A study published in the prestigious journal Nature Climate Change and led by researchers from the Laboratory of Biodiversity and Ecosystem Functioning at Pablo de Olavide University (UPO) provides novel evidence that global warming will increase the proportion of plant pathogens in soils across the globe.

Some of you might have heard that a teaspoon of soil contains millions of microbes. Most of these soil organisms are beneficial to humankind by regulating our climate, supporting the fertility of our soils, and helping us produce food and fiber. Others, however, are capable of devastating entire crops resulting in important economic losses, and even human starvation. Recent global events have reminded society that the unseen majority of microbes can have a real impact on our life, and that learning more about who these microbes are, and what they are doing is integral to maintaining our quality of life.

This new study, conducted by an international team of collaborators, provides experimental and global observational evidence that the proportion of soil-borne plant pathogens will increase in a warmer world. The study also helps put a face to the most common fungal plant pathogens found in soils across the globe, and suggests that soils are a critical reservoir of some of the most important plant pathogens worldwide. This study also provides the first global atlas of soil-borne plant pathogens highlighting the locations on Earth where these organisms are more common today and will be in the near future. The findings open the door further to predict what regions of our planet will be more vulnerable to future microbial plant pests.

“Global warming is already here, and we will need to adapt to the consequences of decades of heavy fossil fuel consumption. Knowing more about how climate change is going to affect the microbial communities which control our capacity to produce food and fiber is fundamental for humanity, especially, if we are up to feeding a continuously growing global population” says Delgado-Baquerizo, main author of the paper. Dr Delgado-Baquerizo is a Ramon y Cajal fellow from the UPO where he runs the Biodiversity and Ecosystem Functioning Lab. He adds that “Here, we provide solid evidence that experimental warming and global air temperatures are positively associated with higher proportions of soil-borne pathogens in soils worldwide”.

To conduct the study, the researchers collected soil samples from 235 different locations across six continents and 18 countries, spanning an entire range of climates from deserts to tropical forests. Moreover, they used a warming field experiment, located in Madrid, maintained by Maestre lab for the last decade. Then, they used DNA sequencing to investigate the association between the proportion of soil-borne pathogens and increases in temperature across different types of soil. Using this information, they generated global maps showing the distribution of soil-borne pathogens today, and in thirty years’ time.

This work contributes to our knowledge of the role of soil organisms in terrestrial environments, which is one of the main goals of the Biodiversity and Ecosystem Functioning Lab at UPO. The new study highlights that large regions of Earth from Asia, Africa, Australia and America contain high proportions of soil-borne plant pathogens. These regions correspond to warm climates such as those from hot deserts and tropical forests. “Our global maps identified the hotspots for soil-borne fungal plant pathogen today, and warn us about an overall global increase in the proportion of these important pathogens with global warming” says Delgado-Baquerizo. “We need to be prepared to face new potential global crises associated with our capacity to produce food and fiber under global change conditions” advises Delgado-Baquerizo.

Delgado-Baquerizo et al. The proportion of soil-borne pathogens increases with warming at the global scale. Nature Climate Change. https://www.nature.com/articles/s41558-020-0759-3