This is the fourth story in a series of articles written by the students of Azim Premji University as part of a field practice and writing workshop for their sustainability minor.

Imagine this. A cloudless sky, the sun beaming down on a field of flowers, and hundreds of butterflies flitting around. Easy to do, right? Now picture a pile of dung with hundreds of butterflies sitting on it. Feels wrong somehow? That was my exact reaction when I encountered mud puddling for the first time on the banks of the Thamirabarani River while visiting the Kalakkad Mundanthurai Tiger Reserve (KMTR). Butterflies are generally associated with flowers; their primary food source is flower nectar, which contains sugars. These lepidopterans are forced to scavenge for mineral salts and amino acids elsewhere, such as wet soil, dung, rotting plant matter or carrion. In this case, males are generally the breadwinners. They collect resources and present them to females while mating to nourish the eggs. The main goal of mud puddling in butterflies is to consume resources for their survival and fitness.

Natural resources are a wicked problem; we never stop needing them, and they never stop draining. Nitrogen is one such resource. From scavenging butterflies to struggling farmers, everyone needs nitrogen. This element is one of the main building blocks for proteins and nucleic acids, DNA and RNA, the blueprints for life itself! Life, as we know it, would not exist without nitrogen. Conducive for life, 78 per cent of our planet’s atmosphere is composed of this gas. Unfortunately, things are never as easy as they seem. Atmospheric nitrogen is not active and is not ready for use.

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A kaleidoscope of Common Albatross butterflies mud puddling on a river bank. Photograph: Surya Ramachandran

Then how are butterflies able to harness active nitrogen? That too from the soil? How did it get there? The answers lie in bacteria that can ‘fix’ nitrogen. These wondrous microbes convert atmospheric nitrogen into usable nitrates, creating a beautiful symbiosis between microbes and plants. In 1840, an organic chemist, Justus von Liebig, discovered that supplementing the soil with nitrogen increased crop yield. Curiously, the vehicle for the nitrogen was guano—the excrement of seabirds and bats. Thus began the hunt for more nitrogen and more poop.

The hunt ended at the Chincha Islands in Peru, where guano was so abundant that mining and export became a lucrative business. The demand was high enough to warrant warfare! Spain blockaded Peruvian ports in 1865 and started the Chincha Islands War. It ended with Spain retreating. Chile also went to war with Peru and Bolivia in 1879 for nitrate deposits. The United States of America joined the craze for nitrogen and passed the Guano Islands Act, which permitted the US to claim any unclaimed land with guano.

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Scan of a page from the Harper's Weekly journal in 1857, documenting guano collection in the Chincha Islands of Peru.

The waging of wars for natural nitrogen sources soon became unnecessary with the advent of artificial nitrogen fixation. In 1909, Fritz Haber discovered the aptly-named Haber’s process to produce ammonia from the atmosphere. Farmers stopped relying on nitrogen-fixing bacteria. Chemical fertilisers became the norm. Agriculture was flourishing. All was well.

Or not. The use of excessive fertilisers overloaded the ecosystem with more nitrogen than it could handle. Weeds have populated fertile land. Fertiliser run-off has caused algal blooms, dangerously affecting aquatic life. In some regions, this damage is so severe that all aquatic life dies, and the algae follow suit, creating dead zones. As of 2008, 400 such dead zones were detected in the Earth’s waters, a number that would have already gone up by now. Today, nitrogen pollution is one of the primary dangers to the planet.

Nitrogen and phosphorus cycles make up one of the nine planetary boundaries. What are planetary boundaries? This scientific concept presents a set of planetary boundaries within which humanity can continue to develop and thrive for generations to come. Crossing these boundaries increases the risk of generating large-scale, abrupt or irreversible environmental changes. And as with us humans, we are hardwired to cross limits. Earlier, the amount of active nitrogen on the planet was limited by natural nitrogen-fixing agents. By inventing artificial nitrogen production, we have pushed that limit, accelerated resource consumption and overshot the planetary boundary for nitrogen.

What happens now? Is there no going back? Even now, reeling the nitrogen cycle back within its limits is possible. That would need a 75 per cent decrease in global fertiliser consumption, which can only happen by transitioning to sustainable agriculture. There are also microbes (denitrifying bacteria) that can convert nitrates back into atmospheric nitrogen. Creating swampy areas and deltas which allow these bacteria to flourish would mean less active nitrogen in the soil and a solution to the planet’s nitrogen problems.

We would like to thank the Ashoka Trust for Ecology and Environment (ATREE) for facilitating the field practice and Krishna Anujan for conducting the writing workshop.