In the second instalment of this two-part blog, Iris Berger, a PhD student in Conservation Science at the University of Cambridge, talks about her field research in India and how farming with nature may help safeguard biodiversity whilst meeting humanity’s growing food needs.

The midday heat, over 40 degrees Celsius, made us drowsy as we ate our dosa south Indian crepes served with coconut and ginger chutney on banana leaves. We were sitting in the shade of cashew trees with red and yellow cashew fruit overhead, like bizarre hats for the nuts below. These few healthy fruits, glistening in the sun, struck a stark contrast with black and wilted cashew flowers that engulfed most nearby trees – a local manifestation of global climate change.

In addition to my research on the bird communities found in different farming systems and natural ecosystems, I am also studying how the cashew pollinator community, and the benefits they provide to cashew nut yield, differ between zero-budget natural farming (ZBNF) and chemical farming. Whilst there is evidence that ZBNF improves soil health, no one has examined ZBNF’s effects on above-ground ecosystem services – such as pollination and natural pest control – both of which are underpinned by biodiversity.

This year, I spent over a month looking at which species, mainly butterflies and bees, were visiting the cashew flowers. The wild bees come in all colours and shapes – from Amegilla species with iridescent blue stripes to golf ball-sized metallic black carpenter bees with a calming, deep buzz. Once, I even had a purple sunbird pay a cautious visit. My cautious first impression is that the difference in the number and diversity of pollinators between ZBNF and chemical farming seems to be pronounced, although statistics are needed to confirm or deny this.

To quantify the benefits of pollinators to cashew yield I put mosquito bags around some branches to assess what happens to cashew yield when you exclude pollinators. I also hand pollinated some flowers to see whether the pollination service provided is sufficient, or whether the yield could be further increased. However, unseasonal late rains and the associated spread of a fungus have resulted in major crop damage this year. The farmers I work with are mostly from marginalized communities, many of them tribal, and the loss in income has devastating consequences on their livelihoods. Now, during the cashew harvesting season, record-breaking heat waves have hit India, bringing a very real risk of heatstroke for anyone out during the day – whether researcher or farm worker.

India is home to more undernourished people than any other, water scarcity and land degradation are rising, and the country is highly vulnerable to climate change, which has formed a vicious cycle with the growing agrarian and biodiversity crises. ZBNF might offer climate adaptation and mitigation opportunities: ZBNF rice production, which is already widespread across Andhra Pradesh, may emit less methane and use less water than chemical-based farming. ZBNF farmers also tend to grow a greater variety of crops, making them resilient to the failure of a single crop type.

The results of Andhra Pradesh’s agricultural transition could have global repercussions. If the state can use ZBNF to deliver high yields sustainably and at scale, then human food needs and biodiversity may be reconcilable even in low-income, food-insecure regions. However, whilst there is ample political support for ZBNF, the evidence is still limited. On the plus side, this means that I can look forward to another field season next year.

Learn more about Iris and her work at

Instagram: iris_berger_

Iris has been using the Leica Ultravid 10×42 HD-Plus binoculars and the Leica Rangemaster CRF 2400-R for her research.

Products in use


  1. Leica Nature Observation Blog

    Hello Satta. We’re happy to hear from you! Thank you for your valuable feedback.

  2. satta

    Thanks, learned and know a lot for sharing everything. It helped a lot. Thank you very much.

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