- Ox-eye daisy, an invasive species that sits snugly in the Kashmir Himalayas landscape, tweaks the soil in which it grows, to leave lasting impacts. It eclipses native vegetation or plants that call the landscape their home.
- This shadow effect hinders native plants from bouncing back even after the daisies were clipped. To restore the landscape to its original form, additional strategies are needed after removal that can spruce up soil health.
- Removal of invaded landscapes must be taken up long-term with regular scientific monitoring and evaluation of target landscapes.
Believed to have been introduced by the British in pre-Independence India for its showy flowers, ox-eye daisies that adorned ornate gardens in Kashmir rapidly spilled out and effortlessly invaded the region’s fragile forest and mountain landscapes over time.
As early as 1972, American botanist R.R. Stewart who extensively documented and studied the flora of the Western Himalayas describes this spilling out as an “escape”, in the publication Flora of West Pakistan – Annotated Catalogue of Vascular Plants of West Pakistan and Kashmir. He writes that ox-eye daisy is “common in gardens and often an escape in Hill stations like Muree Nathia and Dunga Gali (now in Pakistan).”
Indian botanist Anzar Khuroo who has tracked the spread of ox-eye daisies (Leucanthemum vulgare) in the Kashmir Himalayas for over a decade, describes the species as an incredible survivor. “Its seeds and seedlings survive under very dense native vegetation, without any access to light. In a few years, it spreads from small patches to full booms covering tens of hectares of land and turning the entire landscape into a beautiful area with white blooms.”
One never tires of this striking view, but to the scientists, this picturesqueness is also worrying.
“The species grows much faster than the native vegetation, outcompeting it, leaving virtually no space for other native plants to grow around its vicinity,” says Khuroo of the University of Kashmir, Srinagar, India.
The daisy’s impacts on the region’s local flora also concern the pastoral communities dependent on livestock grazing. It completely invades the mountain meadows leaving little room for grasses preferred by the animals. Cattle turn their nose up at the daisies, according to the researchers. R.R. Stewart also says in his book that ox-eye daisies are “not eaten by cattle.”
Ox-eye daisy is one among the at least 100 alien invasive plant species in Kashmir Himalayas. Invasive alien species are known to cause environmental harm to the native ecosystem. Anzar Khuroo and colleagues who have been documenting the invasive species in Kashmir Himalayas since 2007 in a recent study share that its spread is a constant shadow on the soil health in invaded landscapes.
Manually removing ox-eye daisies by plucking them is not enough to restore the invaded ecosystems. Their growth causes persistent changes in soil nutrients, which hinder the successful restoration of invaded landscapes. Khuroo and co-authors say this shadow or legacy effect in the physical, chemical or biological properties of soil due to a particularly pugnacious invasive species persists even after the successful physical removal of the invader.
Legacy effect of invasive plants
It is challenging to get the soil back in shape as it was pre-invasion. “We carried out manual removal by clipping the daisies continuously for three years, but we saw it is not sufficient to ward off this invasion problem in a particular landscape,” Khuroo said.
“The plant shifts the soil’s nutritional balance in such a way that it makes the soil more comfortable for its proliferation. The legacy effect becomes a management challenge because it prevents the recovery of the native plant communities even after removal of the invasive species,” said Khuroo, observing that ox-eye daisy presents an interesting case where the emphasis has to be also laid on additional strategies post removal.
Research scholar and study co-author Rameez A. Khuroo pointed out that for their research, they plucked the plants without uprooting them. “There is one hypothesis that the disturbance (while uprooting the plant) favours the plant growth in that area so we only remove it at the ground level,” Rameez told Mongabay-India.
Citing a modeling study, the team warns that this plant species, native to Europe and western Asia and naturalised and/or invasive in all the continents except Antarctica, will occupy more areas than currently occupied under projected climate change in the future. In its introduced regions, it invades disturbed habitats like grazing pastures, open meadows, roadside areas and forest openings, reducing the native plant species diversity.
The authors drew up a nine-point framework that recommends additional research steps to guide the successful restoration of invaded ecosystems. They include setting up long-term monitoring sites, unraveling how the soil reacts to invasive species, identifying invasion legacies, anticipating additional management interventions, and adopting globally standardised methods and protocols.
Khuroo explains that management strategies to restore invaded landscapes should focus on changing the soil conditions to achieve the desired restoration outcomes. One way is having specific interventions that are organic, for example, the use of biofertilisers. “We need to have more research on what additional management strategies would suit best because managing their impacts on the ecology will have a cost.”
For example, it costs up to Rs. 6000 per hectare to mechanically remove lantana in Indian protected areas. But managed sites are rapidly taken over by lantana again putting a spanner in the management programmes aiming to eradicate the invasive species from the landscape.
Between 1970 and 2017 invasive species cost the world at least USD 1.28 trillion, new research underscored. The draft of the post-2020 biodiversity framework to protect nature calls for a 50% greater reduction in the rate of introduction of invasive alien species, and controls or eradication of such species to eliminate or reduce their impacts.
Hope for more attention on invasive species
Khuroo believes the discussions centred on the post-2020 biodiversity framework and the UN Decade on Ecosystem Restoration will bring more attention to the issue of invasive species in India, which is a signatory to the Convention on Biological Diversity and will work to meet the post-2020 goals once finalised. These new targets will succeed the Aichi Biodiversity Targets.
Environmental scientist T.V. Sajeev, the technical focal point for India in the Asia-Pacific Forest Invasive Species Network, says the research on ox-eye daisy in the context of ecological restoration alerts policymakers and forest managers to the fact that it is crucial to look beyond the removal of an invasive species from the landscape and unpack the chemical profile of the soil after an invasive species has established its foothold.
“Ecosystem restoration is a very sensitive activity. It has to be well-thought-out, and we need an active research program to back it up,” Sajeev, who is with the Kerala Forest Research Institute, told Mongabay-India. Sajeev informs that each category of invasive species requires customised interventions. These categories are long-established invasives such as lantana (Lantana camara), species that have just come in, and those waiting to enter (door-knocking species).
“Restoration is for the long-established species,” shared Sajeev. He adds that while policy attention on invasive species is negligible in India, forest departments in various states are working hard to include restoration in their working plan. “This is a start,” Sajeev emphasised.
In a commentary to Mongabay-India, experts highlighted that from the documentation of the Indian alien flora in the mid-20th century to the publication of multiple checklists, India has long recognised the invasive alien plant species (IAPS) present in the country. But a lack of awareness, prevalent across public and government sectors, is the major hindrance for IAPS-specific policy formulation. Besides, a lack of coordination and consensus persists between several agencies, even between those operating under the same ministry. Networking and information sharing are essential, especially when several Green India Missions are mushrooming in the country, which, if unattended, could be an avenue for invasive alien plant species to spread.
Banner image: Ox-eye daisy in the Kashmir Himalayas in India. Photo by Anzar A. Khuroo.