events such as overexploitation (Pa

events such as overexploitation (Pauly et al., 1998), pollution (Boon
et al., 2002), eutrophication (Cloern, 2001), habitat fragmentation
and destruction (Layman et al., 2007; Melian and Bascompte, 2002),
invasions of species (Vander Zanden et al., 1999) and anthropogenic
climate change (Kirby and Beaugrand, 2009; Muren et al., 2005) all
pose potential threats to the structure and dynamics of food webs,
acting at variable spatial scales and affecting food webs in different
ways (Moloney et al., 2010). Nutrient enrichment, for example,
can drive bottom-up effects, propagated up food webs from lower
trophic levels (Davis et al., 2010; Rosenzweig, 1971), whereas the
removal of top-predators can initiate top-down cascade effects
through to basal trophic levels (e.g. Cury et al., 2003). Successfully
identifying and then monitoring all these processes presents major
obstacles, making the setting of management objectives and the
provision of scientific advice as to how these objectives might be
achieved, difficult prospects.