Bat guano; a “miracle” solution for agriculture in developing countries?

The vast majority of Malawians live in rural areas and rely on subsistence farming, supplemented with small plots of cash crops to meet their daily needs.

Agriculture accounts for 90% of exports and is extremely important to the national economy. However, increasingly dry conditions and the depletion of nutrients through soil erosion, resulting from dated agricultural practices taught in schools, make this lifestyle challenging.

As the 17th least developed country in the world¹ many cannot afford fertilisers and chemicals, or obtain chemicals on loan from the companies to which they will sell their cash crops. Burning crops at the end of the growing season is common, damaging the soil and reducing its ability to retain water and nutrients. This has led to low nutrient soils and reduced yield. In years of drought it results in crops failing and many families struggling to make ends meet.

Rapid population growth has resulted in catastrophic deforestation, the rate of which increases every year. Around 60% of Malawi’s forests were destroyed between 1975 and 20102.

This has led to drastic habitat loss for many species, including bats. How then, in a developing country is conservation possible, when there is such conflict between the needs of wildlife and people?

In Malawi, bats roosting in homes can number several thousand and produce large amounts of guano. In many situations bats are perceived as pests which spread disease, infest the house with parasites and create excessive smell and noise. In situations where roosts are very large they can even cause the ceiling to collapse from a build-up of bat guano.

However, despite the challenges faced by people living with large roosts I have experienced several situations where people have been resourceful enough to use bats to their benefit. A school near Lilongwe has a colony of several thousand bats living across the school buildings. After attempts to exterminate bats failed, they began to routinely sweep the guano from the lofts and surfaces and store it in maize sacks.

Chicken guano is commonly used as a fertiliser in Malawi and the head teacher began to give away the sacks to local farmers, who have been using it to fertilise their crops. I have come across several cases where people “farm” bats naturally roosting in their homes and it is incredibly heartening to see people learn to value the wildlife coexisting with them. A large roost of bats could potentially provide a continuous supply of agricultural fertiliser at no financial cost to the homeowner. Since a large percentage of structures in Malawi have roosting bats, there is capacity to expand the use of bat guano as an agricultural fertiliser.

Encouraging people to use bat guano and educating people regarding its use could have enormous benefits for both people and wildlife. Bat guano has long been used as a soil conditioner and is effective in promoting the physical structure of soil and improving drainage.

It contains high levels of nitrogen,phosphorus and potassium (N,P & K) to support root growth, general condition and health of crops. Guano is most commonly administered as a “tea” by soaking one cup of guano to a gallon of water overnight and then pouring it onto crops which ensures deep penetration into the soil. Bat guano would be a cheap source of fertiliser and, as a natural product, would be less damaging to the environment than cheap agricultural chemicals, which impair soil health and may lead to accumulations of heavy metals.

In Madagascar, a company called Guanomad has already been extremely successful in producing and marketing bat guano products. Bat guano has been used in Madagascar since 1920 on small farms in rural areas and is collected from bat caves around the country in old rice bags3.

Guanomad exports internationally to Europe, Asia and Africa and has developed 7 different products for various agricultural uses. The company produces 11,000 tonnes of guano a year and is valued at USD $10 million. Increasing awareness of bat guano in the international markets is being gained, with over 950 products currently available and countries such as Jamaica, Mexico and Indonesia already promoting its sale as fertiliser. Prices currently range from $1.25 to $12 for half a kilo4 .

The composition of bat guano makes it one of the most effective organic fertilisers available. It contains higher nitrogen and phosphate levels than sheep and cow manures with less carbon. It is only required in small quantities to promote growth making it a very cost effective product.

When used together with manure from other farm animals it can help to prevent common limiting factors, such as a lack of phosphorus, present in high concentration in bat guano. Studies have shown application of bat guano to crops results in significantly taller plants than controls6.

Guano composition differs between species with frugivorous bats producing high phosphate guano and insectivorous bats producing high nitrate guano7. Combining guano from several species may help to alleviate issues of limiting factors in the guano from one species.

However, the collection and use of bat guano comes with some health risks which need to be addressed. Bats are carriers of rabies and there is a high risk that workers collecting bat guano by hand could be bitten by injured and sick bats on the roost floor, which are the most likely to be infected. Bat bites are not usually severe, so are unlikely to result in a bitten person seeking medical help. With insufficient knowledge of rabies, bitten people are unlikely to receive treatment. For example, only 10% of surveyed guano miners in Thailand were aware that bats can transmit rabies8.

Bats carry a wide range of zoonotic viruses in addition to rabies The fungus Histoplasma capsulatum, can cause histoplasmosis in humans after breathing in the spores from the air. A study from Panama showed 10% of captured bats were infected with H. capsulatum but not all species were found to be carriers9.

