often comes as heavy flash floods. Most of this water is lost as surface
runoff, flowing from the mountainous wadis before it has time
to penetrate the rocky soil. Using an ancient system of dams and
walled gardens, the Bedouin direct this surface water into agricultural
plots, giving it time to soak into the soil and thus increasing
the potential for plant growth (Zalat and Gilbert, 2008). The gardens
were traditionally positioned where permeable dykes of rock ran
across the wadi, allowing water accumulation (and hence wells) if
the water had time to seep into the bedrock.
Within these agricultural gardens the Bedouin grow a wide
diversity of intercropped cultivated plants, with vegetables and
other crops growing beneath fruit trees. Wild plants are generally
tolerated within the gardens, with farmers weeding only the immediate
vicinity of their crops. The Bedouin do not use any form of
agro-chemicals, but do apply goat manure as fertiliser. The higher
availability of water combined with a low-intensity approach to
farming mean that these gardens provide a refuge for a variety of
native flora: surveys conducted in 71 gardens by Zalat et al. (2001)
recorded a total of 116 wild species within the gardens.
This study looks at the effects of run-off agroforestry by comparing
the biodiversity of ground arthropods within the gardens to
that of the surrounding natural habitat. Ground-dwelling insects
are particularly suitable for making this kind of environmental
impact assessment, because of their high biomass, ubiquitous presence
(Rosenberg et al., 1986) (even in a relatively sparse desert