Shisham tree is dying, experts are baffled: Getting to the root of problem

Indian rosewood or the shisham tree — used to make durable dark-reddish tables, beds, bookshelfs or chairs — is dying.

 

That is what scientists at the Forest Research Institute (FRI) in Dehradun have been hearing for over two decades.

 

Although one killer has been identified (a fungus), several mysteries surround shisham’s sickness and death.

 

“We don’t know enough,” says Amit Pandey, who heads the forest pathology department at FRI. Many killers could be working together, say scientists. “People are constantly approaching us, claiming that their shisham is dying,” says Pandey.

 

“And, it’s happening across the shisham belt.” Shisham is native to foothills of the Himalayas. Its range extends from Jammu & Kashmir, Himachal Pradesh, Punjab, Uttar Pradesh in the north, Rajasthan in the west, Bihar, Odisha and West Bengal in the east to the Northeastern states.

 

Researchers say farmers are worried because they plant shisham about 20 years in advance to sell them later, especially at the time of their children’s marriage. The tree is also a favourite of a state forest department during afforestation drives in part because it brings revenue.

 

Mortality numbers available so far are old and patchy. For example, in late 2000s as much as 70 per cent of the shisham trees had died in the western districts of Bihar, and about 30 per cent trees died in some districts of Haryana. A 2015 survey showed between 20 per cent and 70 per cent mortality across Uttarakhand.

 

So, to get a better idea on how much shisham is dying, where it is dying less, where it dying more, and whether the reasons at those places are similar or different or a combination of these, Pandey and his colleagues have proposed a national-level project to the environment ministry.

 

Forest Survey of India’s estimates, however, show that shisham, outside the forest, increased from 57 million trees in 2013 to 74 million in 2017. Most of them are young trees though. Which means old trees are either dying or being cut, says a researcher who doesn’t want to be named. Pandey argues that more new shisham trees doesn’t negate the view that trees are not getting sick.

 

“When a disease kills humans, do you compare the number of dead against more being born each year?” he asked. The important question here is how to lessen shisham’s mortality, say researchers.

 

It was sometime in 1997 that FRI scientists began to hear about widespread death of the shisham. “It was scary,” recalled A N Shukla, a plant pathologist who led an all-India project in 2004 to investigate the problem. The team found dead or sick shishams wherever they looked — along the roads and railway tracks, in the agriculture fields, and in forests. Analysis of samples from some of those places led to a common killer — a specific soil dwelling fungus.

 

Researchers, however, blame humans for making it easier for the fungus to attack the shisham. Some human activities damage or weaken shisham’s roots, which helps the fungus penetrate.

Farmers in parts of northern India plant crops near the shisham, some of which get damaged during ploughing of fields.

 

Construction of highways and roads is often done on a higher level than the ground where the trees are. That blocks the natural drainage of water and leads to water logging around trees for months after rains. Waterlogging prevents surface roots from breathing properly, so roots become weak. When the tree senses that, it rushes the food down to feed the weak roots. But the fungus slurps up the food and grows. It then further penetrates into the channels that transport water from roots to the top. The fungus multiplies there and clogs the channels. As a result, the tree begins to die backwards from the top, a condition scientists call “die-back.”

 

The same thing happens when city governments cement or tile the surface around the base of the trees to ‘beautify’ the cities. The roots can’t breathe. Some scientists also found that shisham was dying in the areas where soil had more clay.

 

However, some questions still puzzle scientists — the fungus lived in the soil and around the shisham even before late 1990s. Waterlogging happened then, too, and agriculture activities would have damaged the roots earlier. Then, what happened suddenly that the shisham tree started dying in large numbers? Maybe the fungus evolved to become more virulent and the tree got weaker, thinks Pandey. After Shukla retired from FRI in 2009, the research on shisham mortality moved slow, mostly due to lack of funds.

 

Meanwhile, in 2011, FRI’s genetics department released a shisham variety (which it took 20 years to develop) that could resist the fungus and yielded fat tree trunks. The demand for this variety is so high that the department, which produces about 15,000 saplings a year, can barely meet demand, says Ashok Kumar, who heads the department.

 

Recently, Jammu & Kashmir alone asked for over 30,000 saplings. Kumar, however, fears that if this (or any single type of variety) is grown in large numbers, pests will soon evolve to outsmart the variety. He urges researchers to develop different types of resistant varieties to make it harder for the fungus to evolve.

 

One important factor that scientists haven’t explored yet is whether climate change is contributing to shisham’s death. “You can’t deny its role,” says Sharad Tiwari, forest informatics scientist at the Institute of Forest Productivity in Ranchi. In the FRI’s project, Tiwari has proposed to study whether warming climate over time has made or will make any changes in the ecology where shisham thrived earlier or whether other areas have become suitable for shisham.  

 

It is hard to tell how much shisham’s mortality specifically has impacted business because nobody has studied that yet. However, some furniture manufacturers in the timber market of Uttar Pradesh’s Saharanpur district say that they have been seeing a decline in the supply of shisham timber from the state. “There is at least a 50 per cent fall in the shisham we used to get locally from the state,” says Rakesh Kumar, owner of a furniture manufacturing company. Ashish Mittal, owner of another company, says most manufacturers have moved to mango wood. However, neither Kumar nor Mittal had heard that the shisham is dying.

 

Uttar Pradesh Forest Development Corporation’s data shows total timber produced in the state is declining over the years but how much of that is shisham, government officers don’t disclose. The new FRI project will likely answer some questions.


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