A two hour drive and a 40 minute boat ride along the Ganges north of Calcutta is Green Island. As the name suggests this is an island where the original vegetation that once covered the Ganges Delta remains relatively undisturbed.  I say relatively because while human disturbance is limited, every year when monsoon storms and high tides swell the river level Green Island is flooded, sometimes to a depth a little over a meter.

Studying this type of vegetation is crucial to my work as it represents exactly the kind of plant community that has the potential to be preserved in the fossil record. As the floodwaters scour the leaf litter from the soil surface, and the island margins are eaten away by erosion, leaves are washed into the river where they may be deposited in muds and silts and eventually fossilised. We see many such deposits in the rock record from which we deduce information on past vegetation and climate.

I was in the company of Professor Subir Bera from Calcutta University and his wife who had organised the day. We had special police permission to visit and collect on the island and even had a police escort. On the boat with us were several people from the nearby village who had (as we discovered later) prepared a wonderful lunch of fish and meat curries, rice and fruit, all served on banana leaves.

As the open wooden boat neared the island we could see whole trees, still with green leaves, that had recently fallen in to the water as the riverbanks were eroded. Caught in the branches of one such tree was the body of a goat. Now for most this might seem gruesome but for me it was fascinating because it was another example of taphonomic processes – taphonomy is the study of fossilisation.

As the Ganges undercuts the edges of Green Island whole trees fall into the river - perhaps on their way to being fossilised.
[Photo © copyright Bob Spicer]

Green Island is a little over a kilometre in length and a few hundred metres wide. Here we collected the populations of leaves from 56 different species of trees shrubs and vines. After pressing, drying and mathematically scoring them CLAMP analysis positioned the Green Island vegetation near the Kerala sites we had previously analysed, but in an area of the three-dimensional plot that indicated they were from a slightly cooler site.

Because Green Island is on a flat delta plain I could use meteorological data in the form of a grid in which observations from individual meteorological stations can be interpolated (mathematically extrapolated) for sites such as Green Island that does not have its own measurements.

CLAMP showing the positions of modern forests determined by their leaf architecture.

The plot above shows the positions of the Indian forests that I have analysed so far. In this plot each ball represents a forest. Green Island is Labelled “Green” and the other labelled balls are forests in Kerala. The positions of balls are determined by the numerical score that describes leaf architecture for at least twenty species of woody trees, shrubs and vines from each forest.

Balls that plot close together indicate forests with similar leaf architectures, while that that plot far apart are very different. The balls are colour coded such that blue represents cool climates and red ones hot climates. Orange, green and light blue indicate forests growing in intermediate climates. It is easy to see that the Indian forests (coded maroon) all lie in the warm end of the plot.

In this plot the Indian forests have been treated as if they were fossils. They have found their own position with respect to the other sites for which the climate is known. Despite the fact that the Indian sites all plot close to other warm sites they form a group beyond the limits of the existing cloud of sites, and using this calibration all the Indian sites yield a climate prediction that is several degrees colder than that which is observed.

The next stage is to include the Indian observed climate information so that the shape of the plot will change and the ability of the method to give accurate results for fossils that represent ancient forests growing in warm climates does not suffer from the same error of underestimating temperatures.

About the author

Bob Spicer is Professor of Earth Sciences at the Open University. Founding Director of the OU's Centre for Earth, Planetary Space and Astronomical Research (CEPSAR) his interests are broad. However he is most at home when studying how plants can be used to tell us about ancient climates, and how that information can help us plan for managing our planet in the future.

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For the past week or so the daily maximum temperature in Lucknow has been above 40 °C. Yesterday it was 42°C, and more of the same is forecast for the next five days. In these temperatures the demand for electricity to power air conditioning units exceeds supply and we have experienced frequent outages sometimes lasting hours. Without electricity to drive pumps, the water supply also fails.

It is sobering to think that in a warming world such events are bound to become more commonplace, not just here but across all the lower latitudes. We in the UK will not be immune either as summer heatwaves like that of 2003, which claimed so many lives across continental Europe, are forecast to increase in frequency and severity.

To help improve those forecasts we have been working on improving the warm climate performance of a technique that uses leaf architecture as a proxy for temperature and rainfall. By applying this technique to fossil leaves we can better quantify ancient climates, many of which were warmer than now, and thereby learn how climate might behave in the future.

