Controversy is swirling around moves to cut trenches to reportedly mitigate the human elephant conflict (HEC). Conservationists are levelling very serious charges that this “trench warfare” will do more harm than good to wild elephants and other animals and is a ruse to exploit resources including soil in Protected Areas (PAs). This is while a [...]


Trenches against wild elephants – tried, tested and failed, say experts

Conservationists including former DWC DG Dr. Sumith Pilapitiya raise serious concerns and urge sticking to the National Action Plan presented to the President. Is trench-cutting for so-called HEC mitigation, a ruse to get at resources of PAs?

The disaster that is the trench dug around the Lunugamvehera National Park

Controversy is swirling around moves to cut trenches to reportedly mitigate the human elephant conflict (HEC).

Conservationists are levelling very serious charges that this “trench warfare” will do more harm than good to wild elephants and other animals and is a ruse to exploit resources including soil in Protected Areas (PAs).

This is while a top-level official of the Department of Wildlife Conservation (DWC) is adamant that it is a good management strategy in mitigating the HEC in areas where the conditions are suitable for such trenches.

The need to ‘pilot’ such trenches before wide usage across the country had been underscored by a Presidential Committee set up at the behest of President Gotabaya Rajapaksa.

This Presidential Committee whose mandate was to develop a ‘National Action Plan for HEC Mitigation’ (the Action Plan), appointed in August 2020 was chaired by well-known local and international wild elephant expert Dr. Prithiviraj Fernando and comprised vital stakeholders including the DWC and experts. (See Box)

The Action Plan had been presented to President Rajapaksa in December 2020.

The Director-General (DG) of the DWC, Chandana Sooriyabandara was categorical when the Sunday Times contacted him on Friday that the trenches were ‘piloted’ in two areas in the Ampara district. The piloted trenches were saarthakai (successful) but kalu-gal thibba hinda asarthaka wune (because of rock it was unsuccessful) in one place.

When the Sunday Times requested specific details and was told to contact another DWC official, we found that both so-called trenches had not worked, but plans were afoot to continue the project across the country. (See box)

Strongly protesting against the move to dig trenches, former DWC DG Dr. Sumith Pilapitiya says that trenches as a barrier for elephants has not been effective, based not only on Sri Lanka’s experience but also other elephant range states in the world.

His views are echoed by many conservationists including the 127-year-old Wildlife and Nature Protection Society (WNPS) with an active membership of over 2,000.

“In Sri Lanka, trenches have been tried in combination with DWC electric fences at the Pelawatte Sugar Company and the Lunugamvehera National Park in the south and Kathnoruwa in the northwest, but proved ineffective. Private landowners in the Puttalam area have also tried out trenches but without success,” Dr. Pilapitiya points out, with evidence in hand.

He says that the present State Ministry of Wildlife Protection, Electric Fence and Trench Construction ordered the construction of trenches around the garbage disposal dump in the Ampara area after there was a news item on the BBC about elephants eating garbage there. Within days of these trenches being in place, the elephants were back at the dump. “So, we have to accept that trenches have been ineffective in HEC mitigation.”

As a member of the Presidential Committee which came up with the Action Plan, he says that it is crystal clear that trenches have not worked.

Dr. Pilapitiya points out that since the State Ministry seemed keen on constructing trenches, the Action Plan recommends that modifications to the existing design of trenches should be tried out and tested on a ‘pilot scale’ and incorporated in the Action Plan only if found to be effective. It points out that such ‘test trenches’ will help assess cost, durability and effectiveness. The Action Plan is categorical that tests would need to be conducted for at least a year before effectiveness can be assessed.

“Yet, today we see large lengths of trenches being dug near Wilpattu, Uda Walawe and Lunugamvehera National Parks, with plans for trenches around other PAs and along electric fence lines,” he says, lamenting that he is “baffled” as to why “no one objected or disagreed to a single recommendation” when the Action Plan was presented to the President and the Cabinet Minister and the State Minister of Wildlife and also the ministry secretaries in December 2020.

However, in drastic contrast to the Action Plan, a year later we see that it has been ignored and the State Ministry and the DWC are going ahead with an HEC mitigation measure that the Action Plan identifies as being ineffective, says this expert, questioning strongly why a multi-stakeholder Presidential Committee which included elephant experts was appointed, if politicians and bureaucrats know better and do what has been tried, tested and failed? Is the agenda not HEC mitigation, but is there an ulterior motive?

He adds: “It makes me wonder whether in the guise of HEC mitigation, trenches are being proposed to facilitate natural resource extraction from DWC’s PAs. From the information available to us, it appears that private parties have been and will continue to be granted permission to excavate trenches on the boundaries and within the 1-mile ‘buffer zone’ of PAs, at their own cost with permission to transport the excavated soil for sale.

“It also appears that there is no transparent mechanism for selection of these private parties, so we can only imagine who the beneficiaries of this windfall are!

“The greatest concern I have is that for the first time, the ministry and the agency in charge of biodiversity conservation are legitimizing the extraction of a natural resource (soil in this instance) from the buffer zones of PAs.

“Since the experience in Sri Lanka with trenches as a barrier for HEC has shown them to be ineffective and the Action Plan of the Presidential Committee reinforces these views, I can only conclude that this is an exercise in excavation of soil from a PA with ministry sanction or an attempt to legitimize a resource grab.”

