Scientists are warning that the increasing number of rubber plantations across India’s north-eastern states may threaten the traditional rich diversity of the region’s forests as has happened across Southeast Asia.
The researchers at the North Eastern Space Applications Centre (NESAC) in Umiam, Meghalaya, who have tracked this expansion, have called for a systematic and region-wide monitoring to quantify the losses of natural vegetation and its impact on the local ecosystem.
Tripura, which is India’s second-largest rubber-producing state after Kerala, now has over 70,000 hectares, or nearly 7 % of the state’s land area, under rubber plantations, compared to under 700 hectares in the mid-1970s.
Assam’s rubber cultivation has increased three-fold to over 49,000 hectares over the past decade, while Manipur, Meghalaya, Mizoram and Nagaland have also seen increases in areas under rubber plantations in recent years.
Kasturi Chakraborty and her colleagues who used satellite imagery to zoom into a small patch of land distributed across Assam and parts of Mizoram and northern Tripura have observed a five-fold increase in the area under rubber plantation from about 5sqkm to 28sqkm over a 15-year period.
The NESAC scientists have published their findings in the journal Current Science, brought out by the Indian Academy of Sciences, earlier this week.
“The growth in rubber has happened at the cost of forests, but earlier studies have suggested that the loss of natural forests is at times overlooked because rubber plantations look like forests,” Chakraborty said. “However, monoculture rubber plantations lack rich diversity of native forests.”
Conservation scientists from the UK had also raised similar concerns earlier, saying the increasing demand for natural rubber, fuelled mainly by the tyre industry, is threatening forest areas of southwest China, Cambodia, Myanmar, northeast Thailand and northwest Vietnam.
A study by University of East Anglia researchers had predicted that 4.3 to 8.5 million hectares of new plantations would be required to meet projected the global rubber demand by 2024.
“There has been growing concern that switching land use to rubber cultivation can negatively impact the soil, water availability and biodiversity,” Eleanor Warren-Thomas, a research scholar at the UEA, had said in a news release 2015.
The study by Warren-Thomas, published in the journal Conservation Letters, had suggested that bird, bat and beetle species can decline by 25 % in forests that have converted to rubber.
Three years ago, Koushik Mazumdar, a botany research scholar at Tripura University, had pointed out that rubber plantations also generate waste water.
“Rubber trees are tapped for latex which is processed into rubber sheets – the process uses water and generates waste water,” said Mazumdar, who estimates that processing of rubber in Tripura will generate enough waste water to fill up one-metre tanks the size of 80 football fields over the next decade.
NESAC’s Chakraborty and her colleagues say mixed plantations would be more attractive than monoculture with rubber. They point out that an area of Karimganj in Assam where farmers have cultivated rubber with banana plants and areca nut is an example of such mixed plantations.