The bacterium Xylella fastidiosa has already devastated millions of iconic Mediterranean crops like grapevines, olive trees and almonds by clogging their vascular systems. Now, new research shows climate change could enable this deadly pathogen to expand into key wine-producing areas currently at low risk.
A team from the Spanish National Research Council and University of the Balearic Islands developed techniques to model the future establishment risk of Pierce’s Disease, caused by X. fastidiosa. Using climate projections, they mapped out the disease’s potential spread under different global warming scenarios.
Their findings, published in Scientific Reports, reveal that a planetary temperature rise exceeding 3°C above pre-industrial levels would be a “turning point” allowing X. fastidiosa to advance northward through Europe’s wine regions.
First detected in Europe just a decade ago, X. fastidiosa was previously thought confined to the Americas, where it causes Pierce’s Disease and massive losses in California vineyards annually. Infected plants suffer discolored, necrotizing leaves, stunted fruit development and can perish within years.
The bacterium’s rapid European spread has already forced the destruction of 21 million olive trees in Italy’s Apulia region and devastated 80% of almond orchards in Mallorca. Its main vector is the meadow spittlebug.
As temperatures rise, the models show X. fastidiosa’s risk zone expanding from coastal Mediterranean areas into southern France, Italy and Portugal. Some cooler or mountainous zones may see reduced spittlebug activity, slightly shrinking the ecological niche.
The researchers consider climate change among the biggest challenges for EU agriculture policy. Forecasting risks, they argue, allows prioritizing surveillance to mitigate impacts.
At the country level, they found a 1.5°C warming scenario puts Portugal and Greece at 12% and 2% higher infection risk respectively. A 4°C scenario raises that to a “staggering” 47% and 63%.
France and Italy also face “relevant” risk elevation in hotter projections, though risk remains relatively stable for Spain, the world’s second largest wine producer.
However, zooming into regional appellations reveals some vineyards face grave threat even at 2°C warming, including southeast France, Spain’s Penedés, Portugal’s Bairrada and Italy’s Tuscany among others.
While acknowledging limitations in modeling microscale climates, the researchers stress understanding X. fastidiosa’s spread patterns is crucial. Their interdisciplinary study, combining epidemiology and climate science, aims to inform smarter prevention strategies.