From the hills of India to the mountains and valleys of Kenya and China, tea is grown in some of the world’s most exotic places. Many nations are expanding their tea producing acreage to meet the rising world demand for this popular and satisfying beverage.
Today, more than 45 countries grow tea in big quantities. Among them, Asian countries are the leading ones producing more than 91 percent of the total amount annually. China, India, Japan, Sri Lanka and Taiwan are among the top producing countries.
Tea was first produced in China thousands of years ago. Before long, it was introduced to Japan, then to Europe. People in almost every corner of the world enjoy the beverage and more than three billion cups are consumed daily.
Tea, as a natural beverage, is one of the most popular and lowest cost drinks, next only to water. People drink it for a variety of reasons: daily necessity, health benefits, medical remedy, or simply to enjoy the taste and joy of a cup of drink!
Now there is another benefit to drinking tea. A new research taking place in the Netherlands aims to prove that tea, or rather discarded tea bags, can predict the health of the planet.
Can tea bags really help us understand climate change?
Ecologists at the Netherlands’ University of Utrecht seem to think so, as they have, together with an international group of scientists, devised a novel method for gaining data on climate change.
From an idea picked up during a postgraduate course in 2010 to an international project covered by media from the Netherlands to Sweden, the Tea Bag Index (TBI) is all about ‘crowdsourcing’ valuable research on climate change.
The research is led by Utrecht University’s Joost Keuskamp and Bas Dingemans, and the Netherlands Institute of Ecology’s postdoctoral student, Judith Sarneel, and the rest of the TBI-team on their interactive website.
Measuring the decay rate of plant litter can provide valuable information about the release of carbon from the soil and consequently about climate change. Using tea bags instead of ‘regular’ litter allows for the results to be standardised, especially if the same brand is used wherever the experiment is carried out, and this is the premise behind the development of a universal TBI.
Decomposition—A Critical Process
The decay of organic material or ‘decomposition’ is a critical process for life on earth. Through decomposition, nutrients become available for plants and microorganisms to use in their metabolism and growth. As plant material decomposes, it releases the greenhouse gas carbon dioxide (CO2) into the atmosphere.
A fast decay leads to more CO2 in the atmosphere and slow decay gives rise to higher soil carbon stocks. For better insight in the global CO2 emission from soils, it is important to know more about the rate of decomposition in those soils.
There is a tremendous global variation in the decomposition rate of plant material. In cold environments, for example, the decay is slower than in warm environments. Factors like moisture content, acidity, or nutrient content of soils can have great influence on how quickly plant material decomposes.
To get a clear picture of global decomposition, a lot of information on different soil characteristics and related decomposition rates across the world is needed. Many factors are already known and archived in a soil map of the world. However, an index for decomposition rate is still missing and predictions are often imprecise.
Tea Bag Experiment
In terrestrial ecosystems, Dr Keuskamp explains, soil organic matter is a major carbon store, which holds about three times more carbon than the atmospheric pool. Therefore, changes in soil carbon storage can significantly strengthen or reduce climate change. The global warming prevention protocols identify the need for a more fundamental understanding of decomposition and stabilisation of soil carbon.
In this experiment, the researchers present a newly developed standardised method for global collection and comparison of decomposition rates. The results from this method can be combined with the existing data in the digital soil map of the world, containing a large number of abiotic soil parameters.
This extension will allow for extensive analysis of the interaction between soil conditions and decomposition rates, thereby greatly improving our understanding of global soil carbon dynamics.
Through a simple, standardised, cheap and time-efficient method, the decomposition rates between climatic zones, geographical regions and ecosystems can be compared. This requires measurements from a very large amount of locations and an even larger amount of data points.
Collecting the required amount of data using traditional litterbag experiments is not feasible. Sewing the litterbags, weighing the litter, and placing and recovering the litterbags are time-consuming for one field site—let alone thousands of field sites across the world.
Tea, as sold by tea companies, consists of dried leaf litter. A number of companies are manufacturing tea bags with synthetic mesh (mesh size: 0.25 mm). These tea bags are in fact, mini-litterbags. They are commercially available and come at a very low cost.
Standard Reference Method
In ecological research, different substrates have been used as standard material to be able to compare microbial activity and decomposition rates between ecosystems. As the bulk of plant tissue consists of cellulose, standards were defined by cellulose objects such as filters, ropes, cellophane film and cotton cloth.
The latter developed into the widely used cotton strip tensile strength loss method with standardised cloth. Cellulose decomposition rates often deviate from litter decomposition rates as litter degradation is strongly influenced by its other compounds. The standardisation method uses plant material from different qualities, making this method a better proxy.
Based on pilot tests, the researchers selected two tea types markedly differing in decomposability. The selected teas for use in the TBI were the easily decomposable green tea (dried leaves of camellia sinensis) and the more recalcitrant Rooibos tea (dried leaves of aspalathus linearis).
Using these tea types, both field and laboratory experiments were conducted to assess their decomposition rates and the sensitivity of these rates to field conditions and temperature.
In addition, the researchers conducted a sequential carbon extraction to predict the decomposable fraction of both tea types. The decomposition rates of both Rooibos and green tea were fitted to a two-phase decay function in which the decay of the recalcitrant phase is set at zero.
Due to the use of a labile and a recalcitrant tea species, only one point in time was needed to solve the two unknowns in the equation. The researchers assumed that (i) a strong relation exists between carbon fractionation and the decomposable fraction and that (ii) environmental influence on the size of the labile fraction are equal for both green tea and Rooibos tea.
The researchers are not only calling on all scientists but also the general public to join the experiment. This way, many small efforts will unleash an enormous amount of data. They believe that with this crowdsourcing approach a database can be generated on a resolution and a scale that is impossible to attain by the use of traditional methods. This TBI can be used to improve our understanding of the effect of biotic and abiotic factors on decomposition rates.
There are obvious disadvantages to crowdsourcing in this kind of work. As non-scientists conduct the experiment, the data may have relatively large variances. The accuracy of weighing the material may vary between people and the choice of ‘representative’ location may be interpreted differently. People living in cities can interpret their garden as a good location, while people in the countryside may be looking for an undisturbed soil.
However, as Dr Keuskamp points out, “With crowdsourcing there is power in numbers. The easier and more accessible the method, the more data will be generated. Using scientific scales may produce more accurate data, but far less data than when using improvised scales made from the tea box that anyone can produce. And if more people contribute to this project, more types of soil will be used.”
The simplicity of these litterbag experiments makes them also suitable for soil ecology courses at high schools. The team initiated the design of a learning method for practical lessons in cooperation of schools in Nicaragua, Iceland and the Netherlands.
Reading The Tea Leaves
The TBI has already been tested in twenty countries but requires an even broader implementation to provide the required mass data for meaningful analysis. However, the aspects of low-cost, accessibility, sustainability and fun look set in helping the uptake of this ingenious data gathering method.
The ultimate goal: a global database with results from as many different soil types as possible. So far, people from at least thirty countries have already sent in results through the website.