Singh, former Principal Chief Conservator of Forests for Karnataka.
Srinivasea was dressed in the tan hat, tan collared shirt and blue lapels that are the uniform of the Range Forest Officer. He’s in charge of beating lantana back at least 30 meters from either side of the roads, which helps tourists in cars see wandering elephants or deer or warthogs. He then cuts a thick line through the vegetation to hinder the spread of fire. On the drive out to a lantana-clearing area, he asked the driver to pull the jeep over every few minutes so he could shout at people who had parked. A side effect of clearing lantana from tourist areas is that those tourists often clog the main roads, crawling along so people can pull out their cameras and point them at something that’s just darted into the thicket.
Clearing lantana by hand is a process of slashing, burning, and ripping. Srinivasea’s team first hacks at the weeds until they sever the plant from the ground. They then push it back from the roads where, during the wet season, when there isn’t much risk of fire erupting into an uncontrollable beast, they burn it. They rip out the roots of whatever lantana stalks are left, so at least those particular plants won’t grow back.
Around 90 kilometers from the park entrance, on a patch of land far away from anywhere a tourist might go, officers use heavy machinery to dig out lantana and free up space for grass and animals. The machines are deemed too loud and unsightly for tiger and leopard-spotting zones, but they can clear close to two acres per day.
That’s much faster than cutting and tugging out lantana by hand, but a study published in 2015 by Tarsh Thekaekara, a conservationist with the Shola Trust, a non-profit conservation organisation based in south India, found that nearly 90,000 acres of Bandipur were “either ‘dominated by lantana’ or ‘impenetrable,’” which amounts to 38% of the reserve. It also mentioned that “almost all interventions aimed at 'eradicating' the plant over the last 100 years have failed,” and said plucking lantana from “heavily infested areas” costs way too much to continue for long.
Eliminating lantana has been a Bandipur practice for decades, but they’ve only started using heavy machinery in the last four-five years, according to Srinivasea. Ideally, he said officers would like to wipe out the weed from the experimental clearing ground, but for now the operation is just a test to see how much they can get rid of and how much will stay lantana-free.
“It’s not possible by one day, one month, one year,” Srinivasea said. “It’s a process.”
As the jeep rumbled on, evidence of their work was all around: clumps of severed lantana piled near the edge of a pond, blackened stalks Srinivasea said they’d burned just before dry season. The road rose on the way to the last stop of the day, and Bandipur’s woodland savanna spread out underneath. From that distance, the lantana covered the ground like a fuzzy sea, stretching everywhere toward distant mountains.
Lantana and Fire
A series of fires scorched around 15,000 acres of Bandipur in late February, raging for several days as hundreds of firefighters, forest personnel, and others wrested it under control, with the help of two helicopters that dumped 49,000 liters of water from above.
These kind of blazes regularly burn through south India in part because of how much lantana now covers the landscape. Fire can light it up like kindling and use it to spread across the ground. Lantana also climbs trees, helping flames jump from the ground to the canopy where the fire can do more damage, according to Ankila Hiremath, a plant ecologist at the Ashoka Trust for Research in Ecology and the Environment.
South India’s connected woodland savannas are vast enough that even these huge fires don’t consume nearly enough terrain to threaten them as a whole. The landscape has also adapted to fire: The bark on trees is thicker than in other ecosystems, and small blazes clear shrubs, leaving room for grass to grow. Lantana, though, has crowded the grass’s space, and according to MD Madhusudan, a co-founder of the Nature Conservation Foundation, even fire-adapted woodland savannas aren’t “accustomed to” these blazes, because the landscape hasn’t adjusted to this thicket of “fuel.”
The fires that are fueled by lantana can also remodel the woodland savannas into terrain ripe for more lantana.
S Sandeep, a soil scientist with the Kerala Forest Research Institute, said lantana sprang into a new area of the Wayanad Wildlife Sanctuary after a fire in 2014. This likely had something to do with what happens to soil when everything around it burns, especially after the kind of south Indian fire that can heat the ground up to 800 degrees Celsius -- nearly twice the surface temperature on Mercury.
Soil quality actually increases right after a fire because of all the ash that seeps into the ground, but it only takes a few months for it to harden into poorer version of its former self, a kind of soil that struggles to absorb water and is prone to erosion.
“Once the soil gets degraded, only the most tolerant sort of plants will survive,” Sandeep said.
Those tolerant plants include invasives such as lantana, which reproduces so fast that even if a native species’ seedlings survive the fire, they have little time to repopulate.
Weeding out the problem
Lantana is a flowering plant native to Central and South America that British colonisers thought made a pretty addition to their botanical gardens, and so they first planted it in erstwhile Calcutta in 1807. The shrub’s popularity brought it from botanical gardens into home gardens, and by at least 1829 it had already made its way down to the Nilgiris. Lantana seeds travelled in the mouths of birds and washed into the wild amid sheets of rain, finding a home in the region’s woodland savannas.
As lantana began to spring up in the south, the British were figuring out how to use the woodland portion of those savannas to make money for their empire. Trees were only useful to them if they could be sold for timber, and so the colonisers treated fire as a menace, just as they did in the temperate forests of Europe. The British ignored the indigenous practice of controlled burning that natives used to clear brush, allowing shrubs and bushes to grow and twigs and leaves to pile high.
Controlled burning may also have been able to limit the spread of lantana, and though even the British began to realise in the early 20th century that total fire suppression was a mistake, Indian foresters have been reluctant to swerve away from colonial-era ideas. Without small fires, the invasive weed has warped woodland savanna ecosystems across the south, making it difficult to figure out how much controlled burning is still a good idea.
“You can’t burn it in the same way that you used to,” Thekaekara said. “We have to kind of start from scratch, bringing together indigenous and scientific knowledge.”
Ripping lantana out of the ground probably won’t work either, according to Hiremath, unless it’s coupled with something more.
“It will just come back,” she said. “There’s so much lantana in the larger landscape and it’s so easily dispersed.”
Once a patch of lantana is sliced off and uprooted, she suggests seeding the ground with native plants. Foresters could also light controlled fires that can damage lantana seeds and ward off its creep.
Bilal Habib, an animal ecologist at the Wildlife Institute of India, thinks an effort to eradicate lantana should have started 20 years ago.
“We are at a very critical stage right now,” he said. “We know they are invasive species. They are going to spread and spread. They’ve already taken a toll on our habitats.”
There’s a good chance lantana could come to dominate regions to the north, snaking its way through wooded parts of central India, aided by the warming and drying climate. A few of the former garden decorations have even made their way into the Himalayas, which appear to be warming up just in time to welcome them.
Colin Daileda is a freelance journalist in Bengaluru who has written about climate change for Thomson Reuters, and on other subjects for The Atlantic, Roads and Kingdoms, Mashable, and others.