Every year, patches of forest across Mizoram go up in flames as farmers practicing traditional jhum cultivation clear land to sow new crops. After a year, the land is rested, allowed to rejuvenate and returned to for cultivation only after several years.

On the face of it, the practice seems highly destructive. This is certainly what the state government believes – for the past 10 years, it has strongly promoted a New Land Use Policy that encourages farmers to move away from traditional shifting agriculture to monoculture plantations in the name of promoting conservation and biodiversity.

But a new study confirms what previous studies around the world have already been saying – that traditional shifting cultivation is less destructive to biodiversity than monocultures such as teak and palm oil plantations, which actually lead to a shrinking of biodiversity. This means that the state government's policy may actually lead to a shrinking of biodiversity.

The study in Condor: Ornithological Applications – an international, peer-reviewed journal – by wildlife scientist TR Shankar Raman and Jaydev Mandal, a research scholar from Guwahati University, was published last month. The researchers found that sites of jhum cultivation had a significantly richer number of bird species than oil palm and teak plantations – there were 667% more forest birds in the jhum sites surveyed than in oil palm plantations.

A flawed premise

Jhum cultivation refers to an agricultural practice where farmers clear and then burn patches of forest and vegetation to cultivate crops. Once crops are harvested, they move on to a different plot to allow the land to rest, and bamboo and secondary forests to regenerate. Anywhere between five and 10 years later, they return to that spot to resume the cycle of burning and cultivating.

“Historically, jhum has been considered bad for biodiversity,” Raman said. “Yes, it does have some negative effects on rainforest interior species. So primary forests do need to be protected as there are valuable birds here not found elsewhere. But by saying that they want to protect forest cover, the government is promoting land use that is worse than jhum. This struck me as odd.”

The agriculture department of the Mizoram government states its case for replacing shifting cultivation with oil palm plantations clearly on its website. It attributes increased land degradation in the state to “jhumming, deforestation, loss of biodiversity and productivity, increasing flood”, affecting the livelihoods of Jhumia families.

“Oil palm,” the website says, “stands as an ideal crop capable of achieving conservation of soil and moisture, repair of degraded land, providing ecological balance, food and security of rural and urban poor.”

But the study proves otherwise. It said that habitats structurally similar to mature forests had a far “greater number and proportion of forest bird species”, and monocultures, however stable they might seem, simply did not support as wide a range of avian life.

Shifting land use

Dampa Tiger Reserve is a large, dense forest on Lushai hills in Mizoram that abuts India’s border with Bangladesh on its west. It is home to both local and migratory birds each summer.

Raman first studied wildlife at Dampa in 1994-'95 as part of a field research project for his Master's dissertation in wildlife science at the Wildlife Institute of India, Dehradun. In late 2013, the forest department invited him back to the reserve to conduct a bird survey, which he conducted between February and April 2014.

Mizoram had changed a great deal in the 10 years since he had last studied the area. Teak and oil palm plantations now occupied areas close to the reserve. Since they knew that monocultures were not good for supporting biodiversity, Raman and Mandal decided to do a rapid survey of birds in different land use areas.

They found that sites of jhum cultivation had a significantly richer number of bird species than oil palm and teak plantations. In fact, the richness of bird species in jhum areas was relatively closer to that found in mature forests.

This flies against government wisdom that maintaining teak or oil palm plantations is better in the long run. It is because of this belief that large parts of Dampa’s buffer zone have been replaced with such plantations with government support since the 1980s, as people were encouraged to shift away from jhum.

The big government push for oil palm plantations only started 10 years ago, but it has spread rapidly – from just 110 hectares in two districts in 2005 to 20,377 hectares in all seven districts by 2015. Three companies – 3F Oil Palm Agrotech Private Limited, Ruchi Soya Industries Limited and Godrej Agrovet Limited – have committed to process all oil palm produced in the state.

Jhum beats monoculture

Between March and April 2014, Raman and Mandal surveyed 100 sites in five types of places: oil palm and teak plantations, jhum sites and the edge and interior of mature forests in Dampa.

Their approach was straightforward. They walked slowly along 100 metre-long lines and noted every bird they detected within 30 metres on each side. Each survey or transect was 0.6 hectares and took around 10 minutes to cover. The two rarely did more than eight or 10 lines in a morning. At the same time, Raman and Mandal also noted the kinds of vegetation birds were using, the density of trees and bamboos, and canopy cover.

They recorded 107 species and a minimum of 1,152 individual birds within this area. Almost 90% of these were forest birds. The greatest variety of species was in the interiors of mature forests, the least in oil palm plantations. These findings are in line with other studies on monoculture plantations across the world.