How Declining Solar Activity Could Impact Mediterranean Olive Cultivation

Summary

The arti­cle dis­cusses the threats fac­ing olive cul­ti­va­tion due to cli­mate change, includ­ing declin­ing pre­cip­i­ta­tion and solar activ­ity, which chal­lenges the long-term sus­tain­abil­ity and pro­duc­tiv­ity of olive farm­ing in the Mediterranean. The study high­lights the impor­tance of adap­ta­tion strate­gies, such as genetic improve­ment and eco­log­i­cal prac­tices, to mit­i­gate the impact of cli­mate change on olive pro­duc­tion and main­tain pro­duc­tiv­ity in key grow­ing regions.

As the Mediterranean cli­mate becomes increas­ingly unpre­dictable, olive cul­ti­va­tion faces grow­ing threats.

The severe impacts of cli­mate change will become increas­ingly inter­twined with decades of expected declin­ing solar activ­ity.

According to a recent study, such a sce­nario poses a chal­lenge to the long-term sus­tain­abil­ity, eco­nomic via­bil­ity, and pro­duc­tiv­ity of olive farm­ing.

The research, pub­lished in Communications Earth & Environment, exam­ined 8,000 years of pollen records across the east­ern Mediterranean.

These data pro­vide a long-term per­spec­tive on how cli­matic vari­ables, includ­ing pre­cip­i­ta­tion and solar irra­di­ance, have influ­enced olive yields over time.

A key con­tri­bu­tion of the research lies in show­ing how changes in pho­to­syn­thetic activ­ity strongly mod­u­late olive pro­duc­tiv­ity.

While the phys­i­o­log­i­cal links between pho­to­syn­the­sis and fac­tors such as light, rain­fall, tem­per­a­ture, and car­bon diox­ide are well estab­lished, the new research reveals how long-term fluc­tu­a­tions in solar radi­a­tion and sea­sonal pre­cip­i­ta­tion have his­tor­i­cally influ­enced olive yields across the east­ern Mediterranean.

“Today and in the com­ing decades, the pri­mary dri­vers of water stress in Mediterranean olive-grow­ing regions are declin­ing pre­cip­i­ta­tion and ris­ing tem­per­a­tures and evap­o­tran­spi­ra­tion,” Nick Marriner, co-author of the study and direc­tor of research at the French National Center for Scientific Research (CNRS), told Olive Oil Times.

“Optimal yields occur within a nar­row rain­fall band of 330 to 370 mil­lime­ters. Beyond this win­dow, fruit pro­duc­tion drops sharply,” he added. ​“Compounding this, as rain­fall decreases, evap­o­tran­spi­ra­tion rates are expected to increase, plac­ing addi­tional pres­sure on already mar­ginal grow­ing areas.”

While this pre­cip­i­ta­tion range pro­vides a valu­able bench­mark, it does not apply uni­formly across the Mediterranean.

“Although the indi­ca­tor is based on his­tor­i­cal and mod­ern data, it is not nec­es­sar­ily uni­ver­sally applic­a­ble to all olive cul­ti­vars or regions,” Marriner said.

“In prac­tice, the 330 to 370 mil­lime­ter range is a strong guide­line, but regional vari­a­tions in soil type, orchard man­age­ment and cul­ti­var char­ac­ter­is­tics may shift the opti­mal win­dow slightly,” he added.

The study also high­lights a lesser-known but emerg­ing chal­lenge: the approach­ing Grand Solar Minimum.

According to NASA, ​“dur­ing a grand min­i­mum, solar mag­net­ism dimin­ishes, sunspots appear infre­quently and less ultra­vi­o­let radi­a­tion reaches Earth.”

Such a phe­nom­e­non is expected to have only a slight impact on sur­face tem­per­a­tures, which will con­tinue to rise due to what 97 per­cent of cli­mate sci­en­tists agree is human-caused global warm­ing.

Still, dur­ing this period of reduced solar activ­ity, the inten­sity of solar radi­a­tion reach­ing Earth will decline, which may poten­tially affect pho­to­syn­the­sis.

The researchers iden­ti­fied a 2,350-year cycle in olive pollen pro­duc­tion that closely tracks solar activ­ity, under­scor­ing the role of radi­a­tion in shap­ing long-term yield trends.

“As global tem­per­a­tures rise, higher evap­o­tran­spi­ra­tion rates will fur­ther inten­sify water stress, espe­cially in rain­fed sys­tems,” Marriner said. ​“Our study empha­sizes that with­out irri­ga­tion, these con­di­tions may exceed the adap­tive lim­its of even drought-tol­er­ant cul­ti­vars.”