Normally solitary, giant squirrels are
rarely seen together except about
breeding time.
[Photo © copyright Bob Spicer]

Recently I sampled six forests in Kerala, south India. At a latitude of around 9.5 °N they are well within the tropical zone, yet unlike many low latitude areas, they also experience marked variations in rainfall due to the influence of the Asian Monsoon. They never really dry out though, and so those lush forests host a large number of leeches that make sampling leaves a somewhat bloody affair. Apart from leeches the forests also support a rich variety of animal life such as giant squirrels (Ratufa indica), deer, and even wild elephants. Although Kerala promotes itself as a “green” state there are precious few undisturbed forests remaining. Most have been destroyed to plant tea and the destruction continues as multinational corporations have the power to buy up land and overpower conservation efforts. Soon there will be very little natural vegetation left save for a few protected reserves, with a consequent loss of biodiversity. Of course Kerala is not alone in losing its unique heritage this way, but it is particularly depressing to witness it first hand.

Tea plantations replace natural forest diversity, leaving only a few remnant trees as witnesses to what once was.
[Photo © copyright Bob Spicer]

Leaves from each of these modern sites are numerically scored and analysed using a technique called CLAMP. Results so far show that all the Kerala sites form a coherent cluster in a new area of what we call “physiognomic space” and thus provide opportunities for recalibrating CLAMP for low latitudes, both now and in the past.

This is exactly what we were hoping for. Now I am in the process of collecting and collating decades worth of weather observations for these areas so that the calibration process can take place. At least I will continue to do that if the power stays on and the computers don’t overheat.

About the author

Bob Spicer is Professor of Earth Sciences at the Open University. Founding Director of the OU's Centre for Earth, Planetary Space and Astronomical Research (CEPSAR) his interests are broad. However he is most at home when studying how plants can be used to tell us about ancient climates, and how that information can help us plan for managing our planet in the future.

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On April 10 1949 the Cambridge–trained Indian palaeobotanist Birbal Sahni died after a massive heart attack. His death at the early age of 57 came only days after the then Indian Prime Minister Pandit Jawaharlal Nehru had laid the foundation stone of what was later to become known as the Birbal Sahni Institute of Palaeobotany. Each year, on the anniversary of Birbal Sahni’s death, wreaths are laid at the spot in the grounds of the Institute where he was cremated in accordance with Hindu custom. This year I was privileged to take part in this event that was preceded by an ancient ceremony of prayers and purification.

I did not know quite what to expect when I arrived in the main entrance foyer of the Institute because laid out on the floor beneath the soaring curved staircase were mattresses covered in white sheets surrounding a temporary hearth that had been constructed the previous day. Sitting on the sheets, cross-legged were the staff of BSIP and directly next to the hearth were the BSIP Director, his wife, and a Brahmin priest.

The ceremony began with the priest chanting ancient shlokas, rhythmic poetic prayers, in Vedic Sanskrit.  Sanskrit is the oldest continuously spoken language in the world and as early as 1500 BC its structure, as preserved in the oldest Hindu texts known as the Vedas, is so refined that it clearly has a common older source. Sanskrit is the basis of religious texts in Hinduism, Buddhism, Jainism and Sikhism. It is the oldest known member of the Indo-European family of languages.

As the prayers proceeded and incense sticks were ignited, offerings of rose petals, ghee, sugar solution, and rice were prepared. Then small dry branches of mango wood were arranged within the hearth and set alight. As the smoke rose throughout the building and the prayers continued, we all added the offerings of herbs and other aromatic elements to the fire. I have no knowledge of Sanskrit but I can say that the rhythmic sounds of it expertly spoken were incredibly soothing.  

Sanskrit rythmic poetic prayers and perfumed smoke permeate the BSIP building.
[photo © copyright Bob Spicer]

The prayers were ones for the general well-being, not only of the staff and the Institute, but for all humankind and our shared planet. The concept of such a ceremony is one of purification. There are sixteen such ceremonies in the life of a Hindu marking critical stages in the passage through life. What I was witnessing is the last in this succession. The sounds of the prayers and aroma of the perfumed smoke carried to all parts of the building cleansing and purifying. It was a ceremony that brought everyone together in a common purpose.

The ceremony concluded with the priest tying a length of hand-spun thread, dyed yellow with turmeric and red with turmeric mixed with lime, around our wrists, right hand wrists for the men and left hand wrists for the women. This was a symbol of our common purpose and a reminder of what we had participated in. In the past few days as I have been wearing mine, several people not connected with BSIP have asked how I came to have such a symbol. I have been pleased to explain.

About the author

Bob Spicer is Professor of Earth Sciences at the Open University. Founding Director of the OU's Centre for Earth, Planetary Space and Astronomical Research (CEPSAR) his interests are broad. However he is most at home when studying how plants can be used to tell us about ancient climates, and how that information can help us plan for managing our planet in the future.

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