Historic Blizzard Threatens Olive Groves in Spain

Large swaths of cen­tral and north­ern Spain were blan­keted in up to 50 cen­time­ters of snow over the week­end as the coun­try expe­ri­enced its largest bliz­zard of the past half-cen­tury.

Four peo­ple have been killed by Storm Filomena, which bat­tered the Iberian Peninsula Friday and Saturday, bring­ing tem­per­a­tures as low as –8 ºC. Among the areas hard­est hit by the storm were the Community of Madrid, Castile-La Mancha and Catalonia.

Castile-La Mancha is the sec­ond largest olive oil-pro­duc­ing region in Spain after Andalusia. Together with Catalonia, the two autonomous com­mu­ni­ties pro­duced an esti­mated 197,000 tons of olive oil in the 2020/21 crop year or roughly 12 per­cent of the country’s total out­put.

While it is still too early to deter­mine the extent of the dam­age caused to the area’s olive groves by the storm – roads are still being cleared and some areas remain with­out power – there are some early indi­ca­tions that the region’s olive trees may sus­tain sig­nif­i­cant dam­age.

“Olive trees are not plants adapted to extreme cold tem­per­a­tures or sim­ply sub-zero ones for long peri­ods of time,” said David Marcos, of Viveros Sophie, a nurs­ery spe­cial­iz­ing in the sale of olive trees.

“The dam­age that can be caused is dif­fer­ent depend­ing on the age of the tree, time of year, cold level and period of time,” he told Olive Oil Times.

The two main threats to olive trees from a bliz­zard, Marcos said, are the weight of the snow on the tree limbs and the dam­age caused by the freez­ing tem­per­a­tures.

Having orig­i­nated in the Middle East and later spread across the rest of the Mediterranean basin, olive trees did not evolve with nat­ural cop­ing mech­a­nisms against snow and sus­tained freez­ing tem­per­a­tures.

Their wide-bladed leaves are not effec­tive at drop­ping snow and, in spite of the trees’ rel­a­tive flex­i­bil­ity, heavy snow­fall can cause branches to break. These break­ages, in turn, leave trees vul­ner­a­ble to infec­tions and pests.

However, the snow alone is not usu­ally respon­si­ble for the most dam­age. Instead, it is the cold that has the largest impact on the trees’ health and the qual­ity of the fruits.

“The snow itself does not freeze and even has a mit­i­gat­ing effect against the cold, in addi­tion to let­ting light through. The plants could live under the snow at first,” Marcos said. ​“The prob­lem is seri­ous when, after the snow­fall, the tem­per­a­tures drop and the snow freezes on the tree. In that case dis­as­ter is guar­an­teed.”

According to Aemet, Spain’s state-run mete­o­ro­log­i­cal agency, tem­per­a­tures are expected to hover around freez­ing through­out the week, with lows below 0 ºC through Saturday (the fur­thest date for which data are avail­able).

Aemet has also issued sev­eral severe weather warn­ings for cen­tral and north­ern Spain, with tem­per­a­tures as low as –14 ºC and –10 ºC expected in parts of Castile-La Mancha on Tuesday and Wednesday, respec­tively.

While the snow gen­er­ally causes vis­i­ble dam­age to the trees, Marcos said that the poten­tial for the root sys­tem to be dam­aged by the cold is even more con­cern­ing.

“Another prob­lem is freez­ing the roots,” Marcos said. ​“Young olive trees are the ones which will be affected by this.”

“Although the dam­age does not appear seri­ous in the crowns, if it has dam­aged roots by freez­ing, it will be observed in spring,” he added. ​“When the trees begin to sprout and grow, some can die sud­denly, with a char­ac­ter­is­tic appear­ance – wood with red­dish to dark col­ors, and loss of herbage.”

According to Italian agron­o­mist Angelo Bo, dam­age to roots is quite rare and requires extremely cold tem­per­a­tures for a sus­tained period of time. Based on the Aemet fore­cast, this sce­nario remains pos­si­ble, but seems unlikely.

However, Marcos warned that the bulk of the dam­age would be done to trees heavy with olives, although many pro­duc­ers have already con­cluded their har­vests. He said that the pres­ence of the olives on the trees makes them more sus­cep­ti­ble to dam­age from the cold and increases the risk of branch break­ages.

“But the added prob­lem is that olives being har­vested later will be dam­aged by cold, the oils that are extracted will have a high level of per­ox­ides that as free rad­i­cals will cause a rapid degra­da­tion of the prod­uct that can even begin in the fruit before it is trans­formed into oil,” he said. ​“These oils will never be edi­ble due to a seri­ous oxi­da­tion defect and a typ­i­cal wood fla­vor.”

While the extent of the dam­age remains to be seen and depends heav­ily upon the tem­per­a­tures of the next few days, Marcos said there is some prece­dence for what may be com­ing next for olive grow­ers.

“We have antecedents of this type of weather from February 1956, a month of below-zero tem­per­a­tures, with frozen snow on the tops of the olive trees,” he said. ​“That forced many olive trees to be cut to the base to sprout again and rebuild their branches and leaves over the years.”

“This hap­pened to a large part of the olive groves in cen­tral Spain and large areas stopped pro­duc­ing olives,” he added.

Producers con­cerned about the impacts of the snow­storm on the 2021 olive har­vest can also look east to Italy for clues as to what may be in store.

After the Burian snow­storm brought freez­ing tem­per­a­tures and blan­keted most of the penin­sula with snow in March 2018, pro­duc­ers across the coun­try reported sig­nif­i­cant declines in olive yields. Trees located on exposed hill­sides that bore the brunt of the freez­ing winds were impacted the most.

Along with dam­ag­ing the olives, the freez­ing and thaw­ing of water within the trees also led to necro­sis – the pre­ma­ture death of cells in liv­ing tis­sue – with some of the symp­toms of the con­di­tion show­ing up imme­di­ately while oth­ers man­i­fested them­selves later in the sea­son.

Damage caused to branches also led to some infec­tions in the affected olive trees in the after­math of the storm.

“Burian had some indi­rect effects in terms of pests,” Bo, the Italian agron­o­mist, told Olive Oil Times. ​“In fact, in the months fol­low­ing the cold wave, the wounds on branches affected by the cold were in sev­eral cases an access point for olive knot (Pseudomonas savas­tanoi) and even for the gall midge (Resseliella oleisuga). The lat­ter usu­ally does not cre­ate prob­lems, but in this case found access and spread more eas­ily to the small branches.”

Back in Spain, there is lit­tle for pro­duc­ers to do other than dig them­selves out and wait to see what the weather brings over the next few days.

“The dam­age from this storm can­not be eval­u­ated until the dura­tion and tem­per­a­tures reached are known, which will occur in the next few days,” Marcos said. ​“It can there­fore be seri­ous or light, depend­ing on how tem­per­a­tures evolve these days.”

Ylenia Granitto con­tributed to this report.

• BBC
• Edagricole