THE COST TO BIODIVERSITY
By TA News Bureau:
Prices of natural rubber have been witnessing high volatility and instability in the past twenty years. When the prices were up, planters expanded the acreage, often indiscriminately. One of the major issues that get submerged in the noise of price fluctuations is the harm rubber plantations cause to biodiversity. Many research studies have revealed the destructive environmental impacts of monoculture rubber plantations. Research by Cong Liu of the Biodiversity and Biocomplexity Unit of Japan’s Okinawa Institute of Science and Technology Graduate University (OIST) shows that disruption of natural forests and their conversions into rubber plantations are causing immense damage to nature. His study, under research leader Prof Evan Economo, has relevance to other rubber plantations in Southeast Asia. In an interview to Tyre Asia, Cong speaks of his research where the centrepiece is the ant population whose decline is indicative of habitat destruction
Research has shown that rubber plantations in South Asia are contributing to the destruction of biodiversity. This shows up in hotter and drier weathers. Replacing natural forests with rubber plantations are also blamed for the massive depletion of water resources. The net result will be a perennial drop in rubber output that would affect the livelihood of millions of plantation workers.
Cong Liu of the Biodiversity and Biocomplexity Unit of Japan’s Okinawa Institute of Science and Technology Graduate University (OIST) went for field studies in Xishuangbanna, a prefecture in south-west China’s Yunnan province, reported to be the worst case of habitat destruction. He noted biodiversity losses and regional climate changes. He found depletion of ant species there, home to very large state rubber plantations since the 1960s. There the weather had become hotter and drier.
By studying the responses of different organisms to land use changes. scientists could map the biodiversity impact. As studying all different organisms was not possible, Cong zeroed in on ants, as they are a good surrogate for other invertebrates and perform many roles in the ecosystem, such as decomposition and seed dispersal.
The research team had collected 186 ant species from 11 sites on the rubber plantation, and 24 other forest areas. They sorted the ants by species and measured their functional traits that demonstrated how the ants were interacting with the ecosystems. These included characteristics like body size, eye dimensions, and leg length.
Cong’s research has revealed a sharp decline in ant species in rubber plantations that were converted out of forests. It reflected the negative impact on the ecosystem of commercial rubber plantations.
“Rubber plantation act as environmental filter which can only support only a few species,” Cong told Tyre Asia in an interview. “Rubber plantations, especially big industrial rubber plantations, will have huge negative impact on biodiversity. Many studies have already shown this, not only in the case of ants,” he explained.
When asked why the spread of rubber plantations could inflict profound damage to biodiversity, he said that unlike natural forests which can provide very complex environment, rubber plantations or other plantations can only provide very simple environment such as micro-habitats, food etc that lead to less biodiversity.
Decline of species
Cong thinks that the reduction in the ant population in Xishuangbanna could be used as a guide to study biodiversity damage in other rubber growing regions in Asia. “Ants are very sensitive to environmental changes and have been considered as bio-indicators for long time,” he pointed out.
Explaining his discovery that there was a striking decrease in ant biodiversity at the rubber plantations that he studied, he noted that phylogenetic diversity had also decreased. This was only because of the decline of species richness. Phylogenetics is the study of evolutionary relationships among biological entities – often species, individuals or genes.
“The most interesting part that we did find was the decline of functional diversity that was not random with respect to species’ richness. It means that rubber plantations not only reduce ant species’ richness but also acted as environmental filter.”
As rubber plantations act as an ecological filter, the loss in the number of ant species combined with the reduction of their functional diversity could mean that this may later have effects on other insect groups as well as on ecosystem processes.
Cong thinks the decline of specie is mostly due to conversion of forests to agricultural land use. Studying such patterns may shed light on underlying ecological processes that are of both basic and applied interest.
Currently he is also researching the effects of conversion to rubber plantation on ant taxonomic, functional and phylogenetic diversities.
One is for sure: human-induced disturbances such as deforestation and agricultural activities can dramatically impact the pattern and distribution of genetic diversity within species.
Destruction of forests and replacement by rubber plantations can have important consequences at the levels of species, communities and ecosystems. Understanding the nature and effects of this biodiversity loss in ecologically dominant insect groups like ants remains a critical need for understanding the full consequences of the rapid emergence of agro-ecosystems such as rubber plantations.
Photo credits: Okinawa Institute of Science and Technology