Removal of IAS (Invasive
Alien Species) in Minneriya National Park


  • It is estimated that over 20% of the tank bed is currently taken over by the invasive alien species ‘Agada’ (Xanthium indicum – Common Cocklebur) which is rapidly spreading across the grasslands of the tank bed.
  • This extensive loss of the grasslands of the Minneriya tank bed poses a serious threat to the primary grazing grounds of the elephants, and thereby threatens the famous annual Elephant Gathering.
  • Rapid response in preventing seed dispersal is critical in controlling the spread of any invasive alien species, and hence urgent action is critical to reverse the process of the loss of grasslands at Minneriya.
  • Project Agada also intends to positively impact those who have lost their income sources due to the COVID19 induced downturn in tourism by employing them in the plant removal process.
  • The total budget is estimated at LKR 9.2 million for clearing the IAS from 200 hectares of the Minneriya tank bed.
  • Project Agada: Removal of IAS in Minneriya National Park is proposed by the Federation of Environmental Organizations (FEO) in partnership the Department of Wildlife Conservation (DWC).


  • The failure of the North East Monsoons in 2016 and 2017, together with the changes in water storage in the Minneriya reservoir due to the Moragahakanda dam project, has enabled this invasive alien species to establish itself and spread extensively on the Minneriya tank bed. Under normal circumstances, seasonal flooding of the tank bed controls the spread of this invasive species. It is currently estimated that over 20% of the tank bed has been covered by the alien invasive Agada plant due to the failure of the historical cycle flooding and receding over the last three to four years. This has significantly reduced the foraging areas of deer, sambhar, wild buffalo, etc.

However, this issue is most critical to the survival of elephants and the famous Elephant Gathering, as well as the loss of primary feeding grounds for elephants which may in turn, lead to the escalation of the HEC as elephants look for alternative food sources. 

  • The management measures adopted for any alien plant invasion will depend upon factors such as the severity and stage of the infestation, terrain, cost and availability of labour and other necessary resources. A critical factor in control of an IAS is early detection and rapid response in preventing seed dispersal. Given that the life span of seeds of an invasive species can last up to several years, totally eradicating an IAS within one growing season is not feasible. Hence, consistent follow up control is vital for sustainable management of any IAS.


  • The negative impact of this IAS is seen across the grasslands of most tank beds in the region such as the tank beds of Minneriya, Kaudulla, Giritale, etc. The rapid spread of the IAS is diminishing of the availability of grass lands that are the primary feeding grounds of elephants and other herbivores.
  • The open grasslands of these tank beds are the location of the Elephant Gathering – which is one of Sri Lanka’s most popular wildlife attractions worth over US$8 million annually in foreign exchange revenue.
  • The problem is aggravated by the fact that the IAS Agada plant is itself toxic to herbivores, and thus not a suitable alternative fodder.
  • A well-known negative impact of alien invasive species of any type is the long term, irreversible changes to the biodiversity of the host eco-system, in this case the Minneriya and other tank beds and surrounding eco-systems, central to the survival of wildlife as well as the irrigation system which feeds the primary agricultural regions of Sri Lanka.


  • The Agada (Xanthium indicum, Family Astaraceae) is an invasive alien plant species in Sri Lanka. It is known to thrive in man-made or disturbed habitats relating to marshes, dunes, shores of rivers or lakes and wetland margins. While the mature fruits cling to animal fur and human clothing for dispersal, the primary method of dispersal is via floating on water and depositing with debris along the flood lines of receding water. 
  • No detailed study nor exact estimation of the area effected by the Agada invasion of the Minneriya Tank bed is currently available. However, the Minneriya Park Warden estimates approximately 200 hectares of the tank bed has currently been taken over by Agada, and it is spreading along the flood level and along the canal banks with each season.
  • On 5th June 2020, the FEO carried out a site visit with the DWC to assess the situation and pilot test alternative methods of removal of Agada plants.  Plant removal was tested at three different sites and the feasibility of alternative methods as well as practical issues of implementation was discussed at length with the Minneriya Park Warden and other onsite DWC staff members.
  • Currently, large tracks of grasslands around Katukeliyawa and Palupitiya are thickly covered with mature plants that are over 4 feet tall that have started to seed. Smaller, younger plants have started spreading in areas such as Rambawila and Thalgasduwa.


