36 paolo squatriti
Justinian, but the medieval expansion of silk production in the Mediterranean
benefitted the white mulberry (Muthesius, 1995: 315–335; Laiou and Morrisson,
2007). While the Byzantine state tried to guard the botanical-entomological
combination whose monopoly gave emperors prestige, by the eighth century
Andalusia knew sericulture (and mulberry trees), by the tenth century mulberries
grew on ecclesiastical estates in Calabria, and in the eleventh century the
Peloponnesus was well on its way to becoming Morea (after Morus): the Norman
“theft” of Byzantine silkworms and silk workers in 1147 was not the first breech in
Byzantine control of Mediterranean silk (Noyé, 2001).
Clearly, in the postclassical Mediterranean, special trees traveled outside and in
spite of imperial control, perhaps colonizing new landscapes through the kind of
networks and mobility guaranteed, even during the “early medieval depression,” by
Neolithic-style Mediterranean plant transfers. An enduring background noise of plant
transgressions, muted compared to the torrential rushes empires unleashed, was part
of Mediterranean history.
Empires of plants II: the caliphateA second exemplary episode of imperial intensification within the Mediterranean
Exchange began with the Islamic conquests of the seventh century ce. Over the next
400 years, the caliphate gathered for the first time within a single “House of Islam”
ecosystems earlier divided by geopolitics. As the caliphs held sway (increasingly tenu-
ously from the tenth century) over Mediterranean lands and western and central
Asian ones, they realized the dream of ancient rulers since Cyrus and Alexander.
Inevitably, integrating central Asian, Persian, Fertile Crescent, and Mediterranean
territories into one state and common market was difficult and success was never unal-
loyed. But the late first millennium ce was an important time for plant transfers, and
its impact on Mediterranean taxa was considerable. Most obviously, Asian cultivated
plants crept into the Mediterranean with unprecedented ease.
Since the 1970s the most useful way to make sense of the agronomic effects of the
rise of the Islamic caliphate has been the revolution proposed by Andrew Watson
(2008). Building on insights of nineteenth-century Iberianists and on the extraordi-
narily-florid agricultural literature from medieval al-Andalus and Egypt, Watson
proposed that a series of new, mostly Indian crops was diffused within the House of
Islam, of which the Mediterranean constituted the western appendage. Population
growth, urban demand, Arab landowners’ willingness to experiment (or show off in
their gardens), and especially migrations created the conditions for accelerated move-
ment of domesticated plants (Watson, 1995: 69). Scholars sometimes call this botan-
ical transfer “the Arab agricultural (or Green) revolution” to emphasize its impact.
Many of the new plants disseminated in the early caliphate could endure scorching
temperatures and were suited to summer cultivation. For Watson this was their most
significant characteristic, with the potential to alter ancient farming habits and extend
the working year into traditionally quiet months: after the grain harvest Mediterranean
cultivators quite sensibly had lain low, waiting for the autumn rains. Intensification
made demands, however. As several of the new crops required irrigation, they posed
particular problems to farmers. In the Arab agricultural revolution, a “caliphal pack-
age” was delivered to the Mediterranean containing seeds and plants whose success