Spreading fungal diseases threaten food security

The spread of existing and emerging fungal diseases in plants and animals poses a threat to global food security and biodiversity, according to a new study whose authors suggest halting fungal rot in the most important crops could feed an extra 600 million people a year. Writing in the 11 April online issue of Nature, researchers from the University of Oxford and Imperial College London in the UK, together with colleagues from several institutions in the US, say the fungal threat is largely the result of human activity, and call for more funds to tighten biosecurity worldwide. The last 20 years or so have seen an increase in virulent infectious diseases, both in the wild and managed landscapes. But more recently, there has been an unprecedented number of fungal and fungal-like diseases, causing some of the most severe die-offs ever witnessed among wild plant and animal species, write Dr Matthew Fisher, from Imperial's School of Public Health, Dr Sarah Gurr, Professor of Molecular Plant Pathology at the University of Oxford, and colleagues. In 70% of cases where infectious disease leads to the extinction of a type of plant or animal, behind the scenes is an emergent species of fungus, and this percentage is rising, say the researchers. Fisher, who with Gurr is a corresponding author, told the press: "The alarming increase in plant and animal deaths caused by new types of fungal disease shows that we are rapidly heading towards a world where the 'rotters' are the winners." Fisher, Gurr and colleagues suggest changes in the natural envinronment caused by human activity create new opportunities for fungal diseases to evolve and spread, thereby reducing biodiversity and jeopardizing crops and food systems. Most of the calories people around the world consume come from just five food crops: rice, wheat, maize, potatoes and soybeans. Fungal diseases like rice blast, stem rust in wheat, corn smut in maize, late blight in potatoes, and soybean rust, are right now destroying 125 million tonnes of these crops. The authors say the damage inflicted on rice, wheat and maize alone, costs global agriculture $60 billion a year, with catastrophic consequences in the developing world, where 1.4 billion people, existing on less than $1.25 a day, rely on these cheap foods. In a worst case scenario, the researchers calculate that 900 million tonnes of food would be wiped out if fungal disease epidemics were to strike all the top five food crops in the same year. Although the odds of this happening are extremely small, Fisher, Gurr and colleagues say if it were to happen, the result would be a global famine with 4.2 billion starving people. Fungal diseases affect the environment as well. Trees do an important job of removing carbon dioxide from the atmosphere and reducing the greenhouse effect. But loss and damage due to fungal diseases have prevented the absorbtion of around 230 to 580 megatonnes of atmospheric CO2, say the researchers. This is about 0.07% of global atmospheric CO2, enough to increase the greenhouse effect. In the animal kingdom, over 500 species of amphibians are at risk from new fungal diseases, plus many species of sea turtles, bees, and even coral. Fisher said: "We need to strive to prevent the emergence of new diseases as we currently lack the means to successfully treat outbreaks of infection in the wild." "Crop losses due to fungal attack challenge food security and threaten biodiversity, yet we are woefully inadequate at controlling their emergence and proliferation," added Gurr. The researchers also mention a topic that has been much in the news recently, the decline in US bat populations caused by white nose fungus infection. This will lead to a rapid rise in crop pests, resulting in an additional $3.7 billion of agricultural costs per year or more, they suggest. Fisher, Gurr and colleagues explain how human activity has shaped these trends: since the mid-20th Century, fungal diseases have risen largely as a result of increased trade and travel. They estimate the threat from fungal diseases now outstrips that caused by bacteria and viruses, and is set to increase even further. They urge for tighter control of processes that help the spread of fungal diseases, such as trade in plant and animal products. More funding to develop tools that can predict new fungal diseases is also needed, they add. Gurr said: "We must have better funding channelled into the fight against fungal disease." The National Science Foundation and the National Institutes of Health in the US, plus the BBSRC, NERC, the Wellcome Trust, the Leverhume Trust, Google.org, and the ERA-net project BiodivERsA, provided financial support for the study.