  • As stated above it is critical to remove IAS Agada before the seeds mature.  As we will be unable to clear the entire area of Agada manually before the seeds set and disperse, it is proposed that around 50 % of the plants be removed manually before they set seed (inclusive of roots) whereas the remaining 50 % which are more difficult to remove, will be removed via a slasher.   
  • Manual removal of Agada will be via two crews each, under the supervision and security of the DWC. The hired crews will be transported daily to the work site. The removed plant matter will be immediately removed from the site and disposed daily in locations identified by the DWC.
  • The hired labour will be drawn from those who have lost their income sources due to the COVID19 induced downturn in tourism. This includes large numbers of jeep drivers, guides, hospitality workers, etc. The project will enable them to be productively employed as well as contributing to the conservation of one of the main tourist attractions in Sri Lanka. In addition, those who are selected for the project will be given an awareness training on invasive species control.
  • Plants that are difficult to remove manually and are in urgent need to be removed prior to seeding will be handled by mechanized slashers available with the DWC. The accompanying tractors will be hired locally as well as a crew to clear the path for the slashers and dispose of the cut plant material. As with the waste generated via manual removal, the plant waste generated will be removed from the site and disposed daily in locations identified by the DWC.  
  • The target for this season’s activity will be the clearing of over 80% of the matured and young Agada plants on the Minneriya tank bed. In line with the accepted methods of controlling IAS plants, it is expected that this will minimize the spread of the plant during the next season.
  • The process will have to be repeated for at least two or three more seasons, though at a lower intensity, to manage the negative impact on the grasslands, and its role as the primary feeding grounds for elephants.
  • It is critical to commence this season’s intervention urgently to minimize the seeds set and dispersal which would further exacerbate the problem. Further, the clearing needs to be completed prior to the commencement of the North East Monsoon, and ideally before the recommencement of the tourist season.


  • LKR 9.2 million is estimated for the initial stage of clearing an area of 200 Hectares. 
  • The primary cost is the labour related which will be made up of employing those who have lost their income sources due to the COVID19 induced downturn in tourism, their transport to the clearing site, equipment costs and tractor hire for the transport of the invasive species to the disposal site.
  • Summary of Budget expenses

Manual (100 Hectares) – Rs. 8,005,100.00

  • Labour – Rs. 5,209,600.00
  • Equipment – Rs. 159,000.00
  • Transport – Rs. 1,440,000.00
  • Meals and refreshments – Rs. 52,500.00
  • Supervision & Project Management – Rs. 844,000.00
  • Miscellaneous / Contingency – Rs. 300,000.00

Mechanised (100 Hectares) – Rs. 1,182,125.00

  • Labour – Rs. 320,000.00
  • Equipment – Rs. 259,000.00
  • Transport – Rs. 500,000.00
  • Meals and refreshments – Rs. 3,125.00
  • Supervision & Project Management – Covered under Manual budget
  • Miscellaneous / Contingency – Rs. 100,000.00


  • Project start date: 21st July 2020
  • Over 500 acres cleared so far!
  • Minneriya 70% (350 acres) & Kaudulla 30% (175 acres)


  • Minneriya – 150 acres
      @10,000/- per 2.5 acres   OR   @50,000/- per day for 12 days    LKR 600,000/-
  • Kaudulla – 375 acres
     @5,000/- per 2.5 acres      OR   @25,000/- per day for 30 days  LKR 750,000/-


We would welcome Philanthropists and Corporates who love this country as much as we do, to come forward to support this project by way of much needed funding.

Your contribution will help!

  • Support those less fortunate who are affected by the current situation with their source of income drying up and now, will have employment through this project
  • Reduce further impact on the escalating Human-Elephant conflict, that could arise due to this major loss of fodder for the elephants
  • Ensure that we continue to enjoy the Gathering for years to come

You can make a direct donation to the FEO Bank account detailed below:

Account Name:
Federation of Environmental Organizations

Registered Address:
49/8 Fife Road, Colombo 5

Account Number:
0175 6000 0138

Bank & Branch Address:
Sampath Bank (Branch #175 – Colombo Super Branch)
No 103 Dharmapala Mawatha, Colombo – 7

Swift Code: BSAMLKLX

Bank Code: 7278

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