“Olive trees could suf­fer irre­versible pho­to­syn­thetic dam­age,” he added.

This kind of dam­age has been observed in trees exposed to pro­longed drought and heat stress. The per­ma­nent inabil­ity of the tree to con­vert sun­light into energy can occur.

In such con­di­tions, recov­ery is com­monly con­sid­ered rare or even impos­si­ble.

To con­front this mul­ti­fac­eted threat, adap­ta­tion will be essen­tial. One promis­ing avenue lies in genetic improve­ment.

“Cultivar selec­tion and breed­ing are key tools in adapt­ing to these stres­sors,” Marriner said. ​“Cultivars with early bear­ing capac­ity and tol­er­ance to drought and low irra­di­ance are already being devel­oped, with new vari­eties like Askal, Barnea, Kadesh and Maalot.”

“In addi­tion, prun­ing strate­gies that improve light pen­e­tra­tion and canopy aer­a­tion can help opti­mize pho­to­syn­the­sis under reduced solar radi­a­tion,” he added.

The study esti­mates that the amount of pre­cip­i­ta­tion required for effi­cient fruit devel­op­ment in most Mediterranean olive regions ranges from 290 to 410 mil­lime­ters dur­ing the phe­no­log­i­cal cycle, par­tic­u­larly from March to November.

When pre­cip­i­ta­tion dips below this thresh­old, or when extreme weather short­ens flow­er­ing and fruit­ing peri­ods, both yield and oil qual­ity suf­fer.

Adaptation strate­gies are already being tested across the region.

A 2024 study con­ducted in Spain eval­u­ated 12 olive cul­ti­vars for drought tol­er­ance under field con­di­tions.

Researchers found that vari­eties such as Empeltre and Cornicabra showed greater phys­i­o­log­i­cal resilience under water stress, high­light­ing the poten­tial for select­ing cul­ti­vars bet­ter suited to future cli­mate sce­nar­ios.

Other responses are eco­log­i­cal. In North Africa, for exam­ple, pro­duc­ers are increas­ingly adopt­ing con­ser­va­tion prac­tices such as mulching, uti­liz­ing organic soil amend­ments like biochar, and inte­grat­ing cover crops to improve water reten­tion and soil health.

These prac­tices helped some grow­ers main­tain healthy orchards and achieve high-qual­ity yields even in the record-dry 2023/24 crop year.

“A geo­graph­i­cal shift is already under­way and more may fol­low,” Marriner said. ​“Western Mediterranean [olive oil pro­duc­tion] lead­ers like Spain and Italy have already seen yield declines.”

According to the sci­en­tist, the east­ern Mediterranean is also fac­ing sharp drops in out­put.

“If these trends con­tinue, it is quite pos­si­ble that we will see an expan­sion of olive pro­duc­tion into more tem­per­ate zones, includ­ing north­ern Mediterranean or even Atlantic-fac­ing regions,” Marriner said.

“In drought-affected regions, there will be increased reliance on irri­gated plan­ta­tions, although this raises sus­tain­abil­ity con­cerns and other chal­lenges,” he added.

In Lebanon, a tra­di­tion­ally rain-fed olive-grow­ing coun­try, stud­ies have found that warm­ing tem­per­a­tures are short­en­ing the grow­ing sea­son, poten­tially lead­ing to increas­ingly erratic yields.

Those chal­lenges are well known to local grow­ers. Karim Arsanios, the owner of Solar Olives in north­ern Lebanon, told Olive Oil Times that his farm is con­tin­u­ously test­ing and adopt­ing new mit­i­ga­tion and adap­ta­tion strate­gies.

“At Solar, we adopt a bio­dy­namic approach to agri­cul­ture. We are try­ing to cre­ate an ecosys­tem that goes beyond sus­tain­abil­ity and becomes regen­er­a­tive,” Arsanios said.

According to the researchers, in the con­text of cli­mate change, the bal­ance that sup­ported Mediterranean olive cul­ti­va­tion is increas­ingly frag­ile.

“Understanding the lim­its of olive tree adapt­abil­ity is cru­cial. Our find­ings sug­gest that with­out proac­tive adap­ta­tion strate­gies, key olive-grow­ing regions may strug­gle to main­tain pro­duc­tiv­ity,” the authors wrote in their study.

“Long-term sus­tain­abil­ity will depend not only on bio­log­i­cal and agro­nomic inno­va­tion, but also on rec­og­niz­ing and address­ing the envi­ron­men­tal thresh­olds shap­ing the via­bil­ity of olive agri­cul­ture,” the researchers con­cluded.