The mycelia are fertilised in soil by bat guano, and the highest concentrations can be found in bat caves and roosts which can cause epidemics of histoplasmosis. Most infections are asymptomatic but in severe cases histoplasmosis can cause pneumonia and respiratory failure, particularly in persons with weakened immune systems. This is often the case in developing countries where people suffer from malaria and malnutrition.

It is critical therefore to properly inform and educate people working with bat guano of the possible health risks and methods to reduce their risk of infection. The inhalation of airborne spores of H. capsulatum can result in infection and so use of masks and air filters capable of filtering the spores is essential when working with bat guano.

The fungus proliferates in soils enriched with animal faeces so respiratory protection should be used whenever guano fertilised soil is disturbed. Suppressing dust formation by saturating the guano with water (such as administering it in “tea” form) and avoiding application on windy days can also help to reduce risk. The low cost nature of these solutions would make them effective in developing countries.

Bats are extremely important worldwide for agriculture and human health. Bats naturally predate on mosquitos; in Florida 30,000 south eastern myotis (Myotis austroriparius) consume 50 tons of insects annually of which over 15 tons are mosquitos10.

In countries such as Malawi where malaria is a serious public health risk and many cannot afford malaria medication, bats are an important tool in controlling mosquito populations as well as crop pests. However, 26 species are critically endangered, 51 endangered and 954 listed as vulnerable worldwide, with data unavailable for many species 11.

There is capacity in developing countries for NGOs to educate communities on the benefits and application of bat guano in agriculture. At present in Malawi there is very little awareness and with minimal investment, NGOs could provide training and equipment such as face masks, protective gloves and maize sacks to collect the guano whilst ensuring that minimum disturbance and stress occurs to roosting bats.

This could potentially have a significant real world impact on communities and ecosystems by making farming more sustainable and self-sufficient. In regions where many famers cannot afford to purchase chemical fertilisers it would increase yield of crops and reduce the potential impact of soil degradation and famine.

Conservation of bats is therefore of vital importance not just for the environment, but also for human health and agriculture. Encouraging the use of bat guano in developing countries would not only supply a cheap and readily available local source of agricultural fertiliser, but also encourage people to value and protect their bats, rather than persecuting them as pests.

Bat guano could therefore prove to be a lifeline for changing attitudes towards conservation in developing countries, particularly in Africa where rapidly growing populations will cause increasing pressure and conflict with wildlife.

References

1. UNDP, 2013. Human Development Report. Malawi National Statistics Office, World Bank, UNDP.

2. Kamangadazi, F.,Mwabumba, L , Missanjo, E., Phiri, F. (2016) Selective Harvesting Impact on Natural Regeneration, Tree Species Richness and Diversity in Forest Co-management Block in Liwonde Forest Reserve, Malawi. International Journal of Scientific Research in Environmental Sciences, 4(2), pp. 0047-0054,

3. Buliga, C., 2010. Guano Exploitation in Madagascar. Independent Study Project, p. Paper 904.

4. Kasso, M. & Balakrishnan, M., 2013. Ecological and Economic Importance of Bats (Order Chiroptera). ISRN Biodiversity, Volume 2013, pp. 1-9.

5. Sridhar, K. R., Ashwini, K. M., Seena, S. & Sreepada, K. S., 2006. Manure qualities of guano of insectivorous cave bat Hipposiderous speoris. Tropical and Subtropical Agroecosystems, 6(2), pp. 103-110.6. Almohammedi, A. N., Almehemdi, A. F. & Ajeelee, A., 2014. Impact of bat guano Otonycteris hemprichii camd and seaweed extract on some growth and yield traits of Barakaseed Nigella Sativa L. Journal of Biology, Agriculture and Healthcare, 4(1), pp. 57-65.

7. Shetty, S., Sreepada, K. S. & Bhat, R., 2013. Effect of bat guano on the growth of Vigna radiata L. International Journal of Scientific and Research Publications, 3(3), pp. 1-8.

8. Robertson, K. et al., 2011. Rabies-realted knowledge and practices among persons at risk of bat exposures in Thailand. PLOS.

9. Klite, P. D. & Diercks, F. H., 1965. Histoplasma capsulatum in fecal contents and organs of bats in the Canal Zone. American Journal of Tropical Medicine and Hygiene, 14(3), pp. 433-439.

10. Anthony, E. L. & Kunz, T. H., 1977. Feeding startegies of the little brown bat (Myotis lucifugus) in southern New Hampshire. Ecology, Volume 58, pp. 775-786.

11. Bat Conservation International, 2017. Threatened. [Online]
Available at: http://www.batcon.org/why-bats/bats-are/bats-are-threatened

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