Scientific evidence for the benefits of using Mee tree in cultivations
The chemical composition and properties of the essential oil extract of the Mee tree were studied and it was found to have high levels of Farnesol and its’ analog, Farnesene. Farnesol is considered to act as a pheromone for several insects and as a pesticide for mites. It also has antimicrobial action against certain bacteria and fungi (Suryawanshi and Mokat, 2019) .
Even though there is a scarcity of documented evidence for the use of bat guano in Sri Lanka, there is plenty of documented evidence from world history to understand the importance of bat guano use in cultivation by ancient farmers. Andean people from the small islands of Peru have used bat guano as a soil amendment as far as 1500 years ago (Cushman and Guano, 2013). In Tanzania, the Kisarawe caves are said to harbour three million bats producing one ton of guano per day (Juma, 2001). There are reports that over 3000 tons of bat guano were obtained from these caves between 1934 and 1954 for agricultural use, especially for farms near the areas of the cave of Sukumawera in Mbeya, South Tanzania (Nilsen, 1980).
When considering the chemical composition of guano of insectivorous bats, one study has shown that on average, oxygen was the most abundant element (54.94%). This helps to increase the soil bacteria and other helminths which enrich the soil structure. Additionally, macro-nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium and sulphur were also abundant in the guano (Misra, Gautam and Elangovan, 2019). As mentioned above, when a food chain developed around these trees, eventually bat and bird guano dropped to the paddy field. The average composition in the fresh guano of insectivorous bat and birds are around 50% carbon, 10% nitrogen, 2–7 % phosphorus pentoxide (P2O5) with sulphur abundances of 10–20% (Shahack-Gross et al., 2004; Forbes et al., 2007). These key elements nourished the ancient paddy fields and farmers managed to control their cultivation in an eco-friendly manner. The incorporation of bat guano into the soil enhances crop production and studies have thus emphasized the importance of conservation of insectivorous bats and their guano(Sridhar et al., 2006).
Remnants of insects including agricultural pests belonging to the orders Coleoptera, Lepidoptera, Homoptera and Hemiptera were found in the faecal matter of insectivorous bats in a study done in India (Misra, Gautam and Elangovan, 2019) . There is a lack of published data except for the indigenous knowledge of local farmers that bat pest control contributed to the food security in Sri Lanka. However, there are plenty of published data to provide evidence that both bats and birds increased the yield of the crops. Indonesian cacao plantations produced increased yield when the herbivorous insect population reduced with natural pest control(Maas, Clough and Tscharntke, 2013). According to published data, cotton yield worth USD 741,000 was protected annually in the United States by bats feeding on cotton bollworms (Cleveland et al., 2006). It has been shown that an estimated USD 3.7 billion worth of cotton harvest was saved annually across the US by bat populations. A study conducted in Thailand has shown that bats protects rice worth more than USD 1.2 million annually (Wanger et al., 2014). The same study highlighted that the bats also feed on other major rice pests in Asia such as the brown planthopper (Nilaparvata lugens- - Dumburu Pela Keedawa) and the White-Backed Planthopper (WBP). The bats not only feed on adult male and winged female White-Backed Planthoppers but also consume pregnant WBPs which prevents future offsprings from hatching(Wanger et al., 2014). The western world has understood the value of these bats and has taken steps to attract bats to their farmlands. For example, in California, USA, farmers have installed resting boxes for bats within their farmlands to help control agricultural pests(Tuttle, Kiser and Kiser, 2005).