A very old olive orchard I visited in the hills on the Greek island of Corfu |
This spring my family traveled in Italy and Greece where I
became enchanted with their ubiquitous olive groves. Many are on steep hillsides and some of the trees are
extremely old with beautifully gnarled trunks. I began to think I should try to grow an olive tree at home
in the San Diego area. Then I learned
some sad news about olives – news that suggests that it will become a more
scarce luxury food in the future.
Although olives are an ancient crop, expanding their supply
to keep up with population growth has been difficult. If we compare the
production of crops in the early 1960s with that 50 years later (2005-10)
almost all have increased in total tonnage, but much of that increase has come
through improved yields and not just more extensive planting (see table below). (Table)
How the supply of some vegetable oils has changed over 50 years |
Olives stand out among food oils in that all the increased
supply has come from additional planting.
Global average yields are 20% lower than they were 50 years earlier. No
wonder olive oil is expensive.
But now, olives in those picturesque groves in Southern
Europe are threatened by a deadly disease. It is apparently a new strain of a North American organism
called Xylella fastidiosa. Strains of
that pathogen cause diseases of various crops, but it is not known to affect
olives in California. Somehow a new, olive-infecting strain of Xylella originated in Central America
and traveled to Europe via an ornamental plant. In Italy, the pathogen is being spread by the common spittle
bug and is now killing trees in dramatic fashion.
Thus olives in Italy join citrus in Florida and grapes in
California as examples of crops in jeopardy because of the inadvertent, global
movement of bacterial pathogens or the insects that vector them. The grape infecting strain of Xylella was only a relatively minor
issue for California grapes until a new insect vector, the Glassy
Winged Sharpshooter, was transported into the state – again probably on an
ornamental plant. The disease thatis killing off Florida citrus, and threatening citrus from Texas to California,
arrived on an ornamental plant from Asia with both the vector and the pathogen
(do we see a trend here about the movement of exotic ornamental plants?).
Problems caused by moving plant pests around the world is nothing new. The three-century
delay in the arrival of the potato late blight pathogen allowed that New World
crop to become a staple, only to be decimated leading to the Irish PotatoFamine of the 1800s. Two pests spread
from North American grape species nearly destroyed the European wine industry
in the late 1800s. It is said that
the movement of coffee leaf rust from Africa to Java in the 1870s was the
reason that the English had to switch to tea. However now, with ever increasing global travel and trade,
many more crops are at risk.
Although it would not be a quick solution, genetic
engineering might be a good option for the olive problem as it would be for
citrus, grapes, potatoes and coffee.
Whether that will ever happen is, unfortunately, another question. Apparently the 2015 olive crop inCalifornia is looking good.
Perhaps that will take some pressure off our demand for olive oil from
Italy. In any case, we should
enjoy the luxury of olives before they become even less available.
You are welcome to comment here and/or to email me at savage.sd@gmail.com