IAPS Targeted: Xanthium indicum
The Minneriya and Kaudulla National Parks are key sites for the Elephant Gathering – a seasonal migration event for the Sri Lankan elephant that is vital to the survival of the species. These elephants use the grasslands that form during the dry season, when the water levels in the tanks recede and expose their tank beds. In 2016 and 2017, the area experienced two consecutive monsoon failures of the Northeast Monsoon, and from 2018 there have been inconsistent changes in water storage in the Minneriya reservoir due to the opening of the Moragahakanda Dam, causing consecutive disruption to the natural flooding and receding water cycle in this habitat which helped to curtail the growth of this IAPS.
These events have created ideal conditions for the Agada species to thrive:
- The Xanthium species favours man-made or disturbed habitats relating to marshes, dunes, wetland margins, and the shores of rivers and lakes – of particular relevance to the Minneriya and Kaudulla tank beds.
- The mature fruits of this species cling to animal fur and human clothing, but its main method of seed dispersal is by floating on water, depositing with debris along the flood lines of receding water.
The infestation of Agada impacts both wildlife and humans in the area. The Agada plant itself is toxic to herbivores, so cannot be a form of alternative fodder for grazing animals, and its abundance in the Minneriya and Kaudulla National Parks significantly reduced foraging lands for grazing animals like elephant, sambhar, deer, wild buffalo, etc. This can lead to increased instances of human-elephant conflict as elephants are encouraged to seek food outside of the park. Additionally, the Minneriya and Kaudulla tanks are vital to the irrigation system that feeds the primary agricultural regions of Sri Lanka – changing these ecosystems can have a negative impact on this system.
In 2020, The FEO started our habitat restoration initiative in the Minneriya National Park, tackling what was estimated to be about 200 Ha of land invaded by Agada. After a pilot study and discussions with the DWC, it was determined that we would remove the plants manually when possible, and with a slasher when necessary, and we would do maintenance work over 3 seasons, ensuring the remove any Agada before the seeds matured to minimise spread. As of 2023, we have completed our work in the Minneriya National Park.
As the Minneriya tank is upstream of the Kaudulla tank, any inconsistent water management has a trickle-down effect in Kaudulla – allowing for Agada to also grow rampant in the Kaudulla National Park. So, the FEO has also moved on to clear Agada from this park in 2023, where we have completed our work for the first season and will be doing maintenance work over the next 2 seasons.