The monsoon-predicting plants of Tibet

Scientists at the Institute of Tibetan Plateau Research have discovered that plants found on the Tibetan plateau unfold their leaves as they "sense" the onset of the Indian summer monsoon. The plateau is the highest and largest meadow in the world, and the scientists studied the behaviour of a variant of Kobresia – a species of sedge – that grows at a height of 4,400–5,200 metres above sea level for seven years.

They found that the leaf unfolding rates of sedge and grass species that dominate the meadows are in sync with the onset of the monsoon. This is regardless of air temperature. The finding matches scattered research findings from India on the possibility of trees or plants serving as indicators of rainfall and temperature changes.

Reporting on their findings in Nature magazine, the scientists speculated that leaves unfolded just before the monsoon rains to avoid “damages of pre-monsoon drought and frost to alpine plants”. According to Tianxiang Luo, lead author of the study and professor in ecology and biogeography at the Institute, the interaction between monsoon and the westerlies, both of which influence the Tibetan Plateau’s vegetation, may have influenced different genetic types of sedges and grasses.

Given the strong linkage between leaf unfolding and regional atmospheric circulation, this might be a way to study the interaction of monsoon-westerlies over the Himalayas, often called the world’s Third Pole, Luo said. These are not yet understood sufficiently. What is understood is that temperatures on the Tibetan plateau are rising faster than anywhere in Asia, and this has a strong effect on the Indian monsoon.

Practical value

The findings from the Tibetan Plateau “definitely are of practical value in a field situation because they act as forecasts/forewarning” and call for contingency action by farmers to prevent devastation and crop losses, said K Ravi Shankar of the Centre for Research in Dryland Agriculture, Hyderabad.

Shankar is the senior scientist at CRIDA’s transfer of technology section, and is currently looking at farmers’ adaptation to drought induced by climate change and has studied traditional knowledge systems in agriculture. He has also observed changes in flowering patterns of trees such as palm and neem (Azadirachta indica) before the onset of monsoon. “All these are manifestations of occurrence of climate change,” he said.

In the case of the "flame of the forest" or the Butea monsopserma tree, he said he recorded changes in flowering and fruiting patterns owing to changes in air temperature, pressure and humidity.

Ravi Shankar, however, disagreed with Luo’s team that scientists can attribute leaf unfolding to either monsoon or temperature change. “Shifts in temperature, humidity and pressure are interlinked. Which precedes what is not clear,” he said.

Indigenous knowledge

Sandeep Acharya, a botanist at Tripura’s Central University, who worked with traditional weather forecasters of 19 ethnic tribal communities in the North East Indian state, reported in the Indian Journal of Traditional Knowledge that, “the onset of the rainy season, for example, is easily predicted” by the larger-sized leaves of a local medicinal plant Premna esculenta, which also grows in neighbouring Bangladesh. Other indicators are the increased length of "internodes", or parts of the stem in between two joints, of the golden shower tree Cassia fistula that grows widely in the Indian subcontinent and increased length of the flowers of the medicinal plant Costus speciosus.

Rain can be predicted through the ripening and early rotting of fruits of the medicinal plant known as Devil’s Cotton or Abroma angusta, and unusually early flowering and increased length of the bunch of flowers of another medicinal shrub, the Indian Mallow or Abutilon indicum. Adverse weather conditions such as storms or floods can be predicted by sudden drooping down of petals of flowers of the Cassia tora and unusual secretions by the leaves of the sundew (Drosera burmanni).

Since indigenous knowledge is mainly based on local experience, the lack of benchmarks makes it difficult to harmonise and integrate the knowledge with conventional scientific forecasting systems, the report said. It recommended systematic documentation, quantification and subsequent integration of indigenous knowledge into conventional weather forecasting system as a strategy to help improve the accuracy and reliability of seasonal forecasting information under a changing climate.

In the absence of such integration of traditional and modern weather prediction systems, especially in the era of climate change, the report stated that “countries like India, which are totally dependent on the seasonal rainfall for sustainable agricultural and allied activities, will suffer greatly in near future from deficiencies in short-, medium- and long-range rain forecasting…”

Role of lichens

Lichens – organisms made up of fungus and algae – are also a potential bio-indicator of climate change and pollution, concluded a report in the International Research Journal of Environmental Sciences by Kuldeep Srivastava, scientist at the Indian Meteorological Department and Prodyut Bhattacharya, professor at the University School of Environment Management, Indraprastha University, Delhi.

The report, which reviewed scientific literature, said lichens have been found to be highly sensitive to environmental factors such as temperature, humidity, wind and air pollutants because they don’t have any vessels inside them to conduct water as plants, shrubs and trees do.

Lichens, therefore, absorb water and nutrients passively from their surrounding environment. Changes in the distribution and types of lichen species that grow in a particular place serve as a “powerful tool” to gather information about changes in climate and air quality.

The report observed that unlike countries such as Canada, Israel, Switzerland, United Kingdom and the United States, India is yet to conduct detailed studies on lichens as indicators of changing temperatures, humidity and pollution.

This article first appeared on The Third Pole.