Spain’s pine forests are under unprecedented pressure from a combination of extreme drought and a deadly disease caused by a collaboration between a native beetle and an invasive worm.
This phenomenon threatens to destroy tens of thousands of trees in the east and south of the Iberian Peninsula.
Alarm bells are ringing
Extreme and prolonged drought is hitting hard, especially in the eastern half of Spain, in areas such as Catalonia, the Valencian Community and the Region of Murcia. The government of Catalonia estimates that up to 10,000 hectares of forest could be lost in the coming months. Another threat makes the situation even worse. This threat has so far been mainly limited to the north and west of the peninsula: healthy pines that are green at the beginning of summer die by the beginning of autumn and turn a reddish-brown colour.
The perfect storm
Moreover, this crisis is exacerbated by the effects of climate change. Temperatures above 20 ºC and little rainfall promote the rapid spread of the disease. This leads to what is known as “seca del pino” (pine dieback), which is now spreading rapidly in areas already heavily affected by desertification.
A microscopic killer
The culprit is a parasitic worm, Bursaphelenchus xylophilus or the pinewood nematode. This is a microscopic cylindrical worm that cannot move independently from tree to tree. In Europe, the nematode has found an ally in the native beetle Monochamus galloprovincialis, also known as the “longhorn beetle” or “pine beetle”. This helps the worm spread by infecting the trees.
A major epidemic
The disease is so severe that infected pines inevitably die within one to three months of infection. The initial symptoms are not visible to the naked eye, but eventually lead to the blocking of the water flow within the tree, causing the tree to dry out and die.
Origin of disease
The disease, which originated in the United States, spread through Japan, South Korea, China and Taiwan. In those countries the disease killed millions of trees. From there it came to other parts of the world, including Europe. In Spain, the nematode was first detected in Villanueva de la Sierra, Cáceres. Tens of thousands of trees were burned there in an attempt to prevent the spread.
The only hope: strict control
Pine diebacks can have devastating effects on forest ecosystems. It can also damage wildlife habitat and increase the risk of forest fires. Until a cure is found, solutions include removing trees with symptoms of decay and capturing the beetles en masse with traps during their spring and summer flying period.
Also read: Catalan forests turning into tree graveyard due to drought