Dr Pilapitiya focuses on the adverse effects of trenches:

  • Deep trenches in wildlife landscapes impede wildlife movement, while smaller mammals can fall into the trenches, be severely injured or die.
  • Impacting on rainwater runoff, there could be unforeseen hydrological impacts.
  • While an Environmental Impact Assessment (EIA) is generally required for any activity that could have such adverse impacts, when such activity takes place within a mile (buffer zone) from the radius of a National Park, private, well-connected parties who are allowed to extract soil, get a free pass to do as they please, even though wildlife could be in jeopardy.

Asking whether this is what the guardians of wildlife in Sri Lanka – the Ministry, the State Ministry and the DWC – should be allowing, Dr. Pilapitiya says that if the government is concerned about HEC mitigation, the authorities should implement the National Action Plan.

“At least, try it in one district,” he adds.

The trenches were piloted, says DWC DG, but another official concedes they didn’t workThe trenches were piloted in two areas in Ampara this year, said the Director-General (DG) of the Department of Wildlife Conservation (DWC), Chandana Sooriyabandara.

He said that trenches are a management strategy for HEC but “hema thenatama applicable ne” (not applicable everywhere). If there are conditions such as sandy or muddy soil, there is water collection and an inability to drain water or if there are athara-meda badaka (intervening barriers) such as irrigation canals or other structures, they do not work. The main thing is not only to cut the trenches but also maintain them and for them to be of the right depth.

When asked whether in the piloted trenches any animals had come to harm, he said, “No”. This was because there was a “reasonable space” and if animals fell into the trench, there was a ramp which enabled them to clamber up and leave the same way they had come.

He insisted that trenches in proper identified locations have worked in other countries primarily in HEC mitigation, with a secondary benefit being the curbing of encroachment and preventing cattle coming into these areas.

There are ways and means of dealing with corruption, the DG said, when asked whether there could be illegal activity, etc., by allowing private parties to cut trenches. Monitoring will be by the DWC.

He told the Sunday Times to contact a high-level DWC official for more specific information on the pilot trenches and also where other trenches would be cut.

Declining to be named, this official said:

· One ‘pilot’ trench was cut in Adalachchenai in the Ampara district around May-June to prevent wild elephants coming to the garbage dump. It was 2 kms in length; 8 feet wide and 8 feet deep. However, the rains led to the banks of the trench collapsing and the elephants could go both ways and so this trench did not work. “Asarthaka baavayak thiyenawa (There is an unsuccessful element).”

· The second ‘pilot’ trench to the same specifications as the one in Adalachchenai was started in Buddangala, once again in the Ampara district close to a garbage dump. Half-way through “kalu-gal mathuwuna” (they hit rock) and a decision was made to halt it.

“Sri Lanka has around 4,700 kms of electric fencing across the country except in the Western Province and about 400 kms in different locations have been identified where the wild elephants breakthrough. These are the areas where plans are underway to cut agal (trenches),” the official said, adding that a committee comprising the relevant District Secretary and other stakeholders including the DWC will take decisions on these projects.

Action Plan clear on trenches

Here are the relevant sections on trenches, based on science and evidence, in the Action Plan.

“The use of trenches as a barrier for elephants is based on the premise that elephants do not jump across obstructions… Therefore, when faced with a trench, elephants will try to get over it by striding across it. If the trench is too wide for an elephant to stride across, it will try to get in and climb out of it.

“Therefore, the principle in the construction of trenches is that it should be too wide for an elephant to stride across and too narrow for an elephant to get in. However, elephants come in different sizes and it is not possible to figure out a width that works for all.

“Trench construction over long distances is difficult because of variation in soil conditions…. Trenches may also obstruct the drainage of surface water, leading to issues with irrigation.

“Additionally, it is not possible to construct trenches across roadways, waterways etc. Elephants will cross through any gaps left in a trench system, negating the effectiveness of trenches. Trenches will also obstruct the movement of other animals, hence, will have a wider impact than just on elephants.

“The biggest problem with trenches is that they fill up with water when it rains and the sides cave in. Elephants will also put weight on the sides of trenches and actively break them down. Elephants can also go down and clamber up very steep gradients by sliding down on their backs and using their knees to climb up. Lining trenches with concrete can stabilize the sides and prevent the sides caving in. However, such stabilization tends to be very expensive, tens of millions of rupees per km…

“Trenches have been tried in combination with DWC electric fences…but proved ineffective…..Small trenches as a protection against elephants breaking electric fences by dragging tree trunks onto them have had some success……Therefore modifications of trenches should be tried out and tested on a pilot scale and incorporated in the Action Plan if found to be effective.”

The Presidential Committee was headed by Chairman Dr. Prithiviraj Fernando (Chairman, Centre for Conservation and Research) and Secretary Vernon Perera (Additional Secretary, Ministry of Environment & Wildlife).

The members were: Dr. Sumith Pilapitiya [Former Director General, Department of Wildlife Conservation (DWC)]; Dr. U.K.G.K. Padmalal (Senior Lecturer, Open University of Sri Lanka); Dr. S. Wijeyamohan (Senior Lecturer, Vavuniya Campus, University of Jaffna); Manori Gunawardena (Wildlife Scientist, Born Free Foundation); Chandana Sooriyabandara (DWC Director General); W.A.C. Weragoda (Conservator General of Forests); Madduma B. Weerasekera (Commissioner General of Agrarian Development); Eng. K.D.N. Siriwardana (Director General of Irrigation); and the District Secretaries of Puttalam, Anuradhapura, Polonnaruwa, Moneragala, Hambantota, Ampara and Kurunegala.


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