the vegetative mediterranean 31
the Mediterranean. But so did episodes of woodland regeneration or of expansion of
one species within forests. The point is that Mediterranean forest history is lively: if
anthropogenic change is important to past vegetation, especially woodland, it was
seldom total, irreversible vandalism.
The Mediterranean exchangeEarly modern historians have given some attention to the complex relationship
between plant distribution and imperial power, building on Crosby’s intuition of the
“Columbian Exchange” (Beinart and Middleton, 2004; Walvin, 1997; Beinart and
Hughes, 2007). This is a fruitful way to consider Mediterranean flora over the long
duration, and in “deep” time. Each of several political, military, and economic hegem-
ons in the Mediterranean shaped local plant communities just as they shaped human
ones: empires tend to rearrange nutrient flows within their territories, and to affect
those beyond their confines, and plants have long constituted the basis of human
nutrition (Simmons, 1993: 21). Empires built ecological “bridges” between zones of
the Mediterranean whose pre-imperial contacts were scanty and loose, when they
existed at all (di Castri, 1990). An only partially-intended outcome of this imperial
bridging was increased vegetational change, induced by the introduction of
previously-unfamiliar plants, some as domesticates, others mere hangers-on (“weeds”),
all exploiting the opportunities empire offered in the form of plowed fields, burnt
woods, and markets. Not all the crossings along imperial bridges were successful, but
in the Mediterranean empires created new botanical circumstances.
Thus, the seven centuries of Roman rule demonstrably affected the geographic
distribution of species and composition of plant communities in the basin. Indeed,
the Roman empire jogged the history of plants more than any other premodern
polity. Yet, also, other episodes of hegemony had measurable impact. From the sev-
enth century, the caliphate created the context for the transfer of many, mostly Asian,
plants into the Mediterranean, where several became staples of cultivation. After Selim
the Grim, the Ottoman Empire, great propagator of tulips and horse chestnut trees,
and the more subtle dominations of late medieval city-states (Venice, Genoa,
Marseilles, Barcelona) also determined how people and commodities moved, and
therefore the flow of seeds and plants and the composition of plant communities.
In the “Columbian Exchange” imagined by Crosby, Columbus’ Atlantic sailing
suddenly made possible contacts between Europe, Africa, and the Americas. Across
the Mediterranean instead, Africa, Asia, and Europe had long been engaged in a
botanical conversation, a result of the “imbalances productive of change” Braudel saw
as structural in the region (Braudel, 2002: 46). What we might call the “Mediterranean
Exchange” therefore functioned differently from the Atlantic one: in the case of seas,
at least, size does matter. Against a background noise of small-scale, short-distance,
ongoing transgressions into new habitats by species piggy-backing on the activities of
ubiquitous Mediterranean cabotage, or egged on by climate shifts, the imperial
moments that cadence Mediterranean history represent surges more than new begin-
nings. These surges, however, were qualitatively and quantitatively unlike what
preceded and came after them. Their significance deserves emphasis.
Before plunging into two examples (Rome and the caliphate) of such intensifica-
tion in the botanical exchanges the sea facilitated, it is well to recall that in this